Effects of replacing chemical fertilizers with equal amounts of organic nitrogen fertilizer on mineralization charcteristics of organic carbon in paddy soil under rice-wheat rotation
A combination of field experiments and indoor culture experiments was conducted to study the effects of re-placing chemical nitrogen fertilizer with equal amounts of organic fertilizer on the occurrence and transformation of soil or-ganic carbon and the activity of functional enzymes under rice-wheat rotation.The results showed that:After three con-secutive years of replacing chemical nitrogen fertilizer with equal amounts of organic fertilizer,the soil organic carbon con-tent increased by 2.0％-17.5％,and the total nitrogen content increased by 1.4％-30.5％.Substitution of 10％was most beneficial for increasing the content of organic carbon and total nitrogen in soil aggregates with＞2.00 and＜0.053 mm,while substitution of 40％was most beneficial for increasing the content of organic carbon and total nitrogen in soil aggregates with 0.25-2.00 mm and 0.053-0.25 mm.The mineralization rate of soil organic carbon in each treatment of replacing chemical nitrogen fertilizer with equal nitrogen content of organic fertilizer was generally higher than that in the treatment of only applying chemical nitrogen fertilizer.Replacing 30％-40％was most conducive to improving the accumulated mineralization amount of soil organic carbon,and replacing 30％was most conducive to improving the mineralization rate of soil organic carbon.Replacing chemical nitrogen fertilizers with organic and other nitrogen fertilizers led to de-creased activity of soil exo-β-1,4-glucanase/cellulosidase(S-C1 enzyme).Replacing 20％was most beneficial for impro-ving soil sucrase and β-Glucosidase activity,and replacing 50％was most beneficial for improving soil acid phosphatase activity.In summary,replacing chemical nitrogen fertilizer with organic fertilizer significantly increased the carbon and ni-trogen content of soil aggregates of 0.25-2.00 and＞2.00 mm based on the amount of nitrogen.There was a significant positive correlation observed between soil organic carbon content and soil total nitrogen content,as well as between β-Glu-cosidase and soil sucrase activities.Substitution of 20％was beneficial for soil organic carbon mineralization,and substi-tution of 40％was beneficial for soil carbon fixation.
rice-wheat rotationreplace the same amount of nitrogensoil aggregatesorganic carboncarbon mineral-izationfunctional enzymes
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