AMES, Iowa -- Flooding rains of the past two weeks have had numerous impacts on crop production. “Many effects will not be completely clear until harvest starts; late season flooding is quite rare. Among the management issues created by waterlogged fields this late in the season will be handling, storage and use challenges. Fortunately, post harvest grain management is one area in which there are some choices that can help,” said Charles Hurburgh, professor-in-charge, Iowa Grain Quality Initiative.
Hurburgh offers this advice on handling soybeans and corn.
Soybeans are likely to be higher in moisture and dry down more slowly than in normal years. Any insect or other seed coat damage will magnify the invasion of mold. Tropical storms in the South generally have cause discoloration and mold activity, which in turn leads to further storage problems.
Expect to aerate soybeans from flooded fields. Do not put them into an unaerated structure with no possibility for temperature or moisture control. Remember that the first grain harvested could be quite warm. Warm grain needs to be cooled quickly.
Typically soybeans lose moisture rapidly even with low airflows, but these beans will retain more moisture longer. If development is slowed, then there will be a larger percentage of the wet elongated beans early in harvest. These beans will store “wetter” than they test in electric moisture meters. A general rule for storage management is to add 2 percentage points to readings if green or elongated wet yellow beans are present in a sample. Aerate them down to at least 12 percent moisture, especially if storage into spring is expected.
It is too early to anticipate frost, but an early frost would again magnify the water retention properties as well as add green color to any gray or brown mold discoloration. Soybeans that are discolored enough to create discounts for the total damage factor can be aerated for two to four weeks, and sometimes the discolorations will partially subside.
Beans may be small if plant development is slowed. Small seeds are not inherently a problem for either storage or use. Expect variation in oil and protein however, depending on the development stage at the time of the heavy rain. On average, I would expect 1 to 2 percent lower oil than the average 19 percent. This is what happened in 1993, the last year we had late season heavy rains.
Post harvest quality of flooded corn is more uncertain than soybeans. The key will be the degree to which grain fill and development is retarded by the excess moisture. Generally, retardation in development before black layer will cause higher sugar contents, softer kernels, lower test weights and poor drying/storage properties. This will probably vary by field, which means the first grain harvest will be your way to determine what happened.
Test weight will be the simplest indicator of overall quality. The best measure of test weight is after drying; dry test weights below 54 lb/bu should be considered higher storage risk. Sell or use this corn first, and be sure it is stored in a structure with adequate aeration (0.2 cfm/bu or more). Corn intended for spring and summer marketing should be at least 54 lb/bu, and preferably more. Progressively lower test weights are indicators of progressively less mature and more stressed corn. Low test weight grain is more prone to blue eye mold, which grows slowly in corn down to 14 percent moisture, at warm temperatures.
Test weight increases about 0.25 lb/bu for each percentage point of moisture removed if the corn is mature. Immature corn will have progressively less test weight increase. Some lots in 1993 had test weights in the 40s when wet, and still in the 40s when dry. For this reason, test weight discounts in wet grain, rarely done in normal years, should be validated with actual dryer samples. Frost date will be important in determining the extent to which floods create immature corn. In 1993, there was an early frost as well as excess rain.
At harvest, decision making is always crucial to preserve future storage life. Holding wet corn without aeration for a day or two before drying can shorten the storage life by two to three months later on. Likewise failure to cool grain immediately will reduce storage life. This situation will be magnified in stressed corn. Assign bins and other storage structures based on expected storage time and quality assessment at harvest. Never mix old and new crop corn in the same storage. Clean bins completely before harvest. If corn begins to heat or spoil, plan to move it soon. Storage life can never be recovered; future problems will occur.
Immature corn will probably perform differently in ethanol plants, requiring changes to enzyme mix and fermentation time. From an ethanol perspective, it will be important not to compound the processing challenges with mold deterioration. Decisions made at or just after harvest will make great differences in overall use of the 2007 corn crop.