Time to Cool and Core Storage Bins

By Dirk Maier

It’s been a mostly dry and warm harvest with bins filling quickly with corn and soybeans on farms and at country elevators. With night-time temperature forecast ranging in the mid-30s to high-40s in the next ten days, the time is right to cool corn and soybeans but not necessarily to the same temperatures and ideally without excessive shrink. This article reviews some tools and best practices for cooling and storing corn and soybeans through the winter and into early spring.

Observed Corn and Soybean Quality 

We have been receiving corn for drying and storing at the ISU Kent Feed Mill & Grain Science Complex (FMGSC) in Ames, Iowa, since early September. About 80,000 bu were received between 20-25% moisture content for a high-capacity dryer test. This provided an early glimpse on quality which overall has been good. Due to the impact of Southern Rust in many fields, corn plants shut down earlier in the season resulting in lower yields reflected in smaller kernels compared to normal and test weights about 2-3 lb/bu lower than normal. In terms of composition, starch content is somewhat lower and protein higher. On the other hand, corn is testing well below limits for six mycotoxins of concern and consistently grades No. 1 with less than 2% Broken Corn and Foreign Material (BCFM). 

Soybeans have been harvested well below the 13% marketing moisture content. In much of Iowa, moisture content has ranged from 9-11% which represents a substantial moisture shrink and yield loss. Soybeans received at the FMGSC were between 9-9.5% and are in the process of being reconditioned in one of our higher airflow bins.

Tips for Cooling Corn versus Soybeans

A good decision-making tool for when to turn on aeration fans, how long to run them, and what temperature corn and soybeans will cool to is the ISU Grain Aeration & Storage App available free of charge for Android and I-phones. It allows for determination of the Equilibrium Moisture Content (EMC) and Safe Storage Moisture Content (SSMC) relationships for corn, soybeans and more than a dozen other crops as a function of ambient temperature and relative humidity. For example, the SSMC for soybeans at 50°F is 12.6%. Thus, if soybeans are below that moisture content, it would be a waste of electricity to run aeration fans to cool them below 50°F. Additionally, soybeans cooled to that level and maintained at that moisture content or below will store well into next spring and summer. In comparison, the SSMC of corn at 50°F is 14.3% which is 0.7 percentage points (PPTs) below its market moisture content of 15%. Thus, cooling corn into the mid-30s increases its potential storage time. The SSMC of corn is 14.8% at 40°F and 15.2% at 35°F.