A Study Of Vegetation Composition And Soil Chemistry On Five Year Non-rotational Set-aside Under Four Management Regimes, Essex, UK.

About Set-aside Study

I studied Geography at Coventry University from 1993 until 1997, and this was my final year dissertation. I discovered it on an old floppy disk, so decided to save it from permanent deletion.

This report has not yet been formatted for easy web reading. Plates are missing (they survive in the original print, in my bookcase), but will hopefully be added one day. The appendix is also missing.

The Set-aside scheme was abolished by the EC in 2008, however, this project is still very relevant today. Here we can learn how allowing arable land to return to nature for a few years can quickly improve soil composition and biodiversity. I got a 2.1 for it, so worth keeping!

Jonathan P. Wade BSc. (Hons)

A report presented in the Geography Subject Area, Coventry University, towards the Degree of Bachelor of Science with Honours in Geography,

April 1997.

ACKNOWLEDGEMENTS

I would like to thank Professor Ian Foster for his advice and guidance, and Elizabeth Turner for her technical assistance in the laboratory. I would also like to thank Mr. Richardson of Birkett Hall, Mr. Theobold of White House Farm, Mr. Calderwood of Reeds Farm and Mr. Speakman of Woodham Lodge Farm, who allowed me to carry out my surveys. Also thank you to all those who gave me encouragement, and my parents who chauffeured me to the farms beyond cycling distance.

ABSTRACT

Non-rotational set-aside on four farms in Essex was surveyed in summer 1996. Vegetation data was collected using a 0.25 m2 quadrat, and soil was analysed for pH, C, Cl, PO4, NH4, NO3, NO2, SO4, Si, Ca, Mg, Na, K and particle size. Set-aside had significantly altered the nutrient status of the soil. There were both significant increases and decreases in the various cations and anions examined. Soils generally became more acidic. Nitrates were significantly reduced and ammonium increased. Vegetation development was partially determined by the cover management adopted. It was not possible to relate the developed vegetation with the nutrient status of the soil.

Key Words: Non-rotational set-aside, Natural regeneration, Sown sward, Vegetation development, Species richness, Problem weeds, Soil chemistry.

Apologies for missing pages … I have the original hard copy if you wish to see it

1. INTRODUCTION

1.1. BACKGROUND: THE POST WAR PRODUCTIVIST ERA
1.2. THE POST PRODUCTIVIST ERA
1.3. SET-ASIDE POLICY
1.4. AIMS AND OBJECTIVES OF REPORT

2. VEGETATION AND SOILS OF AGRICULTURAL LAND

2.1. VEGETATION STUDIES ON OLD FIELDS AND ABANDONED ARABLE LAND
2.2. VEGETATION STUDIES ON ARABLE FIELDS
2.3. VEGETATION STUDIES ON SET-ASIDE
2.4. SOIL DYNAMICS UNDER SET-ASIDE
2.5. SUMMARY

3. BACKGROUND TO STUDY AREA

3.1. SOIL SERIES, CLIMATE AND GEOLOGY
3.2. MORE DETAILED SITE DESCRIPTION

4. METHODOLOGY

4.1. VEGETATION ASSESSMENT
4.1.1. DATA COLLECTION
4.1.2. VEGETATION ANALYSIS
4.2. SOIL SAMPLING
4.2.1. SOIL COLLECTION
4.2.2. SOIL ANALYSIS
4.3. DATA ANALYSIS
4.4. HYPOTHESES

5. RESULTS

5.1. VEGETATION SECTION
- 5.1.1. SPECIES RICHNESS, DIVERSITY AND DOMINANCE INDEX
- 5.1.2. ANNUALS, BIENNIAL AND PERENNIALS
- 5.1.3. COVER AND ABUNDANCE
- 5.1.4. FREQUENCY
- 5.1.5. SUMMARY
5.2 SOIL SECTION
- 5.2.1. pH, PARTICLE SIZE AND CARBON
- 5.2.2. WATER EXTRACTS
- 5.2.3. TOTAL DIGESTS
- 5.2.4. SIGNIFICANCE OF NUTRIENT CHANGE UNDER SET-ASIDE
- 5.2.5. SUMMARY

6. TEST OF SPECIFIC HYPOTHESES

6.1. HYPOTHESIS 1
6.2. HYPOTHESIS 2
6.3. HYPOTHESIS 3
6.4. HYPOTHESIS 4
6.5. HYPOTHESIS 5
6.6. HYPOTHESIS 6
6.7. HYPOTHESIS 7
6.8. HYPOTHESIS 8
6.9. SUMMARY

7. DISCUSSION

8. CONCLUSION

9. BIBLIOGRAPHY

10. APPENDICES – (To be added)

LIST OF FIGURES

FIGURE 5.1. PROPORTION OF PERENNIALS, BIENNIALS AND ANNUALS
FIGURE 5.2. MEAN % COVER FOR PROBLEM GRASSES
FIGURE 5.3. MEAN % COVER FOR PROBLEM WEEDS
FIGURE 5.4. MEAN ABUNDANCE FOR PROBLEM WEEDS
FIGURE 5.5. COMPARISON OF THE BORDERS AND CORES OF FIELDS
FIGURE 6.1. SCATTERPLOT OF ABUNDANCE AGAINST TOTAL N
FIGURE 6.2. COMPARISON OF FIELD MARGINS AND FIELD CORES
FIGURE 6.3. SCATTER PLOT OF POTASSIUM AGAINST SPECIES RICHNESS
FIGURE 6.4. MEAN ABUNDANCE OF PROBLEM WEEDS PER 0.25 m2 FOR EACH FIELD

LIST OF PLATES

PLATE 1. BIRKETT HALL
PLATE 2. WHITE HOUSE FARM
PLATE 3. REEDS FARM
PLATE 4. WOODHAM LODGE FARM

LIST OF TABLES

TABLE 5.1. SPECIES RICHNESS, DIVERSITY AND DOMINANCE INDEX
TABLE 5.2. SPECIES REACHING DOMINANCE IN AT LEAST ONE QUADRAT
TABLE 5.3. COVER AND FREQUENCY OF WHITE CLOVER
TABLE 5.4. FREQUENCY DATA FOR VEGETATION
TABLE 5.5. SOIL ANALYSIS DATA
TABLE 5.6. SOIL NUTRIENT CHANGES ON SET-ASIDE
TABLE 5.7. LEVEL OF SIGNIFICANCE FOR SOIL NUTRIENT CHANGES
.TABLE 6.1. ABUNDANCE OF PROBLEM WEEDS AND NUTRIENT CONCENTRATION OF THE SOIL
TABLE 6.2. COMPARISON OF FIELD MARGINS AND FIELD CORES
TABLE 6.3. SPECIES RICHNESS AND SPECIES DIVERSITY FOR SOWN AND UNSOWN FIELDS
TABLE 6.4. COMPARISON OF ABUNDANCE OF WEEDS ON SOWN AND UNSOWN FIELDS
TABLE 6.5. SPECIES RICHNESS, SPECIES DIVERSITY AND NUTRIENT SUPPLY
TABLE 6.6. MEAN % COVER AND FREQUENCY OF CLOVER WITHNUTRIENT CONTENT
TABLE 6.7. COMPARISON OF HEAVILY AND LIGHTLY GRAZED FIELDS
TABLE 6.8. CUTTING REGIME AND ABUNDANCE OF PROBLEM WEEDS AT FARM LEVEL

1. INTRODUCTION

1.1. BACKGROUND: THE POST WAR PRODUCTIVIST ERA

The Post War productivist era experienced massive agricultural restructuring. Intensification, technological change, mechanisation and guaranteed prices all led to the expansion of agriculture in the English countryside (Smith et al., 1993). The traditional English landscape was suddenly considered to be an “inconvenient obstruction to the activities of the agri-businessmen” (Shoard, 1980, p.14). Mechanisation led to the removal of hedgerows, improved drainage removed ditches, and price support and agricultural grants led to the drainage of marshes and removal of woodland to increase production. The use of chemical fertilisers increased yields. Pesticides included herbicides, fungicides, insecticides, molluscicides and rodenticides, which severely reduced the wildlife habitats on farmland and neighbouring habitats. The soil nutrient status of field margins and non-cultivated land led to the impoverishment of plant communities as highly competitive species increased, forcing out many native wild flowers (Smith et al., 1993). The need for a fallow stage in crop rotations was also eliminated, thus further reducing the availability of wildlife habitats on the farm. On some farms in Essex wheat has been cropped continuously for 20 years without a rotation or ley.

1.2. THE POST PRODUCTIVIST ERA

In the 1980’s the productivist era had reached a climax. Production levels had increased above market demand producing huge food mountains. Budget costs had risen resulting in higher food prices (Floyd, 1992). The Council of Agricultural Ministers met in Brussels in 1992 and made dramatic changes in the Common Agricultural Policy (CAP).

1.3. SET-ASIDE POLICY

The initial set-aside policy which was set up in 1988 was a voluntary scheme. Farmers who decided to join the scheme had to take at least 20% of land used for growing arable crops out of production (Ilbery, 1990). A farmer could manage the set-aside as permanent fallow, rotational fallow, non-agricultural use, or woodland. A combination of these options could be used. Under permanent fallow the farmer is committed to set-aside the same parcel or parcels of land for five years. The rotational fallow option enables farmers to set-aside different parcels of land each year as part of the normal arable rotation. The payment for the rotational fallow is lower than for the permanent fallow to take account of the benefit this brings by increasing the yield on the following crop (MAFF/WOAD, 1988).

