Interaction between phosphate and calcium in nutrient uptake by plant roots

Abstract

Abstract Interaction between uptake of calcium and phosphate has been found. A reduction in growth rate and nutrient uptake rates caused by mixing ground barley straw into a soil could be restored by three different treatments: 1. by adding phosphate fertilizers2. by adding gypsum solution, or3. by simply not incorporating straw into the soil. The application of gypsum solution without the incorporation of straw or phosphate fertilizers had a negative effect. A model describing the interation between these two nutrients on the basis of root respiration, ion affinities and the precipitation of calciumphosphates in the immediate proximity of the roots is proposed. During root respiration hydrogencarbonate ions tend to keep calcium ions away from the root growing points. Uptake and translocation of phosphate from the soil to the growing points secures the uptake and supply of calcium. Accumulation of calcium ions at root surfaces may precipitate phosphates and thereby hinder uptake of not only phosphate but also of calcium for a short time. The consequences of this sequence may be very pronounced because calcium is not retranslocated in plants.