DEPARTMENT for ENVIRONMENT, FOOD and RURAL...

$: DEPARTMENT for ENVIRONMENT, FOOD and RURAL AFFAIRSrandd.defra.gov.uk/Document.aspx?Document=NT2106_355_FRP.d… · Web viewPlant uptake of nitrogen from the organic nitrogen fraction$
Projecttitle

Mineralisation of organic nitrogen from farm manure applications

DEFRAproject code

NT2106

DEPARTMENT for ENVIRONMENT, FOOD and RURAL AFFAIRS CSG 15Research and Development

Final Project Report(Not to be used for LINK projects)

Two hard copies of this form should be returned to:Research Policy and International Division, Final Reports UnitDEFRA, Area 301, Cromwell House, Dean Stanley Street, London, SW1P 3JH.

An electronic version should be e-mailed to [email protected]

Project title MINERALISATION OF ORGANIC NITROGEN FROM FARM MANURE APPLICATIONS

DEFRA project code NT 2106Contractor organisation and location

ADAS Gleadthorpe Research CentreMeden ValeMansfieldNotts. NG20 9PF

Total DEFRA project costs £159,298Project start date 1 July 1999 Project end date 31 December 2001

.

Executive summary (maximum 2 sides A4)The overall objective of the study was to quantify nitrogen (N) release from the organic fraction of farm manures following land application. The release of manure organic N was measured from April 1999 to June 2001, following earlier measurements over a c.3 year period (May/June 1996 to March 1999) at two contrasting field experimental sites (ADAS Gleadthorpe and IGER North Wyke). At each site, 9 ammonium-N ‘stripped’ manures (2 cattle slurries, 2 cattle FYMs, 2 pig FYMs, a pig slurry, layer manure and broiler litter) were applied in summer 1996 (3 replicates of each manure type in a randomised block design). The experiments were sown with perennial ryegrass (Lolium perenne) which was cut periodically to quantify plant N uptake and porous ceramic cups were installed to measure nitrate leaching losses. Net manure organic N release was calculated by subtracting the sum of plant N uptake and nitrate leaching loss measurements on the untreated control from those on the individual manure treatments. Soil temperatures were measured continuously at each site (10 cm depth) and manure organic N release curves calculated using cumulative day degrees above 5C (CDD).

Manure organic N release (expressed as a % of the organic N applied) was linearly related to thermal time up to c.2200 CDD at ADAS Gleadthorpe and c.2300 CDD at IGER North Wyke. The greatest amounts of organic N release were from the pig slurry (52% and 67% of organic N applied at Gleadthorpe and North Wyke, respectively) and layer manure (36% and 60%, respectively) treatments. The lowest amounts of organic N release were from the cattle FYM and pig FYM treatments at Gleadthorpe (4% of organic N applied for both treatments), and from the cattle slurry treatment at North Wyke (10% of organic N applied). The relationships between organic N release and CDD were significant (P<0.01), but varied with manure type. The organic N release data from both sites were not significantly different (P>0.05) and were pooled in order to derive ‘generic’ functions for modelling purposes. Comparison of 95% confidence intervals for the slope of each organic N release relationship showed that the data fell into 2 broad groups, with pig slurry and poultry manure having a higher rate of organic N release (0.022 * CDD) than cattle/pig FYM and cattle slurry (0.0076 * CDD). These results were similar to those from the laboratory incubation study carried out in DEFRA project NT1501 which showed that manure organic N release was inversely related (P<0.01) to manure C:organic N ratios, with the largest amounts released from the layer manure and pig slurry treatments, and least from the cattle slurry and FYM treatments.

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Projecttitle


DEFRAproject code

NT2106

At Gleadthorpe, manure organic N release continued beyond c.2200 CDD, albeit at a much slower rate. Grass N uptake on the manure treatments was greater than on the untreated control (P<0.05) in July 1999 (5900 CDD) and June 2000 (7700 CDD), indicating that organic N release was continuing four years after the initial application. In July 2001 (9800 CDD), grass N uptake on the manure treatments was the same as the untreated control (P>0.05), indicating that manure organic N release had stopped in the fifth year after application. During this phase, N release was linearly related to thermal time (P = 0.05) and was the same for both manure groups (P>0.05); slope of relationship (0.0011 * CDD). Manure organic N release virtually ceased at North Wyke at > 2300 CDD. Ploughing and re-seeding at IGER North Wyke in summer 1999 (6900 CDD), three years after the initial application, did not increase (P>0.05) grass N uptake on the manure treatments compared with the untreated control. The data from both sites after 2300 CDD were combined in order to derive ‘generic’ functions for modelling purposes, with a shallow slope for the pig slurry and poultry manure group of 0.0004 * CDD, and the cattle/pig FYM and cattle slurry group of 0.0001* CDD.

The derived relationships were used to predict the contribution that manure organic N would make to crop N uptake and nitrate leaching losses. Arable land: On a loamy sand textured arable soil growing winter wheat under low rainfall conditions (600 mm), manure organic N release from pig slurry and cattle FYM applications (250 kg/ha total N) was predicted to increase crop N uptake in the season after application by 15 and 9 kg/ha N, respectively, regardless of application timing. Nitrate leaching losses from the released organic N were predicted at 10 and 7 kg/ha N in the first winter, and 26 and 18 kg/ha N in the second winter after the pig slurry and cattle FYM applications, respectively. Changing the application timing from September to March made no difference to crop available N supply in the season after application, but increased organic N uptake from the pig slurry in the second crop by 8 kg/ha N (from 1 to 9 kg/ha N) and from the cattle FYM application by 4 kg/ha (from 1 to 5 kg/ha N). On the clay textured arable soil in a low rainfall area (600 mm), the more nitrate retentive nature of the soil was predicted to lead to a greater amount of the organic N being available for crop uptake than on a loamy sand soil. Manure organic N release from September pig slurry and cattle FYM applications was predicted to supply 17 and 9 kg/ha N to the first crop, and 10 and 4 kg/ha N to the second crop, respectively. Under high rainfall conditions (1000 mm), soil type was predicted to have little effect on the amount of released organic N taken up by a winter cereal crop, as overall nitrate leaching losses following all the application timings were predicted to be similar.Grassland: Grass growth during the autumn and winter period was predicted to be sufficient to take up all of the released organic N. The organic N release curves indicated that in the 12 months after application (typically 2000 CDD above 5oC), N release would supply grass crops with 44 and 30 kg/ha N following pig slurry and cattle FYM applications (250kg/ha total N applied), respectively. In the following 12 months (i.e. the second year after application), manure organic N release from the pig slurry and cattle FYM applications would supply a further 8 and 4 kg/ha N, respectively.

This study has provided a much improved understanding of manure organic N supply and has derived organic N release curves based on thermal time, which have enabled the contribution of released organic N to nitrate leaching losses and crop available N supply to be estimated for different manure types and application timings. This information will be of great value in the further development of models that predict organic N release and in the refinement of fertiliser recommendation systems (e.g. MANNER, NGAUGE), enabling farmers and their advisers to take better account of manure organic N supply in their inorganic fertiliser N policies. The information will help DEFRA to fulfil its policy objectives of reducing nitrate pollution from agriculture and improving nitrogen utilisation from livestock manures as part of sustainable farming systems.

