Abstract: A study was carried out to determine the effect of growing grass,the grass yield,and the grass summer survival rate of a stretch of mixed-sowing grassland on three plots of former cropland along the Three Gorges Region.The displaced growths on the former croplands were rice,Manila grass, and soybean.The mixed grasses used in the study were white clover(Trifolium repens),alfalfa(Medicago sativa),orchardgrass(Dactylis glomerata),and tall fescue(Festuca arundinacea).The results show that soil condition significantly influenced the population structure and yields of the grassland.The growth of gramineous grasses was retarded in the poor soil of the former manila grass land,whereas in which legumes grew better,though the yield was the lowest compared to that of grasses sowed on the former rice or soybean cropland.Gramineous grasses grew well on the fertile soil of the former soybean land,but the soil sod inhibited the growth of legumes.The population structure of mixed-sowing grassland was relatively stable on the soil of the previous rice cropland.Compared with alfalfa(M.sativa),white clover(T.repens) was better suited to be mixed with orchardgrass(D.glomerata) and tall fescue(F.arundinacea),and could enhance yield in such soil.The soil fertility also influenced the summer survival rate of cold-season grasses in the Chongqing municipality area.Moreover,rich coverage rate of sod prior to the arrival of the scorching summer of the area ensured the grasses summer survival rate.

Key words: Three Gorges Region, Restored cropland, Mixed-sowing grassland, Summer survival rate

摘要： 选择白三叶(Trifolium repens)、紫花苜蓿(Medicago sativa)、苇状羊茅(Festuca arund inacea)和鸭茅(Dactylisg lomerata),在三峡库区沿江地带3种前茬分别为水稻(Rice)、沟叶结缕草(Manila grass)和黄豆(Soybean)的退耕地进行混播试验,研究当年的生长动态、产草量组成及其越夏率。结果表明:禾本科牧草与白三叶混播,产草量显著高于与苜蓿的混播组合,且产草量比重相对稳定;苜蓿竞争性差,不适宜混播;土壤条件显著影响混播效益及其产草量;结缕草茬的土壤肥力低,禾本科牧草长势差,有利于豆科牧草生长,其产草量显著低于其它两种前茬;黄豆茬土壤肥力好,禾本科牧草早期生长旺盛,将抑制豆科牧草;水稻茬的混播组合相对稳定;土壤肥力直接影响混播牧草的越夏率;伏旱来临之前,良好的草层盖度有利于牧草越夏。

关键词: 三峡库区, 退耕地, 混播草地, 越夏率