Partial Substitution of Chemical Fertilizers with Compost and Natural Biostimulants Enhances Productivity and Seed Quality in Pisum sativum

Partial substitution of chemical NPK fertilizers with compost along with the foliar application of natural biostimulants as humic acid (HA) and licorice root extract (LRE), offers a promising strategy to improve pea (Pisum sativum L.) productivity while enhancing soil features as an effective approach to sustainable crop production. Over two consecutive winter seasons (2023/2024 and 2024/2025), field plots received either 100% NPK or a 25% reduction in NPK supplemented with compost alone or combined with HA and/or LRE. The 75% NPK + compost + HA + LRE treatment increased chlorophyll a and b up to 30%, and green pod yield by 9.06% and 6.44% relative to the full NPK control. Seed mineral NPK content and quality parameters, including total carbohydrates, soluble sugars, and crude fiber, were significantly enhanced, while phytic acid levels declined. Post-harvest soil analyses revealed residual gains in available N, P, K, and organic matter up to 10.83%. A comprehensive correlation study demonstrated strong positive associations among soil nutrient availability, leaf pigment concentrations, vegetative growth, yield components, and seed quality traits (r > 0.85), whereas phytic acid exhibited consistent negative correlations (r ≈ –0.60). These findings support a mechanistic cascade whereby improved soil fertility and natural biostimulant-mediated nutrient uptake boost photosynthetic capacity, drive biomass accumulation, and yield gains, simultaneously seed nutritional value.