Developing a nitrogen fertilizer management model for wheat in calcareous soils using the critical nitrogen dilution curve

Abstract The critical nitrogen (N) dilution curve, which expresses whole-plant N concentration as a function of shoot biomass, can be used management diagnostic tool for cereals. objectives this research were to develop curve wheat grown in calcareous soils and formulate model estimating fertilizer requirement crop at different growth stages. Six fertilization rates (0–250 kg ha −1 ) induce variability plant throughout six site-years (three locations West Delta Egypt two seasons [2020/21-2021/22]). Aboveground biomass ( W ; Mg DM [dry matter] c g DM) determined on five sampling dates during the growing season. A was developed as: $${N}_{\mathrm{c}}=50.141 {\mathrm{W}}^{-0.424}$$ N c = 50.141 W - 0.424 . then topdressing strategy. study relied nutrition index inferred from based uptake, instead relying single recovery efficiency coefficient, variable developed. This approach increased hypothetical requirements low application while decreased high rates, implying that successfully estimate supplemental application. strategy will provide solid basis precisely managing fertilizer, though challenge ahead farm level determining actual concentration.