秸秆还田后少耕对小麦/玉米间作系统中种间竞争和互补的影响

保护性耕作具有提高作物水分利用效率、减少能耗等优点,但能否将该技术集成应用于间作套种,尚需理论研究和具体实验依据。本研究通过2011至2012年度的田间定位试验,探讨不同耕作和秸秆还田方式对小麦间作玉米作物群体竞争、互补作用及产量的影响。试验设3种秸秆还田处理,分别是小麦带25 cm高茬收割立茬免耕(NTSS)、小麦带25 cm高茬等量秸秆覆盖免耕(NTS)及小麦带高茬等量秸秆还田翻压(TIS),以传统耕作(CT)为对照。秸秆还田后少耕间作的土地当量比高于传统耕作间作,且大于1,说明少耕小麦秸秆还田有利于提高间作优势;少耕秸秆还田降低了共生期小麦相对于玉米的竞争力,以NTS处理对小麦竞争力的影响最大,NTSS、NTS和TIS的小麦全生育期相对竞争力分别降低37%~54%、109%~141%和22%~24%。与单作玉米相比,NTSS、NTS、TIS和CT处理间作玉米的相对生长率分别高54%~59%、66%~71%、61%~63%和71%~78%,其中小麦秸秆还田间作处理中NTS更有利于发挥玉米的恢复效应。间作条件下,3种秸秆还田处理的产量较对照高6%~10%(2011年度)和4%~12%(2012年度),其中NTS增产显著。总体来看,间作群体籽粒产量与小麦相对于玉米全生育期的平均竞争力呈二次相关关系,当该竞争力在0.24~0.27时利于获得间作高产。本研究表明,秸秆还田配合少耕是调控种间竞争力的可行途径,其中小麦等量秸秆(小麦留茬25 cm)还田覆盖是优化小麦玉米竞争力的理想耕作措施。

Effect of Straw Returning and Reduced Tillage on Interspecific Competition and Complementation in Wheat/Maize Intercropping System

Conservation tillage has the advantages of enhancing water use efficiency and reducing water/energy consumption simultaneously in common cropping systems. However, this technique has not been well studied and practiced in intercropping system. A field experiment was conducted in 2011 and 2012 growing seasons to investigate the effects of different straw returning ways on crop yields, and interspecific competitiveness and complementation in wheat/maize intercropping system. Three wheat straw returning treatments were designed, which were no-tillage with 25 cm straw standing (NTSS), no-tillage with 25 cm straw covering (NTS), and tillage with 25 cm straw incorporation (TIS). Conventional tillage (CT) was used as the control. In the intercropping system, the land use efficiency (LER) of reduced tillage treatments under straw returning condition increased compared with that of CT, showing the intercropping superiority (LER>1). Simultaneously, the competitiveness of wheat with maize in the whole wheat growing duration decreased in treatments NTSS, NTS and TIS by 37–54%, 108–141%, and 22–24%, respectively. Compared with monocropping maize, intercropping maize had higher rates of relative growth with the increased percentages of 54–59% in NTSS, 66–71% in NTS, 61–63% in TIS and 71–78% in CT. Clearly, NTS showed the most effect on maize growth after wheat harvest. In the intercropping system, the total yields of both crops were 6–10% (2011) and 4–12% (2012) higher in the straw returning treatments than in CT. NTS exhibited the most significant effect on enhancing yield. A quadratic relationship was observed between the total yield of intercropping system and the competitivenessof wheatversus maize, and high yields of both crops were obtained when the competitiveness ranged from 0.24 to 0.27. Our results showed that straw returning in combination with reduced tillage is feasible to regulate the interspecific competitiveness in wheat/maize intercropping system, and NTS treatment is recommended.