Differential phosphorus responses of leguminous cover crops on soils with variable history

Abstract

The response of 8 leguminous cover crops to phosphorus (P) application (7.5 mg P₂O₅ kg^‐1 soil or 15 kg P₂O₅ ha^‐1 to the depth of 15 cm) on soils with variable history was evaluated in a pot trial supplemented with a field experiment in 1993. The soil from a livestock farmer's field showed higher total organic carbon content and extractable cations compared to that from a non‐livestock farmer's field. In the pot trial, P application, on average, increased shoot, root, nodule dry matter and nitrogen (N) accumulation of the legumes by 82%, 45%, 871%, and 900%, respectively, compared to the control. Cajanus cajan, Crotalaria ochroleuca, Centrosema pascuorum, and white‐seeded Mucuna pruriens showed a higher P response than Centrosenza brasilianum and Chamaecrista rotundifolia. The legumes grown on the manured soil showed not only higher biomass and N accumulation, but also higher increase (110% and 117%) in total dry matter and N accumulation because of P application than those grown on the un‐manured soil (27% and 45%). In the field experiment, spreading legume groundcover at 16 weeks after planting was increased by 40% in the un‐manured soil and by 31% in the manured soil. Centrosema brasilimmm even showed a negative response of groundcover to P application. There was little response in erect legume height to P, except for measurements at 6 and 8 weeks after planting, when P increased plant height for Crotaktria on un‐manured soil. Results imply high returns can be expected when P is applied to leguminous cover crops in fairly fertile soil. The relatively low response under the field conditions, compared to pot, suggests caution is needed when P is recommended for legumes grown under environmentally stressed conditions.

Notes

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