Similar phosphorus transfer from cover crop residues and water-soluble mineral fertilizer to soils and a subsequent crop

Abstract

Cover crops provide benefits in agricultural systems with high P availability (i.e., optimal or excessive soil P for plant growth) by reducing losses of soil phosphorus (P) via erosion and leaching, and potentially by increasing soil P availability when P is released during residue decomposition. We quantified P transfer from cover crop residues to soil pools and a subsequent wheat crop in a greenhouse experiment. Soils from two field experiments in California (Davis and Salinas) were labeled with carrier-free 33P and amended at a rate of 15 mg P kg−1 soil with cover crop residues (rye, oat, fava bean, vetch, mustard, rye-legumes mixture) or water-soluble mineral fertilizer. We analyzed plants and several soil pools – resin, microbial, and organic – for P and 33P. In both soils, residues and water-soluble mineral fertilizer had a similar effect on soil pools and wheat P uptake, except for higher microbial and organic P with residues in the Davis soil. Residues contributed 35–40 % (Davis) or 20–25 % (Salinas) of the P taken up by wheat, and 13–22 % (Davis) or 8–14 % (Salinas) of residue P was recovered in wheat. Our results demonstrate that P taken up by cover crops can cycle rapidly in agricultural systems with high soil P availability, with direct benefits for soil P availability and few differences among these cover crop species.