Effect of inorganic and organic fertilizers on productivity of groundnut (Arachis hypogaea L.) varieties in East Hararghe, Eastern Ethiopia

Groundnut (Arachis hypogaea L.) is a high economic value oil crop commonly grown in low-land semi-arid areas of Ethiopia. The crop production is constrained by low soil fertility; however, the nutrient management practice has been given low attention. This study was therefore conducted during the main cropping season of 2015/2016 ​at Babile and Fedis sites of East Hararghe, Ethiopia to evaluate the growth, nodulation, and yield response of groundnut varieties to the application of combined mineral nitrogen, phosphorus, and vermicompost fertilizers, and zinc. Treatments consisted of a factorial combination of three varieties (Ba-ha-Gudo, Ba-ha-Jidu, and Roba); three fertilizers combinations (0: 0 ​kg ​N: P₂O₅ ha⁻¹ with no VC, 46: 46 ​kg ​N: P₂O₅ ha⁻¹ with no VC, and 46: 46 ​kg ​N: P₂O₅ ha⁻¹ with 2.5 ​t VC ha⁻¹); and three rates of Zn (0, 5, and 10 ​kg Zn ha⁻¹) in a randomized complete block design at both sites. The growth, nodulation, yield components, and yield data were subjected to analysis by SAS. The result revealed that plant height was significantly affected by variety and fertilizers combination, the number of branches plant⁻¹ affected by the interaction of variety and fertilizers combination while canopy spread and nodulation parameters were affected by the interaction of variety, fertilizers combination, and Zn rate. Pod plant⁻¹ and hundred seed weight, dry biomass, pod and seed yields, and seed oil content were significantly affected by the interaction of variety, fertilizers combination, and Zn rate. The highest dry biomass (7.26 ​t ​ha⁻¹), pod (3.13 ​t ​ha⁻¹), seed (2.16 ​t ​ha⁻¹) yields and seed oil content (51.3%), net benefit ($1704.2 ​ha^-1) with a marginal rate of return of 242% were obtained from variety Ba-ha Gudo received the combined application of 46: 46 ​kg ​N: P₂O₅ ha⁻¹ and 2.5 ​t VC ha⁻¹ with 5 ​kg Zn ha⁻¹. Therefore, it can be concluded that the Ba-ha Gudo variety is preferably produced using the combined application of 46: 46 ​kg ​N: P₂O₅ ha⁻¹ and 2.5 ​t VC ha⁻¹ with 5 ​kg Zn ha⁻¹ for high productivity in the study sites and similar agro-ecologies.