Effects of Long-term Straw Returning to Field on Soil Organic Car-bon and Structural Characteristics of Humic Acid
In response to the aging of organic matter in black soil and the urgent need for fertiliza-tion and problem solving of straw burning,the changes of soil organic carbon(SOC),humus compo-nent content and humic acid(HA)structure characteristics were studied by means of long-term,small amount,and continuous straw returning experiments.The results showed that compared with ck,the organic carbon content increased by 18.9％,20.0％and 13.1％,14.7％,respectively,under the treatments of straw returning combined with chemical fertilizer and straw returning in surface and subsurface soil;Carbon content of HA increased by 17.5％,57.4％and 10.7％,28.1％,respectively;Carbon content of humin(Hu)increased by 23.1％,23.0％and 20.7％,16.2％,respectively.The in-crease of HA carbon in subsurface soil treated with straw returning and chemical fertilizer accounted for 75.3％of the increase in SOC.The proportion of HA in extractable humus(PQ)increased from 58.2％to 63.6％.Compared with ck,the structural characteristics of HA treated with straw combined with chemical fertilizer were significantly changed,and the ratio of surface layer and subsurface layer(O+S)/C was reduced by 15.8％and 17.7％,respectively.The H/C ratio increased by 4.8％and 5.3％,respectively.I2920/I1720 increased by 110.5％and 131.2％,respectively.The high/medium calo-rific ratio decreased by 35.3％and 28.9％,respectively.The high/medium weight loss decreased by 14.1％and 12.0％,respectively.The combination of straw and fertilizer treatment reduces oxidation degree,condensation degree,and thermal stability of HA structure,enhances its lipophilicity,and simplifies the structure.
straw returning to fieldsoilorganic carbonhumic acid structurehumus component
万方数据
维普