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Projecttitle


DEFRAproject code

NT2106

Scientific report (maximum 20 sides A4)ROAME B: SCIENTIFIC OBJECTIVES AND PRIMARY MILESTONES TO BE ADDRESSEDObjective To quantify nitrogen (N) release from the organic fraction of farm manures following land

application.

I. EXTENT TO WHICH OBJECTIVES HAVE BEEN MET

Data from this project have shown that manure type and soil temperature are important factors controlling the release of manure organic nitrogen (N). Manure organic N release was linearly related (P<0.01) to thermal time (cumulative day degrees – CDD) up to c.2300 CDD, with pig slurry/poultry manure showing faster rates of N release (slope 0.022 * CDD) than cattle/pig farmyard manures and cattle slurry (slope 0.0076 * CDD). After c.2300 CDD, manure organic N release was much slower (slopes 0.0001-0.0004 * CDD). The data from both sites in the study were combined for the two manure type groups to derive ‘generic’ organic N release functions for modelling purposes, which have enabled the contribution of released organic N to nitrate leaching losses and crop available N supply to be predicted. The findings of this work will assist DEFRA in achieving its policy objectives of reducing nitrate pollution from agriculture and improving manure nitrogen utilisation as part of sustainable farming systems.

II. BACKGROUND

In the UK, applications of farm manures to agricultural land supply c.450,000 tonnes of total nitrogen per annum, of which c.300,000 tonnes are estimated to be present as organic N and c.150,000 tonnes as readily available N (principally ammonium and uric acid-N). Typically, 75-90% of the total N content of straw-based farmyard manures (FYM) is present as organic N, 50-60% for poultry manures and 40-50% for slurries (Anon., 2000).

Research in the UK has largely focused on manure readily available N forms, because in the short-term these have the greatest influence on crop N supply, ammonia volatilisation and nitrate leaching losses (Jarvis and Pain, 1990; Unwin et al., 1991; Chambers et al., 1997). However, in the longer-term manure organic N release will have an increasingly important effect on soil N supply, particularly in situations where repeated manure applications are made to land. If manure organic N release occurs during periods of crop growth (spring-summer) fertiliser N requirements will be reduced, but if release occurs during the autumn-winter period, nitrate leaching and denitrification losses are likely to be increased.

Quantifying N release from the organic fraction of farm manures is complicated by the presence of several N forms which differ between manure types, namely: (i) mineral N (principally ammonium-N), (ii) readily mineralisable N (uric acid and urea) and (iii) more slowly mineralised organic compounds. Previous studies have not accounted for these different N fractions when assessing manure organic N release.

Previous work carried out under DEFRA project NT1501 - ‘Fate of Manure Organic Nitrogen’ (Chadwick et al. 2000) characterised the N fractions present in fifty contrasting manure types (20 slurries, 20 farmyard manures-FYM and 10 poultry manures). The work showed that the organic N content of the different manure types varied considerably, with cattle slurry and FYM typically containing 29% and 71% of their total N content in organic forms, pig slurry and FYM 35% and 71%, and broiler litter and layer manure 71% and 54%, respectively. The work also identified differences in the C:organic N ratio of the contrasting manure types, with cattle FYM typically having the highest ratio at 17:1, followed by cattle slurry and pig FYM at 14:1, pig slurry at 11:1, broiler litter at 9:1 and layer manure at 6:1. Generally, organic materials with low C:N ratios breakdown (mineralise) more rapidly than those with higher C:N ratios (Aleef and Nannipieri, 1995; Floate, 1970; Serna and Pomares, 1991). Thus, organic N release is likely to vary according to manure type and C:organic N ratio.

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Projecttitle


DEFRAproject code

NT2106

Further work carried out under DEFRA project NT1528 (Williams et al., 2001) investigated N release following the application of ammonium-N ‘stripped’ manures at two contrasting field study sites. In the first 18 months of the study, c.50% of layer manure organic N was released compared with only c.20% from straw-based FYMs. In this follow-on project (NT2106), manure organic N release was measured from April 1999 to June 2001, following earlier measurements over a c.3 year period (May/June 1996 to March 1999).

III. SCIENTIFIC PROGRESS

1. Field experimentsIn spring 1996, nine manures (two cattle slurries, a pig slurry, two cattle FYMs, 2 pig FYMs, a broiler litter and a layer manure) were collected from commercial farms across England and Wales, and delivered to ADAS Gleadthorpe. Between 5 and 15 tonnes of solid manure and 25m3 of slurry were collected. The manures were selected to provide contrasting carbon:organic N ratios.

1.1 Ammonium-N ‘stripping’The manures were ‘stripped’ of their ammonium-N content by cycles of wetting and drying over a period of 8 weeks. The solid manures were spread on plastic sheets at depths of between 5 and 15 cm. After initial drying, the manures were re-wetted and turned periodically to encourage ammonia volatilisation. The slurries were held in lagoons constructed using straw bales and butyl liners. The slurries were allowed to settle and the supernatant removed by pumping until only c.50 cm of semi-solid manure remained. The dry matter of the supernatant was tested to ensure that solid manure organic matter was not being lost; in all cases the dry matter of the discarded liquid was less than 1%. The semi-solid material was then spread out onto plastic sheets and treated in the same manner as the solid manures to encourage ammonia losses. The procedures were undertaken as quickly as practically possible to minimise organic N release during the ‘stripping’ process. The ‘stripping’ techniques were effective at reducing the readily available N content (mineral N plus uric acid N) of the cattle, pig and poultry manures to < 5%, <10% and < 10% of the manure total N content, respectively.

1.2 MethodologyIn May/June 1996, batches of each ammonium-N ‘stripped’ manure were transported from ADAS Gleadthorpe to IGER North Wyke (Table 1). Field experiments with an untreated control (no N applied), five inorganic fertiliser N treatments (range 30-150 kg/ha) and nine ‘stripped’ manure treatments (Table 2) were established at each site.

Table 1. Soil type and average annual rainfall.

Site Topsoil texture Average annual rainfall (mm)

Topsoil total N (%)

Topsoil organic matter (%)

Topsoil C: N ratio

ADAS Gleadthorpe Loamy sand 650 0.04 1.7 25:1IGER North Wyke Sandy loam 1000 0.08 1.8 13:1

At both sites, there were three replicates of each treatment in a randomised block design, with plots 3 m x 10m. Following land application, the manures were left on the surface for 48 hours to further encourage ammonia volatilisation losses, before being intimately mixed with the soil using a spading machine and rotavator prior to drilling with perennial ryegrass (Lolium perenne) in June 1996. Samples of the incorporated manures were collected from 1m2 mesh squares located randomly across the plots and analysed for dry matter, nitrate-N, ammonium-N, hot KCl extractable N, HCl extractable N, uric-acid N (poultry manure only), total N and organic carbon according to the methods described in Chambers et al. (1998).

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Table 2. Total N loadings and C: organic N ratios of the manures applied at each field site.

