Recent reports have Iowa corn at about 40% harvested and Iowa soybeans about 66% harvested. The late crop has corn moistures running from around 19% in central and western Iowa to 25% and above in northern and northeast Iowa. Due to the later planting and current weather conditions, crops are drying slower in the field.
Cold grain temperatures are the best protection against spoilage at this point. The allowable storage time (shelf life) of corn nearly doubles with a reduction in grain temperature from 50oF to 40oF, as illustrated in Table 1 below. This can allow drying to stop at a higher moisture and for grain to still be stored through the winter. For example, 17% corn has a storage life of 5.3 months at 50oF, but it has a storage life of 9.4 months at 40oF. Soybean storage properties are similar to corn that is 2% drier (i.e. 15% soybeans store like 17% corn).
Table 1. Maximum storage time (months) of corn and soybeans based on grain moisture content and grain temperature.
The forecast is calling for several days of cold weather with highs in the 40's and lows in the 20's. This will be a very good time to get stored grain cold enough to substantially reduce mold activity. The key temperature to watch is actually the dewpoint (condensation temperature) because air moving through wetter material will cool by evaporation to nearly the dewpoint. As I write this, the temperature outside in Ames is 34oF but the dewpoint is 21oF. Excellent cooling conditions.
Tips on cooling stored grain and storing grain through the winter can be found in this recent ICM Blog, “Cool Stored Grain Now.”