Moisture Variation and Modeling of Cotton and Soybean Seeds under Different Storage Conditions

Seed equilibrium moisture is an important indicator to evaluate dynamic change of seed moisture absorption or desorption. In this study, soybean (Glycine max cv. Liaodou 11 and Hedou 13) and cotton (Gossypium hirsutum cv. Fengkangmian 6) seeds with high (12%), medium (8%), and low (4%) initial moisture contents (IMCs) were stored in different levels of storage temperature and relative humidity (RH) to construct models for predicting equilibrium time during storage. Seeds with the 3 IMCs presented desorption under RH = 18.78% except for Liaodou 11 seeds with low IMC under RH 18.78% at 40(C, Fengkangmian 6 with low IMC under RH 18.78% at 15(C and 40(C. All seeds presented desorption under RH 100% regardless of storage temperature. However, under RH 48.10%, moisture desorption or absorption was associated with species/cultivar, IMC, and temperature. Generally, absorption was shifted to desorption with the increase of IMC. In cotton, the equilibrium moisture content (EMC) of seed was increased with the increase of RH under the same storage temperature; whereas it was reduced with the increase of storage temperature under the same IMC. For soybean seed, there was also a positive correlation between EMC and RH under the same temperature, but the EMC was the highest at 25°C and the lowest at 40°C under the same seed IMC except for Liaodou 11 with seed IMC of 8%. In cotton, the safe water contents (SWCs) of seed were 10.5% at 15°C, 9.5% at 25°C, and 6.5% at 40°C. In soybean, the SWCs of seed were 12% at 15°C, 11% at 25°C, and 8% at 40°C. Under some temperature and RH combinations, the seed EMC exceeded its SWC. For instance, RH > 55% at 15°C and 25°C and RH > 60% at 40°C for cotton seeds and RH > 55% at 25°C and RH > 60% at 25°C for soybean seeds. The equilibrium time of seeds was stimulated with the following equations: d = 36.97 + 1.78x – 0.58y – 0.58z – 0.016xy – 0.021xz – 0.0012yz + 0.007y2 for Fengkangmian 6; d = 23.29 + 3.72x – 0.19y – 0.86z – 0.02xy – 0.09xz – 0.008yz + 0.005y2 + 0.03z2 for Liaodou 11; and d = 48.64 + 0.36x – 0.44y – 1.49z – 0.008yz + 0.006y2 + 0.026z2 for Hedou 13. Where d is equilibrium time, x is IMC, y is RH, z is storage temperature. These models were verified using another set of data obtained from the same cultivars with seed IMCs of 5%, 10% and 16% under RH of 12.5%, 25.0%, 75.0%, 85.0% and 100.0% and storage temperatures of 15, 25 and 40°C. F-test showed that there were no significant differences between the predicted values and the observed values, indicating the effectiveness of and fitness of the models.

摘 要以不同初始水分(IMC)大豆和棉花种子为试材, 研究不同贮藏条件下的吸湿解吸规律, 并建模验证。结果表明, 大豆种子, 贮温15℃、25℃和40℃时, 4%IMC在相对湿度(RH)≤18.78%、8%和12% IMC在RH≤48.10%条件下解吸, 其他条件下吸湿。棉花种子, 15℃时, 4% IMC在RH≤7.49%、8%IMC在RH≤18.78%和12% IMC在RH≤48.10%条件下解吸, 其他条件下吸湿; 25℃时, 4% IMC在RH≤18.78%、8%和12%IMC在RH≤48.10%条件下解吸, 其他条件下吸湿; 40℃时, 4%IMC在RH≤7.49%、8%和12% IMC在RH≤48.10%条件下解吸, 其他条件下吸湿。棉花种子, 4% IMC在15℃ RH>55%、25℃ RH>55%和40℃ RH>50%时的安全水分(SWC)依次为10.5%、9.5%和6.5%; 8%IMC在15℃RH>60%、25℃ RH>55%和40℃ RH>45%时的SWC分别为10.5%、9.5%和6.5%; 12% IMC在15℃ RH>55%、25℃ RH>55%和40℃ RH>45%时的SWC分别为10.5%、9.5%和6.5%。辽豆11在15℃ RH>60%、25℃ RH>55%和40℃RH>45%时, 其平衡水分(EMC)超过其SWC(依次为12%、11%和8%); 菏豆13在相同条件下水分平衡时的RH比辽豆11高5%。棉花种子EMC在15和25℃ RH>55%、40℃ RH>60%时超过其SWC; 大豆种子EMC在25℃ RH>55%、25℃和40℃ RH>60%时超过其SWC。棉花种子的水分平衡时间(d)与IMC(x)、RH(y)和温度(z)的预测模型为d =36.97+1.78x–0.58y–0.58z–0.016xy–0.021xz–0.0012yz+0.007y2, 辽豆11的为d =23.29+3.72x–0.19y– 0.86z–0.02xy–0.09xz–0.008yz+0.005y2+0.03z2, 菏豆13的为d =48.64+0.36x–0.44y–1.49z–0.008yz +0.006y2+0.026z2。模型经检验, 预测性良好。