The fallow option dictates that:

1. The land must be kept in good agricultural condition

2. The land must not be left bare, but a green cover crop must be sown, or established by allowing the naturally occurring vegetation to regenerate

3. The cover crop must be cut at least once a year

4. The application of fertilisers and pesticides is prohibited as a general rule

5. The land may be managed for environmental or conservation purposes

6. Existing trees, hedges, watercourses, ponds and pools on or next to land set-aside must be maintained (MAFF/WOAD, 1988).

In the 1992 CAP reform the set-aside policy became compulsory, and stated that 15% of land had to be taken out of agricultural production. The options for set-aside underwent a few changes. Land could be used to grow industrial crops, such as crops grown as biodiesel (oil-seed rape), pharmaceutical products (evening primrose), and solid biofuels (short rotation coppice of willow or poplar). MAFF also developed new schemes to promote set-aside for amenity and conservation use. The countryside Access Scheme was set up in 1994. In this scheme extra payments are made for farmers to open access routes, or entire fields, for recreational use by the public. The Countryside Premium Scheme and Woodland Premium Scheme dictate the specific cover that has to be established in terms of species of grass mixtures or broad-leaved trees, both of which dictate that at least four species from a list of ten native species must be established. Essentially, two types of set-aside developed, one for the purpose of supply management and the other specifically designed for socio-structural, forestry, and environmental purposes.

The Institute of Terrestrial Ecology suggest that the potential objectives for non-rotational set-aside are:

1. To conserve wildlife

2. To promote biological control of pests on nearby arable land

3. To increase stocks of game and fish

4. To manage runoff of nutrients and agrochemicals into adjacent water and land

5. To provide public access and amenity

6. To improve rural landscapes

7. To reduce carbon dioxide emissions

8. To replace fossil fuels with biomass fuels.

(Firbank et al., 1993).

1.4. AIMS AND OBJECTIVES OF REPORT

1. To determine which form of cover management is most beneficial to the creation of diverse vegetation communities on set-aside land.

2. To determine whether the species composition of a field is dependent on the chemical characteristics of the soil.

3. To determine whether five year non-rotational set-aside could be either beneficial to the agricultural quality of the land or detrimental (in terms of soil characteristics and the presence and invasion of hardy and noxious weeds).

These aims and objectives will be met by testing a set of hypotheses which will be set up in Chapter 4.

2. VEGETATION AND SOILS OF AGRICULTURAL LAND

2.1. VEGETATION STUDIES ON OLD FIELDS AND ABANDONED ARABLE LAND

Until the introduction of set-aside very few studies had been carried out on the development of grassland ecosystems, especially on abandoned arable land in the UK. The first studies of succession on abandoned arable land in the UK were at the Rothamsted Experimental Station in Hertfordshire. The Broadbalk and Geescroft Wildernesses were created in 1882 and 1867 respectively (Burnham, 1989).

Cornish (1954) studied the grasslands of the North Downs, and Wells et al. (1976) studied the relationships between vegetation, soils and land-use history on the Porton Ranges. Most previous studies, especially those on old fields in America, were on land which was neither in arable production for any great length of time or intensively managed. The introduction of set-aside policy allows the development of grassland ecosystems on previously intensive arable land to be examined for the first time.

2.2. VEGETATION STUDIES ON ARABLE FIELDS

Before the conservation of wildlife habitats became a popular concern, all non-crop vegetation on farmland was regarded as arable weeds. Various studies have examined weed distributions in arable land e.g. Froud-Williams and Chancellor (1982), Chancellor and Froud-Williams (1984) and Chancellor (1985).

A survey of grass weeds in central southern England in fields of winter wheat revealed that Avena spp. occurred in 32% of fields, Agropyron repens (Elymus repens) in 24%, Poa trivialis in 22%, Alopercurus myosuroides in 19% and Bromus sterilis in 9% (Froud-Williams and Chancellor, 1982). Therefore it can be assumed that these species are most likely to be the most important in the colonisation of set-aside. A second survey of cereal weeds examined dicotyledenous weeds in addition to grasses. The eight most frequent species recorded were Viola arvensis, Galium aparine, Stellaria media, Myosotis arvensis, Polygonum arviculare, Convolvulus arvensis, Bilderdykia (Polygonum) convolvulus and Lamium purpureum. However, surveys in Essex revealed that 22% of fields were infested with Convolvulus arvensis, 14% with Galium aparine, 5% with Polygonum aviculare, 3% with Lamium purpureum, 2% with Rumex obtusifolius and Myosotis arvensis, and 1% with Bilderdykia convolvulus. There was no Stellaria media or Viola arvensis.

Chancellor (1985) examined changes in weed flora of an arable field cultivated for 20 years which had previously been in permanent pasture. Maximum species richness occurred four years into the arable cultivation. Grassland weeds did not persist long under continuous arable cropping, though Trifolium repens survived the whole 20 years. Rumex obtusifolius survived 12 years, Plantago lanceolata 8 years, and of the 13 other species recorded, nine had vanished by five years. This may have some interesting implications for post set-aside management.

2.3. VEGETATION STUDIES ON SET-ASIDE

Various studies and surveys have examined the changes in botanical composition of set-aside fields in the past few years e.g. Poulton and Swash (1992), Fisher et al. (1992), Wilson (1992), Rew et al. (1992), Clarke and Cooper (1992), Shield and Godwin (1992), Brodie et al. (1992), Burch (1996), Turley et al. (1994), Lawson et al. (1994) and Welch (1991, 1994).

Poulton and Swash (1992) monitored the botanical composition for the first year of set-aside in England. It was found that core areas of set-aside were less diverse than the field boundaries. Furthermore, natural regeneration produced higher species richness and greater populations of notifiable weed species, such as Cirsium arvense, C. vulgare, Rumex crispis, R. obtusifolius and Senecio jacobaea. The most frequent species to occur were Agrostis spp.,Elymus repens, Cirsium arvense, Lolium perenne and Sonchus asper.

Fisher et al. (1992) looked at sown covers in Scotland and concluded that sown fields produced a lower frequency and ground cover of broad-leaved species. Very few annual weeds or volunteer crops were present in the sown covers, and it was predicted that perennial grasses would eventually predominate set-aside fields. Lechner et al.(1992) found that cover crops suppressed weeds on set-aside in Germany. 90% of total weeds consisted of just 8 species. Wilson (1992) studied naturally regenerated set-aside in Southern England and found that under natural regeneration annual species declined as the vegetation developed, and perennial species increased. Wilson also investigated the effect of adjacent of semi-natural habitats on the composition of set-aside and concluded that semi-natural habitats can have an important influence on the characteristics of set-aside. Soil characteristics had little effect on vegetation development.

Rew et al. (1992) examined the spatial distribution of vegetation changes in set-aside over a three year period in the south and south-east of England. Boundary vegetation consisted of a greater number of perennial species, and towards the core areas of fields, perennials decreased and annual and biennials increased. However, the annual Galium aparine was a notable exception and decreased from the boundary. It was concluded that there were three main sources of plant origin: Vegetation propagation (e.g. Agrostis stolonifera); increase in wind disseminated species including Sonchus spp. and Crepis spp.; and a decline in the diversity and cover of annuals originating from the seed bank over the three year period.

Clarke and Cooper (1992) examined weed levels in set-aside and the subsequent crops. On set-aside, frequent cutting altered the habits of Alopercurus myosuroides, Bromus spp. and volunteers. On naturally regenerated set-aside Bromus spp., Cirsium arvense, C. vulgare, Elymus repens, Poa spp., Senecio jacobaea, Sonchus spp. andStellaria media dominated the fields. Rotational set-aside had caused no problems for subsequent cropping, but on permanent set-aside perennial species became problematic to farmers.

Shield and Godwin (1992) studied set-aside on a traditional heavy soil cereal site previously in winter wheat on the Bedfordshire/Hertfordshire border. The developed vegetation sward was dominated by Elymus repens which achieved dominance through competition and the sensitivity of annual species to cutting regimes on the set-aside. The most sensitive species to cutting were volunteer wheat followed by Alopercurus myosuroides. Bromus sterilis was most difficult to control under the new conditions. The first year of set-aside was dominated by Bromus sterilis, Alopercurus myosuroides and volunteer wheat. By the second year these decreased and were replaced by Elymus repens. When Elymus repens occurs in high numbers, future crops can often be threatened by Gaeamannomyces graminis (the take-all fungus) and Pseudoncercosporella herpotrichoides (eyespot) which can remain in plant residues after cutting and cause significant reductions in yield.

Talling and Godwin (1994) found that on calcareous clay soils, where set-aside had been mown, decaying Elymus repens occurred in large amounts, and caused a significant crop yield reduction after set-aside. Decaying rhizomes can immobilise nitrogen. They suggest that a herbicide treatment should be carried out prior to set-aside, then a cover sown to prevent the spread of Elymus repens.

Brodie et al. (1992) studied set-aside in Cambridgeshire. The developed vegetation consisted of grasses characteristic of the weed flora of arable fields and disturbed ground. Although the number of species increased over the duration of the set-aside, the diversity index did not. The increase in the number of species was balanced by greater inequality in the relative abundance, i.e. a few species became extremely abundant, with infrequent areas producing higher diversity.

Turley et al. (1994) compared the development of flora during three years of set-aside under three cover managements: perennial rye grass; perennial rye grass and white clover, and natural regeneration. The sown covers suppressed the development of other grass and broad-leaved species, and by the second year sown covers had eliminated cereal volunteers. On the naturally regenerated fields establishment was slower, but the number of non-volunteer species and grass and broad-leaved plants increased over the three years. Within three years, perennial grasses dominated all sites, except for the those on the sandy soils. Weed levels in the first wheat following set-aside were similar, or lower than, those on land which had remained in arable rotation. However, at one of the sites, failure to control Elymus repens with glyphospate at the end of the set-aside period resulted in couch infesting the following wheat crop. The perennial rye grass and clover covers were very effective at excluding other species, after three years few other species were present in the sward. The naturally regenerated swards produced much greater species diversity (7 species present at Boxworth on heavy soil, 27 species at Gleadthorpe on light soil). Also, on the sown covers, thistles were unable to colonise.

