FYM Fertilizer Equivalent & Manure's N-P-K Value

It is the amount of bagged fertiliser — urea, DAP and MOP — that the nitrogen, phosphorus and potassium in your farmyard manure or compost can replace. Manure carries real N-P-K value, so counting it lets you cut how much fertiliser you buy and build soil organic matter at the same time, instead of treating the manure as worthless bulk.

Year-1 available nitrogen = tonnes × N% × availability factor (about 30%, since most manure N mineralises slowly). Phosphorus and potassium are mostly plant-available in the first year, so they are credited in full. Urea-equivalent = available N ÷ 0.46, because urea is 46% N. The tool does the same for DAP (P₂O₅) and MOP (K₂O).

Manure nitrogen is largely held in organic compounds that soil microbes release slowly over several seasons. Only roughly a third becomes plant-available in the first year; the rest carries over and improves later crops. P and K are more readily available, which is why they are credited closer to their full content.

Well-rotted farmyard manure is often around 0.5% N, 0.25% P₂O₅ and 0.5% K₂O on a fresh-weight basis, but it varies hugely with animal, bedding, age and storage. Compost and poultry manure differ again. Use a lab analysis if you have one; otherwise start from typical values and adjust as you learn your source.

Divide the available nutrient by the grade of the bagged product: urea is 46% N, DAP supplies 46% P₂O₅ (and some N), and MOP is 60% K₂O. The tool reports the urea-equivalent, DAP-equivalent and MOP-equivalent kilograms so you can subtract them from your fertiliser plan directly.

Largely yes — credit the manure's available nutrients against your crop's requirement and buy only the shortfall. Keep a little buffer for variability, and remember the slow-release nitrogen pays back in later seasons. Over years, regular manuring lowers fertiliser need further as soil fertility and structure improve.

Yes — it adds organic matter, feeds soil microbes, improves water-holding and structure, and supplies sulphur and micronutrients that bagged NPK lacks. The fertiliser equivalent only counts the major nutrients, so the real agronomic value of manure is higher than the N-P-K credit alone.

Yes — enter the tonnes (or convert your trailer loads to tonnes) and the N-P-K of farmyard manure, compost, vermicompost or poultry litter. The calculation is the same; only the nutrient percentages and availability change. Set them to match your material for a realistic credit.

They are sound planning figures. Real availability depends on manure type, how well it is rotted, soil temperature, moisture and timing of application. Test your manure where you can, apply it evenly and incorporate it promptly to limit losses, and treat the equivalents as a guide for trimming your fertiliser bill.

An application rate tool tells you how many tonnes to spread to hit a target nutrient or rate; this one works the other way — it credits the fertiliser value of the manure you have. Use them together: see the Manure Application Rate and Compost & Manure calculators to plan and credit in one workflow.