Final Report on Project BD1415
Role of organic fertilizers in the sustainable management of
semi- natural grasslands
2005
to
DEFRA, EN, CCW and DARDNI
by
The Institute of Grassland and Environmental Research
North Wyke, Okehampton. Devon,
ADAS, Wolverhampton, Woodthorne, Wergs Rd, Wolverhampton,
Applied Plant Science, Department of Agriculture and Rural
Development/Queens University of Belfast,
Centre for Land and Water Resources Research, Porter Building, St Thomas Street, University of Newcastle upon Tyne,
Department of Biological Sciences, Instsitute of Environmental & Natural Sciences, University of Lancaster.
Section 1
BD1415 Scientific Objectives
1.1 Identify whether optimum amounts and frequencies of application of FYM exist for the maintenance or enhancement of botanical interests of a range of unimproved or semiimproved mesotrophic/neutral grassland communities and quantify the effects of deviations from these optima on botanical composition.
1.2 Identify whether differences exist between the impact of FYM and equivalent amounts of nutrients applied as inorganic fertilizers on the botanical composition and agronomic output of a range of unimproved or semiimproved mesotrophic/neutral grassland communities.
1.3 Identify differences in impact on botanical composition and agronomic output between an organic pelleted fertilizer and equivalent nutrient inputs applied as inorganic fertilizers on a range of unimproved or semiimproved mesotrophic/neutral grassland communities.
1.4 Identify any interaction between the use of FYM and lime inputs on the botanical composition and agronomic output of a range of unimproved or semiimproved mesotrophic/neutral grassland communities.
2. Quantify the agricultural productivity obtained from applying amounts of FYM that maintain or enhance the botanical interests of unimproved or semi-improved mesotrophic/neutral grassland communities and, compare these outputs with those achieved by applying equivalent amounts of inorganic fertilizer.
3. Quantify the impact of length of storage, disturbance/handling and exposure to the prevailing weather on FYM nutrient composition, to enable variations in FYM nutrient inputs to be taken into account.
4.1 Identify the impact of FYM applications on soil microbial communities, including mycorrhizal fungi, compared with application of equivalent amounts of inorganic fertilizer.
4.2 Identify whether broad-scale assessments of microbial communities are more sensitive to changes in soil chemistry than higher plant communities and thus would be a more robust early warning indicator of unsustainable fertilizer practice.
5. Provide guidelines for sustainable fertilizer and liming practices for mesotrophic/neutral semi-natural grasslands.
Extent to which the objectives have been met
The results detailed below show that within the timescale of BD1415, 1999 – 2004, it has only been possible to fully achieve objective 3, for which a detailed account of the research findings is given in Section 5. The research findings to date are inconclusive in relation to the achievement of objectives 1, 2 and 4 and for this reason the project duration has been extended for a further three years. Details of the research designed to achieve these three objectives are given in sections 2, 3, 4 and 6 of this report. The achievement of objective 5 will be based on meeting objectives 1, 2 and 4.
Experimental Details
Sites
Pairs of experimental sites consisting of an unimproved and a semi-improved meadow were selected in April 1999 at each of three locations. One pair of sites was selected to represent either unimproved or semi-improved lowland neutral grassland and these were situated on a Gwent Wildlife Trust reserve near Monmouth (grid ref SO524093) and were, respectively, Pentwyn Meadow (MG5 grassland) and Bush (MG6 type grassland). A second pair of sites was selected to represent upland neutral grassland types in the UK, these were, respectivley, Raisbeck (an unimproved upland MG3 type grassland, grid ref. NY635069) and Gaisgill (a semi-improved upland MG6 type grassland, grid ref. NY627054) in Cumbria. The third pair of sites was selected in Fermanagh Northern Ireland representing, respectively, unimproved neutral grassland of this region, namely Fassagh 1, grid ref. H925566, and a semi-improved neutral grassland at grid ref. H 929567, named Fassagh 2.