Total N loading (kg/ha) C: organic N ratioTreatment Gleadthorpe North Wyke Gleadthorpe North Wyke

Cattle FYM 1 526 632 21.2 19.5Cattle FYM 2 901 848 11.0 11.0

Pig FYM 1 863 1031 14.4 12.2Pig FYM 2 794 861 9.8 8.1

Cattle slurry 1 172 364 13.0 10.3Cattle slurry 2 676 724 14.3 13.3

Pig slurry 577 543 11.8 11.3Broiler litter 674 364 15.4 14.8

Layer manure 659 638 8.8 9.7

The inorganic fertiliser N additions were split into 5 increments applied throughout the season. Phosphate and potash fertiliser dressings were based on the site soil analysis results and applied at recommended rates, after making allowance for the phosphate and potash supplied in the farm manure applications (Anon., 2000).

Grass cuts were taken from the ADAS Gleadthorpe site in July 1996, September 1996, December 1996, April 1997, June 1997, June 1998, July 1999, June 2000 and July 2001, and at IGER North Wyke in September 1996, November 1996, May 1997, July 1997, October 1997, June 1998, August 1999, July 2000 and June 2001. At each cut, yield measurements were made and grass samples analysed for %N and dry matter (Anon., 1986) so that crop N uptakes could be calculated. Inorganic fertiliser N response curves were determined for each cut, to assess the fertiliser N replacement value and N efficiency of the manure organic N additions.

Porous ceramic cups were installed at 90cm depth at ADAS Gleadthorpe and 60cm depth at IGER on the manure and control plots (4 cups per plot) to measure nitrate-N leaching losses (Webster et al., 1993). Samples of soil water were collected every 50 mm of drainage or two weeks which ever occurred sooner throughout winters 1996/97, 1997/98, 1998/99, 1999/2000 and 2000/01, and analysed for nitrate-N. Total nitrate-N leaching losses (kg/ha) were calculated using nitrate-N concentrations from the porous cup samples and estimates of drainage from the ADAS IRRIGUIDE water balance model (Bailey and Spackman, 1996).

Soil temperatures at 10 cm depth were monitored continuously at each site using “Tinytalk” data recorders and soil moisture contents measured gravimetrically each month during the experiment. Manure organic N release rates were related to thermal time, calculated as the cumulative day degrees (CDD) above 5 degrees, so that organic N release curves could be determined for each manure type.

At IGER North Wyke, the site was ploughed and re-seeded in August 1999 to determine whether cultivation would stimulate further manure organic nitrogen release.

Organic N release was calculated by subtracting the sum of grass N uptakes + N leached on the untreated control from the sum of N uptakes + N leached on the manure treatments. The initial readily available N content of the applied manures was subtracted from the manure N uptake values, assuming 100% efficiency of the readily available N applied (inorganic fertiliser N uptake efficiencies were 100% 10%).

2. Results

2.1 Plant N uptakeAt ADAS Gleadthorpe, grass uptake of released organic N (Figure 1) was greatest on the pig slurry treatment at 265 kg/ha N (46% of organic N applied) between June 1996 and June 1997, and smallest on the pig FYM-2 treatment at 23 kg/ha N (3% of organic N applied). Between the first and fourth sampling dates (c.10 months) net N uptake was only 1 kg/ha N on the cattle FYM-2 treatment, with a net immobilisation of 13 kg/ha N measured on the pig FYM-2 treatment. Following cultivation of the site in July 1997, grass N uptake on all the manure treatments was greater than on the untreated control (P<0.05) in June 1998, July 1999 and June 2000. Grass N uptake post cultivation was equivalent to a mean of 5% (range 3-7%) of the organic N applied. Grass N uptake on the manure treatments in July 2001 was the same (P>0.05) as on the untreated control, indicating that manure organic N release had effectively stopped in the fifth year after application.

Note: Nitrate leaching losses only included for 1996/97-1997/98; as drainage losses overwinters 1998/99-2000/01 on the manure treatments were not significantly different (P>0.05) from the untreated control.

Figure 1. Manure organic N release at ADAS Gleadthorpe (June 1996 to June 2000).

Grass N uptake at IGER North Wyke was generally higher than at Gleadthorpe, especially in the first 3 months after application (Figure 2). The greatest N uptake was measured on the pig slurry (68% of organic N applied) and layer manure treatments (61% of organic N applied), and lowest on the cattle slurry-1 treatment (9% of organic N applied). N uptake data from the grass cuts taken in October 1997, June 1998 and August 1999 were not different from the untreated control (P>0.05), indicating that organic N release had ceased c.13 months after the initial application. Similarly, grass N uptakes in July 2000 and June 2001 on the manure treatments were not different from those on the untreated control (P>0.05), indicating that cultivation in August 1999 (3 years after the initial manure application) had not stimulated further manure organic N release.

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Note: Nitrate leaching losses only included for 1996/97; as drainage losses overwinters 1997/98 – 2000/01 on the manure treatments were not significantly different (P>0.05) from the untreated control.

Figure 2. Manure organic N release at IGER North Wyke (June 1996 to July 1997).

Fertiliser N replacement values for the released manure organic N were calculated from the crop N uptake measurements at Gleadthorpe and ranged from 3-50 kg/ha in June 1998, 12-40 kg/ha in July 1999 and 9-20 kg/ha N in June 2000 (Table 3). The crop N uptake measurements on the manure treatments were the same as those on the untreated control (P>0.05) at Gleadthorpe in 2001 and at IGER between October 1997 and 2001, and hence fertiliser N replacement values could not be calculated for these cuts.

Table 3. Fertiliser nitrogen replacement value of released manure organic nitrogen at ADAS Gleadthorpe.

Treatment 1998 1999 2000kg/ha N

Cattle FYM 1 42 17 13Cattle FYM 2 22 40 17

Pig FYM 1 41 15 17Pig FYM 2 23 18 15

Cattle slurry 1 3 13 9Cattle slurry 2 20 12 20

Pig slurry 25 13 16Broiler litter 29 28 15

Layer manure 50 35 13

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2.2. Nitrate leachingIn 1996/97, overwinter rainfall at Gleadthorpe and IGER North Wyke was 85% and 75% of the long-term average (Table 4), respectively. The low rainfall, coupled with large moisture deficits created by the grass cover in the dry summer of 1996, meant that drainage did not begin at both sites until early December 1996. In 1997/98 and 1998/99, relatively wet summers meant that drainage began in late October/early November at both sites. At Gleadthorpe, the drainage volumes were greatest in 2000/01 (278 mm), reflecting overwinter rainfall c.50% greater than the long-term average. At North Wyke, drainage volumes were also greatest in 2000/01 (688 mm), reflecting overwinter rainfall c.40% greater than the long-term average (Table 4).

Table 4. Overwinter rainfall (1st September to 31st March) and drainage.

