Early planting is necessary for maximum corn yields. Under central and western New York conditions, corn planted in late April or early May usually outyields either grain or silage corn planted after mid-May. Early-planted corn also matures earlier and lodges less. A general guideline for the best time to begin planting corn is about 10 days before the average date of the last 32^o F temperature in the spring. If soil conditions are too wet at this time, wait until soil conditions improve. Corn planted in late May under good soil conditions will consistently outyield corn planted in late April under poor soil conditions. A planting depth of about 1.5 inches is recommended for early-planted corn and a depth of about 2 inches for late-planted corn.

To achieve the full yield potential of an early planting date, full-season hybrids (hybrids that match the growing degree days in a region) are necessary (see table below). After the first or second week of May, however, the yield potential of full-season hybrids decreases appreciably. Furthermore, full-season hybrids often do not mature in the fall if planted after the first or second week of May. Therefore, for grain production, full-season hybrids should be planted only in late April or the first 10 days of May. For silage production, full-season hybirds can be planted until mid-May. The majority of corn acreage should be planted to medium-season hybrids (200 growing degree days less than the growing degree days in a region). If planting must be delayed until late May or early June, early-season hybrids are recommended.

The optimal corn population depends on soil type, hybrid selection, and crop use. For many New York soils (well- to moderately well-drained silt loams), modern hybrids require a harvest population of 26,000 to 28,000 plants per acre for maximum economic grain production. Poorly drained or droughty soils, however, cannot support high populations, and plant populations should be adjusted slightly downward. Likewise, hybrids differ in their response to plant populations, so hybrid selection should influence whether the harvest population is at the high or low end of the harvest population range for each particular soil condition. Also, most hybrids require higher harvest populations for silage than for grain production, about 2,000 to 4,000 more plants per acre.

GUIDE TO CORN POPULATIONS FOR NEW YORK STATE
	Grain Corn		Silage Corn
Soil Conditions	Planting Rate (90% Emergence)	Harvest Population1	Planting Rate (90% Emergence)	Harvest Population1
	Plants/A
Very deep loams and silt loams with high moisture-holding capacity	~32,250	28,000–30,000	~36,500	32,000–34,000
Well- to moderately well-drained loams to clay loams	~30,000	26,000–28,000	~34,500	30,000–32,000
Sandy loams, clays, or somewhat poorly drained loams to clay loams	~27,750	24,000–26,000	~32,250	28,000–30,000
Droughty soils including very gravelly, sandy, or shallow soils	~27,750	24,000–26,000	~30,000	26,000–28,000
1Hybrids that respond to high populations should be at the high end of the harvest population range, and hybrids that do not respond should be at the low end of the range for each particular soil condition.

Planting date, tillage practices, pest problems, planter performance, and hybrid selection influence actual corn populations obtained in the field. To compensate for potential problems, it should be assumed that only 90 percent of the kernels planted actually emerge and survive to become harvestable plants in the fall. To obtain 27,000 plants per acre at harvest on a moderately well-drained silt- loam soil, the planting rate should be about 30,000 plants per acre (27,000 divided by 0.90). In some situations such as a no-till situation or an April planting date, it should be assumed that only 85 percent of the kernels will emerge and survive. The planting rate in these situations on a moderately well-drained silt-loam soil should be about 31,765 plants per acre (27,000 divided by 0.85).

 

News Letter Articles
Planting rates for Grain Corn - February 2011 PDF
Corn Silage Hybrids and Plant Populations - April 2010 PDF
Agronomics and Economics of Zone Tillage Depth for Corn Silage Production - April 2009 PDF
Planting Rates for Grain Corn and Silage - February 2009 PDF
How About Planting Rates for Grain Corn When Prices are High?- April 2008 PDF
Recommended Planting Rates for Grain Corn on Silt Loam Soils - February 2006 PDF