Optimising nitrogen use in agriculture to achieve production and environmental goals the key role of manure management Professor David Powlson Rothamsted Research (Dept of Soil Science) & Professor Steve Jarvis University of Exeter
Opportunities for improved resource use in agriculture Improved balances between inputs, offtakes and losses: energy, water (quality and quantity) (climate change) & nutrients soil, water, atmospheric quality biodiversity: scales & mosaics effective use of residues This talk centres on N
N management & circular economy Since 2003 China has adopted the concept of the circular economy improving ecological efficiency & minimising resource & energy inputs Improved N management is central to the application of the concept to agriculture: more efficient N fertiliser use (less N, same production) increased substitution of synthetic fertiliser by manure
Some facts on N fertiliser use & impact on environment N fertiliser essential for global food production Manufacturing 1 t N fertiliser emits 4+ t CO 2 plus N 2 O equivalent to 3+ t CO 2 When applied to soil, 1-5% of N fertiliser emitted as N 2 O N 2 O is 300 times more radiatively active than CO 2 Organic agriculture eliminates N fertiliser BUT yields are lower more land required CO 2 per tonne produce, similar to conventional Essential to use N fertiliser efficiently and minimise all losses (nitrate leaching, N 2 O, NH 3 )
N - response curves: wheat China-UK Shaanxi project 7000 Yield-N Response Curve, Wheat, Mu Jia Zhai 7000 Yield-N Response Curve, Wheat, Xi Wen Dian Yield (kg/ha) 6000 5000 4000 Yield (kg/ha) 6000 5000 4000 3000 0 100 200 300 400 N rate (kg/ha) 3000 0 100 200 300 400 N rate (kg/ha) 7000 Yield-N Response Curve, Wheat, Meng Ji Zhai 7000 Yield-N Response Curve, Wheat, Xinji Yield (kg/ha) 6000 5000 4000 3000 0 50 100 150 200 250 300 N rate (kg/ha) Yield (kg/ha) 6000 5000 4000 3000 0 100 200 300 400 N rate (kg/ha) Large nitrate residues in soil so large yields at N 0 and small yield responses
Sources of N Rain & atmospheric deposition Removal & losses Fertilisers Irrigation water Manure Biological N fixation Crop residues Soil
Supplying winter wheat N requirement from manure and fertiliser sources (from RB209, HMSO 2000) grain yield t/ha 10 9 8 7 6 5 4 3 2 1 0 Target N supply 0 50 100 150 200 250 300 nitrogen kg/ha Fertiliser N supply Manure N supply Soil N supply
Organic manures produced on farm Slurries, solid farmyard manures (FYM), poultry manure Important resources- recycling in soils soil conditioner/structural improvements carbon storage water holding capacity biological activity Nutrient supply NB potential pollution + AD digestion and energy (but..) refinement - chemicals (P), composted materials
Production of manure N in regions of Europe kg per ha agricultural area in 2000
A whole farm system approach Gaseous emissions (NH 3, N 2 O, N 2 ) Inputs Conc. Straw Cattle Fertilisers Outputs Milk Cattle Crops Leaching
The Coates Farm Study, UK (RR, IGER & RAC) Typical 'Cotswold' mixed farm of 244 ha on shallow clay-loam soil over limestone, with: 160 Friesian Holstein dairy cows 300 ewes 120 ha cereals 7-year rotation: first wheat, second wheat, first barley second barley and 2/3 years ley, or second barley or fodder crop and break Plus long leys and permanent pastures grazed by the dairy cattle and sheep.