Site Average rainfall

Actual rainfall (mm) Drainage (mm)

(mm) 96/97 97/98 98/99 99/00 00/01 96/97 97/98 98/99 99/00 00/01

ADAS Gleadthorpe

364 316 322 407 311 522 85 148 124 123 278

IGER North Wyke

756 584 540 646 740 1078 173 189 423 593 688

In the first winter (1996/97) after the manure applications, nitrate-N leaching losses at Gleadthorpe were equivalent to less than 1 % of organic N applied on the cattle / pig FYM and cattle slurry treatments, and c.3% on the pig slurry, broiler litter and layer manure treatments (Figure 1). At North Wyke, leaching losses were comparable to those at Gleadthorpe, except on the pig slurry treatment where losses were equivalent to 10% of the applied organic N (Figure 2).

In the second winter (1997/98), nitrate-N leaching losses at Gleadthorpe increased to 10% and 12 % of the applied organic N on the cattle FYM -1 and cattle slurry -1 treatments, respectively (Figure 1). At North Wyke, leaching losses on all the manure treatments were not significantly different from the untreated control (P>0.05), indicating that manure organic N release had effectively ceased c.13 months after the initial manure application (Figure 2).

In the following winters (1998/99, 1999/2000 and 2000/01), nitrate leaching losses on the manure treatments at both sites were similar to those on the untreated control (P>0.05), indicating that released organic N was not contributing to nitrate leaching losses.

2.3. Organic N releaseThe mineralisation of manure organic N is a microbially mediated process, so temperature is clearly an important factor that is likely to influence the rate of organic N release (Swift et al., 1979). Relationships were derived between the % of manure organic N release measured at Gleadthorpe and North Wyke, and thermal time after application (expressed as cumulative day degrees above 5C - CDD) to produce manure organic N release curves (Figures 3 and 4). Although these curves represent a relatively crude approach to modelling rates of manure organic N release, they are attractive in their simplicity and have been shown to improve the accuracy of predicting manure N availability (Castellanos and Pratt, 1981; Klausner et al., 1994).

At Gleadthorpe, the decay curves (Figure 3) for each manure type were divided into three phases. Phase 1 (up to c.1300 CDD) when grass growth was limited by the dry summer weather after the site was established (total rainfall 89 mm in 3 months). Phase 2 when plant N uptake proceeded rapidly (c.1300-2200 CDD) during autumn 1996 and spring/summer 1997, and Phase 3 (c.2200 CDD +) when release had slowed down. At North Wyke, the better grass growing conditions (total rainfall 122 mm in 3 months) immediately after the ryegrass established meant that the crop N uptake of released N was less limited by drought (Figure 4). After c. 2300 CDD, organic N release had effectively ceased at the site.

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A number of other workers have used thermal time to predict organic N release. For example, Douglas and Rickman (1992) simulated crop residue decomposition as a function of thermal time and observed a rapid decomposition rate up to 1000 CDD which was related to the N content of the residue, followed by a slower phase at >1000 CDD, which was regulated by the lignin content of the crop residue. Clough et al. (1998) measured soil organic matter mineralisation rates on a range of grassland soils and found that mineralisation was linearly related to cumulative soil temperatures above 0C. Similarly, Honeycutt and Potaro (1990) found that cumulative day degrees (i.e. soil thermal units) were useful in predicting net mineralisation. The combination of a release curve approach and CDD data provide a useful means of modelling N release from farm manures, although variability in manure composition and soil and environmental conditions will also influence mineralisation rates.

Figure 3. Manure organic N release curves at ADAS Gleadthorpe.

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Figure 4. Manure organic N release curves at IGER North Wyke.

i) N release up to c.2300 CDD The greatest amounts of organic N release were from the pig slurry (52% and 67% of organic N applied at Gleadthorpe and North Wyke, respectively) and layer manure (36% and 60%, respectively) treatments. The lowest amounts were from the cattle FYM-2 and pig FYM-2 treatments at Gleadthorpe (4% of organic N applied for both treatments), and from the cattle slurry-2 treatment at North Wyke (10% of organic N applied). These results were similar to those from the laboratory incubation study (Chadwick et al., 2000) carried out under project NT1501, which showed that the largest amounts of organic N were released from the layer manure and pig slurry treatments, and least from the cattle slurry and FYM treatments.

At both sites, release of manure organic N was linearly related to thermal time up to c.2300 CDD (P<0.01 and r2 > 70%), but varied with manure type (Table 5).

Table 5. Relationship between manure organic N release (% organic N applied) and thermal time.

Treatment r2 P Slope 95% CI*GT NW GT NW GT NW GT NW

Cattle FYM1 0.85 0.81 <0.001 0.002 0.005 0.014 0.0013 0.0055Cattle FYM2 0.76 0.86 <0.001 0.001 0.002 0.010 0.0004 0.0031Pig FYM1 0.77 0.89 0.001 0.001 0.007 0.014 0.0028 0.0038Pig FYM2 0.73 0.89 0.008 0.001 0.002 0.009 0.0012 0.0024Cattle slurry 1 0.87 0.87 <0.001 0.001 0.007 0.012 0.0022 0.0036Cattle slurry 2 0.90 0.90 <0.001 <0.001 0.005 0.004 0.0011 0.0012Pig slurry 0.88 0.95 <0.001 <0.001 0.021 0.028 0.0051 0.0051Broiler litter 0.93 0.95 <0.001 <0.001 0.010 0.018 0.0017 0.0031Layer manure 0.85 0.97 <0.001 <0.001 0.014 0.027 0.0039 0.0034*95% confidence interval (CI) = standard deviation x t; where t = 2.571 for Gleadthorpe (5 df) and 2.776 for North Wyke (4 df)Comparison of 95% confidence intervals for the slope of each relationship showed that the relationships fell into 2 broad groups at each site. The first group included pig slurry and layer manure which had a higher rate of

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organic N release, compared with the second group which included cattle/pig FYM and cattle slurry that had lower rates of N release (Figures 5 & 6). Broiler litter fell midway between these two groups.

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Figure 5. 95% confidence intervals for the relationship between manure organic N release and thermal time at ADAS Gleadthorpe.

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Figure 6. 95% confidence intervals for the relationship between manure organic N release and thermal time at IGER North Wyke.

The greater amounts of organic N release from the pig slurry and layer manure compared with the cattle slurry & cattle/pig FYMs, was most likely a reflection of differences in the C:organic N ratios of the manure types. Pig slurry and layer manure had lower C:organic N ratios (range 9-12:1) than the cattle slurry and straw-based FYMs (range 10-21:1). The C:organic N ratios of the manures were generally similar to those used in the laboratory incubation study undertaken in DEFRA project NT1501 (Chadwick et al., 2000), values reported in other studies (Nicholson et al., 1996; Chambers et al., 1998) and from the ADAS manure analysis database (Tables 6 and 7). Although, the C:organic N ratio of the broiler litter at 15:1 was greater than the typical value of c.9:1.

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Table 6. Typical carbon to nitrogen ratios of cattle/pig FYM and poultry manures.

