Source: Ohio State University
By Peter Thomison, Allen Geyer and Rich Minyo
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. The widespread root lodging that occurred as a result of windstorms in July is contributing to this problem. 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.
Several years ago Ohio State University conducted a study that evaluated effects of four plant populations (24,000, 30,000, 36,000, and 42,000 plants per acre) and three harvest dates (early-mid October, November and December) on the agronomic performance of four hybrids differing in maturity and stalk quality. The study was conducted at three locations in northwest, northeast and southwest 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.
- 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 October and November. Delaying harvest after early to mid-November 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 per 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 October and December harvest dates. Most of the yield loss, about 11%, occurred after the early-mid November harvest date. In three of the eight experiments, yield losses between October and December 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 October to November harvest dates but little or no change beyond the November harvest dates. Grain moisture, averaged across experiments, hybrid, and plant population, decreased 6.3% points between the October and December harvest dates, with most of the decrease occurring between the October and November harvest dates (5.8 % points); only a 0.5 % point decrease occurred after early-mid November. 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 October 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.