EFFECT OF PHOSPHORUS FERTILIZER RATES AND PRIMING TREATMENTS ON SEED QUALITY OF BAMBARA GROUNDNUT (Vigna subterranea (L.) Verdc.)

Abstract

Bambara groundnut is a protein and energy rich legume crop of African origin with potential to contribute to food and nutrition security. Some studies have evaluated its seed quality but limited explanation exists on the relationship between farmers’ seed management practices and seed quality as well as the effect of phosphorus fertilizer on seed quality. Seed quality enhancement treatments also needs to be investigated in Bambara groundnut. The objectives of this study therefore were; to document seed management practices and evaluate the quality of farmer saved seed from Uganda; to determine the effect of phosphorus fertilizer rates on seed yield and seed quality of Bambara groundnut; and to determine the effect of hydropriming and halopriming with potassium nitrate on seed germination of Bambara groundnut. Four hundred Bambara groundnut farmers were chosen using purposive sampling and information gathered on their seed management practices. A semi structured questionnaire was used in face-to-face interview. Seed colour and size determination, standard germination and electrical conductivity tests were done on seed samples collected from farmers. Field experiment was set at Zonal Agricultural Research and Development Institute, Ngetta in Uganda using RCBD with a 3x4 factorial treatment structure consisting of 3 Bambara groundnut landraces and 4 phosphorus fertilizer rates. Determination of total seed phosphorus content and a standard germination test were done with seeds harvested from this experiment. Landrace that showed poor germination (AbiBam 001, 18.67% at 0 KgPha-1) was selected and stored for 2 months in a deep freezer and subjected to hydropriming and halopriming with potassium nitrate, and a standard germination test done. Results from the survey revealed that farmers obtained seeds mainly from local markets (35.2%), maintained mostly single landraces (52.5%) and recycled their seeds for more than 4 years (39.2%). Seed was sun dried on the ground (81%) and stored mostly in gunny bags on raised platforms (93.5%). Collected Bambara groundnut landraces were identified as Local Bam, AbiBam 001, AbiBam 003, TVSU 688 and TVSU 759. Landraces had varied seed coat colours and significantly differed at p = 0.05 in their seed sizes, final germination percentage (FGP), electrical conductivity, germination velocity index (GVI) and seedling vigour index II (SVI-II). Phosphorus fertilizer rates did not significantly affect seed yield (p = 0.780) and seed phosphorus content (p = 0.831) of landraces but significantly affected FGP (p = 0.001), GVI and SVI-II (p<.001) of landraces. Hydropriming (p = 0.279) and halopriming with potassium nitrate (p = 0.640) did not affect FGP of AbiBam 001 landrace. There exists a wide diversity of Bambara groundnut landraces maintained by farmers in Uganda, some of which have good seed quality, alluded to farmers good seed management practices. Among the landraces evaluated, only AbiBam 001 landrace responded positively to phosphorus application with respect to seed yield and seed quality. Seed priming treatments did not improve germination capacity and vigour in AbiBam 001 landrace. Farmers training by the relevant stakeholders in Uganda will help to further improve the quality of their farm-saved seeds. Further studies should be done on the biochemical and physiological properties of the seed coat of Bambara groundnut. Genetic attributes and phosphorus use efficiency of Bambara groundnut landraces should also be investigated to explain their responses to application of phosphorus.