Effect of storage methods on properties of corn straw after storage

To understand the effects of different storage conditions on physicochemical properties of crop straw, this paper has studied 3 kinds of straw pretreated methods which specifically are the whole plant, baling and crushing, together with 3 storage methods of pretreated straw i.e. stored in the open air, under the covering condition and under the sealed condition with tarpaulin for a period of 5 months. The results show that average of total moisture content of crushed stalks reaches 19.16%, which is respectively 15.71% and 15.34% higher than whole plant and baling straw. Due to the influence of environmental humidity and their own physical and chemical effects, total moisture contents of straw stored in the open air and under the sealed condition are higher than that stored under the covering condition; for the same pile of straw, total moisture content in each layer has the same change, but there are significant differences between the values. Straw temperature changes with the external environment; all are closely related to moisture content, average daily temperature does not change significantly, and the range is only between 3.24 and 3.71℃. The maximum storage temperatures are 40.8, 35.4 and 44.7℃, respectively, when whole plant stalks are stored in the open air, under the covering and sealed condition; the above data for baling straw are 32.7, 30.3 and 35.8℃, respectively; and crushed stalks are 40.5, 39.3 and 43.7℃, respectively. So, the bale of straw is easy safe storage, and when the whole plant and crushing straw are stored for a long time, it should keep the environment ventilated. The calorific value is negatively correlated with total moisture content, the calorific value based on dry basis is higher than that based on receive basis. When the group is on dry basis, the calorific values of whole plant and baling straw are similar, with the average reaching 14 000 kJ/kg, and the calorific value of crushed straw is lower, around 13 000 kJ/kg. When the group is on receive basis, the calorific value presents downward trend over time, showing more obvious decline in February and a negative correlation with the total moisture change. Taking the whole plant stalks as the example, the calorific value is reduced by 1512, 1608 and 1612 kJ/kg respectively from January to May when straw is stored in open air, under the covering and sealed condition; the average calorific value of sealed storage is the lowest, only 11 547 kJ/kg. On the whole, the total moisture and volatile of crushed straw are higher than whole plant and baling straw, and the ash content is lower than them; the total moisture and volatile of sealed storage are higher than stored in the open air and covered storage, and the ash content is lower than them. Therefore, crushed straw is not conducive to energy use, and bale of straw is easier storage than the whole plant, but its cost is higher; sealed storage is not recommended, and because the parameter indices change inconsistently when straw is stored in the open air and under the covering condition, the latter two methods require further study. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.