Why is my fertiliser bill rising every year but yield is flat?

This is a very common trap. Adding more and more fertiliser, especially urea, does not keep raising yield once the crop's need is met; beyond that point the extra fertiliser is wasted money and can even hurt the crop and the soil. A few likely reasons your yield is flat while costs rise: you may be over-applying nitrogen while another nutrient (phosphorus, potassium, sulphur, zinc or others) is actually the limiting factor; your soil organic carbon may be low so the soil holds and supplies nutrients poorly; or much of your fertiliser is being lost through poor timing and placement rather than reaching the crop. The way out is to test the soil and apply a balanced, soil-test-based dose instead of just pushing more nitrogen, improve soil organic carbon over time with FYM, compost and residue management, and fix your timing and placement so less is lost. Get a soil test, follow your Soil Health Card and KVK recommendation, balance all nutrients, and do not over-apply.