INFLUENCE OF SEED ASPECTS AND PHOSPHORUS FERTILIZATION ON SEED QUALITY OF VELVET BEAN (MUCUNA PRURIENS L.) IN WESTERN KENYA

Abstract

Velvet bean (Mucuna pruriens) is known as a high yielding leguminous crop which is used as vegetable and fodder. However, seed morphological variability and seed coat dormancy has been reported, to affect seed germination and field emergence. Some studies have been conducted to explore the effect of phosphorus (P) on seed yields, but none have examined the effect of P on velvet bean seed quality. This study therefore assessed morphological characteristics of velvet bean seed, suitable methods of breaking seed dormancy, and the effect of phosphorus fertilization on germination potential of velvet bean seed. A total of 56 farmers were interviewed to document the agronomic practices used by farmers in the production of velvet bean. Data collection was done using a semi structured questionnaire. Four types of velvet bean seeds were collected from farmers during the survey in Bungoma County, Kenya. Morphological characteristics (seed coat color, hilum color, seed length, width and thickness) and seed quality (electrical conductivity (EC), germination test and imbibition rates) were determined for the 4 seed types. Field experiments (using RCBD with three replications) were established at Mabanga Agricultural and Training Center (ATC)and at the University of Eldoret (UoE) to evaluate the effect of four phosphorus rates (F0= 0Kg P/ha; F1= 15Kg P/ha; F2=30Kg P/ha; F3=45Kg P/ha) on seed quality of 4 types of velvet bean seed. The beans were harvested at five different stages. Germination percentage, percentage of normal and abnormal seedlings, fresh and dried seed weight and speed of germination index were then determined. Seeds harvested from the control experiment (F0= 0Kg/P/ha) at 70 DAF were treated with 6 different dormancy breaking treatments. Most farmers (65%) did not intercrop velvet bean with other crops. However, 30% of the farmers intercropped velvet bean with maize, 2% intercropped with groundnut and rotated with common bean. Seed quality assurance activities carried out in the field by farmers were weeding (98%), removing of diseased plants (25%) and planting plants to be for seed production separately (23%). There were significant differences (P≤ 0.05) among the four seed types in all seed traits measured except seed coat thickness. White seed type recorded a lower electrical conductivity (more vigorous), higher final germination percentage, speed of germination index and imbibition rate at 30°C than other seed types. Physiological maturity was reached at 14 DAF or 28 DAF depending on seed type and locality. Seed type collected at Mabanga (ATC) was dormant unlike seeds collected at the University of Eldoret (UoE). Phosphorus fertilizer affected FGP (Final Germination Percentage) and SGI (Speed of Germination index) (P.001). At Mabanga ATC P0, P1 and P3 were given good values of FGP and SGI while at UoE P0, P1 and P2, depending on seed types. The most effective dormancy breaking treatment varied with locality and seed type. Velvet bean production can reduce fertilizer use in small scale farmers growing maize, harvesting should be done at harvest maturity and mechanical scarification can be used by farmers to break dormancy.