Effect Of Combined Application Of Different Organic Manures And Chemical Fertilizer On Crop Nutrient Uptake And Farmland Carbon Storage In Karst Area

Effects of combined application of different organic manures and chemical fertilizes on crop yield and nutrient uptake, soil carbon pool and soil carbon storage were investigated using the field and pot experiments, so as to obtain an utilization mode of organic fertilizer resource in favor of farmland carbon sequestration in Karst area. Maize straw, cow manure, filter mud and sugarcane straw ash were chosen to combine with chemical fertilizers by three ratios,(1)70%inorganic fertilizer+30%organic manure,(2)60%inorganic fertilizer+40%organic manure and (3)50%inorganic fertilizer+50%organic manure, and no fertilization and chemical fertilizer treatments as control. A field experiment with no fertilization control, chemical fertilizer,50%straw+50%chemical fertilizer,50%cow manure+50%chemical fertilizer,50%filter mud+50%chemical fertilizer,50%sugar cane ash+50%chemical fertilizer was conducted from2012to2013. The main results are summarized as follows:Compared with single chemical fertilizer, combined application of organic manure and chemical fertilizer improve crop dry mass and nutrient uptake and soil organic carbon (SOC) content to some extent. Application of organic manure and chemical fertilizer with appropriate ratio had higher yield than the single chemical fertilizer. Among the organic manure, cow dung had the highest yield.Compared to no fertilization treatment, applying chemical fertilizer had no significant effect on soil SOC. Continuous application of organic manure was beneficial for the improvement of soil SOC when compared to continuous application of chemical fertilizer. In the same organic manure, soil SOC increased with the increasing ratio of organic manure, when the ratio of organic manure to chemical fertilizer exceeded a certain threshold, soil SOC had no significant changes. Soil active organic carbon and carbon management index increased with the increasing ratio of straw, increased firstly and decresed later with the increasing ratio of cow dung and filter mud, but decreased with the increasing ratio of sugar cane ash.Compared with single chemical fertilizer, combined application of organic manure and chemical fertilizer could increase farmland carbon stroage, but varied in different cultivation seasons. In season1, farmland carbon storage was ordered as sugarcane ash>cow dung> filter mud> straw> chemical fertilizer, and60%chemical fertilizer+40%sugar cane ash (GZ2) and50%chemical fertilizer+50%sugar cane ash (GZ3) had the greatest increase in farmland carbon stroage, significantly higher than the other treatments. In season2, farmland carbon storage was ordered as straw> cow dung>sugarcane ash>filter mud>chemical fertilizer, with60%chemical fertilizer+fertilizer+straw (JG2) and50%40%and50%straw (JG3) had the greatest increase in farmland carbon stroage, significantly higher than the other treatments.In conclusion, the combined application of60%chemical fertilizer and40%cow manure or50%chemical fertilizer and50%cow manure was the best treatment in improving crop yield, nutrient uptake and soil carbon storage. Addition of straw and sugar cane straw ash increased soil organic carbon, and the higher the ratio was, the higher the content of soil organic carbon and farmland carbon sequestration were.