麦茬免耕对不同麦玉轮作方式土壤有机碳含量的影响

Effects of No Tillage with Wheat Stubble on Soil Organic Carbon in Wheat-Maize Rotation System

为探讨耕作及轮作方式对小麦、玉米田土壤有机碳的影响,设小麦/玉米→小麦/玉米→小麦/玉米(T1)、小麦-冬油菜→玉米→小麦(T2)、小麦→玉米→小麦(T3)三种轮作模式,以及小麦免耕留茬(N)和传统耕作(C)两种耕作方式,研究6种模式下西北荒漠绿洲区小麦(W)、玉米(M)农田土壤呼吸、土壤有机碳及有机碳组分变化。结果表明,2016-2018年度,在小麦、玉米关键生育时期,免耕处理(NT1-W、NT1-M、NT2、NT3)的土壤呼吸速率分别较相应传统耕作处理减少了5.51%~37.08%、1.26%~6.44%、5.37%~68.63%和16.74%~71.92%,0~5cm土层有机碳含量分别增加了-4.23%~12.75%、13.27%~23.92%、6.78%~15.15%和-11.48%~23.74%。在2018年,5~20cm土层的微生物量碳含量表现为NT1-M>NT2>NT3>CT3>CT1-M>NT1-W>CT2>CT1-W;NT1-W、NT1-M、NT2、NT3处理的土壤水溶性有机碳含量分别较相应传统耕作处理降低了22.97%、9.14%、13.57%和6.55%。小麦间作玉米免耕处理提高土壤重组有机碳的效果最优,0~5cm和5~20cm土层的重组有机碳分别较CT2、CT3高出19.87%~34.60%、18.33%~30.38%和16.15%~31.33%、14.63%~33.89%。总之,免耕轮作使土壤呼吸速率、有机碳含量降低,改善了土壤有机碳组分,但不同轮作模式间有差异;本试验条件下,小麦/玉米→小麦/玉米和小麦-冬油菜→玉米更有利于土壤固碳,可以考虑作为重要轮作模式在研究区域进行推广和应用。

In order to explore the effects of tillage and crop rotation on soil organic carbon in wheat and maize fields,three rotation modes were conducted:wheat/maize intercropping→wheat/maize intercropping→wheat/maize intercropping(T1),wheat-winter rape→maize→wheat(T2) and wheat→maize→wheat(T3),with two tillage modes:no tillage(NT) and conventional tillage(CT).The changes of soil respiration,soil organic carbon and organic carbon components were studied in wheat(W)-maize(M) farmland in northwest desert oasis.The results showed that no tillage decreased soil respiration in key growth stage of wheat and maize,soil respiration of NT1-W,NT1-M,NT2 and NT3 was reduced by 5.51%-37.08%,1.26%-6.44%,5.37%-68.63% and 16.74%-71.92%,compared to the corresponding conventional tillage,respectively.NT1-W,NT1-M,NT2 and NT3 increased soil organic carbon by -4.23%-12.75%,13.27%-23.92%,6.78%-15.15% and -11.48%-23.74%,compared to those under the corresponding conventional tillage respectively in topsoil layer 0-5 cm during 2016-2018.With the increment of planting years,soil microbial biomass carbon content was increased by no tillage,ranking as NT1-M > NT2 > NT3 >CT3 >CT1-M > NT1-W > CT2 > CT1-W in 5-20 cm soil layer;water soluble organic carbon of NT1-W,NT1-M,NT2 and NT3 was reduced by 22.97%,9.14%,13.57%,and 6.55% in 2018,respectively.Wheat/maize intercropping with no tillage is considered to be the best to increase heavy fractions of soil organic carbon,which increased by 19.87%-34.60% and 16.15%-31.33% than CT2,18.33%- 30.38% and 14.63%-33.89% than CT3 in 0-5 cm and 5-20 cm soil layer,respectively.In conclusion,no tillage and crop rotation can decrease soil respiration,improve soil organic carbon and soil organic carbon fractions.However,differences existed under different rotation patterns.Therefore,we concluded that T1 and T2 with no tillage is more conducive to soil carbon sequestration and can be used as an ideal rotation model in the study region.