Journal
AGRONOMY JOURNAL
Volume 101, Issue 6, Pages 1522-1529Publisher
WILEY
DOI: 10.2134/agronj2008.0213x
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Funding
- South Dakota Corn Utilization Council
- South Dakota Soybean Research and Promotion Council
- USDA-CSREES-seed technology [2008-34556-19350]
- South Dakota 2010 initiative
- USDA-CSREES-NRI [2009-35320-0540]
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Competition mechanisms among adjacent plants are not well understood. This study compared corn growth and yield responses to water, N, and shade at 74,500 plants ha(-1) (1x) with responses to water and N when planted at 149,000 plant ha(-1). Plant biomass, leaf area, chlorophyll content, reflectance, and enzyme expression (transcriptome analysis) were measured at V-12. Grain and stover yields were measured with grain analyzed for C-13 isotopic discrimination (A) and N concentration. At V-12, 60% shade plants had increased chlorophyll and reduced leaf area and height compared to full sun plants. In the 2x treatment, plants had 11% less chlorophyll than 1x plants with leaf area and height similar to 60% shade plants. At harvest, plants in the 2x treatment were smaller, had increased water and N use efficiency, and an 11% per hectare yield increase compared with the 1x unstressed treatment. Per-plant yields from 60% shade and 2x treatments were 50% less than 1x unstressed treatment. Yield reduction in shaded plants was attributed to light stress. Lower yield in the 2x treatment was attributed to a population-density induced 20% decrease in the red/near-infrared (NIR) ratio,which resulted in downregulation of C-4 carbon metabolism enzymes (phosphoenolpyruvate carboxykinase, phosphoenolpyruvate carboxylase, and pyruvate orthophosphate dikinase). Although the net impact of high plant density and shade stress on per-plant yield were similar, the stress compensation mechanisms differed.
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