Manure typeand data source

Number of samples

Dry matter (%)

Total N(%DM)

Organic carbon(%DM)

C:N ratio C:organic N ratio

Cattle FYM:ADAS Manure database

36 29.7(8.8)

2.6(0.8)

33.3(9.1)

13.7(5.8)

14.2*

DEFRA project NT1501

14 22.7(3.7)

2.6(0.7)

38.2(1.5)

15.6(3.8)

17.6(3.1)

Mean 50 27.7(7.4)

2.6(0.8)

34.7(7.0)

14.2(5.2)

15.2

Pig FYM:ADAS manure database

6 24.3(4.8)

3.4(1.4)

31.6(4.3)

9.3(2.9)

10.3*

DEFRA project NT1501

6 22.7(7.0)

3.8(0.2)

37.4(1.7)

10.0(0.9)

14.3(2.0)

Mean 12 23.5(5.9)

3.6(0.8)

34.5(3.0)

9.7(1.9)

12.3

Layer manure:ADAS Manure database

76 33.0(6.2)

6.1(1.8)

28.4(3.3)

5.0(1.2)

8.7**

DEFRA Project NT1501

4 44.0(20.5)

4.6(1.1)

18.1(7.4)

3.8(0.9)

7.8(2.2)

Mean 80 33.6(6.9)

6.0(1.8)

27.9(3.5)

4.9(1.2)

8.7

Broiler /turkey litter:ADAS manure database

19 61.0(11.8)

5.8(1.4)

34.8(2.7)

6.3(1.5)

8.6**

DEFRA Project NT1501

6 56.3(11.5)

4.3(1.1)

33.5(6.8)

8.2(2.4)

11.4(4.2)

Mean 25 59.9(11.7)

5.4(1.3)

34.5(3.7)

6.8(1.7)

9.3

( ) standard deviation in bracket

* Assumes ammonium N content of cattle and pig FYM = 10% of total N (Chambers et al., 1999)** Poultry manures - ammonium N plus uric acid N content of layer manure and broiler/turkey litter 46% and

30% of total N, respectively (Nicholson et al., 1996).

CSG 15 (1/00) 12

Table 7. Typical carbon to nitrogen ratios of pig and cattle slurries.

Slurry type and data source Number of samples

Dry matter (%)

Total N(%DM)

Organic carbon(%DM)

C:N ratio

Cattle slurry

ADAS Manure data base:- whole slurry 30 4.8

(3.7)7.4

(3.0)33.5(4.1)

5.3(2.3)

- solid fraction 30 - 3.4*(1.7)

5 12.8(6.2)

DEFRA project NT1501:

- whole slurry 12 11.1(5.1)

4.0(1.0)

35.9(2.9)

9.6(2.4)

- solid fraction 12 - 2.76(0.9)

- 13.3(2.4)

Mean:- whole slurry 42 6.6

(4.1)6.4

(2.4)34.2(3.8)

6.5(2.3)


- 12.9(5.1)

Pig slurry

ADAS Manure data base:- whole slurry 3 1.8

(0.9)17.7(8.1)

27.0(6.4)

1.9(1.5)

- solid fraction 3 - 4.4**(0.9)

5 6.6(3.2)

DEFRA project NT1501:- whole slurry 8 5.7

(6.7)12.6(6.6)

28.9(5.9)

3.2(2.5)


- 9.6(3.3)

Mean- whole slurry 11 4.6

(5.1)14.0(7.0)

28.4(6.0)

7.5(2.2)


- 8.8(3.3)

( ) standard deviation in brackets

* Ammonium-N content 54% of total N** Ammonium-N content 75% of total N

CSG 15 (1/00) 13

The results from the field experiments in this study were in general agreement with those from the laboratory study carried out as part of DEFRA project NT1501 (Chadwick et al., 2000), which showed that the rate of organic N release was inversely related (P<0.01) to the C:organic N ratio of the applied manures. Relationships between manure C:N ratios and N mineralisation have also been reported by Serna and Pomares (1991) who demonstrated a significant relationship between animal manure C:N ratios and N mineralisation (r2=-48%), and Floate (1970) who showed a weak relationship between the C:N ratio of sheep faeces and N mineralised (r2=-31%). Although, Castellanos and Pratt (1981) found no relationship between manure C:N ratios and N mineralised for a range of stored and fresh animal manures.

The amounts of organic N released by the two manure type groups (FYMs/cattle slurry and pig slurry/ poultry manure) were used to derive ‘standard’ organic N release functions. This was initially done for each site separately, as CDD were different at the two sites. The broiler litter results were excluded from the relationships, because of the atypically high C:organic N ratio (C:organic N ratio 15:1) of the broiler litter used in the field study (see Tables 2 and 6). It is likely that a more ‘typical’ broiler litter (C:organic N ratio of c.9:1) would behave in the same way as the layer manure. The relationships derived at each site for the two manure type groups (Table 8) had different slopes (based on a comparison of the 95% confidence intervals). As the results from each of the two manure type groups at the two sites were not significantly different (P>0.05) they were pooled in order to derive ‘generic’ organic N release functions for modelling purposes (Figure 7).

Table 8. Relationship between manure organic N release and thermal time.

Treatment r2 P Slope 95% CIGT NW GT NW GT NW GT NW

FYM & cattle slurry

0.89 0.86 <0.001 <0.001 0.005 0.01 0.001 0.003

Pig slurry & layer manure

0.87 0.96 <0.001 <0.001 0.017 0.027 0.004 0.004

Figure 7. Relationship between % organic N release and thermal time for the two manure type groups up to 2300 CDD (ADAS Gleadthorpe and IGER North Wyke data).

For pig slurry and poultry manure (C:N 9-12; mean = 10):

% organic N applied which was released = 0.022/CDD up to 2300 CDDCSG 15 (1/00) 14

For cattle/pig FYM and cattle slurry (C:N 10-21; mean = 14):

% organic N applied which was released = 0.0076/CDD up to 2300 CDD

ii) N release > 2300 CDD At Gleadthorpe, organic N release continued to occur, albeit at a much slower rate (Figure 8). This may have been due to the stimulation of manure organic N release following cultivations during plot movement at c.2200 CDD. During this second phase, N release was again linearly related to thermal time (P = 0.05). The rate of N release (% N released/CDD i.e. the slope of the regression) was the same for both manure type groups (Table 9). However, due to differences in N release rates during the first phase (Table 8) the initial starting value (i.e. the intercept) was higher for the pig slurry and layer manure group than the cattle/pig FYM and cattle slurry group.

At IGER North Wyke, organic N release effectively ceased at > 2300 CDD for both manure type groups (Table 9 and Figure 9). Even cultivation of the North Wyke site in August 1999 did not increase organic N release (P>0.05).

Table 9. Relationship between manure organic N release and thermal time > 2300 CDD.

Treatment r2 P Slope InterceptGT NW GT NW GT NW GT NW

FYM & cattle slurry

0.67 0.55 0.05 0.10 (NS)

0.0011 0.0002 13.1 26.3

Pig slurry & layer manure

0.68 0.11 0.05 0.31(NS)

0.0011 0.0001 44.1 64.1

Figure 8. Relationship between % organic N release and thermal time for the two manure type groups beyond 2300 CDD (ADAS Gleadthorpe).

CSG 15 (1/00) 15

Figure 9. Relationship between % organic N release and thermal time for the two manure types beyond 2300 CDD (IGER North Wyke).

As with the period up to c.2300 CDD, results from the two sites were combined in order to derive ‘generic’ functions for modelling purposes (Figure 10). Overall, the N release rate differences between the two manure type groups were largely a result of differences in N release up to 2300 CDD.

