Effects Of Straw Return And Chemical Fertilizer On Soil Espiration In Wheat-rape Multiple Cropping System

For the development of agricultural production and management measures to improve thecontribution of straw on crop yield, while reducing CO₂emissions from traditional productiontechniques. The writer tested the soil respiration rate on the basis of the Shi Yang OasisIrrigation in Gansu Province for three consecutive years of wheat/rape field. The soil respirationrate was determined by the EGM-4soil respiration measurement system under differentfertilizer levels and different ways of crop residue amendment. The writer studied the dynamicchanges of soil respiration rate; and explored the main factors of soil respiration rate at the sametime. The main findings are as follows:1. Between different straw mulching modes, the general trend of the soil respiration rate is:burn to field> crushing returning processing> traditional stubble> high stubble no-tillagetreatment. As opposed to the traditional straw mulching modes, wheat straw burning to fieldand smashed straw treatment increased the rate of soil respiration, especially the wheat strawburning to field performances even more notable. However, the high stubble no-tillagetreatment can reduce soil respiration rate, and the effect is more pronounced in the straw of rapegrowth period. Under different fertilization treatments, and N, P fertilization reduction of15%,the soil respiration rate decreased significantly.2. Throughout the observation period, the soil respiration rate of the spring wheat/rapefield has obvious seasonal variation. The soil respiration rate was highest in late August(0.96～1.26μmol m-2s^-1)，and the lowest values occurred in mid-October(0.08～0.12μmol m-2s^-1).The diurnal variation of soil respiration rate which was consistent with the diurnal variation oftopsoil temperature showed a single peak curve. The maximum value appeared between12:00and14:00, and the lowest value emerged at4:00or so.3. That the crushing to field and the burning of the field treatment has obvious effect ofheat insulation on the soil surface （5cm） within two months. The highest moisture content ofaverage value is the high stubble no-tillage treatment, and second is the crushing to field. Themultiple cropping rapes, especially high stubble harvesting straw treatment, help to increase thesoil porosity. Between all the different straw mulching modes, the largest contribution toimprove soil organic matter content is smashed straw processing and the lowest is the burningof straw returning. 4. The soil respiration rate and the temperature of5,10cm soil showed a very significantpositive correlation under different treatments, and appeared exponential change. The lowestcorrelation is burning returning fertilizer no reduced processing, and the correlation coefficientswere0.448and0.366（P <0.01）. The most relevant are the traditional stubble and stubble tillagefertilizer reduction level, the relevant coefficients were0.528and0.511（P <0.01）. The trend ofthe water and the soil respiration rate at various levels in0³0cm soil are basically the same.And they are highly significant positive correlation. The soil respiration rate and the soilporosity are basically negatively correlated under different treatments. The deeper the soillayers, the stronger the correlation between the soil respiration and organic matter content is.And the soil organic matter content of0²0cm showed a significant positive correlation. Thesoil total nitrogen content of0²0cm showed a significant negative correlation.5. The crushing to field and incineration returning treatment not only significant lyincreased the yield of wheat and rape, but also increased the soil respiration. And comparedwith the traditional stubble, the high stubble no-tillage treatment can significantly improve theyield of wheat and rape, as well as significantly reduced CO₂emissions. In addition, thereducing of fertilizer application significantly reduced the yield of wheat and rape; however, itreduced the emissions of CO₂too.