Evaluation of seven fermentation methods for enhancing the fertilizer potential of the liquid fraction of cow manure

Although the use of cow manure as a crop fertilizer has received widespread attention, the impact of different fermentation methods (FMs) on the potential of liquid fraction of cow manure as a crop fertilizer has not been thoroughly assessed. To address this gap, we investigated the effects of seven FMs over a 13-week period on the physicochemical characteristics of cow wastewater and evaluated its potential for reuse as a soil fertilizer. Our findings demonstrated that diverse FMs resulted in variations in average root length (ARL) and germination index (GI), whereas all FMs increased the germination percentage to over 80% after five weeks of fermentation. All FMs steadily reduced the levels of NO₃-N and total phosphorus. Furthermore, total nitrogen, NH₄-N, NO₃-N, and total phosphorus were significantly negatively correlated with the germination percentage, ARL, and GI, indicating that the fermented cow wastewater should be appropriately diluted or combined with other fertilizers. These results provide foundational data for assessing the impact of different FMs on cow liquid manure, which helps to select the optimal composting method according to crop-specific nutritional needs in the future.