Burch (1996) compared five establishment methods on the development of desirable species on a large scale field experiment at Wye College. Burch suggested that one of two establishment methods should be considered to produce the desired effect of balancing weed control with species enhancement. Where weed control is a principal concern, a grass cover should be established in the first couple of years, and then the spread of more desirable species can occur as the sward matures. In less weedy sites, a more “open matrix” approach will offer partial weed control and more favourable establishment conditions for desirable species. It was found that, perennial rye grass produces a dense sward within a couple of years, with associated species. Natural regeneration promotes growth of both desirable grassland species and pernicious weeds. If neither of these approaches produces the required sward, then sown covers of Festuca spp. and Cynosurus spp. can be used. However, Festuca rubra produces a dense cover which prevents other species colonising making it less suitable for achieving a spatial balance.

Lawson et al. (1994) examined set-aside management strategies on the soil seed bank and weed flora at Woburn. On fields at Woburn, naturally regenerated swards were dominated by grass species throughout the three years. Volunteer oats quickly colonised the set-aside, and acted in a similar way to a sown perennial rye grass cover in the first two years, to be replaced by Poa annua, Agrostis gigantea and Bromus sterilis in the third year. Cirsium vulgare, Sonchus spp. and S. Vulgaris appeared on the natural regeneration plots in the second and third years. It was not until the third year that volunteer oats declined and natural species could colonise the land. There was no evidence of the spread of sown species into the natural regeneration plots. Natural regeneration produced more seeds, more species and greater diversity in the seed bank than sown set-aside, indicating that volunteer oats had not been as effective in preventing seed bank expansion on their own as in association with a sown cover.

Welch (1991 and 1994) studied trends in the botanical composition of fields in N.E. Scotland. After one year of set-aside grasses predominated, with Holcus mollis and Poa annua being most abundant. Agrostis gigantea andElymus repens also reached high levels. Cirsium spp., Senecio jacobaea and Avena fatua occurred in most fields. Broom and gorse soon colonised the Scottish fields. Species richness seemed to be unaffected by type of crop last grown, although fields formerly in rape had the greatest average number of species recorded. Generally field margins were no more diverse than the core areas of fields. Colonisation by grasses was much more rapid than on studies in lowland England. After five years of set-aside grasses continued to dominate. Agrostis gigantea and Poa annua were replaced by grasses of permanent grassland, such as Agrostis capillaris, Dactylis glomerata and Holcus lanatus.White clover was the most frequent of the non-weedy dicotyledenous plants. Noxious weed frequencies remained low. Species richness declined during the five years of set-aside, due to the decline in dicotyledenous species. Many species only occurred in edge quadrats and often only a single species would be present. The process of colonisation is thought to be delayed by early cutting which prevents fruits ripening sufficiently for seed dispersal.

Aquilina and Clarke (1994) examined the effect of cutting date and frequency on perennial broad-leaved weeds on set-aside. Rumex spp. were found to increase in fields where the cover was cut at the full flower stage. Cirsium vulgarewas most affected by cutting and spraying treatments. Cirsium arvense was reduced in the second and third years by cutting treatments. On areas of poor plant cover, Cirsium arvense was less likely to be controlled. Sonchus arvensiswas controlled by most treatments, although cutting alone was not as effective as cutting and spraying.

With all treatments, a good plant cover aided the reduction of perennial broad-leaved weeds without which only a cutting and spraying treatment could reduce populations sufficiently.

2.4. SOIL DYNAMICS UNDER SET-ASIDE

Studies on the nitrogen changes under set-aside have been carried out by Froment and Grylls (1992), Sinclair et al.(1992), Farr et al. (1992), Vinten and Smith (1993), Burt and Haycock (1993), Chalmers et al. (1994).

The leaching of nitrates into rivers and drinking water supplies from farmland has become a major environmental concern. Fertiliser application is only one source of nitrogen that crops utilise. Many agricultural soils depend heavily on the mineralisation of organic nitrogen. Parkinson (1993) discusses the effect of sward development on the nitrogen content of the soil and remarks that it may become a major source of significant nitrate losses once the sward has matured, and particularly if the sward is ploughed out. The practice of ploughing out grass and establishing a new crop, whether arable or grass, invariably leads to high losses of nitrate in the year immediately succeeding pasture inversion. This is especially true for grass/clover systems (Parkinson, 1993).

More than 90% of the nitrogen in most soils is in organic form. However, the inorganic component, mainly ammonium and nitrate is significantly greater in agricultural soils. Also, when nitrogen is returned in faeces and urine in grazed systems the leaching loss is generally much higher. The ploughing up of temporary grassland is also a major cause of nitrate leaching (Vinten and Smith, 1993). This is an important factor when considering the effect of set-aside on the local environment.

Burt and Haycock (1993) also argue that, although set-aside will cause a reduction in the amount of fertiliser applied to a farm, the inclusion of a rotational fallow option may mean that set-aside will have less impact on reducing nitrate leaching as periodic ploughing would release substantial amounts of nitrate.

Froment and Grylls (1992) studied soil mineral nitrogen changes under set-aside. This is important as one of the aims of the U.K. government is to reduce nitrate leaching from agricultural systems, therefore it is important that set-aside does not increase the potential for nitrate leaching. A comparison of perennial rye grass, perennial rye grass with white clover, natural regeneration and perennial rye grass receiving a low rate of applied nitrogen was carried out. The findings generally showed that set-aside reduced soil mineral nitrogen, and that soil mineral nitrogen levels were lower for perennial rye grass than natural regeneration or rye grass with clover. It is suggested that this is as a result of a more rapid establishment of a vegetative cover.

Sinclair et al. (1992) carried out a similar experiment, and concluded that there was a potential to reduce leaching of nitrate where a dense cover with a high content of rye grass is established. However, a sward with clover may result in an increase in nitrate leaching from agricultural land. The final conclusion was that “from the point of view of minimising loss of nitrate-N from set-aside land, grass is a better cover crop than clover or natural regeneration” (Sinclair et al., 1992).

Harris et al. (1992) also studied changes in soil mineral nitrogen. Soil mineral nitrogen showed reductions on all fields previously in winter cereals on a farm in Cambridgeshire.

Hewitt et al. (1992) studied soil mineral nitrogen on a sandy loam at Woburn, Bedfordshire, and found that “leaching under autumn sown rye grass was almost as great as under winter wheat” (Hewitt et al., 1992). Natural regeneration was surprisingly effective at decreasing leaching compared to winter wheat. This was after a single year of set-aside.

Farr et al. (1992) examined the effect of cutting management on naturally regenerated set-aside and its affect on the mineral nitrogen content on a farm in Elgin, Scotland. The data collected suggested that timing and frequency of cutting naturally regenerated plant cover had no effect on the level of mineral nitrogen in the soil. Whether the cuttings were left or removed also had no effect on soil mineral nitrogen. However, ammonium levels were found to be greater on set-aside generally.

Chalmers et al. (1994) studied the effects of various cover managements on the soil mineral nitrogen levels, and the levels of soil mineral nitrogen in the following crops. On one year set-aside there appeared to be a similar or smaller risk of nitrate leaching from autumn established set-aside compared with arable rotations. Ploughing increased soil mineral nitrogen on set-aside to levels greater than those on arable fields. During the third year of set-aside the risk of nitrate leaching was less than that of arable fields. Perennial rye grass had the smallest effect on soil mineral nitrogen, whereas perennial rye grass with white clover had the largest effect. Plant cover, nitrogen uptake and recycling via mowings, and other nitrogen supply from fixation by white clover, would have contributed to these differences. Ploughing of set-aside increased the soil mineral nitrogen during the following season compared to the arable rotations for all locations except the perennial rye grass plot at Boxworth. Perennial rye grass with white clover gave the highest increases of soil mineral nitrogen.

Jones et al. (1994) determined that set-aside covers of perennial rye-grass, perennial rye grass with white clover, and natural regeneration all increased the soil mineral nitrogen supply at sites throughout the UK. Melander and Jacobsen (1994) studied nitrogen uptake on set-aside in Denmark, and suggest that a sown cover is needed to reduce N-leaching.

Rose and Harris (1994) examined changes in the soil water quality on five year non-rotational set-aside on clay soils in Cambridgeshire. It was found that under set-aside lack of cultivations and the deterioration of the secondary drainage systems increased surface compaction and surface runoff which led to rapid reductions in the soil mineral nitrogen on fields previously in winter cereals. Nitrate-N concentrations in the drainage water fell to below the EC Directive (11.3 mg l-1) limit within one year of

set-aside. The ploughing up of set-aside encouraged the mineralisation of organic matter, and nitrate produced after ploughing was leached out into the drainage water in concentrations of up to 25 mg l-1 in the autumn, and in excess of 30 mg l-1 in the spring following application of fertilisers. However, it was still concluded that set-aside had beneficial effects on the environment.

2.5. VEGETATION AND SOILS SUMMARY

Previous studies on the vegetation of set-aside have generally shown that annual species dominate set-aside initially, to be replaced by perennials as the sward matures. The most common colonising species are those which were persistent in the previous crops, those which have many seeds in the soil seed bank, and those dispersed from adjacent semi-natural habitats. Perennial species generally spread from the border to the core of the field as the field ecosystem develops. The most common grass species include Avena spp., Elymus repens, Alopercurus myosuroids, Bromus sterilis, Dactylis glomerata and Holcus lanatus. Common dicotyledenous species include Cirsium arvense, C. Vulgare, Rumex obtusifolius and Senecio jacobaea.

