Corn Leaf Orientation Effects on Light Interception, Intraspecific Competition, and Grain Yields

Current environmental concerns justify renewed evaluation of crop management strategies that offer promise for maintaining or increasing productivity while reducing environmental impacts. Field studies were conducted using weed-free conditions to determine the effects of corn (Zea mays L.) leaf orientation on light interception, vegetative and reproductive development, and grain yields. ‘DeKalb 689’ was handseeded in north-south rows to achieve populations of 22 000 and 33 000 plants/acre. Controlled seed positioning in the soil was used to attain across-row and with-row leaf orientations, while conventional planting provided random leaf orientation. Light interception, intraspecific competition among corn plants, and grain yield were affected by leaf orientation and plant population. At selected row positions 8 wk after planting, light interception for across-row leaf orientation exceeded random and with-row orientations by up to 10 and 25%, respectively, while light interception for the high plant population exceeded the low population by up to 15%. Across-row and random leaf orientations produced 8% greater leaf area than with-row orientation. Greater intraspecific competition was indicated for the high plant population due to lower leaf area, leaf biomass, and stalk biomass per plant than the low population. Grain yields were greater at the high than the low plant population for all leaf orientations. At the high plant population, across-row leaf orientation yielded 10 and 21% more than random and with-row orientations, respectively. Therefore, across-row leaf orientation at the high plant population should provide more rapid canopy closure, enhance crop competition with weeds, and reduce dependence on herbicides while enhancing grain yields. Research QuestionManipulation of the corn canopy to enhance light interception through greater light penetration and more uniform distribution offers the potential for reducing intraspecific competition and increasing grain yield. Regulating corn leaf orientation by controlling seed placement in the soil may provide a means to achieve these results. The objectives of this research were to determine the effects of corn leaf orientation on light interception, intraspecific competition, and grain yield. Literature SummaryAt high productivity levels, the primary ecological factor limiting corn yield is light. By improving light-use efficiency of the crop canopy, it should be possible to increase grain yields. Corn yields have been increased by physical manipulation of the leaf angle, by selecting plants with increased leaf angle, and by using aluminum reflectors to increase light flux. These methods permit greater light penetration and provide more uniform distribution of light over greater leaf area. Orientation of corn leaves can be influenced by seed placement in the soil and may offer an effective means for increasing light interception, reducing intraspecific competition, and enhancing the rapidity of canopy closure. Row orientation and plant population have been shown to influence light-use efficiency of some crops. Study DescriptionField studies were conducted in 1990 and 1992 on a Congaree silt loam at Calhoun Research Facility, Clemson, SC (34°37′N, 82°44′W). ‘DeKalb 689’ seed corn was handseeded in north-south rows to achieve populations of 22 000 and 33 000 plants/acre. Different seed planting strategies were used to orient corn leaves across the row middles (across-row), with the corn row (with-row), and randomly. Across-row leaf orientation was attained by placing corn seed in the soil with the point of caryopsis attachment pointed down and the embryo of the seed facing the row middle. Planting corn seed in a similar manner but with embryo facing the row resulted in with-row leaf orientation, while conventional planting provided random leaf orientation. Treatments consisted of the six factorial combinations of plant population and leaf orientation. Plots were maintained weed-free by hand and cultivation. Applied QuestionCan across-row corn leaf orientation enhance light interception and increase grain yield? Differences in light interception among leaf orientations occurred mainly during the period 8 to 10 wk after planting. At the low plant population, there was no detectable difference in yield for across-row and random leaf orientations, but both provided higher yields than the with-row orientation. At the high plant population, yields were different for all leaf orientations — across- row>random>with-row. The high plant population yielded more than the low population for each leaf orientation. Table 1Effect of corn plant size and leaf orientation on light interception at four row positions averaged over plant populations (1990 and 1992 combined). Distance from the row, in.Weeks after plantingLeaf orientation061219------------% PAR intercepted--------------8Across-row80634743Random76563735With-row73462618 LSD (0.05)5.74.46.46.110Across-row89918784Random87878581With-row86838177 LSD (0.05)NS4.64.36.5Table 2Effect of plant population and leaf orientation on reproductive development 15 WAP and corn grain yield at maturity (1990 and 1992 combined). Ear biomassPopulationLeaf orientationper plantper acreYieldplants/acre-------lb-------bu/acre22 000Across-row0.5411 900143Random0.5111 200137With-row0.5111 20012533 000Across-row0.5317 300170Random0.4113 600155With-row0.3210 400140LSD(0.05)0.061 63010