Managing Soil Fertility: Targets to maximise production Dr David P. Wall Teagasc, Johnstown Castle, Co Wexford
Outline Soil fertility trends on dairy farms 5 Steps to soil fertility management Soil Testing Soil ph and Lime Determine P & K requirements Best use of Organic manures Apply a balanced fertilizer programed Soil Fertility and Productivity Targets 2
National Soil Fertility trends Soils Data Base maintained at Teagasc Johnstown Castle 2015 ~ 36,000 samples submitted through Teagasc for soil analysis Samples submitted for analysis from each county in Ireland 3
2007 2008 2009 2010 2011 2012 2013 2014 2015 Proportion of soil samples in each Index 100% 90% Dairy: National soil ph trend >6.5 6.2-6.5 5.9-6.2 5.5-5.9 <5.5 14% 16% 17% 12% 17% 16% 18% 18% 19% 80% 70% 60% 50% 13% 19% 15% 15% 20% 20% 13% 21% 15% 17% 19% 21% 19% 17% 17% 22% 20% 19% 40% 30% 28% 28% 29% 29% 26% 26% 26% 25% 24% 20% 10% 27% 22% 19% 25% 23% 20% 14% 19% 20% 0% Wall et al. 2015 n = 113,606 soil samples (average 12,622 samples/annum)
1970 1971 1972 1973 1974 1975 1976 1977 1978 1979 1980 1981 1982 1983 1984 1985 1986 1987 1988 1989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 2014 Tonnage of Lime ('000 t/yr) Lime usage 1970-2014 2000 1500 1000 500 0 Year 5
Soil P & K fertility status and trends Phosphorus fertility declining high status soils Low proportion of soils at target index Large proportion with sub-optimum P Potassium fertility Majority soils with sub-optium K Steady decline in soil K fertility over last decade 6
N, P and K use between 1990 and 2011 relative to 1990 (N= 379,000 kg,p= 65,000 kg, K=158,000 kg) High fertilizer N allowance and most restrictive P allowance in Europe N P = 20,000 kg K = 52,000 kg K P 7
Percentage of samples in each P index 100 90 80 70 60 50 40 30 Soil P Fertility trends Dairy 36 35 37 36 28 31 30 29 All farms ~153,500 soil samples Reducing soil P loss 22 risk 28 27 27 27 28 19 23 29 23 23 25 25 27 27 Lower N fertiliser and slurry nutrient 19 17% 23 23% 26 24 23 24 20 efficiency 29 32% 19 22 25 25 28 10 9 10 11 11 0 2006 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 29 28% Index 4 (High) Index 3 (Optimum) Index 2 (Low) Index 1 (V.Low) 8
Soils with Optimum Soil Fertility Good Overall Fertility : Soil ph > 6.2; Soil P and K Index 3 Optimum 10% 90% 9
What quantities of nutrients are required? Nutrient off-take from the grazing platform Milk (18,000 litres/ha) + 3Cows & Calves LW/ha 110 kg N 20 kg P 31 kg K 5 kg S EC Fertiliser? 50 kg Nutrients required For 12 t DM/ha Lock-up(P, N, S, K) Losses (N, S, K, P) 10
What quantities of nutrients are required? Highly Stocked Grazing Block Typical Maintenance EC Fertiliser N 250 kg/ha P 25 kg/ha K 45 kg/ha S 20 kg/ha 50 kg Lock-up(P, N, S, K) Losses (N, S, K, P) 11
Steps to Soil Fertility Management Index Description 1 Very Low 2 Low 3 Target 4 High 12
Soil Testing Cost / Benefit ~ 10% of soils are optimised for P, K & lime If no soil test and assume Index 3, then you are likely to be wrong in 90% of fields!! Cost Consider relative to fertilizer cost?» 1 sample = 4 ha for 5 years @ 25» 1.25 /ha/yr (50c per acre)» 1 kg of P = 2!!! N P K Fertilizer = 300-500 / tonne??? 13
Soil testing Why & How? How? Sample Area Minimum 20 cores per sample Full 10 cm depth When? Late Autumn / Early Spring ideal» Results ready for fertiliser planning for the coming year 14
Steps to Soil Fertility Management 15
Soil ph and Liming 4.5 5.0 5.5 6.0 6.5 7.0 7.5 P Soil P reserve less available Fertilisers less available N K Optimum ph for grassland = 6.2-6.3» Maximum nutrient release from soils» Soil biological activity 67 % of grassland soil < 6.2 Response to fertiliser N, P and K on acid soils???? 16
Phosphorus Fixation Effect of soil ph on P Availability High Med Fixation by Iron & Aluminium Plant Available P Fixation by Calcium Low D.P. Wall, 2015 ` 3 4 5 6 7 8 9 Soil ph Acidic Soils Alkaline Soils 17
Effect of P and Lime of soil P availability Sheil, Wall & Lalor, 2015, FAI Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015 18
Effect of P and Lime of grass yield Average response across 2 sites D.P. Wall et al., 2015 Average soil ph: 5.2 6.4 5.2 6.4 Wall, D.P. et al. Teagasc, Soil Fertility Conference, 2015 19
Lime in grassland N fertiliser Offtake 1 bullock 25 kg of Lime 1000 litres milk 3 kg of Lime 100 kg = 180-220 kg lime 1 ha 5 t/ha silage DM 75 kg of Lime Grassland Example Up to 250-625 kg/ha/yr of lime in drainage 150 kg/ha N 300 kg 10,000 litres milk 30 kg Lime loss in drainage 250-625 kg Total lime required 580 955 kg/ha/yr 1-2 ton/acre every 5 years 20
