Antecedent effects of catch crops upon the cycling of phosphorus in agro-ecosystems and scavenging of plant-fixed phosphorus by the soil microbiome

All plants require phosphorus (P) for growth. Modern agriculture depends on regular inputs of phosphate fertilizer, replenishing soil following crop removal. Large proportions of P in soils are strongly bound, effectively unavailable to plants. Catch crops - plant varieties grown to reduce nutrient losses between main crops when there is otherwise no vegetation cover - are successfully used to reduce nitrogen (N) leaching from soils, 'trapping' mineralised N in plant tissue which is released following vegetation decomposition. Much less is known regarding the effectiveness of catch crops in limiting P losses and provisioning P to main crops. Once captured, P in senescent catch crops will be present as nucleic acids or ATP, but with a greater proportion in the form of phytate, a complex storage molecule which once in soil is inaccessible to plants. However, phytate can be assimilated by fungi and bacteria. For these stores to become available to crops, microbial enzymes (various phytases and phosphatases) are required to hydrolyse phytate. An important consideration if catch crops are to be developed to increase P use efficiency is the effect antecedent crops have on supporting and conditioning the phytate-hydrolysing members of the soil microbiome and their mobilisation of P to render it available to main crops. This project will explore such phenomena in relation to plants currently commonly used as catch and cover crops, and consider novel species which may have enhanced capabilities in this respect.

Aims: (i) identify candidate plant species with optimal properties to accumulate P from soils when grown as catch crops; (ii) determine the ability of such species to support soil microbiomes with increased capacities to hydrolyse phytate; (iii) explore the potential for such species to be used as a practical means to improve soil phosphorus management and supply, as novel catch crops in production systems.