Effects of short-term application of organic manure on the growth of forage maize (Zea mays L. cv. Kwangpyeongok) and soil bacterial communities

While chemical fertilizers (CF) ensure rapid crop growth, relying exclusively on them can disrupt natural nutrient cycling and lead to environmental concerns such as nutrient imbalance. In contrast, organic amendments offer a sustainable alternative by promoting resource circulation; however, their efficacy is often variable and difficult to control, depending on complex interactions among application rates, plant types, and field conditions. Therefore, gaining comprehensive insights into their optimal use is essential to maximize agricultural benefits. This study evaluated the effects of composted Hanwoo manure (HM) applied at standard (HM_1x) and quadruple (HM_4x) rates on forage maize growth and soil microbial communities compared with CF and no treatment (NT). Growth parameters indicated that plant length was highest in the CF (219.33 cm) and HM_4 × (217.30 cm) groups, followed by HM_1 × (176.78 cm) and NT (172.02 cm). Soil analysis indicated that organic matter (OM) and available phosphorus (P₂O₅) were significantly higher in HM-treated soils than in NT. Microbiological analysis revealed distinct shifts in community composition linked to these chemical changes. In HM-treated soils, the relative abundance of Proteobacteria and Candidatus Saccharibacteria, known for their roles in OM decomposition and nutrient cycling, significantly increased. Conversely, the CF group showed a higher prevalence of Saprospiraceae, a phosphorus-removing bacterium, which is consistent with the observed reduction in available phosphorus in both soil and plant tissues in the CF treatment. Collectively, this study demonstrates that applying sufficient amounts of composted HM, where appropriate, can result in crop growth comparable to that of CF. Notably, we observed that such growth performance coincided with specific patterns in soil microbial communities related to nutrient availability. By highlighting these co-occurring trends, our research offers valuable insights into the biological dynamics of compost application for sustainable agriculture.