Soil Fertility Management The Optimum Nutrient Balance Stan Lalor Teagasc, Johnstown Castle ASA Conference 20 Mar 2014, Portlaoise Outline Soil fertility & fertiliser trends Balancing Lime, P and K fertiliser applications Sulphur Building Soil fertility Soil fertility management targets 20 Mar 2014 2 20 Mar 2014 1
('000 tonnes) 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 50 51 49 43 42 44 43 39 37 32 26 20 29 29 27 37 ('000 tonnes) 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013 124 126 123 107 106 111 111 101 93 85 70 52 75 73 81 Soil Fertility Management 93 Balanced Approach to Nutrients N P K S ph Lime 20 Mar 2014 3 P and K usage Total P Use Total K Use 60 140 50 120 40 30 100 80 60 20 40 10 20 0 0 Source: DAFM 20 Mar 2014 4 20 Mar 2014 2
Tonnage of Lime ('000 t/yr) 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 Soil Fertility Management Lime usage Lime usage 1970-2013 2000 2000-2009 175 kg/ha/yr 1500 1000 500 0 Year Source: DAFM 20 Mar 2014 5 Impact of price 350 300 Litres of milk required to pay for a kg of P or K (2005 = 100) 250 200 150 100 50 0 2005 2006 2007 2008 2009 2010 2011 2012 2013 P K 2005 Milk Source: CSO 20 Mar 2014 6 20 Mar 2014 3
Optimum Soil Fertility 2013 2013 55% low in P 52% low in K 62% low ph (<6.2) Good Overall Fertility - All Grass: Soil ph > 6.2; Soil P and K Index 3 or 4 Optimum 10% 90% low in either ph, P or K 20 Mar 2014 7 So What? 90 % of grassland soils were sub-optimal in 2013 Danger of working without soil test results Wrong to assume average/okay in 90% of fields Soils with low ph Poor return on fertiliser inputs Soils with low P and K Need to identify and nourish them 20 Mar 2014 8 20 Mar 2014 4
Steps to Soil Fertility Management Information Interpretation Index Description 1 Very Low 2 Low 3 Target 4 High Action 20 Mar 2014 9 Soil ph and Liming 4.5 5.0 5.5 6.0 6.5 7.0 7.5 P Soil P reserve less available Fertilizers less available N K Optimum ph for grassland = 6.2-6.3» Maximum nutrient release from soils» Soil biological activity 60% of grassland soil with low ph Response to fertilizer P on acid soils???? 20 Mar 2014 10 20 Mar 2014 5
Lime and P availability 20 18 16 Change in 14 12 Soil test P after 12 months (mg/l) 10 8 6 4 2 0 17.7 8.1 5.7 0.8 Control Lime P P + Lime 1. Lime increased the STP 2. Additive benefits of P and lime Sheil et al, 2013 Average change in soil test P (Morgan s) across 16 soils treated with P (100 kg/ha of P), Lime (5 t/ha of lime), and P + Lime and incubated over 12 months in controlled conditions. 20 Mar 2014 11 Soil ph, Lime & Molybdenum Molybdenum (Mo) Combines with Sulphur in rumen to lock up Copper Soil Mo availability increases with soil ph (>6.2) Avoid over-liming McGrath et al 2008 More Likely if: Poor drainage (or wet weather) Species: Clover > Yorkshire fog > Meadow grass > Fescue > Timothy Low Nitrogen inputs» (Higher N higher yields Dilution of Mo in herbage + less clover) Reduction of 5 t/ha in Lime rate is precautionary Use experience e.g. previous Cu problems Lime on a Rotational basis (reduce risk of Cu deficiency) 20 Mar 2014 12 20 Mar 2014 6
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 20 Mar 2014 13 Soil Index & Advice Index 1 & 2: Requires additional nutrients to build soil reserves Target Index 3: Maintain balance Index 4: Draw on soil reserves Build up Advice Maintenance Build up Maintenance Maintenance Nutrient offtake Replace offtake Replace offtake Replace offtake 1 2 3 4 Soil Index 14 20 Mar 2014 14 20 Mar 2014 7
How much P and K for maintenance P (kg) K (kg) Milk (1000 litres) 0.9-1 1-1.5 Liveweight (100 kg) 1 0.5-1 Silage (1 ton DM) 3-4 25 Grain (1 ton grain + straw) 3.8 10-15 20 Mar 2014 15 Soil P and K build up - Grassland Index 2 Apply Apply for build 5 years up + or maintenance until soil test in shows Index increase 1 and 2 Index 1 P 10 kg/ha (8 units/acre) 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 20 Mar 2014 16 20 Mar 2014 8
Calculating Offtake http://fertilizer-assoc.ie/fertilizer-calculator/calculator.php 20 Mar 2014 17 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 18 20 Mar 2014 18 20 Mar 2014 9
Sulphur >30% of Irish soils require S for optimum yield Plants contain approx. 1 kg S for every 12 kg N No soil test Soil texture Light texture (>50% sand) Low organic matter (<3% org C) On responsive soils: Silage 20 kg/ha of S per cut Grazing 20kg/ha per year When Silage with N Grazing 2-4 splits late spring to July 20 Mar 2014 19 Fertiliser programmes (P K S) Sulphur Standard compounds for Index 3 situation P: 50% early 50% split in summer Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec High K N-P-0 compound High P N-0-K compound / Straight K Low P and K higher rates / Slurry Products: K:P ratio of 2:1 3:1 ideal for grazing Slurry or K:P 4:1 6:1 ideal for silage Adjust based on soil tests, crops, stocking rates 20 Mar 2014 20 20 Mar 2014 10
to Build or not to Build??? Is it cost effective to build soil P (or K)? Cowlands study in Johnstown Castle ~ 50 kg/ha of P to raise soil P by 1 mg/l ~ 125 kg/ha to raise by 1 Index 250 /ha to raise by 1 Index ( 500 /ha to go from Index 1 3) Need to be sure you ll use the extra grass Silage Yes harvest costs, etc Grazing Index 1 vs. Index 3 for P ~ 1.5 t/ha of DM» Need to be set up to utilise this grass» Equivalent to winter feed for 1 LU!!!!!!! Stocking rate increase and/or reduced feed costs would be needed to justify costs 20 Mar 2014 21 Soil Fertility Management Targets Have soil analysis for whole farm Soil ph between 6 and 6.5 in all fields P and K Index 3 in all fields Index 4 is a resource Exploit it Index 1 & 2 identify and nourish Optimise slurry first then top up with fertilizer as required Nutrient inputs in proper balance Fertilizer planning is key 20 Mar 2014 22 20 Mar 2014 11