Improving Efficiency Through Soil Sampling & Nutrient Budgeting

Although GPS sampling helps to identifying variations within a field, even doing a basic routine sample is beneficial to farm businesses.  A basic routine sample is carried out by taking around 25 corers from a W shape across a field and a sample of the mixed soil is tested for the main nutrients and pH.  A basic routine sample will therefore provide an average result for the whole field.

The results from the routine sampling showed that the pHs ranged from 5.0 in some older pasture to 6.7 in an arable field that had recently had lime applied.  Phosphate indices ranged from very low to moderate plus and potash indices ranged from low to high.

Of particular interest, were the results from some fields that were sown to grass for silage.  The grass had been yielding well so it was unexpected that these fields were low in phosphate and potash and required between 2t/ha and 7.8t/ha of lime.  Assuming a crop yield of 50t/ha fresh weight, to help bring the phosphate and potash levels up to moderate and replace silage crop offtakes requires 125kg/ha of phosphate and 320kg/ha of potash to be applied.  To bring levels up to optimum James intends to apply wood ash and digestate from the AD plant; straight nitrogen will be applied to help meet the silage crop’s nitrogen requirements.  The wood ash, a by-product will supply lime, phosphate and potash; digestate will supply nitrogen, phosphate and potash.  Correcting the pH of the soils will also make the nutrients more available.

Over the next few months nutrient budgeting will be carried out for all the fields sampled to ensure targeted applications of lime and nutrients are made.  When soil analysis is combined with nutrient budgeting it facilitates the best use of nutrients from inorganic and organic fertiliser by matching applications to crop requirements and reducing loss of nutrients to the environment.