Multivariate Evaluation of Integrated Nutrient Management Effects on Growth and Yield Determinants of Summer Squash (Cucurbita pepo L.) under Sustainable Production Systems in Nepal

Summer squash (Cucurbita pepo L.) is a short-duration, high-value vegetable crop of increasing importance in Nepal; however, its productivity is frequently constrained by imbalanced fertilizer use and declining soil fertility. This study evaluated the effects of organic, inorganic, and integrated nutrient management practices on growth, flowering, and yield of summer squash under subtropical conditions of Nepal. The experiment was conducted during March–June 2024 at the Directorate of Agricultural Research, Tarahara, Sunsari, Nepal, using a Randomized Complete Block Design with eight treatments and three replications. Treatments comprised bio-fertilizer, poultry manure, vermicompost, farmyard manure (FYM), Jeevamrit, recommended NPK (235:176:117 kg ha-1), integrated application of half recommended NPK combined with FYM, and an unfertilized control. Analysis of variance revealed significant treatment effects for all vegetative, flowering, and yield parameters. The integrated application of ½ NPK + FYM produced the most balanced and superior performance, resulting in higher leaf number, greater lateral branching, earlier flowering, increased fruit size, higher fruit number, and maximum fruit yield (46.07 t ha-1), closely followed by sole NPK application. The control consistently recorded the lowest growth and yield. Regression and multivariate analyses (PCA and clustering) indicated that yield improvement was primarily driven by fruit number, individual fruit weight, and vegetative vigor, while delayed flowering was negatively associated with productivity. Overall, the findings demonstrate that integrated nutrient management, particularly the combined use of half recommended NPK with FYM, enhances growth–yield relationships and offers a productive and sustainable nutrient strategy for summer squash cultivation under similar agro-climatic conditions.