| Research the dynamic change on soil organic carbon, soil respiration emission characteristics and its influencing factors under different tillage treatments in drought area saline is the basic of the comprehensive evaluation of soil fertility and soil carbon balance. Hetao irrigation area of Inner Mongolia is one of the largest saline soil area in China with a saline area of 394,000 hm2, accounting for 68.65% of total arable land in this irrigation area, which has a huge development potential. Our previous studies have found that burying straw layer plus plastic mulching under the surface 35 ~ 40 cm has been recommended as an effective practice for reducing soil salinity and enhancing crop productivity. At the same time, the combination of plastic film and straw could regulate the deeper soil environment, which may effect the changes of soil organic carbon and CO2 emissions. However, related research especially based on field experiment research is not well documented, which is not conducive to correctly evaluate the comprehensive effect. Therefore this research proposed to reveal the effects of soil organic carbon and the of soil respiration by different tillage treatment.Based on a four-year field experiment in the Hetao Irrigation District of Inner Mongolia, China, we investigated the combined effects of burying straw layer and plastic mulching on dynamic changes of total soil organic carbon(SOC), microbial biomass carbon(MBC), dissolved organic carbon(DOC), soil respiration, temperature, water, salinity and the relationship among them. The experiment had four treatments: deep plough with no plastic film mulching(CK); deep plough with plastic film mulching(PM); buried maize straw layer at a depth of 40 cm with no mulching(SL); and a buried maize straw layer at a depth of 40 cm plus plastic film mulching(PM+SL). The analysis showed that:1. PM+SL significently influenced SOC distritution at different soil layers.After 3 years, the PM+SL and SL treatments significantly enhanced the allocation of SOC to the 20-40 cm layer than CK and PM, but the SOC value of PM+SL significantly decreased in the topsoil(0-20 cm) the CK and SL treatments showed a constant trend. The similar situation appeared after 4 years.While the SOC content under PM+SL and SL treatments increased by 5.84 and 10.78%(P< 0.01) in the 0-40 cm soil layer but that under PM decreased 6.79%(P< 0.01) while that under CK changed little after 4 years. Although PM+SL had less SOC than SL, it showed the highest contents of MBC and DOC due to the combined effect of plastic mulching and straw layer. Significant positive correlations(P< 0.01) were observed between SOC and MBC and between SOC and DOC. Soil temperature and salinity before sowing and at maturation had significant(P< 0.01) positive correlations with SOC and MBC, but soil water content showed significant(P< 0.01) negative correlations with SOC, MBC and DOC. We concluded that integrating buried straw layer with plastic mulching increases the labile SOC in an arid saline soil.2. PM+SL got a significent effect on soil respiration and its impact factors.Soil respiration of 4 kinds of tillage treatments in 2013 and in 2014 showed a decreasing trend in the sunflower growth period, PM+SL made the highest one in the whole growth period, PM followed, SL’s respiration was similar with the CK one except a lightly higher in the bud stage. At 10:00 and 15:00 of the flowering and mature stage the respiration values made the same performance: PM+SL>PM > SL> CK; 0-40 cm soil temperature of all tillage methods got the same trends, differences appeared only in the harvest period, 0-40 cm soil moisture values of PM+SL were lowest in all treatments, but PM+SL was significantly better than other treatment in controlling salinity and keeping organic matter; Soil respiration rate got a significant positive correlation(P< 0.01) with soil temperature, a negative correlation not significant with soil moisture and salt content, while a positive correlation but not significant with 0-40 cm organic matter content. Fitting equation showed soil respiration in salinity soil was affected by the combined effect of temperature, moisture and salinity.Therefore, PM+SL could make a salinity controlling and temperature keeping effects and enhance root growth and metabolic activity of microorganisms in this region.3. PM+SL got a significent effect on carbon sequestration.PM+SL were significantly higher than other processing in crop yield and net primary productivity, PM+SL and PM had a higher CO2 emissionsdue due to the plastic mulching, thus the net ecosystem productivity under PM+SL is lower than under SL, but PM+SL was also a great significant method for crop production in this region as a carbon sequestration treatment. With increasing crop yield, PM+SL can also advance the effect of farmland carbon absorbing, thus it still got the highest comprehensive benefit. So in this drought and salinization area, PM+SL can be used as a treatment of increasing crop yield and carbon sequestration. |
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