Studies on the characteristics of soil under set-aside have been almost entirely devoted to nitrogen changes and reductions in nitrate levels. Few papers give mention to other nutrients which are essential to plant growth.

3. BACKGROUND TO STUDY AREA

Four farms were chosen for this study. The prerequisites for each farm were that:

It must be approaching the end of a permanent fallow option
Had an intensive cropping history
Be within the Chelmsford district so that soil types and climatic factors for all farms will be as similar as possible.
They must each have a different management regime for set-aside.

The farms chosen for the study were Reeds Farm, Writtle (OS 665 075), Birkett Hall, Woodham Ferrers (OS 794 012 ), Woodham Lodge Farm, Woodham Ferrers

(OS 786 007), and White House Farm, Rettendon (OS 768 969). Reeds Farm and Woodham Lodge Farm have naturally regenerated set-aside; Reeds Farm was cut once a year and Woodham Lodge was cut two to three times a year. Woodham Lodge had areas in the Woodland Premium Scheme. Birkett Hall had two types of sown cover and was used for grazing by horses. White House farm was in the Countryside Premium Scheme and sown with native grass mixtures. At White House some border areas were also set-aside for game conservation and had fertiliser applied to promote a rapid growth of cover.

3.1. SOIL SERIES, CLIMATE AND GEOLOGY

Soil Series

Birkett Hall, White House Farm and Woodham Lodge Farm are on the Windsor soil series:

Windsor (712c): Tertiary clay. Slowly permeable seasonally waterlogged clayey soils mostly with brown subsoils. Some fine loamy over clayey and fine silty over clayey soils and locally, on slopes, clayey soils with only slight seasonal water logging. The soils are generally suited to dairying with some cereals: winter cereals and short term grassland in Essex: some deciduous and coniferous woodland (Soil Survey of England and Wales, 1983). Windsor soils are non-calcareous, liming is necessary. Soil phosphorous levels are low but magnesium levels are satisfactory and potassium reserves are high (Allen and Sturdy, 1980).

Reeds Farm at Writtle is on the Hornbeam series:

Hornbeam 3 Chalky Till (592d): Deep fine loamy over clayey soils with slowly permeable subsoils and slight seasonal waterlogging. Some slowly permeable. Seasonally waterlogged fine loamy over clayey soils. Calcareous subsoils in places. The soils are generally suited to cereals and other crops (Soil Survey of England and Wales, 1983). Hornbeam soils are naturally acid and need regular liming (Allen and Sturdy, 1980).

Climate

Average annual rainfall at the Writtle Agricultural College

1941 – 1970 569 mm

1967 – 1976 547 mm

Driest month: February

Wettest month: November

August has the maximum moisture deficit and the highest potential transpiration. The growing season (i.e. The number of days when the average soil temperature at 30 cm rises above 6°) lasts from March 19 to December 10, a total of 266 days (Allen and Sturdy, 1980). However, in the year from January to December 1996, the region only received 40-55% of the long term average rainfall (Abel, 1997). The United Nations has recently classified East Anglia as semi-arid (Vidal, 1997).

Geology

The base geology is the London Clay. It is overlain by Chalky Till in the Writtle area (Reeds Farm) and by Tertiary Clay in the Woodham Ferrers and Rettendon area (Woodham Lodge Farm, Birkett Hall and White House Farm).

3.2. MORE DETAILED SITE DESCRIPTION

Birkett Hall

Birkett Hall was set aside from agricultural production in two stages. The first fields were set aside in 1990, then the rest of the farm was set aside in 1992 under the land diversification scheme to be used as livery stables. It now holds about 40 horses. In total about 140 acres were in a five year non-rotational set-aside, and it is continuing to remain grass for horses rather than return to arable crop production after set-aside.

Birkett Hall consists of six fields now, each subdivided into smaller grazing plots, but consisted of twenty-five fields before extensification in the 1960’s. A rotation system was still used right up until the set-aside period even though the land was capable of producing a continuous wheat crop with sufficient fertiliser treatments. Of the six fields, the four largest were studied for the floristic survey. Soil samples were taken from all fields. The four studied for flora were Springfield, Cowbridge, Saunders and Chaplefield. The other fields were Bell Meadow and Front Meadow (See plate 1).

Springfield and Cowbridge were set aside in 1992 and sown with a rye/white clover mix. Wheat was grown prior to set-aside.

Bell Meadow was set aside in 1990 and also had wheat prior to set-aside. A more expensive grazing mixture was sown which consisted of a greater variety of grazing species. The west end of the field was used as allotments until 1984, when it was ploughed up and used for farmland.

Saunders was set aside in 1990 and sown with the expensive grazing mix. Prior to set-aside there was wheat for two years.

Chaplefield was set-aside in 1992 and had a crop of peas prior to set-aside, and was sown with the rye/clover mix.

Front Meadow was set aside in 1992 and sown with rye/clover, and had a wheat crop prior to set-aside.

White House Farm

White House farm was set-aside in 1991 and at the time of the survey was in its final year of a five year non-rotational set-aside option. The set-aside is approximately 130 acres and some of the land is in the Countryside Premium Scheme. It has been sown with a native grass species mix. There are three large fields in the set-aside scheme all almost equal in size. Prior to set-aside a rotational system of farming was employed which consisted of two years of wheat, one year barley and one year of vining peas or oilseed rape.

Two of the fields have areas set aside for game conservation, which had some fertiliser applied to promote growth, but these areas had not been managed in the year up to 1996 when the survey was carried out. Adjacent to Back Field, the largest of the three fields, there is some woodland, of which approximately half has been recognised to be ancient woodland (See plate 2).

Woodham Lodge Farm

Woodham Lodge Farm consists of one extensive area of set-aside approximately 250 acres in size, which surrounds the Lodge Farm House. It was in the fourth year of a five year set-aside period at the time of survey. The land had been left to naturally regenerate, with the exception of some border areas which are under the Woodland Premium Scheme. The set-aside is cut two to three times a year to prevent seeding

(See plate 3).

Reeds Farm

Reeds Farm was set aside in 1989. It consists of two quite different areas of set-aside. The North Field is a single rectangular block surrounded on two sides by wheat, and by woodland and a tall hedge on the other two. Prior to set-aside this field had been cropped for wheat continuously for eight years. The other area is the South Field which is divided into four parts by a driveway which runs north to south and the River Cam which runs from west to east. Prior to set-aside a potato crop was harvested. Both areas were left to naturally regenerate after the last crop, and cut just once a year (See plate 4).

PLATE 1

PLATE 2

PLATE 3

PLATE 4

4. METHODOLOGY

4.1. VEGETATION ASSESSMENT

The vegetation assessment was carried out on nine fields. At Birkett Hall, Springfield, Cowbridge, Chaplefield and Saunders were studied. For White House Farm, Front Field and Back Field were studied. For Reeds Farm, both areas of set-aside were studied (North Field and South Field), and for Woodham Lodge Farm, there was just one large extensive field to examine.

4.1.1. DATA COLLECTION

The vegetation assessment was carried out using a 0.25 m²quadrat. A systematic method was used by placing the quadrat down every twenty paces along a prescribed transect. Sampling started on the border of a field following a transect through the centre of the field to the opposite side. Two to three transects were taken depending on field size.

For each quadrat, all monocotyledonous and dicotyledonous species were listed and the percentage cover of each species estimated. Also, for Elymus repens (couch), Phleum pratense (timothy), Avena fatua (common wild oat),Rumex obtusifolius (broad-leaved dock), Senecio jacobaea (ragwort), Cirsium arvense (creeping thistle) andCirsium vulgare (spear thistle) the number of individual plants present was recorded.

In total 455 quadrat cells were recorded for the nine fields, averaging 50 quadrats per field. Hubbard (1992) and Rose (1991) were used to identify species.

4.1.2. VEGETATION ANALYSIS

To analyse the quadrat data a series of indices were used. The quadrat data has been interpreted in a number ways to provide comparisons of the vegetation cover for the nine fields surveyed. The methods used by Poulton and Swash (1992) were followed to examine the vegetation characteristics, by determining species richness, a diversity index and a dominance index, as described below:

Index Definition

Species richness Total number of species recorded per field

Diversity index Average number of species per quadrat in field

Dominance index Number of species in field achieving dominance in at least one quadrat

In addition to the indices used by Poulton and Swash (1992), three more indices have been developed to analyse the data in a more specific manner:

Index Definition

Frequency The frequency of occurrence of each species recorded as a percentage of all quadrat cells for the field.

Abundance The mean number of plants present per 0.25 m² for couch, broad-leaved dock, ragwort, creeping thistle and spear thistle.

Cover The mean percentage cover per 0.25 m²for broad-leaved dock, ragwort, creeping thistle, spear thistle, couch, slender foxtail, barren brome and false oat grass.

Under the Weeds Act 1959 the occupier of land is obliged to control problem weeds i.e. Cirsium arvense, Cirsium vulgare, Rumex crispus, Rumex obtusifolius and Senecio jacobaea (Willoughby, 1996). These weeds are controlled by herbicides on arable land, but during set-aside have the opportunity to spread. For analysis of cover,Cirsium arvense, C. Vulgare, Rumex obtusifolius and Senecio jacobaea are classed as problem weeds.Arrhenatherum elatius, Bromus sterilis, Elymus repens and Alopercurus myosuroids are classed as problem grasses. For the analysis of abundance, Elymus repens is examined in addition to the problem weeds.

Finally, a comparison of the species composition of the field margins and field cores for Front Field, Back Field, Spring Field and South Field was carried out.

