The growth and activity of winter wheat roots in the field: nutrient inflows of high-yielding crops

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Abstract
Nutrient inflows, that is the amount of nutrient absorbed per unit root length per unit time, have been determined for several winter wheat crops (cv. Hustler) with grain yields in the range 8–11 t/ha (85% D.m.). Inflows reached a maximum in April or May with values in the range 13–34, 0·5–1·6, 3·5–13, 0·9–1·8 and 0·35–0·60 × 10–14 mol/cm root/sec for N, P, K, Ca and Mg respectively. The concentration in the soil solution necessary to maintain inflows by diffusion of nutrient through the soil was calculated using a nutrient uptake model. For an October-sown crop the model predicted that soil solution concentrations of 165 μΜ N, 14 μΜ P and 56 μΜ K were needed to sustain the observed maximum inflows, whereas for a September-sown crop, with a larger root system, even lower values of 106 μΜ N, 8 μΜ P and 36 μΜ K were needed. It appears that nutrient transport is unlikely to limit uptake by winter wheat crops growing in moist, well fertilized soils, at least for crops up to about 17 t/ha of total dry matter.