Farm Business Update 2014: Aylsham, Johnny Johnston and soil fertility


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Farm Business Update 2014 presentation of Johnny Johnston taken from the Aylsham Event.

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Farm Business Update 2014: Aylsham, Johnny Johnston and soil fertility

  1. 1. Meetings for Natural England - January/February 2014
  2. 2. Fertile soil, crop production and the environment Johnny Johnston Lawes Trust Senior Fellow Rothamsted Research
  3. 3. Defining soil fertility A fertile soil is one that produces optimum yields in an economically sustainable way for the grower has least adverse environmental impact among other attributes must contain adequate plant nutrients
  4. 4. Plant-available nutrients in soil Plants take up nutrients like nitrogen, phosphorus, potassium, magnesium, sodium through the roots from the soil solution when present in plant-available forms and these can be supplied by fertilizers BUT fertilizers are not an end in themselves but a means to an end in achieving optimum yields by supplementing the indigenous supply in the soil So knowledge of the soil supply is critically important Hence soil analysis is an important management tool in decisions as to how much fertilizer/manure to apply
  5. 5. Need to think about fertilizers in two groups Group 1 - nitrogen and sulphur fertilizers Irrespective of the fertilizer type most of the nitrogen is converted to nitrate and sulphur to sulphate, the forms in which these two nutrients are taken up by the plant any residue of nitrate and sulphate is not retained in soil - nitrate may be converted to nitrous oxide, a greenhouse gas or be leached out when water drains through the soil - sulphate is leached out and takes calcium with it leading to soil acidification Both nitrogen and sulphur need to be applied annually
  6. 6. Need to think about fertilizers in two groups Group 2 - phosphate, potash and magnesium fertilizers Negligible amounts of these three fertilizers are likely to be leached from soil Part of any residue remains in soil – usually the topsoil – in plant-available forms so an increasing and valuable reserve accumulates and soil analysis can be used to measure the amount Deciding on the amount of each of these three fertilizers to apply depends on the amount in the soil which can be taken up by plant roots
  7. 7. Nitrogen use increased from the 1960s Availability of nitrogen fertilizers – ammonium nitrate was no longer required for munitions Introduction of cultivars able to respond to extra nitrogen Availability of agrochemicals to control weeds, pests and diseases Winter wheat yields on Broadbalk Inefficient use of nitrogen has both a cost to the farmer and can have an adverse environmental impact
  8. 8. Crop % SOM Fertiliser N applied N0 N1 N2 N3 Potatoes 4.32 24.2 38.4 44.0 44.0 tubers, t/ha 1.73 11.6 21.5 29.9 36.2 Sugar beet 4.32 27.4 43.5 48.6 49.6 roots, t/ha 1.73 15.8 27.0 39.0 45.6 Spring barley 4.32 4.18 5.40 5.16 5.08 grain, t/ha 1.73 1.85 3.74 4.83 4.92 N0, N1, N2, N3: 0, 72, 144, 218 kg N/ha for root crops 0, 48, 96, 144 kg N/ha for barley Silty clay loam soil, Rothamsted Effect of soil organic matter on N-use efficiency - 1
  9. 9. Crop % SOM Fertiliser N applied N0 N1 N2 N3 Potatoes 3.51 27.1 40.6 50.7 59.0 tubers, t/ha 1.31 25.7 35.6 41.7 43.2 Spring barley 3.37 2.58 5.12 6.85 7.81 roots, t/ha 1.31 2.19 5.00 6.73 7.05 Winter wheat 3.37 4.81 7.21 8.09 8.08 grain, t/ha 1.31 3.54 7.32 8.05 7.82 Winter barley 3.37 3.57 5.92 7.00 7.98 grain , t/ha 1.31 3.05 6.01 7.32 7.83 N0, N1, N2, N3: 0, 100, 200, 300 kg N/ha for potatoes 0, 50, 100, 150 kg N/ha for cereals Sandy loam soil, Woburn Effect of soil organic matter on N-use efficiency - 2
  10. 10. Effect of soil organic matter on N-use efficiency - 3 Yields, t/ha, of barley. Hoosfield, Rothamsted. Annual treatment since 1852; PK fertilisers ♦, 35 t/ha FYM ■. (A) cv Julia, 1976-79 (B) cv Triumph, 1988-91 (C) cv Cooper, 1996-99.
  11. 11. Efficient use of N requires sufficient plant-available potassium in soil Importance of both nitrogen and potassium in crop nutrition Achieving large yields of most arable crops requires the rapid expansion of the leaf canopy in spring so that the plant can capture sunlight energy to convert carbon dioxide to sugars and then to dry matter Nitrogen is a major driver of leaf canopy expansion which it does by increasing both the number of individual cells and the size of cells Some 80-90% of the total cell volume is water and to maintain cell turgor (rigidity) there must be osmotic solutes within the water and plants prefer K. So more and bigger cells, more water and thus more K Compared to crops poorly–supplied with N cereals with adequate N can contain 10-15 t/ha more water and sugar beet 30-35 t/ha more water
  12. 12. 30 35 40 45 50 55 0 50 100 150 200 Saxmundham - Sugar beet –roots – t/ha 192 mg Kex/kg 114 mg Kex/kg 0 2 4 6 0 50 100 150 Hoosfield - Spring barley - grain – t/ha 329 mg Kex/kg 55 mg Kex/kg 0 10 20 30 40 0 72 144 216 485 mg Kex/kg 130 mg Kex/kg Potato tubers – t/ha Exchangeable K in soil and applied N interactions N fertiliser, kg/ha
