What Worked, What Didn't Work During the Drought of 1988?

As we begin to evaluate the success of corn pollination during the 2012 drought, it might be useful to also evaluate which management decisions were most beneficial during this growing season. Although a season like 2012 is rare and extreme, it will likely happen again. Taking some time now to evaluate your management decisions might help during a future growing season.

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

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.
	1978-1987			1988		Percent		Max	Min
Location	N	Yield		N	Yield	change		Yield	Yield
Arlington	756	185		166	131	-29		175	84
Janesville	706	184		166	151	-18		186	104
Lancaster	706	146		166	71	-51		111	35
Fond du Lac	718	138		151	114	-17		151	71
Galesville	718	157		151	162	3		217	104
Hancock	719	170		151	198	16		236	166
Chippewa Falls	510	141		---	---	---		---	---
Marshfield	510	125		126	99	-21		127	58
New London/Waupaca	514	152		126	172	13		195	113
White Lake	54	135		58	94	-30		111	64
Spooner	534	115		116	87	-24		145	34
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

Plant density

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)
Location	18100-20500	22500-24100	28600-29900	33300-36800	LSD(0.10)
	Grain yield (bushels/A)
Janesville	125	133	137	139	7
Lancaster	64	62	50	48	9
Fond du Lac	109	112	118	108	NS
Hancock	160	175	193	188	9
Galesville	133	163	172	174	9
Chippewa Falls	39	34	32	20	NS
Marshfield	88	87	89	85	NS
New London	109	112	118	108	NS
Spooner *	78	71	66	51	11
* 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
LSD(0.10)	NS		LSD(0.10)	8

Tillage


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)
Arlington-Experiment 1	62	64	NS
Arlington-Experiment 2	83	69	NS
Arlington-CS rotation	75	77	NS
Arlington-CSW rotation	70	72	NS
Janesville-Experiment 1	117	112	NS
Janesville-Experiment 2	117	109	NS

Rotation

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)
Continuous corn	61	56
Corn-Soybean	97	82
Corn-Soybean-Wheat	--	72
LSD(0.10)	16	15