Figure 10. Relationship between % organic N release and thermal time for the two manure type groups beyond 2300 CDD (ADAS Gleadthorpe and IGER North Wyke data).

For cattle/pig FYM and cattle slurry:

% organic N applied which was released = 0.0004/CDD

For pig slurry and poultry manure:

% organic N applied which was released = 0.0001/CDD2.4. Implications for crop N supply and N leachingThe relationships derived for the two manure type groups (FYM/cattle slurry, and pig slurry/poultry manure) were used to estimate how much of the released organic nitrogen would be utilised by cereal and grass crops following 1st September, 1st November and 1st March application timings. The estimates were made for pig

CSG 15 (1/00) 16

slurry and cattle FYM applications (Figures 11, 12 and 13) to loamy sand and clay textured soils, and for contrasting climatic areas with 600 and 1000 mm annual rainfall, respectively. The MANNER decision support system (Chambers et al., 1999) was run on a fortnightly basis and used to predict how much of the released manure organic N would be lost by leaching. It was assumed that for grassland, the manures were surface spread and on arable land they were incorporated into the soil by ploughing.

The predictions showed that up to the end of November c.10% and 4% of the applied organic N would be released from a 1st September pig slurry and cattle FYM application timing, and less than 1% would be released from both manure types following a 1st November application. Between the end of November and the beginning of March (when soil temperatures are low and little mineralisation occurs), manure N release from the September and November applications was predicted at less than 1% of the organic N applied.

Figure 11. Predicted pattern of manure organic N release from 1st September manure application.

Manure organic N release was predicted to proceed rapidly between the beginning of March and the end of September, reflecting the warm spring and summer soil temperatures, with 39% and 14% of the applied manure organic N released from the pig slurry and cattle FYM applications for all three application timings. Predicted organic N release from the previous 1st September application slowed after the beginning of October, because the cumulative day degrees exceeded 2,300, with less than 1% of the applied organic N released from both manure types between the end of September and the end of November. For the other two application timings, N release slowed between the end of September to end of November period, because of the cooler autumn soil temperatures, with c.5% of pig slurry and 2% of cattle FYM organic N released over this period.

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Figure 12. Predicted pattern of manure organic N release from 1st November manure application timing.

Figure 13. Predicted pattern of manure organic N release from 1st March manure application timing.

The following spring, N release from the 1st November (18 months previous) and 1st March (12 months previous) applications continued until the middle of May, whereafter the cumulative day degrees exceeded 2,300 for both application timings. During this period (beginning of March to middle of May) c.5% and 2% of applied organic N was released from the pig slurry and cattle FYM applications, respectively.

CSG 15 (1/00) 18

Arable rotationsIn winter cereal rotations, N mineralised before mid November is only likely to make a small contribution to crop N uptake, because less than 10 kg/ha of soil N is typically taken up by an autumn sown cereal crop before the beginning of March (Sylvester-Bradley et al., 1998). MANNER predictions showed that under low rainfall conditions (600 mm) on a loamy sand textured soil, all of the N released from a 1st September application upto the end of November would be lost by leaching, and following a 1st November application c.90% of the released N would be leached (260 mm overwinter drainage). In contrast, on a clay textured (more nitrate retentive) soil, leaching losses would account for c.80% and 30% of released N from a 1st September and 1st

November application, respectively. Following a 1st March application timing, no leaching of released organic N was predicted on either the loamy sand or clay textured soils.

Under high rainfall conditions (1000 mm), MANNER predicted that there would be no difference between the soil types in the amount of released N that would be lost by leaching, with all of the N released before the end of November lost following 1st September and 1st November application timings. Following a 1st March application timing, no leaching of released organic N was predicted on either the loamy sand or clay textured soils.

On both soil types, manure application timing was predicted to have little effect on the amount of released organic N that was taken up by a winter cereal crop, with N uptake effectively ceasing at the end of June (Sylvester-Bradley et al., 1998) and any N released thereafter at risk from leaching loss the following winter. The most important effect of application timing was on the amount of N that was leached in the first and second winter drainage seasons in a winter cereal cropping rotation. At manure application rates of 250 kg/ha total N, pig slurry and cattle FYM would typically supply 100 and 188 kg/ha of organic N, respectively (Table 10). The predictions indicate that on a loamy sand soil, manure organic N release from the pig slurry and cattle FYM applications would contribute 15 and 9 kg/ha N to crop supply in the first season from all three application timings. However, the 1st March compared with the previous 1st September application timing was predicted to increase the amount of released organic N available for uptake by a second crop by 8 kg/ha N (from 1 to 9 kg/ha N) for the pig slurry and 4 kg/ha N (from 1 to 5 kg/ha N) for cattle FYM. On the clay textured soil (under low rainfall conditions), lower leaching losses (compared with the loamy sand soil) were predicted to lead to more of the released organic N being available for crop uptake. The 1st September pig slurry and cattle FYM applications on the clay soil were predicted to supply 17 and 10 kg/ha N to the first cereal crop (compared with 15 and 9 kg/ha N on the loamy sand) and 5 and 4 kg/ha N to the second crop (compared with 1 kg/ha N for both manures on the loamy sand), respectively. Under high rainfall (1000mm) conditions, there were no predicted differences in crop N recovery between the two soil types.

Under both low and high rainfall conditions (600 mm and 1000mm), delaying the manure applications from 1st

September to 1st November was predicted to reduced leaching losses in the first winter drainage season by 8 kg/ha N for the pig slurry and 6 kg/ha N for cattle FYM on both soil types. However, the limited ability of the following winter cereal crop to take up released N during the following autumn period, was predicted to lead to increased leaching losses (2-3 kg/ha N) in the second season from the 1st November, compared with 1st

September timing on both soil types.

Overall, manure application timing was predicted to have little effect on the quantities of crop available N and nitrate leached manure organic N release. Although the timing of N leaching losses was changed, with a greater proportion in the second winter than the first, through delaying manure applications from September to November/March.

Table 10. Predicted amount of released N lost by leaching and taken up by a winter cereal crop following contrasting application timings of pig slurry and cattle FYM (250 kg/ha total N applied).

