Optimization of the composting process from rice straw for agricultural and environmental sustainability

Abstract

The open burning of rice straw is a major source of air pollution and smog in South Asia. While composting offers a sustainable alternative, previous efforts have often failed due to suboptimal conditions and a lack of validation for local use. This study optimized the co-composting process for rice straw using locally available organic sources, i.e., cow dung, and grass clippings in a pit system under natural climatic conditions in Pakistan. We systematically tested nine mixing ratios of chopped rice straw with cow dung and grass clippings, separately and in combination (1:1), in a pit composting system. At maturity (20 weeks period), the quality of produced compost was assessed by studying the physicochemical properties of the produced composts and a phytotoxicity bioassay using okra seeds. Results demonstrated that a 5:5 vol/vol ratio of rice straw to cow dung combination produced statistically significant improvements (p ≤ 0.05) in compost quality. The mature compost was characterized by an ideal C/N ratio (1:27), balanced nutrient content (N: 0.64%, P: 0.31 mg/kg, and K: 0.21%), and significantly reduced phytotoxicity, as confirmed by enhanced growth of okra seedlings. This study provides a validated, farmer-friendly protocol that not only mitigates the harmful practice of burning rice residues but also converts waste into a valuable organic fertilizer, offering a practical solution to farmers to improve soil health and reduce environmental degradation.