Effect of straw returning and reduced tillage on interspecific competition and complementation in wheat/maize intercropping system

Abstract

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 to 2012 growing seasons, in order to investigating the effects of different straw returning ways on crop yields, and interspecific competitiveness and complementation in wheat/maize intercropping systems. 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 competitiveness of wheat versus 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.