| Farmland ecosystem is an important carbon source and carbon sink. The increase of carbon dioxide emissions from farmland ecosystem was indirectly caused as a result of the growing field of fertilizer and other inputs of artificial inputs. The crop respiration and the dynamic change of soil carbon pool are playing the important roles in carbon emission in farmland ecosystem. The research was based on a long-term field experiment, 9 treatments were set up with different levels of straw returning(straw mulching, half straw mulching, no straw mulching) and fertilizer level(100% fertilizer, 80% fertilizer and no fertilizer). and location monitoring the variation of soil organic carbon storage, soil respiration and its main influence factors, crop carbon sequestration capacity under the wheat-fallow rotation,wheat-maize rotation, and wheat-beans rotation respectively in Guanzhong area of Shaanxi Province in long term, and to estimate the carbon balance. Also, combined with soil nutrient content, the research selected the suitable scientific and efficient mode of straw mulching and the fertilizing mode in Guanzhong area, also to reveal the dynamic change law of soil carbon pool and its influencing factors under different planting patterns of soil under the condition of long-term location experiment, and providing theoretical and technical support for the construction of agricultural low carbon emission technology system. Main conclusions are as follows:Soil respiration showed obvious seasonal variation. The average soil respiration rate in crop growth period was decreased by straw mulching; however, the average soil respiration rate increased with the increase of fertilization. Throughout the research period, the total amount of soil respiration in different treatments was fluctuated, but the overall trend showed a potential downward trend.Soil respiration is controlled by soil temperature and soil moisture jointly: the average soil respiration rate was positively correlated with the average temperature of 5cm soil depth and the average water content of 10-20 cm soil depth.The statistics of available nutrient storage and the content of available nutrient in 0-40 cm underground are significantly increased by straw mulching and fertilizer after three consecutive years of rotation. In the three rotation mode, for the statistics of availablephosphorus storage and the content of available phosphorus of soil, the straw mulching+100%fertilizer treatment was more than other treatment; for the statistics of available potassium storage and the content of available potassium of soil, the half straw mulching+100%fertilizer treatment was more than other treatment. However, the the statistics of alkali-hydro nitrogen storage and the content of alkali-hydro nitrogen of straw mulching+100% fertilizer treatment was the highest in both wheat-maize rotation and wheat-soybean rotation. Besides,the half straw mulching+100% fertilizer treatment is best in wheat-fallow rotation.The amount of crops carbon sequestration in different crop rotation patterns was different,and the straw mulching incorporation fertilization could significantly increase the total amount of total carbon sequestration. The net carbon emissions of wheat-fallow rotation,wheat-soybean rotation and wheat-maize rotation were 55.46 kg·m-2C, 69.72 kg·m-2C, 84.22kg·m-2C respectively. The net carbon emissions of straw mulching+80% fertilizer treatment was the lowest in wheat-fallow rotation, and the net carbon emissions of straw mulching+100% fertilizer treatment was the lowest in both wheat-maize rotation and wheat-soybean rotation.To comprehensive analysis of soil nutrient status and net carbon emission under three rotation models can be seen: the effect of carbon balance of straw mulching+100% fertilizer is best in three rotation model. |
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