INFLUENCE OF INORGANIC AND ORGANIC FERTILIZERS ON GROWTH, YIELD, AND SEED QUALITY OF FOUR GROUNDNUT (Arachis hypogaea L.) VARIETIES
Groundnut (Arachis hypogaea L.) is a vital oilseed and protein crop in sub-Saharan Africa. As a legume, groundnut can fix atmospheric nitrogen into its root nodules. However, fertilizer application is still necessary when other essential nutrients needed for improving the quality and productivity of the seeds are limited in the soil. This study therefore investigated the effects of organic (Super GRO at 200 ml/ha) and inorganic fertilizers (NPK 15:15:15 at 200 kg/ha, single superphosphate (SSP) at 60 kg/ha) on the growth, yield, and seed quality of four groundnut varieties (SAMNUT 23, SAMNUT 24, SAMNUT 25, and SAMNUT 28). Data collected were subjected to two-way analysis of variance to test significant differences among the varieties and fertilizer treatments at p<0.05. The inorganic fertilizers (NPK and SSP) had a marked influence on both pod and seed yield when compared to the organic fertiliser (Super GRO), where the latter promoted higher vegetative growth. Varietal differences indicated that pod and seed yield were significantly highest in SAMNUT 24 and lowest in SAMNUT 23. Regardless of variety and fertiliser, the percentage moisture, ash, fibre, protein, fat, and carbohydrate ranged from 9.60-9.91%, 1.22-1.19%, 2.20-2.10%, 18.63-19.47%, 39.67-40.58%, and 27.20-28.38%, respectively. SAMNUT 24 had the highest protein content in its seeds, while SAMNUTS 28 and 23 had the highest fat and energy values when they were compared to other varieties. The organic Super Gro promoted higher carbohydrate accumulation with limited protein, fat, and fibre and energy values when compared to inorganic fertilisers. The foregoing results indicated that SAMNUT 24 and SAMNUT 25 responded positively to fertiliser application, most importantly, the inorganic fertilisers. The cultivation of these varieties under inorganic fertilisers should be encouraged where there is low soil fertility.