Growth, Yield and Protein Content of Cowpea (Vigna unguiculata) Applied with Organic Fertilizers

Aim: This study aimed to explore the effects of organic and inorganic fertilizer combinations on soil properties, growth, yield, and protein content of cowpea (Vigna unguiculata) from November 2024 to February 2025 in Barangay Ipil, Bulanao, Tabuk City, Kalinga.Using a Randomized Complete Block Design with three replications, treatments included vermicompost, cow manure, and Black Soldier Fly (BSF) frass at 3 tons/ha, applied alone or with recommended inorganic fertilizer rates.Results showed no significant differences in plant height, pod number, and pod weight across treatments.However, organic fertilizers at 3 tons/ha yielded comparably to full inorganic rates.The combination of half the recommended inorganic rate with 3 tons/ha BSF frass produced the highest pod yield and the best return on investment (77.15%).This suggests that combining reduced inorganic fertilizer with organic amendments can sustain cowpea productivity while lowering input costs.Methodology: The study was conducted from November 2024 to February 2025 at Barangay Ipil, Bulanao, Tabuk City, Kalinga, using a 459 m field arranged in a Randomized Complete Block Design (RCBD) with seven treatments and three replications.Treatments included the recommended rate of inorganic fertilizer (30-40-45 kg NPK ha), organic fertilizers (vermicompost, cow manure, and Black Soldier Fly frass) applied at 3 tons per hectare, and combinations of organic fertilizers with half the recommended rate of inorganic fertilizer.Cowpea seeds were directly sown at 20 cm 50 cm spacing after applying organic fertilizers ten days before planting, followed by basal and side-dress application of inorganic fertilizers.Standard crop management practices including manual weeding, irrigation, and pest monitoring were employed.Soil samples were collected before and after treatment for analysis of pH, organic matter, cation exchange capacity (CEC), and bulk density at the Cagayan Valley Integrated Agricultural Laboratory (CVIAL).Data gathered included plant height, pod length, number of pods, pod weight, yield per plot, and seed protein content.Cost and return analysis was also computed to determine the economic viability of treatments.All quantitative data were analyzed using ANOVA appropriate for RCBD, with mean differences compared using Tukey's Honestly Significant Difference (HSD) test at 5% significance level.Results: The combination of BSF frass with half the recommended rate of inorganic fertilizer resulted in the highest cowpea yield, performing similarly to the full inorganic rate.Though differences were not statistically significant, this approach shows promise as a cost-effective and sustainable fertilization strategy.Further research is recommended across different soil types, climates, and seasons to validate its long-term impact on yield and soil health.Conclusion: Cowpea plants treated with 3 tons/ha of organic fertilizers showed pod yields comparable to the full inorganic rate.The highest yield and ROI (77.15%) were recorded from the treatment combining half the inorganic rate with BSF frass, suggesting its potential as a sustainable alternative to full inorganic fertilization.