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P&K Balances

May 2021

The figures for P&K balances over the last five years in England and Wales shows an interesting trend. On the surface, there doesn’t appear to be too much concern when looking at the difference between the nutrients removed by crops, and what is applied to those crops annually. On fields where these inputs are applied, for winter wheat, winter barley and oilseed rape there is some fluctuation around 0 (where the offtakes by the crop match the inputs applied to that crop). The story for potash is possibly slightly more concerning than it is for phosphate, particularly for winter cereals.

Phosphate & Potash Balances (On fields where applied) Eng & Wal 2015-2019

However, this is only part of the story. The figures used in this calculation only account for the balances on fields where phosphate and potash applications were made. When looking at the bigger picture, including fields where no applications were made, the overall balances are more dramatically negative. These figures do not account for any manures that are applied, which will improve the situation slightly, however, this will in no way account for the full difference.

Phosphate & Potash Balances (all fields) Eng & Wal 2015-2019
Phosphate & Potash Balances (all fields) Eng & Wal 2015-2019

This data suggests that when applications are made to crops, the appropriate rates are applied. Which must mean that there are a significant proportion of crops that are not receiving any inputs.

Financial implications

In the current climate, there is no doubt significant financial pressures on many farm businesses, with low yielding crops from the difficult 2020 season causing some potential cash flow issues. Allied to that is the reduction of the Single Payment over the coming seasons, which is unlikely to be fully replaced by any environmental scheme. Cutting out unnecessary costs is clearly important regardless, but any decision to reduce inputs should be clearly thought out and the implications fully understood. Where soil indices are above the target index, there is scope to reduce phosphate and potash inputs, in order to run down overly high indices. However, if soils are at the target (and clearly if they are below the target) any reduction in inputs compared to the maintenance dressing will only serve to erode the soil levels and create a bigger bill to rectify the situation in the future. This can be made worse depending on how quickly soil levels deplete, which will vary for different soils. Once they are at the target index, it is usually much more cost effective to maintain this level, than letting them become depleted and having to suffer the burden of building them back up to the target.

Opting not to apply P or K on any soils that are not above the target index for the crop being grown should not be seen as an easy win for cost saving. Soils that are well supplied with nutrient are fundamental to help buffer crops against any adverse weather conditions faced during the season. Attempting to rectify issues during the season can be unpredictable at best, especially considering the unreliable weather patterns that have occurred over the last few seasons. Phosphate and potash removed from a field at harvest has a measurable cost; even if it was not applied as a dressing to the crop, it will have come from the reserve in the soil, thus effectively reducing the capital value of this asset.

Although the days of yield being king appear to be over, where an investment has been made to plant a crop, an economically optimal yield will always be the aim. These crops will require sufficient quantities of all nutrients for growth, which in the case of potash, is significantly greater than the amounts that are removed at harvest. Maintaining soils at the target index is the safest way to ensure these crops are able to access the required quantities at the appropriate times to optimise growth, yield and therefore financial returns.