Abstract: Nine maize hybrids differing in maturity duration were planted in Harbin in 2014 and 2015 to study their characteristics of accumulation, distribution and translocation of dry matter, and to provide theoretical guidance for selecting suitable maize varieties adapting to wholly mechanized maize production. The results showed that kernel number and yield of midlate maturity hybrids were higher than those of midearly and superearly maturity ones, but the yield difference between midlate and midearly hybrids was not significant. Dry matter accumulated before or after silking increased with hybrid’s longer growth stage. Difference in dry matter accumulated after silking between midlate and midearly hybrids was not significant. The grain accounted for the main proportion of dry matter after maturity, and the order from high to low proportion of other organs was stem, leaf, cob, bract, and leaf sheath. The harvest index of midearly hybrids was four percents higher than that of superearly and midlate ones. Matter translocation from vegetative organs were different, and dry matter translocation from leaf was found in the three types of hybrids, but dry matter translocation from leaf sheath was not observed in the superearly maturity hybrids and was found once a while in the midearly and midlate maturity ones. The percentage of dry matter accumulated after silking was from 56% to 69%, and the contribution rate of dry matter accumulated after silking to yield was from 89% to 98%. Therefore, the grain yield depended on assimilation products after silking but not on dry matter translocation from vegetative tissues in Harbin. The amount of dry matter accumulated before and after silking was significantly positively correlated with effective accumulated temperature above 10 ℃ from seedling to silking, and significantly negatively correlated with effective accumulated temperature above 10 ℃ from silking to mature.

Key words: antibiotic resistance genes, ecological risk, pig farm, bioaerosol, conditioned pathogen, sampling time