Managing Soil Fertility: Targets to maximise production. Dr David P. Wall Teagasc, Johnstown Castle, Co Wexford

Transcription

1 Managing Soil Fertility: Targets to maximise production Dr David P. Wall Teagasc, Johnstown Castle, Co Wexford

2 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

3 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

4 Proportion of soil samples in each Index 100% 90% Dairy: National soil ph trend > <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 n = 113,606 soil samples (average 12,622 samples/annum)

5 Tonnage of Lime ('000 t/yr) Lime usage Year 5

6 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

7 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

8 Percentage of samples in each P index Soil P Fertility trends Dairy All farms ~153,500 soil samples Reducing soil P loss 22 risk Lower N fertiliser and slurry nutrient 19 17% 23 23% efficiency 29 32% % Index 4 (High) Index 3 (Optimum) Index 2 (Low) Index 1 (V.Low) 8

9 Soils with Optimum Soil Fertility Good Overall Fertility : Soil ph > 6.2; Soil P and K Index 3 Optimum 10% 90% 9

10 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

11 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

12 Steps to Soil Fertility Management Index Description 1 Very Low 2 Low 3 Target 4 High 12

13 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 25» 1.25 /ha/yr (50c per acre)» 1 kg of P = 2!!! N P K Fertilizer = / tonne??? 13

14 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

15 Steps to Soil Fertility Management 15

16 Soil ph and Liming P Soil P reserve less available Fertilisers less available N K Optimum ph for grassland = » 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

17 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 ` Soil ph Acidic Soils Alkaline Soils 17

18 Effect of P and Lime of soil P availability Sheil, Wall & Lalor, 2015, FAI Wall, D.P. et al. Teagasc, Soil Fertility Conference,

19 Effect of P and Lime of grass yield Average response across 2 sites D.P. Wall et al., 2015 Average soil ph: Wall, D.P. et al. Teagasc, Soil Fertility Conference,

20 Lime in grassland N fertiliser Offtake 1 bullock 25 kg of Lime 1000 litres milk 3 kg of Lime 100 kg = kg lime 1 ha 5 t/ha silage DM 75 kg of Lime Grassland Example Up to kg/ha/yr of lime in drainage 150 kg/ha N 300 kg 10,000 litres milk 30 kg Lime loss in drainage kg Total lime required kg/ha/yr 1-2 ton/acre every 5 years 20

21 Lime requirements Advice is to apply lime in a 3-5 year cycle Grassland typically requires between 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

22 Steps to Soil Fertility Management Index Description 1 Very Low 2 Low 3 Target 4 High 22

23 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 Low Medium High

24 Maintenance P and K advice Grazed Swards Silage Swards Soil P Stocking Rate (kg/ha Org N) Cut Index < >210 Cut Once Twice Grazed Swards Silage Swards Soil K Stocking Rate (kg/ha Org N) Cut Index < >210 Cut Once Twice

25 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

26 Steps to Soil Fertility Management 26

27 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 IFS Conference, Cambridge. 6-7 Dec,

28 Slurry Value 1000 gallons =?? Soiled Water All Year N P K kg Cattle Slurry (Splash plate) Spring N P K kg Summer N P K 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 kg 50 kg 28 / 1000 gals 10 / ton 28

29 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

30 Steps to Soil Fertility Management 30

31 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

32 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

33 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

34 Nitrogen fertiliser selection 34

35 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