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Pig slurry Cattle FYMOrganic N

applied* (kg/ha N)

100 188

Sept Nov Mar Sept Nov MarLoamy sand

Clay Loamy sand

Clay Loamy sand

Clay Loamy sand

Clay Loamy sand

Clay Loamy sand

Clay

600 mm rainfallLeached -year 1 **

(kg/ha N)10 8 2 <1 0 0 7 6 1 <1 0 0

Crop uptake - year 1

(kg/ha N)

15 17 15 17 15 15 9 10 9 10 9 10

Leached - year 2**

(kg/ha N)26 22 29 25 28 24 18 15 20 17 20 17


(kg/ha N)

1 5 6 10 9 13 1 4 5 8 5 8

Leached -year 3**

(kg/ha N)1 1 1 1 1 1 2 2 2 2 3 2

1000mm rainfallLeached -year 1 **

(kg/ha N)10 10 2 2 0 0 7 7 1 1 0 0


(kg/ha N)

15 15 15 15 15 15 9 9 9 9 9 9

Leached - year 2**

(kg/ha N)26 26 29 29 29 29 18 18 20 20 20 20


(kg/ha N)

1 1 6 6 8 8 1 1 5 5 5 5

Leached - year 3**

(kg/ha N)1 1 1 1 1 1 2 2 2 2 3 3

* Assumes 40% of pig slurry and 75% of cattle FYM total nitrogen is present in organic form (Chambers et al., 2001), assuming 250 kg/ha total N applied** Leaching losses predicted by MANNER (Chambers et al., 1999) drainage was assumed to have finished on 31 March

GrasslandN GAUGE (Brown and Scholefield, 1998) model predictions indicated that grass N uptake between October and March on a typical sward receiving 400 kg/ha N annually would be 38 kg/ha. This uptake exceeded the predicted manure organic N release from all application timings during the same period by c.20 and 30 kg/ha for the pig slurry and cattle FYM applications, respectively. This indicates that on grassland, all of the released manure organic N is likely to be taken up by the grass crop and that application timing will have little impact on the amount of released manure organic N lost by nitrate leaching.

The manure organic N release curves indicate that in the 12 month period (typically 2000 CDD above 5oC) after the pig slurry and cattle FYM applications (supplying 250 kg/ha total N), organic N release would contribute 44 and 30 kg/ha N to grass N uptake, respectively. In the following 12 months (i.e. 12-24 months after application), manure organic N release would provide a further 8 and 4 kg/ha N from the pig slurry and cattle FYM applications, respectively.IV. CONCLUSIONS & IMPLICATIONS FOR DEFRA

At ADAS Gleadthorpe, grass N uptake on the manure treatments was greater than on the untreated control (P<0.05) in July 1999 (5900 CDD after application) and June 2000 (7700 CDD after application), indicating that organic N release was still continuing four years after the initial manure application in 1996.

CSG 15 (1/00) 20

In July 2001 (9800 CDD after application), grass N uptake on the manure treatments was the same (P>0.05) as on the untreated control, indicating that manure organic N release had effectively stopped in the fifth year after application.

At IGER North Wyke, ploughing and re-seeding in summer 1999 (3 years after the initial manure application) did not increase (P>0.05) manure organic N release in 1999/2000, nor were there any increases in 2001.

The release of manure organic N varied according to manure type, with two manure type groups identified, viz: (i) cattle/pig FYM & cattle slurry (C:N ratios 10-21:1) which released organic N at a slower rate and (ii) pig slurry & poultry manure (C:N ratios 9-12:1) which released manure organic N at a faster rate.

Manure organic N release was related to thermal time (cumulative day degrees-CDD above 5C) and followed 2 distinct phases:

Phase 1 up to c.2300 CDD: The proportion of manure organic N released was linearly related to thermal time. A single function was used to describe the overall relationship for the two manure type groups across both sites:

For cattle/pig FYM and cattle slurry: % manure organic N released = 0.0076 * CDD

For pig slurry and poultry manure: % manure organic N released = 0.022 * CDD

Phase 2 beyond 2300 CDD: The release of manure organic N continued at a much slower rate than in the first phase, with N release described by a simple linear function for each of the manure type groups across both sites:

For cattle/pig FYM and cattle slurry:% manure organic N released = 0.0004/CDD

For pig slurry and poultry manure:% organic N released = 0.0001/CDD

However, differences between the manure type groups were still apparent due to different rates of N release in the first phase (i.e. up to 2300 CDD). Therefore, the combined first and second phase organic N release functions were:

CSG 15 (1/00) 21

Prediction of % N released from cattle/pig FYM and cattle slurry =(0.0076 * 2300) + [(CDD-2300)* 0.0004)]

Prediction of % N released from pig slurry & poultry manure =(0.022 * 2300) + [(CDD-2300)* 0.0001)]

The relationships allowed the contribution of manure organic N release to crop N supply and nitrate leaching losses to be predicted.

On an arable loamy sand textured soil with 600 mm of annual rainfall, manure organic N release from pig slurry and cattle FYM applications (250 kg/ha total N) was predicted to supply 15 and 9 kg/ha N to the first winter cereal crop after application regardless of timing. For a September timing, nitrate leaching losses following the pig slurry and cattle FYM dressings were predicted at 10 and 7 kg/ha N in the first winter after application, and 26 and 18 kg/ha N in the second winter after application, respectively. The greater leaching losses in the second winter after application reflect the limited period (typically March to June) of N uptake by winter cereal crops. Changing the application timing from September to March was predicted to make no difference to the amount of released organic N taken up by the winter cereal crop in the first season after application, although N uptake by the second cereal crop was predicted to increase by 8 kg/ha N (from 1 to 9 kg/ha N) from the pig slurry and 4 kg/ha N (from 1 to 5 kg/ha N) from the cattle FYM application.

Under low rainfall conditions (600 mm rainfall), lower leaching losses on the clay textured soil (because of the more nitrate retentive nature) were predicted to lead to more of the released N being taken up by a cereal crop than on the loamy sand soil (1-2 kg/ha N in the first year and 3-4 kg/ha in the second year).

Under high rainfall conditions (1000 mm of rainfall), soil type was predicted to have no effect on the amount of released N taken up by a winter cereal crop, as N leaching losses from all application timings were similar.

In grassland systems, it was predicted that all of the released manure organic N would be taken up by a growing grass crop during the autumn and early winter period. The manure organic N release curves indicated that in a 12 month period after pig slurry and cattle FYM applications (supplying 250 kg/ha total N), organic N release would contribute 44 and 30 kg/ha N to grass N uptake, respectively. In the following 12 months (i.e. 12-24 months after application), manure organic N release would provide a further 8 and 4 kg/ha N from the pig slurry and cattle FYM applications, respectively.

This study has provided a much improved understanding of manure organic N release. The derived

organic N release curves for different manure type groups, based on thermal time, has enabled predictions of the contribution of released organic N to nitrate leaching losses and crop N supply to be made for contrasting manure application timings. This information will be of great value in the development of manure N mineralisation models and fertiliser recommendation systems (e.g. MANNER, NGAUGE), enabling farmers and their advisers to take better account of mineralised organic N in their inorganic fertiliser N policies.

V. KNOWLEDGE TRANSFER

The results from this project have been promoted at the following conferences, in publications and to visiting scientists:

(i) Chadwick, D.R., John, F., Pain, B.F., Chambers, B.J. and Williams, J. (2000). Plant uptake of nitrogen from the organic nitrogen fraction of animal manures : a laboratory experiment. Journal of Agricultural Science, 134, 159-168

(ii) Williams, J.R, Chambers, B.J., Bhogal, A., Chadwick, D.R. and Pain, B.F. (1999). Field studies of farm manure organic nitrogen mineralisation. Proceedings of the 8th International Conference of the FAO ESCORENA Network on Recycling of Agricultural, Municipal and Industrial Residues in Agriculture (Eds. J.Martinez and MN Maudet), FAO/CEMAGREF, pp 101-111.