Lime requirements Advice is to apply lime in a 3-5 year cycle Grassland typically requires between 0.5-1 t/ha/yr Target soil ph: Mineral soils 6.3, Peat soil 5.5 Exceptions High Mo soils and grassland don t exceed ph 6.2» Lime requirements reduced by 5 t/ha Where advice is > 7.5 t/ha» Split application» 7.5 t/ha now» Remainder after 2 years» Precaution to reduce risk of trace element problems 21
Steps to Soil Fertility Management Index Description 1 Very Low 2 Low 3 Target 4 High 22
Interpreting soil test results - P & K Convert test result into soil Index (P & K grassland index below) Target = All soils in Index 3 for P and K! Only ~ 25% at present Soil Index Description Soil test P (mg L -1 ) Soil test K (mg L -1 ) 1 Very low 0 3.0 0 50 2 Low 3.1 5.0 51 100 3 Medium 5.1 8.0 101 150 4 High 8.1 151 23
Maintenance P and K advice Grazed Swards Silage Swards Soil P Stocking Rate (kg/ha Org N) Cut Index < 130 131-170 171-210 >210 Cut Once Twice 1 30 34 39 43 +20 +30 2 20 24 29 33 +20 +30 3 10 14 19 23 +20 +30 4 0 0 0 0 0 0 Grazed Swards Silage Swards Soil K Stocking Rate (kg/ha Org N) Cut Index < 130 131-170 171-210 >210 Cut Once Twice 1 85 90 95 100 +120 +155 2 55 60 65 70 +120 +155 3 25 30 35 40 +120 +155 4 0 0 0 0 0 0 24
Soil P and K build up - Grassland P 10 kg/ha (8 units/acre) Index 2 Apply Apply build for up 5 years + maintenance or until soil in test Index shows 1 and increase 2 Index 1 16% P 25 kg 20 kg/ha (16 units/acre) 16% P 50 kg K 30 kg/ha (24 units/acre) Muriate 50% K 25 kg 60 kg/ha (48 units/acre) Muriate 50% K 50 kg 25
Steps to Soil Fertility Management 26
Contribution to Slurry Value Cattle Slurry K 69% N 12% P 19% Majority of the value is in P and K Aim to get best use of both P and K in slurry Timing or method» No effect on P and K» Big effect on N Lalor et al. 2013. IFS Conference, Cambridge. 6-7 Dec, 2012. 27
Slurry Value 1000 gallons =?? Soiled Water All Year N P K 4-0.7-5 50 kg Cattle Slurry (Splash plate) Spring N P K 6-5 - 38 50 kg Summer N P K 3-5 - 38 50 kg 5 / 1000 gals 24 / 1000 gals 26 / 1000 gals Trailing Shoe + 3 units N / 1000 gallons In spring or summer Pig Slurry FYM (1 ton) N P K N P K 19-7 - 20 3-2.5-12 50 kg 50 kg 28 / 1000 gals 10 / ton 28
Decisions with slurry 1. Where to spread» P & K requirements» Target fields with: low soil P and K High requirements (e.g. silage) 2. When to spread» Maximise N availability» Weather as important as season, but spring generally best» Trailing shoe / band spreader will also increase N value 29
Steps to Soil Fertility Management 30
Nutrient Balance What is the Weakest Link? Nutrient in shortest supply limits determines yield Especially true with P and K Fertilizer Planning Soil tests & Cropping Slurry & fertilizers» Straight K» N-P products» N-K products N P K Fertilizer» Sulphur and micro nutrients N P Fertilizer K Fertilizer 31
Cost of lost production at Index 1 & 2 Example Dairy 2 cows / ha Maintenance advice (grazing: Index 3 ) = 13 kg/ha P & 35 kg/ha K Cost of maintenance P & K = 60 /ha/yr Production loss in Index 1 vs. Index 3 Approximately 2.0 t/ha/yr of grass DM (range 1-5 t/ha) Worth ~ 360 /ha/yr Soil ph needs to be right as well! Additional P and K for build up = 20 kg/ha P & 60 kg/ha K Additional Cost = 90 /ha/yr until soil P / K increases Long-term investment benefits of increasing to Index 3 Return on Investment 4:1 ( grass production : soil fertility) 32
Nitrogen fertiliser selection Urea or Stabilised Urea Why look at it now? Cost & yield Urea-N costs less than CAN-N: 26% less (CSO, 2014) Is there a yield penalty? Internationally urea is more available than CAN GHG Ag. approx. 1/3 national emissions Committed to reduce by 20% by 2020 N addition causes N 2 O loss Smart solutions? Ammonia (NH 3 ) Ag. accounts for c. 98.5% of national emissions Committed to reduce by 30% by 2030 Urea looses NH 3! 33
Nitrogen fertiliser selection 34
Soil Fertility Management Targets Have soil analysis for whole farm Soil ph between 6 and 6.5 in all fields Note: target ph 5.5 for peat soils P and K Index 3 in all fields Index 4 is a resource Exploit it Index 1 & 2 should be increased to Index 3 Optimise slurry first then top up with fertilizer as required Nutrient inputs in proper balance Fertilizer planning is key Increase farm sustainability with N fertiliser source selection 35