Bruce MacKellar, Roger Betz
Michigan State University Extension
What is the potential for corn to dry in the field over the winter months? In all honesty, not particularly good on a per day basis during the December through February timeframe. However, there are a lot of days during this period, and even small amounts of drying per day can lead to much lower moisture levels by early spring. With corn moisture levels remaining above 30% in many June planted corn fields, the cost of drying corn this fall is going to be very high. The key factor to consider in deciding whether to leave corn in the field until spring is to assess the risk of yield losses by leaving corn in the field.
Joe Lauer, University of Wisconsin Corn Extension specialist, conducted a study looking at corn yield losses over winter during 2000 and 2001. The results are in Table 1.
| Table 1. Corn yield losses over winter, 2000 and 2001. | ||||||
|---|---|---|---|---|---|---|
| Year | November | December | January | February | March | April |
| 2000 | No loss | 45% | 58% | 59% | 65% | 38% |
| 2001 | 5% | 5% | 9% | 19% | 7% | 10% |
| Mean | 3% | 22% | 32% | 37% | 32% | 24% |
| Moisture | 37% | 28% | 27% | 23% | 20% | 15% |
The numbers in Table 1 reflect harvest losses for corn combined with the weather conditions during each month. The year 2000 data had heavy snowfall, which severely impacted how much of the corn could be harvested because of snow on the ground. The 2001 year had much less snow, hence less overall losses. The moisture levels are averaged over five years for samples collected.
We ran a partial budget analysis investigating the net revenue per acre impact of leaving 150 wet bushels per acre corn in the field over winter to dry to 18% moisture compared to taking 30% moisture corn to an elevator to dry. The results showed that even at a 30% (45 wet bushels per acre) yield loss in the field, there was a $20 per acre advantage to leaving the crops in the field.
The results of this analysis are shown in Table 2 and reveal the impact of various yield loss results compared to corn moisture levels at harvest this fall.
| Table 2. Estimated net revenue per acre impact of leaving corn in the field to dry over winter at various yield loss and harvest moisture levels compared to fall delivery to elevator. | ||||||||
|---|---|---|---|---|---|---|---|---|
| Moisture | Loss % | |||||||
| 5% | 10% | 15% | 20% | 25% | 30% | 35.0% | 40% | |
| Bushel | ||||||||
| 7.5 | 15 | 22.5 | 30 | 37.5 | 45 | 52.5 | 60 | |
| 35 | $232 | $204 | $176 | $148 | $120 | $92 | $64 | $37 |
| 34 | $217 | $189 | $161 | $134 | $106 | $78 | $50 | $22 |
| 33 | $203 | $175 | $147 | $119 | $91 | $63 | $35 | $8 |
| 32 | $188 | $160 | $133 | $105 | $77 | $49 | $21 | -$7 |
| 31 | $174 | $146 | $118 | $90 | $62 | $34 | $7 | -$21 |
| 30 | $159 | $131 | $104 | $76 | $48 | $20 | -$8 | -$36 |
| 29 | $145 | $117 | $89 | $61 | $33 | $5 | -$22 | -$50 |
| 28 | $130 | $103 | $75 | $47 | $19 | -$9 | -$37 | -$65 |
| 27 | $116 | $88 | $60 | $32 | $4 | -$24 | -$51 | -$79 |
| 26 | $101 | $74 | $46 | $18 | -$10 | -$38 | -$66 | -$94 |
| 25 | $87 | $59 | $31 | $3 | -$25 | -$52 | -$80 | -$108 |
| 24 | $72 | $45 | $17 | -$11 | -$39 | -$67 | -$95 | -$123 |
| 23 | $58 | $30 | $2 | -$26 | -$54 | -$81 | -$109 | -$137 |
| 22 | $44 | $16 | -$12 | -$40 | -$68 | -$96 | -$124 | -$152 |
| 21 | $29 | $1 | -$27 | -$55 | -$82 | -$110 | -$138 | -$166 |
| 20 | $15 | -$13 | -$41 | -$69 | -$97 | -$125 | -$153 | -$181 |
| 19 | $0 | -$28 | -$51 | -$84 | -$111 | -$139 | -$167 | -$195 |
The values in Table 2 were calculated using 150 bushels per acre wet bushel yield, which had a test weight of 50. Drying charge was calculated at 0.4 cents per bushel per point of moisture above 15%. A shrink calculation of 1.4% per percent of moisture above 15% was used to calculate the number of marketable bushels. Drying charges, trucking charge for hauling the water in wet corn and a deduction of 0.05 cents per bushel for test weight were calculated on a wet bushel basis.
Factors that can contribute to overwinter yield losses
As you might expect, there are several factors that can contribute to overwinter yield losses and the risks for loss can be substantial.
Lodging. Corn has the potential to lodge, which can substantially reduce harvestable yield. This is particularly true where stalks have been weakened by tar spot or other leaf diseases or stalk rots. Leaf diseases causing loss of green leaf tissue during the growing season can cause the plants to scavenge carbohydrates from the stalk, reducing stalk strength and increasing the potential for lodging.
Ear size and weight can also play a role in this, with heavy ears creating more potential for lodging. In addition, activity of insects such as corn borer and, to a lesser extent, western bean cutworm can impact stalk and ear shank strength, causing more lodging and corn ear drop.
Winter weather. No precipitation events are created equal. Wet snow tends to be more problematic than dry snow. Ice storms can also add weight that can increase lodged corn. High wind conditions during any of these events, including wind driven thunderstorm rainfall during the winter, can cause significant lodging.
Wildlife damage. Deer can be a significant factor in making the decision of leaving corn in the field to dry. Overwintering deer can choose to yard up in standing corn as an alternative to woodlands and swamps, causing unacceptable levels of yield loss. The extent of damage that will occur is directly correlated with the numbers of deer in your area. If you expect to have fields you will not harvest until late winter or early spring, contact your local Department of Natural Resources biologist to request extra doe antlerless deer tags this fall and round up hunters to proactively reduce the deer herd in your area.