Effects of intercropping on field-scale phosphorus acquisition processes in a calcareous soil

Abstract

Calcium uptake by plants and the ratio of calcium to phosphorus (Ca/P) in the uptake have been recently identified as important drivers of P acquisition in neutral to alkaline soils. However, this has rarely been studied under field conditions and no data are available for the effects of intercropping. Durum wheat and faba beans were cultivated, both as sole crops and as intercrops, in a P-deficient, calcareous soil over three consecutive growing seasons. We measured a range of plant, soil, and rhizosphere properties at the flowering stage and grain yield at harvest. Root dry weight, N fixation, rhizosphere acidification, the ratio of Ca/P in the uptake, and available P in the soil were all higher for faba beans intercropped with durum wheat. However, its growth was limited by other factors, probably including water availability. However, durum wheat growth and nutrient acquisition were markedly facilitated by intercropping with faba beans. The facilitation of P acquisition by durum wheat was caused by the acidification of its rhizosphere, the subsequently higher solubility of Ca-P minerals, and the lack of competition by faba beans for P. The results confirm the importance of Ca uptake and the ratio of Ca/P in the uptake for P acquisition by plants in calcareous soils and, more specifically, for a cereal intercropped with faba beans.