4.2. SOIL SAMPLING

4.2.1. SOIL COLLECTION

Soil samples were collected from the top 7.5 cm using a 2 cm soil corer. Samples were taken along transects within the field following the vegetation assessment. At least 25 samples were taken for each field, following the ADAS guidelines for the sampling of soils under long leys (MAFF, 1979). The bulked sample was placed into a polythene snap-bag. The samples were then air-dried in aluminium trays and sieved through a 2 mm mesh. The less than 2 mm fraction was rebagged and stored until needed for laboratory analysis.

4.2.2. SOIL ANALYSIS

The soils were analysed for organic matter content (by loss on ignition), pH, Cl, NH₄, NO₃, NO₂, PO₄, SO₄, Si, Ca, Mg, Na, K and particle size. These cover the major nutrients required by plants (Russell, 1961). Soil water extracts were analysed on the auto-analyser for Cl, NH₄, NO₃, NO₂, PO₄ and Si. SO₄ was analysed using a Palintest Photometer. A digest was carried out to measure the total Ca, Mg, Na and K in the soil.

Ca, Mg, Na and K were measured on the Atomic Absorption Spectrophotometer (Varian Model 1475).

For a full laboratory methodology see Foster (1986).

Soluble and exchangeable ions

15 g soil and 150 ml of dionised water was placed into a stoppered polythene bottle and placed on a flask shaker for 15 minutes. The bottle was then transferred to a centrifuge for 15 minutes at 3000 rpm. The liquid was decanted and then filtered through glass fibre paper using Buchner apparatus, and bottled for analysis.

Digest for total cation content

Approximately 0.6 g of sample was digested in a mixture of Perchloric acid (2 ml), Nitric acid (10 ml) and Sulphuric acid (2 ml). Once digested, the samples were diluted with H₂O and re-heated. Once cooled, the solution was filtered using Buchner apparatuus and made up to 100 ml volume with H₂O and 3 ml of Lanthanum chloride.

The pH was tested immediately after filtering using a Corning pH Meter (model 12).

Particle size analysis

Particle size analysis was carried out using a Malvern Laser. This was done as the particle size distribution of a soil can affect the competitive abilities of some plant species.

Low temperature loss on ignition

To determine the organic matter content of the soil, a sample was taken and oven-dried. Approximately 10 g soil was weighed into a crucible and placed into a muffle furnace for 12 hours at 450°C. The reduction in mass was recorded, and percentage organic matter determined using the equation:

Loss on ignition (%) = (MD – K) – (MF – K) ´ 100

MD – K

MD – oven dry soil

K – crucible mass

MF – crucible and soil mass after ignition

Phosphates (PO₄)

The auto-analyser was used to determine phosphates by colorimetry. Orthophosphate reacts with molybdate in acid solution to form phosphomolybdic acid. This is then reduced by ascorbic acid to an intensely coloured ‘molybdenum blue’ complex. The greater the level of phosphate in the soil water solution, the greater the intensity of the reaction. This is measured on an automated analyser at 660 hm.

Total Oxidised Nitrogen – Nitrates and Nitrites (NO₃ and NO₂)

The method for total oxidised nitrogen is based on the reduction of nitrate to nitrite by hydrazine-copper reagent and determination of the total nitrite content by the formation of an azo dye measured colorimetrically at 520 hm. To determine the nitrate concentration alone the determination is repeated with dionised water replacing the reducing reagent to give only the nitrite concentration. The nitrate concentration is the difference between the nitrite concentration and the total oxidised nitrogen concentration.

Chloride (Cl)

Chloride reacts with mercuric thiocyanate forming mercuric chloride which in turn reacts with ferric ions to give red ferric thiocyanate. This is measured using the auto- analyser at 480 hm.

Ammonium (NH₄)

Phenol and dichloroisocyanurate decompose in alkaline solution releasing hypochloric ions. Nitroprusside is added as a catalyst. The absorbance of the substituted indophenol is measured at 650 hm.

Silicate (Si)

Silicates in solution react with molybdate to form a silicomolbdate complex. This complex is reduced to “molybdenum blue” which can be measured at 660 hm. Interference by phosphate is prevented by the addition of oxalic or tartaric acid.

Sulphates (SO₄)

Measured using a Palintest Photometer 5000. 10 ml sample used as instructed in the Palintest manual.

4.3. DATA ANALYSIS

To compare the chemical characteristics of set-aside with arable soils, boxplots have been produced using an SPSS Spreadsheet. To test the significance of the difference between set-aside and arable soils, a student T-test was carried out using an Excel spreadsheet. Full details of the boxplots and results for the T-test can be found in the appendix.

To test the specific hypotheses, a mean value for the soil data of each field was determined to compare with the vegetation data. Total N was determined using the equation:

Total N (mg kg^-1) = NO₃ (mg kg^-1) * 0.2259 + NO₂ (mg kg^-1) * 0.3045 + NH₄ (mg kg^-1) * 0.7762

To test for relationships between soil data and vegetation data, the Student T-test was carried out.

A full COSHH assessment was carried out for the laboratory work. COSHH sheets can be found in the appendix.

4.4. HYPOTHESES

The results obtained from this methodology will be used to test the following hypotheses. Hypotheses 1 – 8 are specific hypotheses which will be tested in Chapter 6. Hypotheses 9 and 10 are general speculative hypotheses which will be covered in Chapter 7.

1. High levels of N, P, and K result in a greater abundance of thistles, docks and ragworts.

2. Greater species richness is experienced on field margins.

3. Sowing a grass cover produces a lower species richness and species diversity after five years than natural regeneration.

4. Sowing a grass cover restricts the spread of weeds.

5. Greater species diversity and species richness is found in areas of lower nutrient supply.

6. Sowing clover results in higher nitrogen levels in the soil.

7. Heavily grazed fields have a higher nitrogen content than lightly grazed fields.

8. The annual cutting of set-aside promotes the spread of problem weeds.

9. Land under a 5 year non-rotational set-aside scheme is beneficial to the nutrient status of the soil, and therefore the future crop.

10. Land set-aside for five years could be detrimental to the environment with respect to increased nitrate leaching after the ploughing of the cover crop.

5. VEGETATION SECTION RESULTS

5.1. VEGETATION SECTION

5.1.1. SPECIES RICHNESS, DIVERSITY AND DOMINANCE INDEX

Species Richness

The most species rich field was South Field at Reeds Farm. Thirty-two species were recorded; 5 annuals, 4 biennials and 23 perennials, which included 11 grass species. Twenty-five species were recorded at Woodham Lodge Farm. The least species rich fields were at Chaplefield and the North Field at Reeds Farm, with thirteen and fifteen species respectively (Table 5.1).

Diversity Index

Woodham Lodge Farm had the highest species diversity with an average of 3.74 species occurring in each quadrat cell. The South Field at Reeds Farm had an average of 3.69 species occurring per quadrat. Front Field at White House Farm has the lowest diversity, only an average of 2.11 species occurring per quadrat (Table 5.1).

Table 5.1: Species richness, diversity index and dominance index.

	SpeciesRichness	DiversityIndex	DominanceIndex
Springfield	21	3.52	7
Cowbridge	19	3.48	8
Saunders	18	3.00	8
Chaplefield	13	2.59	4
Front Field	18	2.11	4
Back Field	23	3.00	3
North Field	15	2.39	2
South Field	32	3.69	10
Woodham Lodge	25	3.74	2

Dominance Index

The South Field at Reeds Farm has the highest dominance index, with 10 species reaching dominance. At Lodge Farm, only creeping thistle and slender foxtail dominated any one area.

Table 5.2: Species reaching dominance in at least one quadrat

5.1.2 ANNUALS, BIENNIALS AND PERENNIALS

All fields surveyed are dominated by perennial species. The two most species rich fields are South Field at Reeds Farm, and Woodham Lodge Farm, both of which were left to naturally regenerate. The two least species rich fields are Chaplefield, Birkett Hall, and North Field at Reeds Farm. Chaplefield is dominated by Lolium perenne, and North Field by Festuca spp. (Figure 5.1).

Comparison of Borders and Cores

Core areas have a lower species richness generally, although on South Field there is little difference between the two areas. For Front Field, Back Field and Spring Field, no biennials occur in the core of the field (Figure 5.5).

5.1.3. COVER AND ABUNDANCE

Cover of Problem Grasses

There are notable variations in the grass species which dominate a farm. On North Field, Reeds Farm, and at White House, Festuca spp. dominate. At Woodham Lodge Alopercurus myosuroides dominates, and on the South Field, Reeds Farm, Arrhenatherum elatius dominates. At Birtkett Hall Lolium perenne dominates, however Elymus repens is abundant on Cowbridge (Figure 5.2).

Cover of Problem Weeds

Cirsium arvense has produced the greatest cover for all the problem weeds, although it was not very widespread on North Field and Chaplefield. Senecio jacobaea is a problem on both fields at Reeds Farm, Front Field at White House and Chaplefield at Birkett Hall (Figure 5.3), although generally produced less cover than Cirsium arvense orRumex obtusifolius.

Abundance of Problem Weeds

Elymus repens is the most abundant species overall. Cirsium arvense is the most abundant of the broad-leaved weed species. Rumex obtusifolius is present in large numbers on Springfield and Woodham Lodge (Figure 5.4).

Figure 5.1
Figure 5.2
Figure 5.3

Figure 5.4

Figure 5.5

5.1.4. FREQUENCY

Table 5.4 shows the frequency data for all the species recorded in each of the nine fields. Grasses, clover, problem weeds and the woody perennials will be discussed in turn.