Experimental design
A factorialized randomized block design with three replicates of the treatments shown in Table 1 was established at each site in 1999 in a small-plot (7m x 5m) experiment.
Details of the amounts of inorganic fertilizer N, P and K inputs to treatments 9 – 12 each year at the different sites are given in Table 2.
The amount of lime applied was based upon the results of soil pH assays carried out in March 1999 at each site and was calculated to raise soil pH to about 6.0.
Site management
All the sites were cut for hay each year, the dates of cutting and baling are provided in Table 3. The regrowths following the hay harvest were grazed in late summer/autumn by cattle at Pentwyn and Bush, and by sheep at the other two pairs of sites.
For the Northern Ireland sites, the harvest and baling dates have not varied by more than 10 days. In most years with uncertainties in the weather during July and August in County Fermanagh it has only been possible to make hay bales one year (2000) out of the five. For the west of Northern Ireland it is normal to get a good hay crop 1 in 10 years. In those years when small hay bales have not been made, large round bales have been harvested.
Table 1. Treatments
number / Yr 1 / Yr 2 / Yr 3 / Yr 4 / Yr 5 / Yr 6
1 / Control / 0 / 0 / 0 / 0 / 0 / 0
2 / Continuation of previous inputs
3 / 6 t fym /ha / 6 / as yr1 / as yr1 / as yr1 / as yr1 / as yr1
4 / 12 t fym /ha / 12 / as yr1 / as yr1 / as yr1 / as yr1 / as yr1
5 / 24 t fym /ha / 24 / as yr1 / as yr1 / as yr1 / as yr1 / as yr1
6 / 6 t fym /ha / 6 / 0 / 0 / as yr1 / 0 / 0
7 / 12 t fym /ha / 12 / 0 / 0 / as yr1 / 0 / 0
8 / 24 t fym /ha / 24 / 0 / 0 / as yr1 / 0 / 0
9 / Inorganic (kg/ha) equiv. treat 4 (* see footnote) / NPK / as yr1 / as yr1 / as yr1 / as yr1 / as yr1
10 / Inorganic (kg/ha) equiv. treat 5 (* see footnote) / NPK / as yr1 / as yr1 / as yr1 / as yr1 / as yr1
11 / Inorganic (kg/ha) equiv. treat 7 (* see footnote) / NPK / 0 / 0 / as yr1 / 0 / 0
12 / Inorganic (kg/ha) equiv. treat 8 (* see footnote) / NPK / 0 / 0 / as yr1 / 0 / 0
13 / Lime only / + lime / 0 / 0 / 0 / 0 / 0
14 / 12 t fym /ha + lime / 12 fym
+ lime / 12 fym / 12 fym / 12 fym / 12 fym / 12 fym
15 / 12 t fym /ha + lime / 12 fym
+ lime / 0 / 0 / 12 fym / 0 / 0
16 / Organic pellets (HPS)at 125 kg/ha / 17.5N
3.5P
7.9K / as yr 1 / as yr1 / as yr 1 / as yr 1 / as yr 1
17 / Inorganic equiv to treat 16 / 17.5N
3.5P
7K / as yr 1 / as yr 1 / as yr 1 / as yr 1 / as yr 1
18 / Organic pellets (HPS) at 250 kg/ha / 35N
7P
15.8K / as yr 1 / as yr 1 / as yr 1 / as yr 1 / as yr 1
19 / Inorganic equiv to treat 18 / 35N
7P
14K / as yr 1 / as yr 1 / as yr 1 / as yr 1 / as yr 1
(*) The exact amounts of inorganic N applied each year were based on FYM nitrogen availabilities as predicted by MANNER (the ADAS manure N model (17)). Inorganic P and K amounts quoted are based on P and K availability guidelines for FYM (9). These guidelines were used to calculate amounts of P and K based upon actual FYM analyses. Amounts of P and K are weights of the element (1.0 kg P = 2.29 kg P2O5; 1.0 kg K = 1.20 kg K2O).
