Environmental conditions such as frost and wet, cloudy weather in the fall can delay crop maturity and may result in elevated grain moisture. In these scenarios, checking fields prior to harvest to prioritize harvest order, ensuring proper combine set-up, and proper grain handling can help prevent grain spoilage during storage.
What to Watch For
Crop maturity in the fall can be delayed by periods of wet, cloudy weather. In some cases, frost can kill the crop prior to physiological maturity resulting in elevated grain moistures. Additionally, corn stalk and ear diseases and soybean pod diseases can cause loss of yield potential and reduce grain quality. In these scenarios, you will be challenged with harvesting and handling grain with higher than desired moisture levels. These harvest conditions can also result in grain damage with the addition foreign material in the bin.
Impact on Your Crop
Checking on your fields before harvest is a key management tool that can help reduce yield loss and quality decline, especially in poor environmental conditions. Temperature and humidity can influence drydown rate, which declines quickly in late September and October (Table 1).1 Consider lodging, soybean pod shattering, corn ear mold and stalk rots, and insect feeding when planning your harvest schedule. The pinch and push tests can help determine the extent of stalk rots. After these checks are made, a harvest plan can be developed to reduce the risk of yield and grain loss.
Tips to Manage
A very important factor in handling high moisture grain at harvest is proper combine adjustment. Proper adjustment can help in harvesting corn between 20—30% moisture and can help minimize the degradation of wet grain quality.
- Ground speed needs to be adequate to keep the separator and cleaning shoe at full speed.
- The corn head should be kept high to reduce wet material from entering the combine and maintain the ability of the combine to thresh and separate grain.
- Level the concave from side-to-side before changing the concave clearance for uniform adjustment.
Check the manufacturers recommendation for additional adjustments for harvesting wet crops.
- Combine settings. Balance the need for aggressive shelling action to get small kernels off the cob against the extra kernel damage that can occur when small, light kernels are blown out of the combine.
- Manage fines and chaff. Fine particles and chaff affect airflow movement and increase mold problems in storage. Consider cleaning grain to remove fines and chaff, “core” bines to pull fines out of the center, or make sure that fines and chaff are uniformly distributed throughout the storage bin rather than being concentrated in certain areas.
- Dry grain uniformly. Check grain moisture content of every load of grain and reset dryer controls based on changing moisture levels. Make sure that the moisture content of dried corn is low enough for safe storage (15% for winter storage, 14% for storage into spring and summer, 13% for storage of a year or more), and consider reducing these moisture levels by about a percentage point for corn that is immature, frost-damaged, or low test weight.
- Dry corn gently. High drying temperatures can result in lower test weight and in more cracked and broken kernels. Natural-air drying (no heat) gives better test weight and less kernel damage than gas-fired drying. Use slow cooling methods after gas-fired drying to minimize quality problems.
- Aerate stored grain to 20-30°F for winter storage.
- Check stored grain frequently so that you can quickly address minor spoilage problems before they become big, costly problems.
- Moldy grain can have a shorter storage life than clean grain. Don’t mix new with old grain.
- Temporary grain piles should be at commercial facilities not on farm sites. Small piles tend to spoil more rapidly than large piles and large piles are easier to aerate.
To keep wet grain going into storage from heating and losing quality, run the aeration fan continuously whenever grain exceeds 18% moisture and grain temperature is above 50°F. The length of time corn can be kept under constant temperature and moisture content before it loses 1/2% dry matter (the maximum loss to maintain current market grade) is shown in Table 2. General rules of thumb for corn above 16% moisture are shelf life is half as long at given temperature for every 2 points of moisture greater than 16% and shelf life is half as long for every 10°F increase in temperature. Soybeans in storage have a shelf life similar to corn that is 2% greater in moisture content (Table 1).
|Table 1. Field Drying Rates for Corn in Minnesota|
|Date||Corn Moisture Los per Day|
|Sept. 15 - Sept. 25||0.75 - 1.0%|
|Sept. 26 - Oct. 5||0.50 - 0.75%|
|Oct. 6 - Oct. 15||0.25 - 0.50%|
|Oct. 16 - Oct. 31||Very little|
Harvest traffic on wet soils can cause ruts and soil compaction and can create an uneven soil surface and affect seed soil contact during planting if left in the field. To minimize the detrimental effects of ruts and compaction, manage traffic patterns. Traffic pattern management usually involves uniform machinery sizing and use of global positioning system (GPS) guidance of equipment. Some guidance for managing soil compaction during a wet harvest include:
- Use surface or shallow tillage to reduce ruts in the field.
- Reduce equipment tire pressure and axel loads.
- Maintain repeated travel patterns to help contain and reduce soil damage.
- Use a cover crop and rely on the freeze/thaw conditions in winter to address shallow compaction. Subsoiling may be necessary if compaction is deeper than 6 inches in the soil.
- To help spread overall pressure on the soil, use tracks, low tire pressure, or dual wheels on equipment and consider reducing load size in equipment transporting grain out of the field.
Maximum Storage Time (months) for Corn and Soybeans
|Temperature||% Moisture Content|
Nielsen, R. 2015. Information resources for challenging crop harvest conditions. Purdue University; Coulter, J. 2008. Maturity, frost, and harvest moisture considerations for corn. University of Minnesota; Digman, M. Combine considerations for a wet corn harvest. University of Wisconsin; Wilcke, W. and Wyatt, G. 2002. Grain storage tips. University of Minnesota; Wilcke, B. 2004. Drying, handling, and storing wet, immature, and frost-damaged corn. University of Minnesota; Hurburgh, C. 2016. Wet weather creates challenges for harvest. Iowa State University; Dorn, T. Managing high moisture, stored grain through winter. University of Nebraska; Stahl, L. 2014. Storing, drying, and handling wet soybeans. University of Minnesota; Arriaga, F. and Luck, B. 2016. Guidelines for soil compaction management during a wet harvest season. University of Wisconsin.