Roots, plant production and nutrient use efficiency

The role of roots in obtaining high crop production levels as well as a high nutrient use efficiency is discussed. Mathematical models of diffusion and massflow of solutes towards roots are developed for a constant daily uptake requirement. Analytical solutions are given for simple and more complicated soil-root geometries. Nutrient and water availability in soils as a function of root length density is quantified, for various degrees of soil-root contact and for various root distribution patterns. Aeration requirements of root systems are described for simultaneous oxygen transport outside and inside the root.

Experiments with tomato and cucumber are discussed, which were aimed at determining the minimum root surface area required in an optimal root environment. Experiments on P-uptake by grasses on various soils were performed to test model calculations. Model calculations on the nitrogen balance of a maize crop in the humid tropics suggested practical measures to increase the nitrogen use efficiency.