Estimating maize nutrient uptake requirements
2010
Setiyono, T.D. | Walters, D.T. | Cassman, K.G. | Witt, C. | Dobermann, A.
Generic, robust models are needed for estimating crop nutrient uptake requirements. We quantified and modeled grain yield-nutrient uptake relations in maize grown without significant biotic and abiotic stresses. Grain yield and plant nutrient accumulation in above-ground plant dry matter (DM) of commercial maize hybrids were measured at physiological maturity in on-station and on-farm experiments in Nebraska (USA), Indonesia, and Vietnam during 1997-2006. These data were used to model the nutrient requirements for yields up to 20Mgha⁻¹ using the QUEFTS (QUantitative Evaluation of the Fertility of Tropical Soils) approach. The model required estimation of two boundary lines describing the minimum and maximum internal nutrient efficiencies of N, P and K (IE, kg grain per kg nutrient in plant DM), which were estimated at 40 and 83kg grainkg⁻¹ N, 225 and 726kg grainkg⁻¹ P and 29 and 125kg grainkg⁻¹ K, respectively. The model predicted a linear increase in grain yield if nutrients are taken up in balanced amounts of 16.4kg N, 2.3kg P and 15.9kg K per 1000kg of grain until yield reached about 60-70% of the yield potential. The corresponding IEs were 61kg grainkg⁻¹ N, 427kg grainkg⁻¹ P and 63kg grainkg⁻¹ K. The model predicted a decrease in IEs when yield targets approached the yield potential limit. A spherical model was derived from QUEFTS model outputs and found to be particularly suitable for practical applications such as estimating fertilizer needs. The proposed spherical model offers generality across environments and management practices, allowing users to estimate the optimal N, P and K uptake requirements based on two inputs: estimated yield potential and yield target. Further improvements in modeling the relationship between N uptake and grain yield can be made by taking into account differences in harvest index. Accuracy in the simulation of N uptake using the spherical model was improved from an RMSE of 35kg Nha⁻¹ to 25kg Nha⁻¹ when harvest index was accounted for, suggesting that the relationship between N uptake and actual yield is affected by both yield potential and efficiency in biomass partitioning.
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