MATHEMATICAL GROWTH ANALYSES OF CORN (ZEA MAYS L.) GROWN IN NARROW AND WIDE ROWS (CGR, NAR, LAI)
Abstract
Growing corn (Zea mays L.) in rows narrower than 78-cm has been shown to increase grain yield. There has been no explanation for this yield increase other than an increased leaf area index (LAI). A detailed growth analysis study would indicate the changes in the growth and development of the crop which were responsible for the yield increase. In 1983 and 1984, at the Purdue Agronomy Farm, West Lafayette, Indiana, two hybrids, Pioneer 3732 and Beck 65XS, produced an additional 723 and 538 kg grain ha('-1), respectively, when grown in rows 38-cm apart (narrow rows) as compared to the more traditional 76-cm row width (wide rows). The narrow rows were suggested to have relieved moisture stress since both years were abnormally dry. A quantitative growth analysis based on weekly whole plant samples, from plant stages V4 to R6, indicated that until the end of the season the narrow row crop growth rate, CGR, of both hybrids was larger than the wide row CGR. This was due to a larger narrow row LAI. The net assimilation rate was unaffected by row width. The specific leaf area was smaller for the narrow row crops. During the sampled period (V4 to R6) the relative growth rate was smaller when either hybrid was grown in narrow rows. This was caused by proportionally more photosynthates being deposited in stalks instead of leaves for the narrow row crops. The narrow row crops remobilized proportionally less of the vegetative dry weight during the grain fill period. The leaf area ratio of both hybrids was smaller for the narrow row crops. There was no difference between row widths for the concentration of nitrogen in the canopy or the stalk. The larger dry weight resulted in more total nitrogen in the canopy and stalk. It was suggested that an increased rate of nitrogen remobilization from the stalk and canopy of the narrow row crops produced a larger concentration of nitrogen in the grain, and this in turn increased the rate of dry weight accumulation within the grain. There was not a difference due to row width for the relative rates of nitrogen mobilization (g N g N('-1)).
Degree
Ph.D.
Subject Area
Agronomy
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