(iii) Chadwick, D. and Ostle, N. (1999). Isotopic detection of possible organic-N uptake by Lolium perenne (L). Annual meeting of the Stable Isotope Mass Spectrometry Users Group, book of abstracts, p39-40. IGER, North Wyke.

(iv) Chambers, B.J, Smith, K.A., Pain, B.F. and Chadwick, D. (1998). Short and long-term nitrogen supply from organic manures. SCI Symposium - Managing Nitrogen in Crop Rotations, London, March 1998 (abstract).

(v) Chadwick, D., John, F., Pain, B., Chambers, B. and Williams, J. (1997). Mineralisation of organic nitrogen from animal manures. In: Proceedings of 11th International World Fertilizer Congress, Fertilization for Sustainable Plant Production and Soil Fertility, Volume II (Eds. O. van Cleemput et al), pp29-35.

(vi) March 1999, Presentation of results to visiting scientists from University of Santiago, Spain.

(vii) Williams, J.R., Chambers, B.J., Chadwick, D.R., Bhogal, A. & King, J.A. (2001). Organic nitrogen release from farm manures. In: 11th Nitrogen Workshop, Book of Abstracts. INRA, Reims, France, pp 381-382.

(viii) Presentation at IGER ‘Grassland Management - Practice into Profit’ meeting - 18th July 2000. Reports from the meeting, including reference to the project were published in:Farmers Guardian, 4 August 2000Beef Farmer, Summer 2000Farmers Weekly, 14 July 2000 Farming News, 20 July 2000

(ix) Presentation and paper at MAFF Nitrate Review meeting, November 2000, University of Warwick.

(x) MAFF Environmental Newsletter, ‘Factors affecting the fate of organic nitrogen’, February 2001, p8

(xi) Poster presentation ‘Availability of organic N from livestock manures’ prepared for Muck 2001 (cancelled due to Foot and Mouth Disease)

(xii) Williams, J.R., Bhogal, A., Chadwick, D.R. and Chambers, B.J. Nitrogen release from the organic fraction of farm manures (advanced draft)

VI. REFERENCES

Aleef, K and Nannipieri, P. (1995). Methods in Applied Soil Microbiology and Biochemistry. Academic Press, London

Anon. (1986). The Analysis of Agricultural Materials. Reference Book 427. Ministry of Agriculutre, Fisheries and Food.

Anon. (2000). Fertiliser Recommendations for Agricultural and Horticultural Crops. Department for Environment Food and Rural Affairs. Reference Book 209 (seventh edition). HMSO, Norwich

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Bailey R.J. and Spackman, E. (1996). A model for estimating soil moisture changes as an aid to irrigation scheduling and crop water-use studies: I Operational details and description. Soil Use and Management 12, 122-129.

Brown, L and Scholefield, D. (1998). A model to optimise nitrogen use according to grassland management, soil conditions and weather patterns for economic and environmental targets. In: Ecological Aspects of Grassland Management (Eds. G. Nagy and K. Peto), EGF, Hungary, pp 651-654.

Castellanos, J.Z. and Pratt, P.F. (1981). Mineralisation of manure nitrogen - correlation with laboratory indexes. Soil Science Society of America Journal 44, 354-357.

Chadwick, D.R., John, F., Pain, B.F., Chambers, B.J. and Williams, J. (2000). Plant uptake of nitrogen from the organic nitrogen fraction of animal manures : a laboratory experiment. Journal of Agricultural Science 134, 159-168.

Chambers, B.J., Smith, K.A. and van der Weerden, T.J. (1997). Ammonia emissions following the land spreading of solid manures. In : Gaseous Nitrogen Emissions from Grassland (Eds. S.C. Jarvis and B.F. Pain), CAB International, UK, pp 275-280

Chambers B.J., Williams, J.R and Chadwick, D.R. (1998). MAFF project NT1501- Fate of Manure Organic Nitrogen. Final report to MAFF, London

Chambers, B.J., Lord, E.I., Nicholson, F.A. and Smith, K.A. (1999). Predicting nitrogen availability and losses following land application of organic manures to arable land. Soil Use and Management 15, 137-144.

Chambers, B.J., Nicholson, N., Smith, K., Pain, B., Cumby, T. and Scotford, I. (2001) Managing Livestock Manures – booklet 1: Making better use of livestock manures on arable land. Available from ADAS Gleadthorpe Research Centre (Tel: 01623 844331).

Clough, T.J., Jarvis, S.C. & Hatch, D.J. (1998). Relationships between soil thermal units, nitrogen mineralisation and dry matter production in pastures. Soil Use and Management 14, 65-69.

Douglas, C.L., Jr. & Rickman, R.W. (1992). Estimating crop residue decomposition from air temperature, initial nitrogen content and residue placement. Soil Science Society of America Journal 56, 272-278

Floate, M.S. (1970). Decomposition of organic materials from hill soils and pastures II. Comparative studies on carbon, nitrogen and phosphorus from plant materials and sheep faeces. Soil Biology and Biochemistry 2, 173-185.

Honeycutt, C.W. and Potaro, L.J. (1990). Field evaluation of heat units for predicting crop residue carbon and nitrogen mineralisation. Plant and Soil 125, 213-220.

Jarvis, S.C. and Pain, B.F. (1990). Ammonia volatilisation from agricultural land. The Fertiliser Society. Proceedings No.298. Greenhill House, Thorpe Wood, Peterborough.

Klausner, S.D., Kanneganti, V.R. and Bouldin, D.R. (1994). An approach for estimating a decay series for organic nitrogen in animal manures. Agronomy Journal 86, 897-903.Nicholson, F.A., Chambers, B.J. and Smith, K.A. (1996). Nutrient composition of poultry manures in England and Wales. Bioresource Technology 58, 279-284.

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Serna, M.D. and Pomares, F. (1991). Comparison of biological and chemical methods to predict nitrogen mineralisation in animal wastes. Biology and Soil Fertility 12, 89-94.

Swift, R., Heal, O.W. and Anderson, J.M. (1979). Decomposition in Terrestrial Ecosystems. Blackwell Scientific Publications, Oxford. 372pp.

Sylvester-Bradley, R., Gay, A.P., Scott, R.K. and Clare, R.W. (1998). HGCA Project Report 151. Assessments of Wheat Growth to Support its Production and Improvement (Volume III). HGCA, Caledonia House, 223 Pentonville Road, London N1 9NG.

Unwin, R.J., Shepherd, M.A. and Smith, K.A. (1991). Controls on manure and sludge applications to limit nitrate leaching. Does the evidence justify the restrictions which are being proposed? In : Treatment and Use of Sewage Sludge and Liquid Agricultural Wastes (ed. P.L’Hermite). Elsevier Applied Science, London. pp 261-270.

Webster, C.P., Shepherd, M.A., Goulding, K.W.T. and Lord, E.I. (1993). Comparison of methods for measuring the leaching of mineral nitrogen from arable land. Journal of Soil Science 44, 46-62.

Williams J.R., Chambers B.J., Chadwick D.R., Bhogal A. & King J.A. (2001). Organic nitrogen release from farm manures. In: 11th Nitrogen Workshop, Book of Abstracts. INRA, Reims, France, pp 381-382.

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