title / Mineralisation of organic nitrogen from farm manure applications / DEFRA
project code / NT2106
Department for Environment, Food and Rural Affairs CSG 15
Research 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 Unit
DEFRA, Area 301, Cromwell House, Dean Stanley Street, London, SW1P 3JH.
An electronic version should be e-mailed to
Project title / MINERALISATION OF ORGANIC NITROGEN FROM FARM MANURE APPLICATIONS
DEFRA project code / NT 2106
Contractor organisation and location / ADAS Gleadthorpe Research Centre
Meden Vale
Mansfield
Notts. NG20 9PF
Total DEFRA project costs / £159,298
Project start date / 1 July 1999 / Project end date / 31 December 2001
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Executive summary (maximum 2 sides A4)To tab in this section press the tab key and the Control key togetherPress the DOWN arrow once to move to the next question.
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 5°C (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.
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.
CSG 15 (9/01) 3
Projecttitle / Mineralisation of organic nitrogen from farm manure applications / DEFRA
project code / NT2106
CSG 15 (9/01) 3
Projecttitle / Mineralisation of organic nitrogen from farm manure applications / DEFRA
project code / NT2106
Scientific report (maximum 20 sides A4)
To tab in this section press the tab key and the Control key together
Press the DOWN arrow once to move to the next question.
CSG 15 (9/01) 3
Projecttitle / Mineralisation of organic nitrogen from farm manure applications / DEFRA
project code / NT2106
ROAME B: SCIENTIFIC OBJECTIVES AND PRIMARY MILESTONES TO BE ADDRESSED
Objective
· 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.
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 experiments
In 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.