Interaction of microbial inoculants and low-chemical fertilizer rates in enhancing the quality of sugarcane mudpress-chicken manure compost

Sugarcane mudpress and chicken manure are agro-industrial wastes that could become environmental pollutants in certain localities but proper handling and treatment could convert them into value-added products. This study explored the use of composting and microbial inoculation to generate organic fertilizers from these so-called wastes. Raw materials of sugarcane mudpress and chicken manure were collected and characterized in terms of microbial load and NPK content. Mixtures of mudpress and manure were heaped and composted in 50 kg lots in a two-factorial experiment with two replications involving different treatments (control, those added with 2-10% (w/w) of complete chemical fertilizer, and/or microbial inoculants at an addition rate of 2% (w/w) of Trichoderma sp. and Azobacter sp.) Composting significantly reduced the population of lactose-fermenting and coliform bacteria in the materials from almost 3 log colony-forming unit (cfu/g) total solids to only about 1 log cfu/g. Composting time and chemical fertilizer addition-microbial inoculation had significant interaction effects on total bacterial population in mudpress-chicken manure mixture significantly lower numbers were attained in most treatments after 30-d composting. Composting time and treatment also had significant interaction effects on nitrogen content of the compost, with the highest N content in those composted for 30 and treated with combined inoculation and low fertilizer levels. Testing in pechay (Brassica napus L.) showed that treatments in compost with the most consistent plant-growth-promoting effects were those with microbial inoculation alone, with microbial inoculation combined with 5% or 10% chemical fertilizer, or with 10% chemical fertilizer alone. These treatments significantly enhanced height, fresh weight and dry weight of the test plants over those of the control.