Effects of long-term organic manure application on the distribution and organic carbon content of soil aggregates in wheat field of northwest semi-arid region
The long-term positioning test of loessal soil area in National Soil Quality and Stability Observation Station in Anding District of Gansu Province was taken as the research object,the effects of long-term fertilization on soil aggregate distribution and organic carbon content in wheat field in semi-arid region were studied.The results showed that the proportion of soil aggregates showed the trend of decreasing first and then increasing,and organic carbon content of soil aggregates showed the trend of increasing with decreasing of aggregates particle size in the soil depth of 0～20 cm.Compared with mineral fertilizers(NPK)treatment,long-term mineral fertilizers combined with organic fertilizer(NPKM)and organic fertilizer(OM)all increased significantly content of aggregates over 0.25 mm and the mean weight diameters of soil aggregates,and improved significantly contribution rate of large aggregates(>1 mm)on organic carbon.The organic carbon contents of soil aggregates and soil organic carbon storage of aggregate were decreased with soil depth,and soil organic carbon in the aggregate sizes over 1 mm was sensitive to the change of soil organic carbon under long-term application of organic fertilizer.Compared with NPK,NPKM and OM treatments increased significantly organic carbon contents and reserves of soil aggregates in the soil depth of 0～20 cm,and organic carbon storage of aggregates were increased by 34.1%and 25.2%in the soil depth of 0～10 cm,and by 26.89%and 17.95%in the soil depth of 10～20 cm,respectively.However,long-term application of NPK fertilizer had no obvious effect on the contents and reserves of organic carbon of soil aggregates.In conclusion,under the condition of loessal soil of the semi-arid Loess Hilly Region of Northwest China,long-term application of organic fertilizer(NPKM and OM)could increase significantly content of aggregates over 0.25 mm and its stability,and increase organic carbon stock of soil aggregates,and the effect of increasing carbon and fertilizing soil were remarkable,but the effect of single application of chemical fertilizer was not obvious,so it is necessary to strengthen the application of chemical fertilizer combined with organic fertilizer to achieve soil fertility.
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