Effect of soil phosphorus availability and residue quality on phosphorus transfer from crop residues to the following wheat

© 2017, Springer International Publishing Switzerland. Background and aims: Legume break crops provide a series of agronomic benefits to the following wheat crop in a rotation. Phosphorus-efficient break-crop plants can mobilise P from non-labile pools in the soil and this could be made available to wheat plants after the decomposition of the break-crop residues. This study aimed to examine the contribution to P uptake by wheat plants, of residues from five different break crops with different maturities and C:P ratios. Methods: Wheat plants were grown in a soil that varied in P status (Olsen P 7 to 30 mg kg−1) and was labelled with 32P and amended with crop residues at a rate of 1% (w/w). Soil and plant samples were taken after 42 days of plant growth. Wheat plants were analysed for growth and P uptake. Soil samples were analysed for P availability and microbial P content. Results: Wheat growth was suppressed with the addition of residues to the soil, with P uptake closely related to shoot growth. The residue-P contribution ranged between 5 and 52% of the P taken up by wheat plants. The amount of P transferred from the residues to the wheat ranged between 6 and 15% of total residue P. Microbial P increased 2-fold in the low- and moderate-P soils with the addition of residues. Conclusions: The transfer of P from break-crop residues to the wheat plant (as % total residue P) is small in the short term regardless of residue quality and soil P status but incorporating residues increased the microbial P uptake in low- and moderate-P soils.