If sun drying is managed properly, it can produce high-quality grain. To improve sun drying:
Spread the grains in thin layers of ideally 2–4 cm. Very thin layers tend to heat up very quickly with a negative effect on head rice recovery. If layers are too thick, a large moisture gradient develops with dry grains on the top and wet grains on the bottom, which re-absorbs moisture after mixing, resulting in cracked grains.
Turn or stir the grain every 30 minutes. During good weather conditions, mixing or turning the grain is the most important activity for maintaining good quality. Variation in moisture content within the grain causes rewetting and subsequent cracking of drier grains.
Additional measures to maintain optimum quality during sun drying
On hot days, grain temperature can rise above 50–60ºC. If this is the case, cover the grain at mid-day to prevent over heating.
Cover the grain immediately if it starts raining. Rewetting of grain results in fissured grains and high grain breakage during milling.
Prevent contamination of grain with other materials and keep animals off the grain.
Monitor grain moisture content and grain temperature.