P&K Nutrient Calculator

This essential tool for farmers and agronomists provides clear, accurate guidance on nutrient requirements to ensure both crop performance and soil fertility are maintained.

Nutrient Offtake Calculation

Quickly calculate the phosphate and potash offtakes for most UK crops at harvest. Enter the crop details and yield and the app will calculate the nutrient offtakes on the bottom lines. These quantities are often termed ‘maintenance dressings’, and usually provide the recommendation for fertiliser use when the soil Indices are at target level (with some exceptions, such as potatoes). If the soil Index is above the target level a fertiliser dressing may be reduced or considered unnecessary. The cost of such maintenance dressings should of course be charged to the crop being grown.

Nutrient Deficiency Correction

If soil Indices are below the target level the Calculator provides a guide to the nutrient quantities required to correct the deficiency. This will vary according to the level of deficiency and the soil type. The quantity will usually be more than can reasonably be applied in one season, and the Calculator asks by how much and how quickly you want to correct the deficiency, i.e. over how many years. The desired improvement can be input by Index or more precisely by mg/litre as determined by soil analysis. Once all relevant information has been input (for one or both nutrients) the results will provide a guide to the total quantity of nutrient(s) which will be required. The annual dressing is also shown, according to the timescale selected. The bottom line shows this annual deficiency-correcting application, together with the maintenance dressing. The cost of the nutrient(s) required to correct the deficiency should not be charged to the crop being grown but should be accounted for across the rotation.

Straw Offtake & Value

Managing straw is a critical decision for soil health and the farm balance sheet. The app now includes a dedicated straw offtake calculator. By entering straw yield and current fertilizer prices (TSP & MOP), you can instantly determine:

• Nutrient offtake from straw removed (kg/ha).
• Actual nutrient costs (£/kg).
• The total financial value of the nutrients in the straw (£/ha). This information can help to determine whether selling straw off farm makes financial sense, or to help indicate a price required if the decision is made to sell.

It is important to read the notes attached to the Calculator.