GRASSES

Lolium Perenne (Perennial rye-grass)

On the fields at Birkett Hall, where perennial rye grass was sown, the relative frequency of occurrence is over 90% for each field, with a maximum of 100% for Chaplefield. On Chaplefield a majority of quadrats had a cover entirely consisting of perennial rye grass.

Festuca spp. (Fescues)

Festuca spp. are frequently spread over both the Back Field and Front Field at White House Farm, where they were planted as part of the Countryside Access Scheme, and also at Reeds Farm on the North Field where they have started to dominate by means of natural regeneration.

Elymus repens (Couch)

Couch grasses are of a higher frequency on Cowbridge at Birkett Hall, and also on the naturally regenerated fields of Reeds Farm. They are not, however, very frequent at Woodham Lodge, although they do occur in some dispersed patches, especially in close proximity to large oaks.

Arrhenatherum elatius (False oat grass)

False oat grass is only very frequent at Reeds Farm in the South Field where it occurs in 47.8 % of quadrat cells. It does not occur in any quadrat cell in the North Field at Reeds Farm. The second highest frequencies recorded for false oat grass are at Woodham Lodge Farm (11%).

Bromus sterilis (Barren brome)

Barren brome is not a great problem generally, although it is quite frequent on the South Field at Reeds and also on Saunders at Birkett Hall, although it occurs mainly in marginal areas of a field and not core areas.

Alopercurus myosuroids (Slender foxtail)

Slender foxtail is only frequent at Woodham Lodge Farm (75.8%). It is present on the other set-aside fields but only in scattered areas.

Holcus lanatus (Yorkshire fog)

Yorkshire fog occurs in the South Field of Reeds in 21.3% of quadrat cells, and also occurs at Woodham Lodge Farm, and Front Field at White House. It is not recorded on any of the other fields studied.

TRIFOLIUM REPENS (WHITE CLOVER)

With the exception of Woodham Lodge the only fields where clover was present in significant numbers was at Birkett Hall where it was sown. At Woodham Lodge it tended to occur in small but frequent patches. The largest cover and frequency occur on Springfield. Cowbridge is adjacent to Springfield and was also sown with clover, but the cover is very small in comparison.

Table 5.3: Cover and frequency of White Clover

Mean % Cover

Frequency

Cowbridge

2.2

4.5

Springfield

20.0

54.0

Chaplefield

13.3

32.8

Saunders

9.3

22.2

North Field

South Field

Front Field

0.6

2.2

Back Field

Woodham Lodge

1.0

16.1

PROBLEM WEEDS

Cirsium arvense (Creeping Thistle)

Creeping thistle is very common to all fields, especially on the backfield at White House and at Woodham Lodge where it occurs in over 50% of quadrat cells. Only in the North Field at Reeds Farm is it less frequent, where it only occurs in 2.8% of quadrat cells.

Cirsium vulgare (Spear Thistle)

Spear thistle is present at Reeds Farm and Birkett Hall, but only in low numbers. It was present at White House, but did not occur in any of the quadrat cells. The highest frequency in 5.6% in Saunders at Birkett Hall.

Rumex obtusifolius (Broad-leaved docks)

Broad-leaved docks occur in quadrat cells on all fields. The only area which had a very high abundance of broad-leaved docks was Springfield ‘top end’ (frequency for total field 18%). There were also a large population of docks present on Bell Meadow at Birkett Hall where the old allotments were located.

Senecio jacobaea (Common ragwort)

Common ragwort is most frequent on the North Field at Reeds Farm, occurring in 16.7% of quadrat cells (Plate 3). It was recorded on all fields except the Back Field at White House (where it was present amongst the thistles, but not within a quadrat), and Cowbridge at Birkett Hall. Hoary ragwort is also present on the Front Field at White House in 4.4% of quadrat cells.

Heracleum sphondylium (Hogweed)

Hogweed is generally present close to the field margins and not in the core areas. The highest frequencies occur on the South Field at Reeds Farm and at Woodham Lodge Farm (6.6% and 5.6% respectively). The only recording of hogweed at Birkett Hall was on Cowbridge, occurring in 1.5% of quadrat cells. It was however present in most hedges.

Galium aparine (Cleavers)

Cleavers were only recorded on the Front Field at White House, and occurred in 6.7% of quadrat cells.

Convulvulus arvensis (Lesser Bindweed)

Lesser bindweed was recorded on all fields except at Woodham Lodge. The highest frequency was on the South Field at Reeds Farm where it occurred in 29.5% of quadrats (Plate 3).

WOODY PERENNIALS

Quercus petraea (Sessile oak)

On the Back Field at White House sessile oak occurred in 7.3% of quadrats, most of which were on the margins of the field.

Prunus spinosa (Blackthorn)

On Back Field at White House blackthorn occurred in 14.6% of quadrats, and had a high cover in the marginal areas alongside the blackthorn hedges. Blackthorn was also present in the South Field at Reeds Farm in 3.3% of quadrat cells.

Crataegus monogyna (Hawthorn)

Hawthorn was present only in the Front Field of White House at 4.4% of quadrat cells.

Populus alba (White poplar)

White poplar was recorded in 1.2% of quadrat cells on the Back Field at White House, and in 1.4% of quadrat cells in the South Field at Reeds. It was also present in the margins of the North Field at Reeds, and the Front Field at White House.

5.1.5. SUMMARY

Highest species richness and diversity occurs on naturally regenerated fields. Perennial species dominate all fields, including the cores of fields. The margins are more diverse. For each farm studied, different grass species dominated the sward. The main problem weed is Cirsium arvense. Senecio jacobaea is a problem at Reeds Farm. Bromus sterilis is not a problem on any of the farms. Woody perennials are generally only present on field margins. On Woodham Lodge Farm, the trees planted as part of the Woodland Premium Scheme had failed to grow. Almost all the trees had died (Plate 4). Most tree species recorded occurred on Back Field at White House Farm.

Table 5.4

Table 5.4 cont.

5.2. SOIL SECTION RESULTS

5.2. SOIL SECTION

For the full soil results see table 5.5.

5.2.1. pH, PARTICLE SIZE AND CARBON

Mean pH on set-aside is lower than that of arable fields. The lowest pH was recorded on Chaplefield and on Springfield at pH 5.7. Thirteen of the set-aside fields were slightly acid (i.e. pH 5.6 – 6.5) and seven fields were neutral (i.e. pH 6.6 – 7.5). The highest set-aside pH recordings were at White House Farm. Of the arable soils, on White House 1 the soil was slightly acid (pH 6.0), whereas all other arable soils were neutral.

Particle Size Analysis

The fields of White House have the highest clay and fine silt percentage. Saunders Lakeside has the highest sand content (47.3%). All soils are generally silty clay soils or silty loams.

Carbon – loss on ignition

The carbon, in the form of organic matter, of the soils varied considerably from 5.73% at Reeds North Field, to 13.93% at Birkett Hall, Front Meadow. The mean levels for set-aside is 8.99% and for the arable fields is 7.60%. The organic matter for the arable field at Reeds does not differ greatly from the set-aside levels (5.66% on the wheat field).

5.2.2. WATER EXTRACTS

Chloride

Chloride levels are higher on the set-aside (mean 38.5 mg kg-1) than on the arable fields (mean 26.7 mg kg-1). Chlorides are highest on the fields at Birkett Hall

(50 mg kg-1 Cowbridge SE and Bell Meadow)

Phosphate

Phosphate levels are higher on the set-aside, mean 3.35 mg kg-1 compared to

1.82 mg kg-1 on arable. Highest occurred on Front Meadow (8.20 mg kg-1) at Birkett Hall. Reeds Farm has the highest arable phosphate levels (3.10 mg kg-1).

Ammonium

Ammonium is higher on set-aside soils (mean 2.48 mg kg-1) than on the arable soils (mean 0.96 mg kg-1). Highest levels on set-aside are on Bell Meadow and Springfield ‘bottom-end’ at Birkett Hall. Ammonium is generally quite low on all arable fields.

Nitrate

Mean nitrate levels are much higher on arable soils than on set-aside soils. Highest set-aside levels occur on Bell Meadow (11.42 mg kg-1) and Front Meadow

(13.19 mg kg-1) at Birkett Hall. However the arable soils are quite variable, at White House nitrate levels are at only 10.04 mg kg-1 and 10.01 mg kg-1, whereas at Woodham Lodge nitrates are at 44.81 mg kg-1, the highest recorded, over three times higher than Front Meadow.

Nitrite

Nitrite levels are generally very low. Set-aside mean 0.56 mg kg-1, arable mean

0.29 mg kg-1. Highest levels occur at Bell Meadow (2.38 mg kg-1) and Front Meadow

(1.81 mg kg-1) and lowest for the North Field at Reeds (0.05 mg kg-1).

Silicate

Higher on set-aside with a mean of 6 mg kg-1. Highest levels recorded on Front Field (11 mg kg-1) and Middle Field (13.5 mg kg-1) at White House, and on Cowbridge SE at Birkett Hall (11 mg kg-1). The arable fields have very consistent levels.

Sulphate

There was little variation between set-aside and arable fields. Set-aside was slightly lower (mean 208 mg kg-1). Highest levels occurred on Cowbridge SE and Springfield ‘grazed field’ at Birkett Hall, and the arable field at Woodham Lodge. Lowest levels were on Springfield ‘bottom end’, and on South Field at Reeds Farm.

Calcium

Calcium levels are quite low on set-aside (mean 11.65 mg kg-1). Many of the fields at Birkett Hall had no extractable calcium present, although the highest calcium levels were found on Saunders by the lake on the sandier soils. The highest levels recorded were on the second arable field at White House (143 mg kg-1).

