Integrated nutrient management to enhance productivity of haricot bean ( <i>Phaseolus vulgaris</i> ) in southern Ethiopia

Abstract Haricot bean ( Phaseolus vulgaris L.) productivity in Ethiopia is low, mainly because of low soil fertility and inadequate nutrient supply related to the limited availability and high cost of chemical fertilizers for smallholding farmers. Therefore, it is important to develop an integrated nutrient management plan to increase haricot bean productivity while improving soil fertility. In this study, a field experiment was conducted to evaluate the effects of sole and combined applications of Rhizobium inoculum (inoculated (Rh) and non-inoculated (−Rh)), vermicompost (VC) (0, 2.5 and 5 t VC ha −1 ) and inorganic phosphorus (P) (0, 30, and 60 kg P ha −1 ) on biological nitrogen fixation (BNF), haricot bean productivity and soil properties in southern Ethiopia during the 2021 growing season. The treatments were arranged in a randomized complete block design (RCBD) with three replications. The results of the present study revealed that most growth and yield parameters of haricot bean significantly (p &lt; 0.05) improved with the sole and combined application of Rh, VC and P compared with those of the control treatment or plots not supplied with any of these treatments. Most growth and yield parameters of haricot bean significantly improved with increasing VC application rates but not with increasing P rates. The combined application of 30 kg P ha −1 with 5 t VC ha −1 or Rh resulted in a significantly higher grain yield and BNF than did the individual treatments. Most soil chemical properties and soil moisture retention capacity significantly improved with VC application, and the effect of VC on most soil properties increased with increasing VC application rate. Generally, the current results demonstrate the economic and environmental benefits of the integrated application of organic and inorganic fertilizers to the study area to increase the productivity and profitability of haricot bean and boost the fertility of the soil.