Impact of organic liquid fertilizer on plant growth of Chinese cabbage and soil bacterial communities

Organic liquid fertilizers from livestock manure are increasingly recognized as sustainable amendments influencing soil bacterial communities. Yet, their direct impacts on bacterial composition and crop functionality remain unclear. Addressing this gap, we developed a bio-liquid fertilizer (LBF) by culturing Chlorella fusca in a purified pig manure-based medium. We compared its effects with chemical (CLF) and fermented (FLM) liquid fertilizers on Chinese cabbage (Brassica rapa subsp. pekinensis). We aimed to determine how organic bio-liquid fertilizers enhance crop health and soil bacterial balance, contributing to sustainable agricultural practices. Although LBF did not surpass CLF in promoting growth, it significantly increased antioxidant compounds (polyphenols, flavonoids), sugars, and antioxidant activities, including nitrite-scavenging capacity and reducing power. Soil bacterial communities were strongly correlated with key chemical properties (Na, K, NO3–-N, Ca, pH). Notably, Litorilinea decreased under CLF, and Sphingomonas and Nocardioides declined under FLM, whereas LBF treatment increased all three genera, suggesting improved bacterial conditions. These findings demonstrate that a well-designed organic bio-liquid fertilizer can bridge knowledge gaps by enhancing plant functionality and promoting beneficial soil bacteria. This approach supports more efficient nutrient recycling and may foster greater resilience and sustainability in modern farming systems.