Magnesium

Magnesium is higher on the arable fields (mean 12.4 mg kg-1) than on the set-aside (mean 5.1 mg kg-1). The lowest levels under set-aside occur at Birkett Hall. The highest levels occur on South Field at Reeds Farm, and Front Field and Middle Field at White House Farm.

Sodium

Mean sodium levels are slightly higher on the arable soils, but overall there is little variation.

Potassium

Mean potassium is slightly higher on set-aside soils. On Front Meadow and Cowbridge SE at Birkett Hall concentration reached 68 mg kg-1 and 64 mg kg-1 respectively, but also fell as low as 17 mg kg-1 and 18 mg kg-1 on Saunders Roadside and Chaplefield.

5.2.3. TOTAL DIGESTS

Calcium

The mean total calcium present in the soil is higher on the arable fields. The soils of Birkett Hall and Brazils Farm have the highest levels generally (Table 5.5).

Magnesium

Mean magnesium is higher on set-aside. Highest levels occur at White House on Front Field (6188 mg kg-1). The amount of magnesium appears to be determined by the clay content of the soil.

Sodium

Mean sodium in the soil is similar on both set-aside and arable fields.

Potassium

Mean potassium is lower on arable fields. Set-aside mean is 7475 mg kg-1 and arable mean is 6493 mg kg-1.

Table 5.5

Table 5.5 cont.

5.2.4. SIGNIFICANCE OF NUTRIENT CHANGE UNDER SET-ASIDE

The results of the students T-test are in the Appendix.

Table 5.6: Soil nutrient changes on set-aside

INCREASE	DECREASE	NO SIGNIFICANT CHANGE

NH4	NO3	SO4
Cl	Ca	Na
PO4	Mg	Na*
C (LOI)	Ca*	Mg*
NO2	K*
Si	pH
K

* Total digest sample

Table 5.7: Level of significance for soil nutrient changes

99.9%

99%

95%

Not Significant

NH4

C (LOI)

SO4

PO4

NO3

Na*

Ca*

NO2

Mg*

* Total digest sample

5.2.5. RESULTS SUMMARY

The soil results show definite evidence that set-aside has resulted in a change in the nutrient status of the soil. pH is generally slightly lower, and organic matter is higher.

Levels of Cl, PO4, NH4, Si and K have all increased on set-aside. Ca and Mg have both decreased as has levels of NO3. Most of the nutrients have undergone significant changes under set-aside (See Boxplots, Appendix).

6. TEST OF SPECIFIC HYPOTHESES

This section will examine each of the specific hypotheses set up in Chapter 4.

6.1. HYPOTHESIS 1

“HIGH LEVELS OF N, P AND K RESULT IN A GREATER ABUNDANCE OF THISTLES, DOCKS AND RAGWORTS”.

Table 6.1. shows the mean accumulative abundance of problem weeds per 0.25 m² (Cirsium arvense, Cirsium vulgare, Rumex obtusifolius and Senecio jacobaea) for each field and the nutrient status of the soil.

Table 6.1: Abundance of problem weeds and nutrient concentration of the soil (mg kg^-1).

	Abundance*	NH₄	NO₃	NO₂	Total N	PO₄	K
Woodham Lodge	1.94	2.40	9.74	0.76	4.29	1.50	38.00
Front Field	1.77	3.60	8.17	1.33	4.81	2.90	33.00
Back Field	1.54	0.90	1.71	0.29	1.88	2.00	42.00
South Field	1.49	1.40	0.60	0.10	1.26	7.80	51.00
Saunders	1.20	1.95	1.81	0.24	1.99	2.30	20.00
Springfield	0.94	2.50	7.15	0.41	2.68	1.85	31.75
Cowbridge	0.75	3.10	2.71	0.32	3.12	4.53	54.33
Chaplefield	0.40	2.20	1.11	0.19	2.02	2.00	18.00
North Field	0.33	0.50	0.35	0.05	0.35	3.70	33.00

* Mean cumulative abundance of Cirsium arvense, Cirsium vulgare, Rumex obtusifolius and Senecio jacobaea per 0.25 m².

Correlation data:

Abundance and Total N		0.606
Abundance and PO₄		-0.025
Abundance and K		0.276

The two fields with the highest abundance of problem weeds are Woodham Lodge and Front Field, which also have the two highest levels of nitrates. North Field has the lowest abundance, and also the lowest nitrate, nitrite and ammonium levels. The results do suggest that higher levels of nitrate cause a greater abundance of problem weeds. South Field has low nitrate levels, but high phosphates and potassium levels make more nutrients available to plant growth. The high nitrate concentration at Woodham Lodge has allowed Cirsium arvense to thrive where other arable weeds and grasses do not have the competitive ability to do so as a result of the rigorous mowing regime.

A correlation for abundance and total N gave a value of 0.606. However, this is not statistically significant.

Figure 6.1. Scatter plot of abundance against total N

6.2. HYPOTHESIS 2

“GREATER SPECIES RICHNESS IS EXPERIENCED ON FIELD MARGINS”.

Figure 6.2: Comparison of field margins and field cores

For the four fields studied, the field margins are more diverse in each case. The core areas have fewer species, however they are not dominated by annuals, suggesting that the fields are maturing. Table 6.2 gives a full species list for the margins and cores.

Table 6.2

6.3. HYPOTHESIS 3

“SOWING A GRASS COVER PRODUCES A LOWER SPECIES DIVERSITY AND SPECIES RICHNESS AFTER FIVE YEARS THAN NATURAL REGENERATION”.

Table 6.3: Species richness and species diversity for sown and unsown fields

		Species Richness	Species Diversity
SOWN	Springfield	21	3.52
FIELDS	Cowbridge	19	3.48
	Saunders	18	3.00
	Chaplefield	13	2.59
	Front Field	18	2.11
	Back Field	23	3.00
	MEAN	18.7	2.45

UNSOWN	North Field	15	2.39
FIELDS	South Field	32	3.69
	Woodham Lodge	25	3.74
	MEAN	20.7	3.27

T-test for species richness 0.18

T-test for species diversity 0.28

The T-test shows that these relationships are not statistically significant.

The mean values for both species richness and species diversity are higher on the naturally regenerated fields. There is not a great difference in the diversity index and species richness for the sown and unsown fields. On North Field the dominance by Festuca spp. has resulted in a much lower diversity, as commented by Burch (1980), and has in effect acted like a sown Lolium perenne sward in preventing the colonisation by other species. As the sown swards have developed, more perennial species have the opportunity to colonise the land, especially in the more marginal areas.

6.4. HYPOTHESIS 4

“SOWING A GRASS COVER RESTRICTS THE SPREAD OF WEEDS”.

Table 6.4: Comparison of abundance of weeds on sown and unsown fields

		Abundance *
SOWN	Springfield	0.94
FIELDS	Cowbridge	0.75
	Saunders	1.20
	Chaplefield	0.40
	Front Field	1.77
	Back Field	1.54
	MEAN	1.10

UNSOWN	North Field	0.33
FIELDS	South Field	1.49
	Woodham Lodge	1.94
	MEAN	1.25

T-test 0.39

* Mean cumulative abundance of Cirsium arvense, Cirsium vulgare, Rumex obtusifolius and Senecio jacobaea per 0.25 m².

The mean abundance of problem weeds is higher under the naturally regenerated land. However, there is not a great difference between the two. North Field has a lower abundance of weeds than any of the other fields. This is as a result of Festuca spp. dominating the field and preventing the colonisation of other species. Chaplefield has a very low abundance, and also has a very high cover of Lolium perenne (some quadrat cells with 100% cover). Perennial rye grass is very efficient in preventing other species colonising. Although North Field has a low abundance of weeds, ragwort has reached problem levels. Pesticide drift from neighbouring fields may have contributed to the relatively low abundance, as well as the high Festuca cover. Woodham Lodge has a very high frequency of Cirsium arvense. The only grass on Woodham Lodge to have reached any significant levels is Alopercurus myosuroides, a problem weed itself, and is not effective in preventing the spread of Cirsium arvense.

The T-test shows that this relationship is not statistically significant.

6.5. HYPOTHESIS 5

“GREATER SPECIES DIVERSITY AND SPECIES RICHNESS IS FOUND IN AREAS OF LOWER NUTRIENT SUPPLY”

Table 6.5: Species richness, species diversity and nutrient supply (mg kg^-1).

	Species richness	Species diversity	NH₄		NO₃		NO₂		Total N		PO₄		K
Woodham Lodge	25	3.74	2.40	9.74		0.76		4.29		1.50		38.00
Front Field	18	2.11	3.60	8.17		1.33		4.81		2.90		33.00
Back Field	23	3.00	0.90	1.71		0.29		1.88		2.00		42.00
South Field	32	3.69	1.40	0.60		0.10		1.26		7.80		51.00
Saunders	18	3.00	1.95	1.81		0.24		1.99		2.30		20.00
Springfield	21	3.52	2.50	7.15		0.41		2.68		1.85		31.75
Cowbridge	19	3.48	3.10	2.71		0.32		3.12		4.53		54.33
Chaplefield	13	2.59	2.20	1.11		0.19		2.02		2.00		18.00
North Field	15	2.39	0.50	0.35		0.05		0.35		3.70		33.00

South Field has the greatest species richness and also low nitrate, nitrite and ammonium content. However, the phosphate and potassium levels are high, which may reflect the previous crop of potatoes or the fact that the diverse cover has improved the nutrient supply. Woodham Lodge also has a relatively high species diversity and species richness, but has a high nitrate content. North Field and Chaplefield which have relatively low species richness and species diversity also have low nitrate, nitrite and ammonium contents. The results do not show any clear relationship between species diversity and species richness with nutrient supply.

