Seaweed Extract as an Alternative Fertilizer for Yield and Quality Enhancement in Cowpea (Vigna unguiculata L) under Rainfed Low Input Agricultural Systems

Abstract

ABSTRACT A two-year field experiment (2020–2022) was conducted under rainfed conditions to evaluate the effect of foliar application of seaweed liquid extract (SLE) on yield, grain quality, nutrient uptake, nutraceutical content, and antioxidant activity of cowpea (Vigna unguiculata L.). The experiment followed a Randomized Complete Block Design with eight SLE concentrations: 0% (T1), 2% (T2), 5% (T3), 10% (T4), 15% (T5), 25% (T6), 50% (T7), and 100% (T8), each replicated thrice. Results revealed that SLE significantly enhanced grain yield, recording a maximum of 990 kg ha−1 at 25% concentration compared to 545 kg ha−1 in the control. The same treatment also resulted in the highest crude protein, carbohydrate, and ash content, with notable increases in nitrogen (25.03 g kg−1), phosphorus, potassium, and micronutrients such as iron and zinc. Similarly, nutraceutical properties including total phenols (124.3 mg GAE/100 g) and flavonoids (104.7 mg Rutin/100 g) increased, accompanied by higher antioxidant activity as confirmed through DPPH, ABTS, and FRAP assays. Multivariate analyses, including PCA and composite desirability index, consistently identified 25% SLE as the optimum level, while 100% concentration showed inhibitory effects. Overall, foliar application of SLE at 25% significantly improved yield and grain quality, supporting its use in sustainable, low-input cowpea production systems.