Effects of moisture content of compost on its physical and chemical properties
湿度对堆肥理化性质的影响

Water, an important processing parameter, is essential to the activity of microorganisms in composting. To understand the effect of composting on physical and chemical properties is of great important to optimize composting parameters, improve its efficiency and reduce capital investment and operational costs. The researches of moisture content in composts are summarized to find out the main existed problems and to suggest its development in the future. The Previous studies indicated that it was not in favor of composting when the moisture content was below 45% or above 65%. If the moisture content in composting is too high, the increase of compaction and the reduction of free air space and bad air permeability in compost pile cause insufficient oxygen supply for microorganisms, resulting in less increase in temperature of composting; therefore, decomposition rate of organic matters decrease and the period of composting will be prolonged. If the moisture of composting is too low, the metabolism of microorganisms will be limited which may lead to inhibit the microbial activity and the mature of composts; therefore, both of the efficiency of composting and the quality of composts are reduced. The existence of spatial variation of moisture content in compost pile, due to aeration, heat dissipation and water evaporation, can also result in the decrease in the composting efficiency and the quality of compost. In addition, retention capability of fertilizer is influenced by the compost moisture, too. It is concluded that the optimal moisture content for composting usually ranges from 50% to 60%.