Inter-cropping and mixed-cropping can increase the yield and stress resistance of maize. The inter-and mixed-cropping of different maize cultivars with different mature plant heights can improve aeration and transmittance conditions and increase the leaf area index, marginal effect, and rate of photosynthesis, all of which can increase grain yield. The inter-and mixed-cropping of different maize cultivars with different levels of resistance to disease, pests, lodging, and drought can also increase yield size and stability. The yield of maize can also be increased by inter-and mixed-cropping of different maize genotypes. In all these cases, suitable stripe arrangements are vital to success-here defined as creating a larger, more stable yield. However, previous studies on inter-and mixed-cropping have mainly focused on 1:1 stripe arrangements. There is currently a dearth of research into optimal stripe arrangements for inter-and mixed-cropping of maize. For these reasons, the present study was designed to investigate the effects of stripe arrangement on inter-and mixed-cropping outcomes with respect to maize yield, resistance to disease and lodging, photosynthesis capability and microclimate, and establish optimum stripe arrangement for inter-and mixed-cropping of different maize genotypes.
A study with four maize cultivars: Yudan 610 (YD610, 281 cm, high resistance to Curvularia Leaf Spot), Zhengdan 958 (ZD958, 246 cm, susceptibility to Curvularia Leaf Spot), Denghai 662 (DH662, 254 cm, high resistance to lodging), and Xundan 20 (XD20, 249 cm, susceptibility to lodging) was conducted during 2010 and 2011. The inter-and mixed-cropping system YD610||ZD958 incorporates the YD610 and ZD958 cultivars, which differ markedly in height. This system was implemented in Luohe and Zhengzhou. The treatments were an inter-cropping raw ratio of 1:1 (I1:1), inter-cropping raw ratio of 2:2 (I2:2), raw ratio of 2:4 (I2:4), mixed-cropping (M), and two monoculture cultivars (YD601S and ZD958S). The inter-and mixed-cropping system DH662||XD20, which incorporates DH662 and XD20, which are similar in height, was implemented in Anyang and Xinxiang. Six treatments were used in each inter-and mixed-cropping system. Specifically, these treatments were an inter-cropping raw ratio of 1:1 (I1:1), inter-cropping raw ratio of 2:2 (I2:2), raw ratio of 2:4 (I2:4), mixed-cropping (M), and two monoculture cultivars (DH662S and XD20S). The effects of stripe arrangement yield, land equivalent ratio (LER), resistance to disease and lodging, photosynthesis, and microclimate were studied in both inter-and mixed-cropping systems.
The results showed the yields of YD610||ZD958 and DH662||XD20 inter-and mixed-cropping systems to be significantly higher than that of either monoculture system. The LER of raw ratio of 2:4 (I2:4) of YD610||ZD958 inter-cropping system was 8.1%, 2.1%, and 1.2% higher than the treatments with I1:1, I2:2, and M. The LER of raw ratio of 2:2 (I2:2) of DH662||XD20 inter-cropping system was 6.2%, 4.0%, and 9.3% higher than the treatments of I1:1, I2:4, and M. Higher resistance to disease and lodging, better aeration and transmittance condition, larger leaf area index (LAI), and photosynthetic rate (Pn) of inter-and mixed-cropping systems were found to be the main causes of the increase in yield. The results suggested that a raw ratio of 2:4 (2 rows for the taller cultivar and 4 rows for the shorter cultivar) was the optimum stripe arrangement for maize inter-and mixed-cropping systems incorporating cultivars of different heights, while the raw ratio of 2:2 was the optimum stripe arrangement for maize inter-and mixed-cropping systems incorporating cultivars of similar heights.