Physical and Chemical Properties Evaluation of Liquid Organic Fertilizers (LOFs) and Their Effects on Promoting Rice Growth

With growing importance in sustainable agriculture and environmental protection, the use of liquid organic fertilizers (LOFs) as a replacement for or supplement to chemical fertilizers has grown in popularity. The effectiveness of LOFs depends on the content of elemental nutrients as well as plant growth regulators. Three types of materials, i.e., brassica vegetables, mushrooms, and soybeans, were fermented for 60 days to produce LOFs. The soybean-based fertilizer (SOF) contained the highest concentrations of mineral nutrients (0.99% N, 0.11% P), organic carbon (6.75%), and IAA (24 µg/mL), followed by the mushroom-based fertilizer (MOF) and brassica-based fertilizer (BOF). During fermentation, polyamines (PAs) in LOFs dramatically increased with time, with MOF and SOF containing higher concentrations of PAs than BOF. Greenhouse-grown rice ( Oryza sativa L.) plants at 21 d old were sprayed with diluted (1:75) solutions of LOFs or chemical fertilizers (CF) before being treated for 7 and 14 days with 100 mM NaCl. For both non-stress and salt-stress groups, the root and shoot dry weights, chlorophyll contents, net photosynthesis rates, and endogenous PAs of the LOF- and CF-treated plants were significantly higher than those of the plants receiving no fertilizers. The SOF was the most effective and enhanced growth and photosynthesis at a similar level as the chemical fertilizer and had good potential to be employed as an eco-friendly substitute for chemical fertilizer.