Field Drying and Harvest Losses in Corn

October 29, 2019
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By:  Peter Thomison

According to the USDA/NASS (https://www.nass.usda.gov/) as of Sunday, Oct. 27th, 37 percent of Ohio’s corn was harvested for grain, compared to 62 percent for last year and 56 percent for the five-year average. Late corn plantings and sporadic rain in some areas are not helping with field drying. Some growers are delaying harvest until grain moisture drops further. However, these delays increase the likelihood that stalk rots present in many fields will lead to stalk lodging problems (Fig. 1). Leaving corn to dry in the field exposes a crop to unfavorable weather conditions, as well as wildlife damage. A crop with weak plant integrity is more vulnerable to yield losses from stalk lodging and ear drop when weathering conditions occur. Additional losses may occur when ear rots reduce grain quality and can lead to significant dockage when the grain is marketed. Some ear rots produce mycotoxins, which may cause major health problems if fed to livestock.

Fig. 1. Stalk rot and lodging increases with harvest delays (Source: C. Young, OSU Extension, 2017).

Several years ago we conducted a study that evaluated effects of four plant populations (24,000, 30,000, 36,000, and 42,000 plants/A) and three harvest dates (early-mid Oct., Nov. and Dec.) on the agronomic performance of four hybrids differing in maturity and stalk quality. The study was conducted at three locations in NW, NE, and SW Ohio over a three-year period for a total of eight experiments. Results of this study provide some insight on yield losses and changes in grain moisture and stalk quality associated with delaying harvest. The following lists some of the major findings from this research.

Key Findings:

  • Results showed that nearly 90% of the yield loss associated with delayed corn harvest occurred when delays extended beyond mid-November.
  • Grain moisture decreased nearly 6% between harvest dates in Oct. and Nov. Delaying harvest after early to mid Nov. achieved almost no additional grain drying.
  • Higher plant populations resulted in increased grain yields when harvest occurred in early to mid-October. Only when harvest was delayed until mid-November or later did yields decline at plant populations above 30,000/acre.
  • Hybrids with lower stalk strength ratings exhibited greater stalk rot, lodging and yield loss when harvest was delayed. Early harvest of these hybrids eliminated this effect.
  • The greatest increase in stalk rot incidence came between harvest dates in October and November. In contrast, stalk lodging increased most after early-mid November.
  • Harvest delays had little or no effect on grain quality characteristics such as oil, protein, starch, and kernel breakage.

In this study, yields averaged across experiments, populations and hybrids, decreased about 13% between the Oct. and Dec. harvest dates. Most of the yield loss, about 11%, occurred after the early-mid Nov. harvest date.  In three of the eight experiments, yield losses between Oct. and Dec. harvest dates ranged from 21 to 24%. In the other five experiments, yield losses ranged from 5 to 12%.

Grain moisture content showed a decrease from the Oct. to Nov. harvest dates but little or no change beyond the Nov. harvest dates. Grain moisture, averaged across experiments, hybrid, and plant population, decreased 6.3% points between the Oct. and Dec. harvest dates, with most of the decrease occurring between the Oct. and Nov. harvest dates (5.8 % points); only a 0.5 % point decrease occurred after early-mid Nov. Population effects on grain moisture content were not consistent. Differences in grain moisture were evident among hybrids on the first harvest date in early-mid Oct. but were generally negligible on the later dates.

A Field Loss Calculator for Field Drying Corn

Agronomists at the University of Wisconsin have developed a “Field Loss Calculator” Excel spreadsheet available at: http://corn.agronomy.wisc.edu/Season/DSS.aspx  that allows producers to calculate the costs of harvesting today versus allowing the crop to stand in the field and harvesting later. The spreadsheet accounts for higher drying costs versus grain losses during field drying. It allows the user to account for elevator discounts and grain shrink.