免耕与翻耕条件下农田土壤呼吸的比较

采用开路式土壤碳通量测量系统于2010年3-10月在冬小麦-大豆轮作期对免耕与翻耕田土壤呼吸速率、5cm深土壤温度和湿度进行测定,以研究耕作措施对农田土壤呼吸的影响。结果表明,在冬小麦、大豆生长时段,免耕与翻耕田土壤呼吸速率的季节变化趋势基本一致。冬小麦生长时段免耕与翻耕田土壤呼吸速率的平均值分别为2.50±0.14和2.40±0.29μmol.m-2.s-1,大豆生长时段分别为2.82±0.28和3.50±0.52μmol.m-2.s-1。冬小麦生长时段免耕与翻耕田土壤呼吸无显著差异,但大豆生长时段二者存在显著差异(P<0.05),差异最明显的阶段在大豆开花期(7月下旬-8月中旬)。利用温度影响函数(指数函数)和湿度影响函数(二次函数)耦合的模拟模型进行土壤呼吸与土壤温度和湿度的回归分析,得出免耕条件下土壤温度和湿度可以共同解释25.3%的土壤呼吸变异(R2=0.253,P<0.05),翻耕条件下二者可以共同解释44.0%的土壤呼吸变异(R2=0.440,P<0.01)。可见,一方面,耕作措施对土壤呼吸的影响因种植作物而异,与翻耕相比,免耕显著降低了大豆田土壤呼吸,但对冬小麦田无显著影响;另一方面,免耕下土壤温度和湿度对土壤呼吸的影响比翻耕要小。

Comparison of Soil Respiration from Farmlands under No-tillage and Tillage Regimes

In order to examine the effects of tillage regime on soil respiration in a farmland, authors measured the soil respiration rates under no-tillage and tillage treatments by using a portable soil CO2 fluxes measurement system in a winter wheat- soybean farmland from March to October in 2010. Soil temperature and moisture at depth of 5cm were also measured during soil respiration measurements. The results indicated that soil respiration rates under the no-tillage and tillage treatments developed with similar seasonal variations during both the winter wheat and soybean growth periods. Mean soil respiration rates for the no-tillage and tillage treatments were 2.50±0. 14 and 2.40 ±0.29μmol·m -2·s-1 during the winter wheat growth season, respectively, while they were 2.82±0. 28 and 3.50 ± 0. 29μmol·m -2·s-1 during the soybean growth season, respectively. Mean soil respiration rates were not significantly different between no-tillage and tillage treatments in the winter wheat growth season, while it was significantly different （P 〈 0. 05） between the two treatments in the soybean growth season. For the soybean growth season, the most obvious significant difference in soil respiration rates could be found during the stages of flowering （ late July to mid-August）. Further investigations indicated that soil respiration could be well simulated by an empirical model in which the effects of both soil temperature and moisture on soil respiration were considered. This model explained 25.3% and 44. 0% variances in soil respiration rate under no-tillage （ R2 = 0. 253, P 〈0. 05 ） and tillage treatments （ R2 = 0. 440, P 〈0. 01 ）,respectively. Based on the results, on the one hand, the effects of plowing regimes on soil respiration were contingent on specific cropping systems. No-tillage, in comparison with tillage, significantly reduced soil respiration in the soybean plots, but had no significant effects on soil respiration in the winter wheat plots. On the other hand, the effects of both soil temperature and moisture on soil respiration under the tillage regime were more obvious than those under the no-tillage regime.