Our last major drought year was 1988. There were numerous experiments established around the state by Dr. Paul Carter. Below I summarize his results for a number of management decisions that were important at the time including hybrid selection, plant density, date of planting, tillage and rotation decisions. The question is, "How do these decisions affect grain yield during a drought growing season?"
Hybrid performance was lower than the previous 10-yr average at 8 of 11 locations (Table 1). No grain yield was harvested at Chippewa Falls. Three locations, Galesville, Hancock (irrigated) and New London, had greater yields than the average of the previous 10-years. All other locations had 18 to 51% lower yields with Lancaster significantly lower than normal. Harvest grain moisture averaged 18.7% to 24.7% among the trials. Plant lodging was less than 6% at all locations. At 9 of 11 locations, the maximum yielding hybrid was better than the 10-year average.
|Table 1. 1988 Wisconsin Corn Performance Trials Summary.|
|Fond du Lac||718||138||151||114||-17||151||71|
|Yield= bushels per acre|
N= number of hybrids tested
Percent change= the yield during 1988 compared to the average yield of the previous 10 years
The plant density which produces maximum yield has been increasing over time, but what happens during a growing season with drought? During 1988, a plant density experiment was established at nine locations with target densities of 18,000; 24,000; 30,000 and 36,000 plants per acre. At 7 of 9 locations, grain yield either increased or was not affected as plant density increased (Table 2). At Lancaster, grain yield decreased 16 bu/A from low to high plant density, while at Spooner grain yield decreased 27 bu/A. So even during drought years when a response to plant density is not expected, higher plant densities were only detrimental at two locations. The best recommendation would be to manage for potential yield with higher plant density because the only risk for return on investment is minor seed costs.
|Table 2. Grain yield (bu/A) of corn planted at target plant densities of 18000, 24000, 30000 and 36000 plants/A at various locations in Wisconsin during 1988.|
|Actual Harvest Plant Density (plants/A)|
|Grain yield (bushels/A)|
|Fond du Lac||109||112||118||108||NS|
|* At Spooner target plant density was lower and resulted in harvest densities of 15900, 18600, 22000, and 24500.|
Date of planting
Earlier planting dates are typically recommended for avoiding drought growing conditions. However, during 1988 the planting dates of May 13 and May 18 were higher yielding than earlier planting dates (Table 3). Some of the better performance of later planting dates has to do with timing of when drought (heat and water stress) occurs during the life cycle of the corn plant. Another interaction is the distribution of rainfall during the growing season.
|Table 3. Grain yield (bu/A) response to planting date during 1988 at Arlington, WI.|
|Experiment 1||Experiment 2|
|Planting date||Grain yield (bu/A)||Planting date||Grain yield (bu/A)|
|April 18||59||April 27||67|
|May 13||63||May 26||84|
During the 1980s, no tillage was becoming popular as a management practice. Usually due to cool, wet soils corn often experience "slow growth syndrome" and yielded lower than conventionally tilled fields. During 1988, there were no differences between no-till and conventional-till in six experiments conducted at Janesville and Arlington (Table 4).
|Table 4. Corn grain yield (bu/A) response to tillage during 1988 at Arlington and Janesville, WI.|
|Location||Conventional tillage||No tillage||LSD(0.10)|
Rotation is probably the easiest management decision we have available to get "free" yield. During drought (stress) years it is even more important. Rotated corn increased grain yield 16 to 36 bu/A (29 to 59%) over continuous corn grain yield.
|Table 5. Corn grain yield (bu/A) response to crop rotation during 1988 at Arlington, WI.|
|Rotation||Grain yield (bu/A)|