长期保护性耕作对土壤有机碳和玉米产量及水分利用的影响

摘要

[Objectives] Conservation tillage is widely used in dry farmlands of northern China in recent years .A long term field experiment (2003-2013 ) was conducted to explore impact of the conservation tillage on soil organic carbon ( SOC) , spring maize yield and water utilization .We demonstrated the cause of yield improvement in the conservation tillage further , and then provided theoretical and technical support for dry farmland tillage .[Methods] There were three treatments, conventional tillage (CT), reduced tillage (RT) and no-tillage (NT). Annual variations of SOC (0-20 cm and 20-40 cm), soil moisture at 20 cm depth, crop water consumption, maize yield and water use efficiency were analyzed , and effect of the three tillage methods on above factors was also analyzed .Correlation analysis between maize yield and above factors was done in our study .[Results] 1 ) The conservation tillage can improve soil organic carbon (SOC) content, the annual SOC (0-20 cm) contents of the RT and NT treatments were increased by 11.2%and 3.4%compared with CT respectively , and the SOC (20-40 cm) of the RT and NT treatment were increased 5.53 and 3.29 g/kg.The increased rates of 0-20cm SOC stock of RT and NT were C 0.365 and 0.754 t/(hm2· a) respectively.2) The conservation tillage significantly increased crop yields:the average annual yields of 2003-2013 of the RT and NT treatments were 5.83 t/hm2 and 5.39 t/hm2 respectively, which are 14.7%and 6.1%higher than that of CT.3) The maize yield under the tillage had significant quadratic relationship with the soil 0-20 cm layer water content , and had significant power equation relationship with crop water consumption .4 ) The conservation tillage can increase soil moisture , reduce water consumption during maize growth and improve water use efficiency ( WUE ): compared with the CT and RT , NT increased the average moisture contents of 2003-2013 by 1.90 and 1.66 percentage points , whereas decreased annual water consumption by 16.1 mm and 7.6 mm;compared with CT , RT and NT increased WUEs by 16.1%and 10.2%, and precipitation use efficiencies ( PUE ) by 13.9% and 5.8% respectively .[Conclusions] The long-term conservation tillage can improve SOC and soil water content and decrease useless water consumption effectively, thus improve yield and water use efficiency .RT has the best performance , followed by NT.In general, promotion of conservation tillage is an effective way for increasing yield and water conservation in dry farmlands .%[目的]通过研究保护性耕作对旱地春玉米土壤有机碳( SOC )、产量及水分利用的影响,分析保护性耕作的增产机制,为旱作农田耕作技术应用提供理论和技术支持. [方法]采用2003 2013 年连续11年的田间定位试验,设传统耕作(CT)、少耕(RT)和免耕(NT)3种耕作措施,分析土壤0—20 cm和20—40 cm土层有机碳含量、土壤0—20 cm含水量、作物耗水量、玉米产量和水分利用效率的年际变化和耕作处理间的差N,并对玉米产量与影响因素的相关性进行分析. [结果]1 )保护性耕作能有效提高土壤有机碳含量,少耕、 免耕处理0—20 cm土层有机碳含量11年平均值较传统耕作分别提高了11.2%和3.4%;至2013年,少耕、免耕20—40 cm土层有机碳含量分别较传统耕作增加了5.53 和3.29 g/kg; 土壤0—20 cm 有机碳储量净增加速率分别为C 0.365 和0.754 t/( hm2 · a).2)保护性耕作具有明显的增产效果,少耕产量最高,增产效果最好,2003 2013 年均产量为5.83 t/hm2 ,较传统耕作提高了14.7%;免耕次之,年均产量为5.39 t/hm2 ,较传统耕作增产6.1%. 3)各耕作处理玉米产量与土壤0—20 cm土层含水量之间存在显著的二次方程关系,与作物耗水量之间具有显著的乘幂方程关系.4 )保护性耕作可以增加土壤水分,减少玉米生育期内的耗水量,提高水分利用效率,其中免耕土壤0—20 cm土层水分含量最高,2003 2013年平均含水量为15.2%,较传统耕作和少耕提高了1.90和1.66个百分点,且生育期耗水量最少,2003 2013年均耗水量为403.5 mm,较传统耕作和少耕减少了16.1 mm和7.6 mm; 少耕、 免耕的水分利用效率较传统耕作分别提高了16.1%和10.2%,降水利用效率较传统耕作提高13.9%和5.8%. [结论]长期保护性耕作可以有效地提高土壤有机碳含量、增加土壤水分、 减少作物耗水量,从而显著提高了玉米产量和水分利用效率,3种耕作措施中以少耕效果最好,免耕次之,在旱作农田推广少、免耕保护性耕作措施是一种增产、节水的有效途径.