Pub Ii cation AE-84 December 1972
Drying Soybeans with Heated and Unheated Air
B. A. McKenzie, Agricultural Engineering Department
FOREWORD
Soybeans do not usually require drying at harvest time as a regular practice. The crop does not adapt well to early harvest at high moisture contents until the plant has died from either complete maturity, or a killing frost or freeze. Prior to that time, the range in bean maturity from completely green and soft to fully mature and hard, presents problems in harvesting, and may affect yield.
The maturity spread problem has usually best been solved by letting the soybeans mature and field dry. Field and weather conditions in the Fall are usually such that field drying has worked well with little risk. There has been little pressure to develop forced drying procedures. Farmers have little experience, and there is very little technical information based on drying studies on soybeans. Most information is derived from experience with other crops.
In two of the last three years, however, in 1970 and again in 1972, there have been serious problems in getting the crop harvested. A number of producers are turning to drying as a way of increasing the number and length of available operating days, decreasing the potential field loss, and insuring the best possible quality of the harvested bean in the storage.
GENERAL DRYING REQUIREMENTS AND LIMITS
There is no doubt that drying as an emergency or continuing practice can aid in soybean harvesting and storage. Once the bean plants have matured or been frosted and have died, the immature beans shrivel and dry so that seed moisture is more uniform. Moisture content of beans standing in the field may swing from \6% in the morning from a heavy dew or rain to as low as 9 - 11^ during the heat of the afternoon In good drying weather.
In periods of cold, wet, rainy weather such as the Fall of 1972, the moisture on the standing beans may hover around 16 - 20>G and never approach safe storage levels. These high moisture beans can be very successfully harvested provided the soil conditions will support equipment, and the weather is favorable to dry the foliage.
Basically, all grain drying methods are adaptable to soybeans, with some restrictions on the use of heat, and on handling practices. The successful use of unheated air depends on the drying rate required and the conditions of the air aval I able.
Cooperative Extension Service, Purdue University, Lafayette, Indiana