Effects of Compost Application on Growth, Gas Exchange, and Green Yield of Cowpea [ <scp> <i>Vigna unguiculata</i> </scp> (L.) Walp.] Varieties

ABSTRACT Cowpea is an important dual‐purpose legume cultivated for its leaves, fresh pods, and grains, yet productivity in Ethiopia remains low due to poor‐yielding varieties and nutrient‐deficient soils. This study evaluated the effects of compost application on growth, physiological performance, and yield of two cowpea varieties (Bole and Kenkety) under the environmental conditions of Hawassa University, southern Ethiopia, during the main rainy season. Four compost rates (0, 2.5, 5.0, and 7.5 t ha −1 ) were tested in a randomized complete block design with four replications. Compost application significantly ( p &lt; 0.05–0.001) increased plant height, leaf number, leaf area, leaf dry weight, photosynthesistranspiration, pod number, pod diameter, and green pod yield. Varietal effects were significant ( p &lt; 0.05) for plant height, leaf number, leaf dry weight, photosynthesis, transpiration, pod number, and pod diameter. The interaction effect ( p &lt; 0.05) was observed for shoot biomass, primary branch number, leaf fresh weight, and pod length. Maximum plant height (54.51 cm), leaf area (5005.60 cm 2 ), and photosynthesis rate (23.78 μmol m −2 s −1 ) were achieved with 7.5 t ha −1 compost. The combination of the Bole variety with 7.5 t ha −1 compost produced the highest biomass and pod length. These results indicate that applying 7.5 t ha −1 compost to the Bole variety is effective for improving cowpea growth, physiological performance, and yield in the study area. However, as the study was conducted at a single location and season, multi‐location and multi‐year trials are required to validate these findings. The results highlight the potential of compost as an eco‐friendly fertilizer to enhance cowpea productivity and contribute to food security.