The high-yield plot in the Corn Illustrated project was harvested last week. And while the CI staff expected a 10-20 bushels per acre advantage for corn after beans vs. corn after corn in that plot, the sizable advantage didn't materialize. Now it's time to attempt to figure out why that may have occurred.
Two hybrids were included in the plot. This plot was irrigated approximately four times during the summer. Since the plot was to shoot for top yields, not compare fungicides, the entire plot was sprayed with fungicide at silking. Yields either hit or approached 200 bushels per acre.
As it turns out, Dave Nanda, long-time plant breeder, believes it may have been sprayed just a touch too soon. There appeared to be about one day when pollination was affected based on the shape of many ears and kernel set. Then pollination appeared to return to normal. Since the entire plot was sprayed, there wasn't an opportunity to compare areas that were sprayed with areas that weren't sprayed.
On the plus side, the crop was very healthy, still showing some hints of green at harvest. This plot was planted the last week of May, a factor that Nanda believes could have cost about 20 bushels per acre in the high-yield attempt. Wet soils earlier in May prevented earlier planting. Compared to the same hybrids planted the same day in different plots on similar soils a couple miles away, moisture content of the grain was seven to eight points higher here, running in the low 20's, while running about 15% in the other plot.
The tell-tale factor was likely nitrogen. Nitrogen was side-dressed at the appropriate time on the high yield plot, but was applied as liquid on the surface and worked in on the second plot that where the corn was much drier. That was done because that plot featured different row spacing that would not have allowed sidedressing without excessive plant loss.
Some 25 to 20 inches of rain fell on both plots from about June 1, just a few days after planting, through early July. Nearly 17 inches came in one week in early June. Based on the signs of severe nitrogen loss that Nanda saw in the second plot with varying row widths by the end of August and into September, it's highly likely that those plots simply ran out of nitrogen. Yields were in the 80 to 125 bushel per acre level on reasonably good land. The plots were not irrigated, but also did not sit on soil with gravel underneath.
The high yield plots also received approximately 75 pounds more N per acre than the other plots. The intent was to make sure that N was not limiting on those plots. So questions remain. Did the extra N delay maturity on the high-yield plots, making moisture content wetter? Or was the row width plots drier because they ran out of N and died prematurely? Or did the fungicide help make the high yield plots healthier, extending plant life but also making those plots slower to mature and dry down?
Dave Nanda, the plant breeder and consultant for the Corn Illustrated project, will begin to explore these questions and others after he gets a closer look at the entire set of data. One thing is for certain- this year's plots contain many surprises. These should lead to opportunities for learning and further follow-up on principles related to how corn grows and develops.