黄淮海地区农田土壤有机质平衡的研究

研究得出，本地区农田土壤有机质年矿化率多在2-5%，各种还田有机物的腐殖化系数约为0.2-0.4。连续4年测定，玉米秸还田形成的新腐殖质的分解速率（r）为0.2458，减半期为2.8年。采用腐殖化系数0.3及新形成腐殖质的分解速率0.2458作为代表值，计算了每年定量加入超过维持原有土壤有机质含量水平所需要的有机质情况下的腐殖质积累速度。据此估测出,本地区土壤有机质含量0.7-0.9%左右的低产田，适当增施化肥使粮食年亩产达到500公斤以上，每年以其秸秆产量的一半（约350公斤）以上还田，5-6年后土壤有机质含量便可增长到1%以上，从而可以基本满足作物稳产高产对土壤有机质状况的要求。

A STUDY ON THE ORGANIC MATTER BALANCE IN THE SOIL OF FARMLANDS IN THE HUANG-HUAI-HAI PLAIN

Yearly mineralization rates of soil organic matter, humification coefficients of various organic substances incorporated into the soil, and the decomposition rate of humus formed from corn stalks were studied in the Huang-Huai-Hai Plain. Using 0.3 and 0.2458 as the representative values of humification coefficient of incorporated substances and decomposition rate (r) of the humus formed from them, respectively, the accumulation rates of humus originated from the organic substances incorporated into a field soil in an amount exceeding the requirement for maintaining the original soil organic matter content were estimated. It can be predicted that in condition of 7500 kg/ha yearly grain yields obtained by proper application of chemical fertilizers and yearly incorporation of half of the crop residues of aerial parts into the soil, the soil organic matter contents of farmlands with low yields and low soil organic matter contents (0.7-0.9%) in the Huang-Huai-Hai Plain may increase to>1% after 5-6 years. Such a level of soil organic matter contents is generally considered to be enough for meeting the requirement to obtain high and stable crop yields on farmlands in this region.