Table 2. Amounts of inorganic fertilizer nitrogen (N), phosphorus (P) and potassium (K) inputs in kg of the element /ha that were applied to treatments (Trt) 9 and 11 (equivalent to 12 t FYM /ha) or to treatments 10 and 12 (equivalent to 24 t FYM /ha) at each of the unimproved (UI) or semi-improved (SI) meadows each year.
N / P / K / N / P / K / N / P / K
Year / Field / Trt / Kg/Ha / Kg/Ha / Kg/Ha
1999 / UI / 9, 11 / 10.0 / 7.0 / 70.0 / 6.0 / 7.0 / 17.0 / 9.0 / 5.0 / 46.0
10, 12 / 20.0 / 14.0 / 140.0 / 13.0 / 14.0 / 35.0 / 18.0 / 9.0 / 92.0
SI / 9, 11 / 10.0 / 6.0 / 66.0 / 6.0 / 7.0 / 17.0 / 9.0 / 5.0 / 46.0
10, 12 / 19.0 / 12.0 / 132.0 / 13.0 / 14.0 / 35.0 / 18.0 / 9.0 / 92.0
2000 / UI / 9, 11 / 10.0 / 7.1 / 70.3 / 6.0 / 6.8 / 17.6 / 9.0 / 4.6 / 46.2
10, 12 / 20.0 / 14.2 / 140.6 / 13.0 / 13.6 / 35.3 / 18.0 / 9.1 / 92.3
SI / 9, 11 / 9.0 / 6.0 / 65.8 / 6.0 / 6.8 / 17.6 / 9.0 / 4.6 / 46.2
10, 12 / 19.0 / 12.0 / 131.7 / 13.0 / 13.6 / 35.3 / 18.0 / 9.1 / 92.3
2002 / UI / 9, 11 / 7.0 / 6.0 / 79.0 / 5.5 / 5.0 / 15.5 / 15.0 / 15.0 / 30.0
10, 12 / 14.0 / 11.0 / 158.0 / 11.0 / 10.0 / 31.0 / 30.0 / 24.0 / 109.0
SI / 9, 11 / 7.0 / 6.0 / 79.0 / 5.5 / 5.0 / 15.5 / 15.0 / 15.0 / 30.0
10, 12 / 14.0 / 11.0 / 158.0 / 11.0 / 10.0 / 31.0 / 30.0 / 24.0 / 109.0
2003 / UI / 9, 11 / 10.0 / 8.7 / 96.8 / 14.5 / 28.7 / 41.3 / 7.0 / 7.0 / 72.0
10, 12 / 19.0 / 17.4 / 193.5 / 29.0 / 57.3 / 82.9 / 14.0 / 13.0 / 144.0
SI / 9, 11 / 10.0 / 8.7 / 96.8 / 14.5 / 28.7 / 41.3 / 8.0 / 6.0 / 66.0
10, 12 / 19.0 / 17.4 / 193.5 / 29.0 / 57.3 / 82.9 / 15.0 / 12.0 / 132.0
2004 / UI / 9, 11 / 5.0 / 4.4 / 52.3 / 6.0 / 6.1 / 21.2 / 8.0 / 5.3 / 77.7
10, 12 / 9.0 / 8.9 / 104.5 / 12.0 / 12.1 / 42.4 / 16.0 / 10.6 / 155.5
SI / 9, 11 / 5.0 / 4.4 / 52.3 / 6.0 / 6.1 / 21.2 / 8.0 / 5.3 / 77.7
10, 12 / 9.0 / 8.9 / 104.5 / 12.0 / 12.1 / 42.4 / 16.0 / 10.6 / 155.5
Mean/field / 9, 11 / 8.3 / 6.4 / 72.8 / 7.6 / 10.7 / 22.5 / 9.7 / 7.3 / 53.8
Mean/field / 10, 12 / 16.2 / 12.7 / 145.6 / 15.6 / 21.4 / 45.3 / 19.3 / 13.0 / 117.4
Table 3. Cutting and baling dates at the different sites.
