SOIL TYPE: Heavier, finer textured soils have better water holding capacity and can support higher populations than lighter, coarser textured soils
PLANTING DATE: As plant population increases, an early planting date becomes more important
HYBRID: Some hybrids tolerate high populations better than others. Maturity is important. Shorter, earlier hybrids usually more responsive to high populations than taller, later hybrids
SOIL FERTILITY: High populations need high soil fertility
MOISTURE: Need plenty of moisture for higher populations to be advantageous
ROW SPACING: Optimum row spacing decreases as plant population increases (in much of the Corn Belt).
Optimizing plant density
- "Can’t grow an ear in air!"
- Optimum range is between 28,000 and 32,000 plants per acre.

Row spacing

Handouts

Wisconsin studies
Michigan study
Paired "Twin" Rows

Moisture influences response to row spacing. In Northern areas of the Corn Belt response to row spacing has not been consistent. Response has not been very large in Wisconsin. Consequently, most corn growers in Wisconsin plant corn in 30-inch rows. Intensive managers in Wisconsin are growing corn in <30-inch rows.

30-inch v. 36- to 38-inch rows = 5-8% yield increase
30-inch v. less than 22-inch rows = 2% to 5% yield increase

Equipment Changeover Costs to Narrow Rows (Paskiewicz, 1996)
Replacing rims and tires	$8,000
Convert corn head	$6,500
Convert planter	$5,000
Convert sprayer	$500
Variable costs (fertilizer, fueld, etc.)	?
Tillage using residue clearing	?
Requires more time at planting	?
Cultivation difficult or impossible	?

Planting date

Handouts

Depends on soil type - A light soil dries out and warms up faster in the spring than a heavy soil

Optimum date is usually May 1 to 7 in southern to northern Wisconsin

ADVANTAGES of EARLY PLANTING

HIGHER YIELDS: Maturity is important - late hybrids usually respond better to early planting than early hybrids
Better response to fertilizer
Better DRYDOWN in the fall
Other benefits of early planting
- Stronger roots and stalks
- Lower ear height
- Plant height may be shorter
- In much of the Corn Belt, tasseling and silking may occur before hot, dry weather arrives
Earlier planting earlier shading of soil surface less water loss by evaporation

Early planting does not cost more than late planting

Delayed planting during early May corn yields decrease 0.3 to 0.5% per day delay
Delayed planting during late May, corn yields decrease 1.5 to 2.3% per day delay.
Planting corn after May 20 returns $45 to $85 less per acre and costs $0.20 to $0.50 more per bushel to dry than planting May 1 to May 5.

Figure 1. Grain yield response of full-season corn planted on various dates at Arlington, WI. The optimum date to plant corn is May 1. Risk is defined as the standard deviation (i.e. spread) of the points along the mean.

Seeding Depth

Normally 1 1/2 -2"
Warmer soil temperatures are near the surface
Mesocotyl pushes the growing point to within 1-inch of the soil surface

Checking Planting Results

Although the operator's manual serves as a guide for setting the planter, make your final adjustments in the field to account for varying soil conditions. Two major adjustments are planting depth and seeding rate.

Planting depth, influenced by leveling adjustments, generally is controlled by either gauge wheels or press wheels. Adjustments of these are outlined in the owner's manual. Plant deep enough to ensure that adequate moisture exists for germination and early growth, but not so deep that emergence is poor or delayed.

Because considerable soil can be moved by the planting unit, the depth should be determined by measuring from the seed to the impression left by the press wheel rather than to the original ground level. To achieve a good stand, this depth should be from 1 1/2 to 2 1/2 inches for corn and from 1 to 1 1/2 inches for soybeans or grain sorghum.

Seeding rate in the field can be checked by uncovering and counting seeds in a row length equivalent to 1/1,000 of an acre (Table I). Multiply the seeds counted by 1,000 to obtain the number of seeds planted per acre. Following operator manual recommendations, adjust the seed metering mechanism as necessary to obtain the desired population. Also, dig up some seeds in each row to verify seed is being planted at the correct depth and spacing.

Table 1. Length of row to equal 1/1,000 acre for various row spacings.

Row Spacing	Row Length
10"	52' 3"
15"	34' 10"
19"	27' 6"
30"	17' 5"
36"	14' 6"
38"	13' 9"
40"	13' 1"

Planting Season

Theory of Yield

The Dimensions of Planting

Plant Density

Row spacing

Planting date

Seeding Depth

Checking Planting Results

Further Reading