In some designs the air supply troughs are oriented at a right angle to the air exhaust troughs. Rice mixes as it flows around the channels. The LSU type dryer costs significantly more than an equivalent capacity column dryer and because of this, column dryers are the type most commonly installed. Most rice drying operations use column dryers and carefully control the amount of moisture removed per pass and count on moisture equalization between kernels to reduce moisture variability. Rice is subject to lower milling yields if it is dried too quickly.
Quality is maintained by drying in several passes through a dryer.
Between passes, rice is stored in temporary holding bins. This is called tempering and allows moisture levels to equalize within kernels. Most tempering is accomplished in about two hours although drying schedules often dictate that the rice be held for about 24 hours between passes. The two step system works only if flat storage has adequate air flow for drying. Late season drying in flat storage may be slow because of low air temperatures.