A fertilization model based on the concepts of nutrient flux density and nutrient productivity

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Abstract
Fertilization is modelled on the basis of two concepts, nutrient flux density in the soil (amount of nutrient available per unit of soil and unit of time) and nutrient productivity (growth rate per unit of nutrient in plant). The nutrient productivity is used to calculate the nutrient uptake rate which is required to maintain the internal nutrient status constant at optimum and which, therefore, is required to be matched by the nutrient flux density. By supplying fertilizer nutrients as an addition to the flux density, high utilization of the added nutrients may result. A simple application of the model is, therefore, to increase the current nutrient flux density to a specified rate by the fertilizer additions. Increased accuracy of fertilization is possible by adjustment of the dosage also to the potential uptake rate of the crop. The relationships in the model are discussed on the basis of nitrogen nutrition but the use of complete fertilizers is recommended. The parameters needed, including weather data, to calculate fertilizer dosages over the growing season are discussed. A computer-adapted technique is suggested, using an irrigation system to distribute a liquid fertilizer. In this way experiments can be done to increase knowledge about nutrient dynamics and crop properties and to improve the model so as to develop more efficient fertilization routines with minimal nutrient leaching and environmental hazards.