An environmental and economic assessment on the impact of possible reductions in the maximum chemical nitrogen allowances for main arable crops
Nitrogen rate recommendations for arable crops are based on an economic optimum (Nopt) above which further yield increases do not cover the cost of the additional fertilizer, they are therefore, below the rate to achieve maximum yield.
04 September 2025
Type Report
By Teagasc
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Research also shows that the residual nitrate-N at harvest of a crop remains relatively stable until applications exceed Nopt, and then increase steadily as additional fertilizer N is applied. Reducing recommended N rates for arable crops is therefore unlikely to provide any environmental benefit but risks reduced yield and profitability in a farming system with already tight margins.