Effect Of No-tillage And Straw Addition On Respiration Rate,Nitrification And Denitrification In Farmland Soil

To gain insight into no-tillage and straw incorporation on soil respiration, nitrification and denitrification in farmland, two soybean growing seasons and one winter-wheat growing season field experiments were conducted in2010and2011. Winter-wheat (Triticum aestivum) and soybean (Glycine max), conventional crops in China were selected as the experimental material. The experimental treatments include conventional tillage (T), no-tillage (NT), NT with rice straw covers on the surface (NTS), and T with straw incorporation (TS). The soil respiration rate (Rs) was measured using the LI-8100automated soil CO2flux system, and the gross nitrification (Gn) and denitrification (D) were determined using the BaPS technique. In this study, we determined the total organic carbon, total nitrogen content and nitrate nitrogen content in soils, as well as the soil enzyme activities closed to the soil carbon and nitrogen cycling. Furthermore, this study explored the effects of no-tillage and straw addition on soil carbon and nitrogen cycling. Results indicated that,No-tillage and straw addition did not change the seasonal variation patten of Rs from winter-wheat field. Compared with T, no-tillage and straw addition significantly reduced the Rs, with the range between17.8%and77.1%(p＜0.01). No-tillage and straw addition greatly reduced the temperature sensitivity (Q10) of Rs from winter-wheat field. The Rs in four treatments were positively correlated with the soil temperature, and negatively correlated with the soil moisture content in all treatments except T (p<0.01). No-tillage and straw addition did not change the time variation of Gn and D rates compared with T, while significantly increased the Gn (p<0.01), with the range between224%and766%. In addition to TS, NT and NTS increased the D significantly; the D in NTS was as high as6.21times of that in T. The Gn in all treatments were negatively correlated with the soil temperature, and positively correlated with the soil moisture content (p<0.01). NT and NTS treatments made the D had a significant correlation with soil temperature and soil moisture (p<0.01).The Rs of soybean showed no certain trend in four treatments. Compared with T, NT decreased the Rs only in the later growth period (p<0.05) and TS increased the Rs in the early growth period (p<0.05); while NTS had inconsistent influence on Rs No-tillage and straw addition increased the Q10and improved the correlation between the Rs and soil temperature, as well as the Gn of later growth period (p<0.05). No-tillage and straw addition made the Gn had no significant correlation with soil temperature or moisture content (p>0.05). The D of soybean soil could not be observed with the BaPS system.