Effects Of Tillage Measures And Conversion On The Emission Of Soil CH₄, N₂O And Carbon Sequestration Capability In Wheat-maize Farmland

A field experiment was carried out at experimental plot of Shandong Agriculture University in 2007²009 to study the effects of tillage measures and conversion on the seasonal and diurnal variation emission of soil CH₄&N₂O in wheat-maize farmland was using the Static-Chamber&the Gas Chromatography(GC) method and systematically analyzed its GWPs. Comprehensive evaluation five tillage measures using the Multi-index comprehensive evaluation method combined with soil carbon sequestration potential and crop yield. The objective is to carry out better with greenhouse gas reduction exhaust potential and soil carbon sequestration potential on basis of better yield. Provide data supportion to estimation of greenhouse gas emission and soil carbon sequestration amount. At the same time, provide theoretical basis to making reasonable tillage measure accord with agricultural sustainable development in this area. The main result was as follows:1 Effects of tillage measures and conversion on the emission of soil CH₄&N₂O in wheat-maize farmlandCH₄&N₂O flux had obvious seasonal and diurnal variation under different tillage measures. All treatments were the sink of CH₄ absorption and emission source of N₂O in different growth periods, CH₄&N₂O flux present seasonal variation trend of lower in winter and higher in summer. By correlation analysis showed that, there was positive correlation between CH₄ uptake flux and soil temperature of 5cm depth, and negative correlation with soil water content of 0²0cm depth; in the same time, there was positive correlation between N₂O emission flux and soil water content of 0²0cm and ammonium N of 0¹0cm depth. Comparison of CH₄&N₂O flux among different treatments indicated that CH₄ uptake flux under PR≈PH>PC>PS>PZ and N₂O emission flux under PZ>PH>PS≈PR>PC. PR has the highest of CH₄ uptake flux and the lowest of N₂O emission flux. PH, PR and PZ was subsoil tillage after basing on original tillage measure manifested as its will increase CH₄ uptake and N₂O emission flux, this phomenon showed that althought increased to N₂O emission appreciably, but CH₄ uptake flux was improved greatly. GWPs of CH₄&N₂O have an obvious difference under different tillage measures, total GWPs of wheat seasonal was PZ>PH≈PS>PR>PC; total GWPs of maize seasonal was PC≈PR>PZ>PH>PS. Total GWPs of wheat- maize farmland was PZ>PH>PR>PS >PC.2 Effects of different tillage measures and returning straw on soil organic carbon content in wheat fieldThe results showed that, all treatments of straw returning had higher values than treatments with no straw returning, and that of conservation tillage was higher than conversional tillage. The soil organic carbon content in 0-10 cm soil layer of all treatments was higher than that in 10-20cm soil layer except conversional tillage treatments. Multi factor variance analysis showed that tillage measures, straw returning and their interaction significantly affected the organic carbon content in 0-20cm soil layer at various growth stages of wheat. Under the condition of straw returning and according of SOC content variation of two year, we calculated soil carbon sequestration amount in 0²0cm layer that PS>PR>PC>PH>PZ, it showed that PS and PR has good carbon sequestration potential3 Effects of tillage measures and conversion on crop yield in wheat-maize farmlandAll treatments yield of wheat has an obvious difference under different tillage measures with straw returning that PR>PC>PH>PS>PZ. After subsoil tillage measures, all treatments yield of wheat was significantly increased that PZ>PH>PR, it showed that must be subsoil tillage after two or three years with conservation tillage, and with strew returning could promote crop growth and increasing yield.4 Comprehensive evaluations of different tillage measuresComprehensive evaluations five tillage measures using the RSR value mothed of Multi-index comprehensive evaluation methods showed that, PR was a potential measure of greenhouse gas reduction exhause and soil carbon sequestration meanwhile has a basis on better yield, PH and PS took the second place, PC was poor and PZ was the poorest.Combined with the results of a 10-years located experiment of our team shows that it has trend of yield reduction carried to PR with several years, but after subsoil tillage, it will beneficial to breaking plough pans, promote to growth of crop roots, and has abvious effect on yield-increasing and carbon sequestration, therefore, measure of 2+1, 3+1 is a reasonable measures in coordination and unification of crop yield, soil carbon sequestration and greenhouse gas reduction exhaust.