Correlation data:

Species richness and Total N	0.03317
Species diversity and Total N	0.04782
Species richness and PO₄	0.53779
Species diversity and PO₄	0.24512
Species richness and K	0.65011
Species diversity and K	0.51964

The correlation data shows that species richness and species diversity are not related to the mineral nitrogen. However, species richness correlates well with both phosphate and potassium content.

Figure 6.3: Scatter plot of potassium against species richness

There is a positive correlation between potassium and species richness. The hypothesis will have to be rejected as there is no statistical evidence that lower nutrient levels cause greater species richness, in fact the opposite appears to be true for phosphates and potassium.

6.6. HYPOTHESIS 6

“SOWING CLOVER RESULTS IN HIGHER NITROGEN LEVELS IN THE SOIL”.

Table 6.6: Mean % cover and frequency of clover with nutrient content (mg kg^-1)

		% Cover	Frequency	NH₄	NO₃	NO₂	Total N
SOWN	Cowbridge	2.2	4.5	3.10	2.71	0.32	3.12
WITH	Springfield	20.0	54.0	2.50	7.15	0.41	2.68
CLOVER	Chaplefield	13.3	32.8	2.20	1.11	0.19	2.02
	Saunders	9.3	22.2	1.95	1.81	0.24	1.99
	MEAN	11.2	28.4	2.60	3.66	0.31	2.45

NOT	North Field			0.50	0.34	0.05	0.35
SOWN	South Field			1.40	0.60	0.10	1.26
WITH	Front Field	0.6	2.2	3.60	8.17	1.33	4.81
CLOVER	Back Field			0.90	1.71	0.29	1.81
	Woodham Lodge	1.0	16.1	2.40	9.74	0.76	4.29
	MEAN	0.32	3.7	1.79	3.73	0.46	2.50

T-test for Total N	0.48
T-test for NH₄	0.16
T-test for NO₃	0.36
T-test for NO₂	0.21

The T-test shows that none of the relationships are actually statistically significant.

For the fields sown with clover, nitrates and nitrites are lower, and ammonium is higher. Springfield has the highest cover of clover on Birkett Hall, and also the highest nitrate concentration for Birkett Hall. However, other than this, the evidence is not conclusive that clover increases the mineral nitrogen concentration of the fields. This may change however once the field has been ploughed and mineralisation occurs. During mineralisation the ammonium will be converted to nitrate. Also, organic matter will be mineralised.

6.7. HYPOTHESIS 7

“HEAVILY GRAZED FIELDS HAVE A HIGHER NITROGEN CONTENT THAN LIGHTLY GRAZED FIELDS”.

To test this hypothesis the fields of Birkett Hall will be examined alone.

Table 6.7: Comparison of heavily and lightly grazed fields

		NH₄	NO₃	NO₂	Total N
HEAVILY	Bell Meadow	5.20	11.42	2.38	7.34
GRAZED	Springfield ‘grazed’	0.90	8.71	0.29	2.75
	Saunders	1.95	1.81	0.24	2.00
	Front Meadow	4.00	13.19	1.81	6.64
	MEAN	3.01	8.78	1.18	4.68

LIGHTLY	Springfield	3.03	6.62	0.44	3.97
GRAZED	Cowbridge	3.10	2.71	0.32	3.12
	Chaplefield	2.20	1.11	0.19	2.02
	MEAN	2.78	3.48	0.32	3.04

T-test NH₄		0.41
T-test NO₃		0.07
T-test NO₂		0.10
T-test Total N		0.16

Nitrates are more twice as high on the heavily grazed fields. Saunders has been heavily grazed, but has very low NO₃, NO₂and NH₄ levels. Bell Meadow and Front Meadow generally have very high nutrient contents. Heavily grazed fields increase the cycle of nitrogen through the system by returning nitrogen back to the soil in faeces and urine.

The T-test shows that for both nitrate and nitrite the relationship is statistically significant at the 90% confidence level.

6.8. HYPOTHESIS 8

“THE ANNUAL CUTTING OF SET-ASIDE PROMOTES THE SPREAD OF PROBLEM WEEDS”.

Table 6.8: Cutting regime and abundance of problem weeds at farm level

Farm	Cutting Regime	Abundance*
Woodham Lodge	2-3 times per year	1.94
White House	Once a year	1.66
Reeds Farm	Once a year	0.91
Birkett Hall	Grazed	0.83

* Mean cumulative abundance of Cirsium arvense, Cirsium vulgare, Rumex obtusifolius and Senecio jacobaea per 0.25 m².

Figure 6.4: Mean abundance of problem weeds per 0.25 m² for each farm

Cutting could be responsible for the spread of problem weeds. Birkett hall has the lowest mean abundance of weeds and is not cut at all, but grazed. Woodham Lodge has the highest mean abundance and is cut the most frequent. At Woodham Lodge, Cirsium arvense is responsible for the majority of the cover.

6.9. SUMMARY

Although the mean data suggests that a majority of the hypotheses are correct, statistical testing does not give significant results. The only significant relations were for the heavily and lightly grazed fields, where nitrates and nitrites were higher. The frequent cutting of a field produces a higher abundance of weeds. Field margins have a greater species richness.

7. DISCUSSION

Set-aside has produced some significant changes in the soil nutrient status. Within just five years, nitrate levels have been reduced substantially, phosphates have accumulated, as has the organic matter content of the soil. On both sown and naturally regenerated fields a grassland sward has developed, dominated by perennial species.

The set-aside has improved the wildlife habitats on the farms. However, the data collected does not show any strong evidence that the soil nutrient status effects the characteristics of the developed vegetation. Although there are trends, these are not statistically proven. It is more likely that other factors play an important part in the vegetation development on set-aside, such as competition, the soil seed bank and dispersal patterns.

The management regime certainly affects the spread of weeds, as seen on Woodham Lodge Farm where the fields cut two to three times a year aid the spread of Cirsium arvense. This was a surprising result, as the object of frequent cutting is to reduce the weed population of the field. Field margins are still more diverse than core areas, suggesting that the length of time for a grassland ecosystem to fully mature exceeds the duration of a non-rotational set-aside period.

The sowing of a grass cover only slightly reduced the species diversity and species richness of a field, which suggests that sowing a grass cover to prevent the spread of weeds will not necessarily reduce the ecological value of a field. At Birkett Hall, Lolium perenne was sown, and it was evident that the faunal species, especially on the field margins, was very diverse.

The sowing of a grass cover will not necessarily prevent the spread of Elymus repens as suggested by Talling and Godwin (1994). On Cowbridge at Birkett Hall, Elymus repens managed to reach quite high levels in the sward.

In the naturally regenerated fields, the species diversity and species richness may have been higher, but many of the species present are not considered to be desirable by conservationists. For example, on South Field, the most diverse field studied, Arrhenatherum elatius, Cirsium arvense, Convulvulus arvensis, Elymus repens and Senecio jacobaea all occurred in relatively high numbers. All of these are considered to be problem weeds, which can often restrict colonisation by more desirable species.

Although the conservationist encourages the development of a diverse grassland sward, farmers are not compensated for reduced yields that may occur as a result of the residue of problem weeds in the soil, and the associated diseases with them. If Elymus repens is not eradicated sufficiently it could cause problems to the future yields on Reeds Farm.

The high organic matter and ammonium levels on set-aside will provide a large source of nitrates once the sward is ploughed out at the end of the set-aside period. Nitrate leaching may increase dramatically once mineralisation increases in the more moist conditions in the autumn after set-aside. Although nitrate leaching is reduced during the set-aside period, the sudden increase caused by farmers throughout the country ploughing up grass leys may cause serious problems.

8. CONCLUSION

Set-aside has certainly altered the soil nutrient status of the fields. Previous studies had only concentrated on the mineral nitrogen content of set-aside soils, and more importantly changes in the nitrate levels. This study has revealed that other nutrients essential to plant growth have changed in five years of set-aside. This may be beneficial to the future crops on set-aside, especially where phosphates, ammonium and potassium for example have increased significantly. Both wheat and barley utilise a lot of phosphates in early growth (Russell, 1961).

Natural regeneration may produce greater species richness, but many problem weeds are associated with the sward. Sown swards help to reduce the spread of broad-leaved weeds, and are still relatively rich in species.

This study has successfully investigated the vegetation and soil characteristics of set-aside in Essex. However, a greater data set would allow more conclusive statistical testing, which may reveal that more of the hypotheses could be accepted.

To produce more significant results, future research should concentrate on a selection of species, such as just the problem weeds, and a few grass species, spread over more fields. However, non-rotational set-aside is not as popular as rotational set-aside, and the area of land set-aside has been reduced to just 5%, so it may prove to be difficult to do such a survey in a small area. Surveys of farms spread over larger geographic areas are complicated by larger variations in the climate and soil type. However, set-aside still provides an excellent opportunity to investigate succession and evolution of vegetation and soils on previously arable land.

9. BIBLIOGRAPHY / REFERENCES

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A Study Of Vegetation Composition And Soil Chemistry On Five Year Non-rotational Set-aside Under Four Management Regimes, Essex, UK.

About Set-aside Study

ACKNOWLEDGEMENTS

ABSTRACT

1. INTRODUCTION

2. VEGETATION AND SOILS OF AGRICULTURAL LAND

2.3. VEGETATION STUDIES ON SET-ASIDE

2.4. SOIL DYNAMICS UNDER SET-ASIDE

2.5. VEGETATION AND SOILS SUMMARY

3. BACKGROUND TO STUDY AREA

4. METHODOLOGY

5. VEGETATION SECTION RESULTS

5.2. SOIL SECTION RESULTS

5.2.5. RESULTS SUMMARY

6. TEST OF SPECIFIC HYPOTHESES

7. DISCUSSION

8. CONCLUSION

9. BIBLIOGRAPHY / REFERENCES

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