Response of Field Beans (<i>Phaseolus vulgaris</i> L.) to Unacidulated Phosphorus Source in an Andosols in Kenya

Abstract

The agronomic effectiveness of minjingu rock phosphate (MRP) was compared with that of highly soluble phosphate triple superphosphate (TSP), in pot studies with field bean (P. vulgaris L. ) in a greenhouse at the field station of Faculty of Agriculture, University of Nairobi, Kenya. MRP finely ground with 30 Grade % P and TSP with 99.6 Grade % P fertilizer at rates 0, 30, 45 and 60mg P pot^-1 were applied on 2kg soil pot^-1. The soil used in the study was an acid humic andosol from fields with moribund tea bushes, tea bushes planted in 1958 and 1979 and newly cleared forest in Kagaa, Kenya. Shoot and root dry matter yields, dry seed yield responses and their response estimates were determined and showed positive significance in most cases when TSP fertilizer was applied on the soils except that from moribund tea field. The relative agronomic effectiveness (efficiency) of MRP on biomass and also seed yield of beans was found to be significantly inferior to TSP in most of the soils except that from moribund tea field where both sources were found to be ineffective. This study confirms that inspite of its high reactivity, MRP is still agronomically ineffective as nutrient source of Phosphorous for growing P. vulgaris in acid soils.


Journal of Agriculture, Science and Technology Vol. 2 (1) 1999: 32-45