Mineralization of N, P, K, Ca and Mg from Sesbania and leucaena leaves varying in chemical composition
Lupwayi, N.Z. | Haque, I.
The N, P, K, Ca and Mg release patterns of the leaves of four accessions of Sesbania species and two accessions of Leucaena species were evaluated in a 5-week laboratory incubation. Leaves of these leguminous trees, applied at an equivalent rate of 3 t dm ha-1, were significant sources of N, K and Mg, but insignificant sources of P and Ca relative to the soil (control). Nitrogen in sesbania leaves was mineralized more rapidly than that in leucaena leaves; one sesbania accession released as much N as that released from urea fertilizer applied at an equivalent rate of 60 kg N ha-1. Mineralizable N ranged from 15 to 53% of leaf N and it was negatively correlated with hemicellulose content and hemicellulose-to-N ratio. The results indicate that additional N and P may be required if these leaves are used as sources of nutrients for crops. In acid soils low in Ca, additional Ca may also be required.
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