1999 / 24 July / 27 July
2000 / 18 July / 22 July
2001 / 26 July / 31 July
2002 / 16 July / 20 July
2003 / 5 August / 9 August
2004 / 27 July / 30 July
Raisbeck
1999 / 13 July / 16 July
2000 / 20 July / 21 July
2001 / FMD / FMD
2002 / 16 July / 17 July
2003 / 4 July / 6 July
2004 / 21 July / 23 July
Gaisgill
1999 / 29 July / 30 July
2000 / 19 July / 21 July
2001 / FMD / FMD
2002 / 15 July / 16 July
2003 / 4 July / 6 July
2004 / 21 July / 23 July
Fassagh 1 and 2
1999 / 8 July / 8 July
2000 / 18 July / 20 July
2001 / FMD / FMD
2002 / 18 July / 19 July
2003 / 11 July / 12 July
Summary of results for 1999 – 2004
Soil chemistry
Details of methods and statistical analysis of data are provided in section 2. At the start of the project in 1999 the soil at Raisbeck had a higher pH and exchangeable calcium content than Pentwyn, reflecting the previous liming practice at the former site. The soil at Raisbeck also had approximately twice the organic matter/soil carbon and soil nitrogen and higher extractable phosphorus (P), total P, exchangeable potassium (K), and sodium (Na) contents than at Pentwyn reflecting previous manuring practice at Raisbeck. There was no history of either lime or fertilizer inputs to Pentwyn, or Bush, during the ten years prior to the start of the project. Although extractable P amount was higher at Raisbeck than Pentwyn the amounts were low in comparison with agriculturally improved grassland. Extractable P amount in the soil at the agriculturally improved site at Gaisgill was over four times greater than at Raisbeck and was the principle soil chemical difference between these sites. The soil chemistries of Pentwyn and Bush were similar at the start of the project, with both sites having low amounts of N, P and organic matter amounts. The main difference was that the soil at the Bush site had a higher exchangeable K and a slightly higher base status than Pentwyn. The low soil N and P amounts at Bush are likely to be key factors influencing changes in botanical composition at this site.
Annual addition of 24 t FYM appears to have had a small positive effect on soil pH, which would accord with published information on “liming” effects of FYM application. To date, no significant “liming” effect was observed where 12 t FYM has been applied annually.
Liming was associated with maintenance of soil Mg amount at Raisbeck and Gaisgill. At Pentwyn and Bush liming was associated with a greater reduction in soil Mg amount compared with unlimed treatments.
No treatment effects on soil N or P amount were found during the first five years of the project at any of the sites. This lack of treatment effect on soil minerals is considered not surprising within this relatively short timescale.
More detailed discussion of the soil chemistry results are presented in Section 2.
Herbage dry matter and mineral results
Details of methods and statistical analysis of data are provided in section 3. Clear divergence in treatment effects on dry matter and mineral yields were found in a matrix analysis in 2004 at the unimproved meadow sites at Raisbeck and Pentwyn. Annual applications of 24 t FYM or annual NPK inputs showed major divergence from the unfertilized controls. Liming per se showed little divergence from the unfertilized control. The extent of divergence from the control of the less extensive FYM treatments was much greater at Pentwyn than at Raisbeck, which possibly reflects an effect of past management history between these sites. Raisbeck had received periodic FYM and lime applications prior to the start of this project, whereas Pentwyn had not received any inputs for many years.
Key variates influencing the separation of treatments at both sites were phosphorus and calcium/magnesium. Divergence in dry matter and mineral yield between the more intensive and the lower input treatments could provide potential agronomic “benchmarks” against which to assess ecological sustainability. The robustness of such “benchmarks”, however, can only be validated against the maintenance of the cover of positive indicator species of nature conservation value over a longer period of time than five years.