  13. 13. Immediately Readily available Less readily Much less readily available P and extractable P available and available and in soil solution extractable P extractable P Pool 1 Pool 2 Pool 3 Pool 4 Olsen P as determined in most UK labs Current concepts about plant-available, inorganic phosphorus in soil Grain yield: with adequate P, 6.9 t/ha; with too little P, 2.9 t/ha Importance of adequate plant-available soil P Phosphate ions taken up from soil solution, i.e. from pool 1 600,000litres water in topsoil with 0.31 mg P/L = 0.18kg P/ha Yet maximum P required about 0.6 kg P/ha per day - so P in pool 1 replenished 3-4 times per day Total P in annual crops 20-40 kg P/ha so there must be enough plant-available P in pools 2 and 3 Current recommendation to maintain soil at P Index 2
  14. 14. How much P should there be in the readily-available pool? As nutrient supply increases, yield increases rapidly then more slowly to reach a maximum. The soil supply that gives near maximum yield is the critical level Examples of critical Olsen P for arable crops. Although yield varied according to weather and nitrogen supply, the critical value changed little
  15. 15. Efficient use of nitrogen depends on adequate plant- available soil P
  16. 16. Annual variation in winter wheat yield and critical P Fitted plateau yields of winter wheat and the critical Olsen P associated with 98% of that yield. Saxmundham: 1st wheats, squares; 2nd wheats, triangles; 3rd/4th wheats, diamonds. Exhaustion Land: continuous wheat, circles. Filled symbols denote crops receiving sufficient N to achieve maximum yield; open symbols denote crops receiving insufficient N. Red symbols, recent data from HGCA experiments
  17. 17. A risk assessment approach to plant-available P levels in soil Number (and percent) of soils in different critical Olsen P groups in relation to soil type Soil type and crop Range of Olsen P, mg/kg 6-15 16-25 26-35 Well-structured silty clay loam Winter wheat 14 (88) 2 (12) Spring barley 5 (83) 1 (17) Poorly-structured sandy clay loam Winter wheat 20 (46) 17 (40) 6 (14) Spring barley 9 (50) 5 (28) 4 (22) Poorly-structured heavy silty clay loama Spring barley 2 (25) 4 (50) 2 25) a excluding the results from soils with 1.5% SOM
  18. 18. Yield at 95% Olsen P Variance Soil maximum associated accounted for organic C with 95% yield % t/ha mg/kg % Field experiment Spring barley 1.40 5.00 16 83 grain, t/ha 0.87 4.45 45 46 Potatoes 1.40 44.7 17 89 tubers, t/ha 0.87 44.1 61 72 Sugar beet 1.40 6.58 18 87 sugar, t/ha 0.87 6.56 32 61 Pot experiment Grass dry matter 1.40 6.46 23 96 g/pot 0.87 6.51 25 82 Effect of soil organic matter on plant-available P Explaining annual variation in maximum yield and associated Olsen P • Annual weather rainfall and sunshine • Soil conditions seedbed, soil structure
  19. 19. Soil structure
  20. 20. Compaction effects on soil structural conditions
  21. 21. Effect of a plough pan on the growth and distribution of winter wheat roots in (a) December, (b) March and (c) June. Total root length per unit ground area for panned (solid bars) unpanned soil (open bars). Effect of soil pan on root growth
  22. 22. WoburnRothamsted Without deep loosening Wye Double Digger Depth - cm Cone resistance - bars Plough depth Winged subsoiler Effect of using the Wye Double Digger in 1977 and a winged subsoiler in 1977 and 1979 on cone resistance in 1981
  23. 23. Importance of soil structure Root tips cannot enter very small pores, for cereals they must exceed 0.05 mm Even with good structure, roots of annual crops rarely explore more than 25% of the top soil to take up nutrients Roots need to grow freely and quickly (especially for spring sown-crops) to access the nutrients they require to achieve optimum yields. This is especially so for P because the phosphate ion, H2PO4 -, only moves about 0.13 mm per day, the root must get to the P not P to the root! Using nitrogen efficiently, possibly using less and ensuring more is in the crop, requires adequate plant-available P and K in the soil. A cost benefit to the farmer and less nitrate to be lost to the environment Most P is transferred from soil to water in eroded soil. A good soil structure aids water infiltration and minimises surface runoff Developing and maintaining a good soil structure is not easy but has benefits to the farmer and the environment
  24. 24. Soil sampling and minimum cultivation Illustration of the % of extractable P found at different depths of a soil which had received only surface cultivations for 10 years 0 10 20 30 40 50 60 7.5-10.0 cm 5.0-7.5 cm 2.5-5.0 cm Samplingdepths % of P in top 15 cm (6 in) of soil
  25. 25. Soil sampling after starting minimum cultivation and following changes in soil P status over time An illustration of the potential for a soil sample to show an over-high value when taken to the standard depth in a field where minimum cultivation has been practiced Ploughdepth Normal representative soil sample Ploughed soil Ploughdepth Normal representative soil sample Ploughed soil Min-till soil Soil surface Normal soil sample depth Skewed soil sample in min-till Min-till soil Soil surface Normal soil sample depth Skewed soil sample in min-till Min-till soil sample depth Representative soil sample in min-till Min-till soil sample depth Representative soil sample in min-till