Almeida, D.S. and Menezes-Blackburn, D. and Rocha, K.F. and de Souza, M. and Zhang, H. and Haygarth, P.M. and Rosolem, C.A. (2018) Can tropical grasses grown as cover crops improve soil phosphorus availability? Soil Use and Management, 34 (3). pp. 316-325. ISSN 0266-0032
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Abstract
Tropical grasses grown as cover crops can mobilize phosphorus (P) in soil and have been suggested as a tool to increase soil P cycling and bioavailability. The objective of this study was to evaluate the effect of tropical grasses on soil P dynamics, lability, desorption kinetics and bioavailability to soya bean, specifically to test the hypothesis that introducing grass species in the cropping system may affect soil P availability and soya bean development according to soil P concentration. Three grass species, ruzi grass (Urochloa ruziziensis), palisade grass (Urochloa brizantha) and Guinea grass (Megathyrsus maximus), were grown in soils with contrasting P status. Soya bean was grown after grasses to assess soil P bioavailability. Hedley P fractionation, microbial biomass P, phytase-labile P and the diffusive gradient in thin films were determined, before and after cultivation. It was found that grasses remobilized soil P, reducing the concentration of recalcitrant P forms. The effect of grasses on changing the P desorption kinetics parameters did not directly explain the observed variation on P bioavailability to soya bean. Grasses and microorganisms solubilize recalcitrant organic P (Po) forms and tropical grasses grown as cover crops increased P bioavailability to soya bean mainly due to the supply of P by decomposition of grass residues in low-P soil. However, no clear advantages in soya bean P nutrition were observed when in rotation with these grasses in high-P soil. This study indicates that further advantages in soya bean P nutrition after tropical grasses may be impeded by phytate, which is not readily available to plants. © 2018 British Society of Soil Science