Mean annual N flows at Coates Farm as tonnes N, 1996-2000 Seed 0.4 Legumes 5.1 Fertiliser 38.4 Concentrates Atmosphere 11.7 5.0 Leaching 15.9 silage, kale, lucerne, straw 15.4 Volatilisation Product 3.8 grazed grass 11.7 INTERNAL TRANSFERS mineralization 42.5 25.7 recovered in manure 9.0 Denitrification 4.0 Missing 11.3 # # increase of 0.002% N/yr
Farm manures = VARIABLE MATERIAL: problems of knowing resource Quantity and nutrient content Nos and type of livestock Diet Volume (dilution) Handling and nutrient loss Rate of release of nitrogen Immediate NH 4, urea Long term-organic forms Months years
Manure stores Slurries Solid manure - farm yard manure (FYM)
Manure Spreading
How much N is produced? during housing UK (from RB 209) TYPE Housing period % year Excreted (undiluted) tonnes N kg Dairy cow 50 9.6 48 Sow + litter 100 2.6 13 1000 laying hens 97 41 660
Understanding manure N utilisation Ammonia Run off Manure N Plant uptake Nitrous oxide Organic N Mineralisation Ammonium N Soil organic N Nitrate Nitrification Leaching
Manures - forms and availability of N (IGER/ADAS, unpublished data) N content (kg t -1 fresh weight) 30 25 20 15 10 5 0 Mineral N Readily mineralisable N Uric acid N Organic N 11%DM 6%DM 20%DM 23%DM 56%DM 44% DM Cattle slurry Pig slurry Cattle FYM Pig FYM Broiler litter Layer n=12 n=8 n=14 n=6 n=6 manure n=4
Manures - predicting release rates of organic N in the field (ADAS/IGER) 100 % organic N remaining 80 60 40 20 0 Cattle slurry Pig FYM Cattle FYM Poultry manure Pig slurry 0 1000 2000 3000 4000 Cumulative day degrees above 5 o C
Sources of information in the UK Fertiliser Recommendations Handbook RB209 Codes of Good Agricultural Practice Managing manure booklets MANNER (ADAS) DSS
Improved use of manures on-farm farmer confidence/knowledge of manure nutrient content: manure management to nutrient management analysis conventional & for eg NIR look-up tables in national handbooks and literature on-farm portable test kits ( include the Quantofix and the Agros Meters + hydrometer based method) COMPUTER PROGRAMS: `MANNER` and `PLANET` are available for free in UK. nb importance of a representative sample
Calculating N requirements for winter wheat (from RB209) Nitrogen a) Estimate total N in FYM kg/t b) Estimate available N in FYM kg/t c) N supplied by FYM equivalent to inorganic fert N kg/ha d) Requirements for wheat kg/ha e) Inorganic fert N required kg/ ha f) Surplus available N for subsequent crops 7.0 (analysis or typical values) 0.7 (analysis or typical values) 25 (standard calculation) 220 (advice) 195 (difference between c and d) 0 (but nb long term supply)
UK farmer attitude to manure nutrient management 12% 10% 36% Always Often Sometimes 17% 25% Occasionally Never farmers recognise that manures contain valuable nutrients, but do not always take them into account need to have clear messages need to instil confidence
Knowledge take-up Reducing inputs and surplus 100% Stage 1: starting 80% Stage 2: accelerating Stage 3: finishing 40% time
Ways forward 1 Need field trials: requirements Soils/climate Cropping management Interaction with other nutrients Long term
Ways forward 2: understanding controls over farm nutrients; budgets and balances Natural conditions (weather, soil, hydrology etc) Political/ economic conditions Agricultural management choice Crop growth Soil processes Inputs (ferts/fixation etc) Nutrient balance Offtake (products/losses etc) DEPOSITS CAPITAL WITHDRAWALS
How to tighten budget and nutrient supplies improved fertiliser usage practical adjustments alternative strategies tactical fertiliser methods appreciate all inputs improved knowledge of soil supplies improved manure/slurry use
Ways forward 3: understanding N losses Ammonia Nitrous oxide Leaching/run-off New application methods ammonia Run off Manure N Organic Ammonium N N Mineralisation Soil organic N Nitrate Nitrification Plant uptake Nitrous oxide Leaching
Nitrogen losses NH 3, N 2 O NH 3 NH 3, N 2 O NH 3, N 2 O, NO 3 NH 3, N 2 O, NO 3 NH 3, N 2 O, NO 3
Reducing NH 3 emissions from slurry spreading - machines 38% Reduction in emission Band spreader Trailing shoe 72% Splash plate 85% Shallow injector
Effect of DM on NH 3 emissions - cattle slurry Loss as % TAN applied 100 80 60 40 20 0 y = 4.9x + 12.6 R 2 = 0.58 0 2 4 6 8 10 12 Slurry dry matter content (%)
Improving N management Understand the value of livestock manures (and their pollution potential) Provision of independent advice Backed by field experiments Adopt new techniques for spreading: (reduced ammonia loss) Optimise all inputs according to crop demands & pollution potential
AND FINALLY: consider the bigger picture FERTILISERS FEEDS etc SOIL TRANSFER IN FOOD HUMAN MINERALISATION FIELD IMMOBILISATION TRANSFER IN MANURES TRANSFER IN CROP FARM EMISSIONS TO AIR AND WATER EMISSIONS TO AIR AND WATER CATCHMENT/ GLOBAL CYCLES