Evaluating Heap Composting as a Low-Input Alternative to Aerobic Turning for Manure Stabilization

Livestock and poultry manure is an important recyclable nutrient resource in Chinese agriculture, and heap composting, a low-input static method, is the most common treatment approach on farms. However, most studies have focused on aerobic composting, whereas systematic evaluations of physicochemical evolution and maturity/quality development during heap composting remain limited, hampering reliable assessment of compost performance and land-application readiness. Here, we compared heap and turned composting of chicken manure amended with rice bran under natural aeration. Five treatments were applied: manure alone (CM), manure with rice bran (CM+RB), covered heap compost (CM+RB+C), single-turned compost (CM+RB+ST), and multi-turned compost (CM+RB+MT), monitored for 66 days. Rice-bran addition rapidly induced the thermophilic phase and substantially enhanced organic decomposition, while turning further prolonged the thermophilic phase. Humic acid content increased in all rice-bran treatments, indicating clear humification, with only slight variation among aeration intensities. Nitrogen transformation also differed: turned piles showed faster nitrification, suggesting enhanced aerobic nitrogen conversion under stronger aeration. Compost maturity improved across treatments, and all rice-bran treatments except CM+RB+C achieved a germination index > 70%. Overall, heap composting largely achieved stability, humification, and maturity close to those of aerobic turning, while markedly reducing labor and energy inputs, supporting its suitability for small-scale manure recycling.