Abstract: The seed equilibrium moisture is an important indicator in evaluating dynamic changes of seed moisture absorption or moisture desorption. In this study, soybean and cotton seeds with different initial moisture contents (IMC) were used to explore the laws of the seed moisture absorption or moisture desorption under different storage conditions(temperature and humidity). The soybean seeds presented moisture desorption when the storage temperature(ST) was 15℃, 25℃, 40℃ and the relative humidity (RH) was less than 18.78% (4% IMC) or 48.10% (8% IMC and 12% IMC), and presented moisture absorption in other storage conditions. The cotton seeds presented moisture desorption under conditions of ST=15℃ and RH<7.49% (4% IMC), 18.78% (8% IMC) or 48.10% (12% IMC). The cotton seeds also presented moisture desorption when ST=25℃, RH<18.78% (4% IMC) or 48.10% (8% IMC and 12% IMC), or ST=40℃, RH<7.49% (4% IMC) or 48.10% (8% IMC and 12% IMC), and moisture absorption in other storage conditions. The safety water content of the cotton seeds with 4% IMC under the condition of ST=15℃ and RH>55%, ST=25℃ and RH>55%, or ST=40℃ and RH>50% was 10.5%, 9.5% and 6.5%, respectively. For cotton seeds with 8% IMC, the safety water content under the condition of ST=15℃ and RH>60%, ST=25℃ and RH>55%, ST=40℃ and RH>45% was 10.5%, 9.5% and 6.5%, respectively. The cotton seeds with 12% IMC had the same safety water content under the condition of ST=15℃ and RH>55%, ST=25℃ and the RH>55% or ST=4℃ and RH>45%. The equilibrium moisture of Liaodou 11 with 4%, 8% and 12% IMC under the condition of ST=15℃ and RH>65%, ST=25℃ and RH>55% or ST=40℃ and RH>45% was above its safety water content (12%, 11%, and 8%). The RH which was above its safety water content of Hedou 13 was about 5% higher than that of Liaodou 11. The equilibrium moisture was above its safety water content when ST=15℃, 25℃ and RH>55% or ST=40℃ and RH>60% for cotton seeds; As well as when ST=25℃ and RH>55% or ST=25℃, 40℃ and RH>60% for soybean seeds. The predictive model of equilibrium time (d) depends on IMC (x), RH (y) and temperature (z) was d =36.97+1.78x–0.58y–0.58z–0.016xy–0.021xz–0.0012yz +0.007y² for cotton seeds, and d=23.29+3.72x–0.19y–0.86z–0.02xy–0.09xz–0.008yz+0.005y²+0.03z² for soybean seeds. Through the model test, F<2.39, which indicated that the conformity was high between the predictive value and the test value. The predictive model for Hedou 13 was d=48.64+0.36x–0.44y–1.49z–0.008yz+0.006y²+0.026z². The predictive models we constructed are very useful in predicting moisture equilibrium time.

Key words: Cotton seed, Soybean seed, Moisture absorption or moisture desorption, Modeling, Model verification