Effect of turning and covering techniques on pig manure-straw composting property

Experiments were carried out to investigate the effect of turning frequency and covering on manure-straw compost properties in natural rotting box frame system. Six treatments were conducted, which had different tuning frequency that are one time per week ,one time every two week and non-turning respectively, and each treatment have cover or non-cover. By taking various kinds of indexes test and statistical analysis, the results indicated that the turning could remarkably promote material volume decreasing (P=0.0001), temperature rising (P=0.0000) and degradation of TOM (P=0.0080), and improve GI remarkably (P=0.0330), but turning also increase the NH3 emissions and then causing the TN(total nitrogen) losses notably (P=0.0190). There was no significant difference between turning of one time per week and one time every two week in material decrement, pH value, EC(electric conductivity), the degradation of TOM(total organic matter) and GI(germination index), but the one time per week could shorten high temperature phase significantly (P=0.0000) and increase NH3 emissions (P=0.0190). The covering could prolong high temperature phase remarkably (P=0.0001), decrease the NH3 emissions and nitrogen losses remarkably (P=0.0130) as one time every two week or non-turning, but it could also slow down the decomposition course. Based on the economic and environmental factors, the conclusion is as follows: non-covering with turning one time every two week is the optimum scheme for pig manure-straw composting. This conclusion could provide references for small and medium-sized enterprises to composting with agricultural wastes.