排序方式： 共有45条查询结果，搜索用时 15 毫秒
31.
32.
33.
The effects of different types of organic fertilizers on the chemical and enzymatic properties of an Oxisol were studied after being fertilized for four consecutive years (26 crops) in a greenhouse under intensive cultivation of vegetables. Seven treatments, consisting of five types of organic fertilizer treatments, one "sequential application" (SA) treatment, and a chemical fertilizer treated plot were compared. The organic fertilizers used were dairy cattle dung compost (DCDC), hog dung compost (HDC), chicken dung compost (CDC), pea residue compost (PRC) and soybean meal (SBM). After 4 years of cultivation, the soils were analyzed for their chemical properties and enzymatic activities. The microbial carbon (C) and nitrogen (N), basal respiration and nitrification rate were also measured. The results showed that the SBM significantly lowered the soil pH, and that the HDC and DCDC raised the soil pH. The SBM and CDC resulted in the lowest soil electrical conductivity. The SBM had no significant effect on soil organic C and total N contents when compared with the CF plot. However, the DCDC resulted in the highest contents of soil organic C and total N. The organic fertilizers applied did not significantly affect the soil available copper, zinc, cadmium, lead and nickel. The effects of the different organic fertilizers on soil enzymatic activities depended on the types of organic fertilizers applied. The SBM and CDC often resulted in a lower microbial C (or N) and respiration rate, while in contrast DCDC and PRC resulted in high measurements. Most of the measured soil enzymatic activities in the SBM treatment, except for acid phosphatase, were the lowest. Differing contents of different heavy metals in the organic fertilizers resulted in different Mehlich III extractable heavy metal contents in the soils. From the point of view of the soil chemical and enzymatic properties, SBM is not an appropriate organic fertilizer for continuous application to an Oxisol. 相似文献
34.
35.
36.
37.
38.
39.
体外成熟培养20～22h牛卵母细胞激活及孤雌发育的研究 总被引：3，自引：0，他引：3
本研究将体外成熟培养 2 0～ 2 2h的牛卵母细胞 ,用Ca2 + 上升因子单一激活或组合Ca2 + 上升因子和蛋白质抑制因子激活 ,其结果单一激活的卵子激活率在 19.2 %～ 2 8.0 % ,复合激活的卵子激活率在 84 .2 %～ 86 .8%。单一激活组的卵子激活率显著高于对照组 (P <0 .0 5 ) ,复合激活组的卵子激活率显著高于单一激活组 (P <0 .0 1) ,而单一激活组之间和复合激活组之间无显著差异 (P >0 .0 5 )。复合激活组的卵裂率及孤雌发育都显著高于对照组。 相似文献
40.
TRAN DANG KHANH TRAN DANG XUAN ILL MIN CHUNG SHINKICHI TAWATA 《Weed Biology and Management》2008,8(4):267-275
Barnyardgrass is one of the most noxious paddy weeds in the world and causes great trouble to many crops. In a bioassay, the aqueous extract of paddy soil infested with barnyardgrass showed phytotoxic action against the growth of the tested crops and paddy weeds, of which rice was the most suppressed among the crops. In contrast, barnyardgrass was the least affected paddy weed. By the use of a separation resin, 18 compounds belonging to terpenes, derivatives of cinnamic acid and ferulic acid, long‐chain fatty acids, and steroids that were potentially involved in the phytotoxic activities in barnyardgrass‐infested soil were isolated and identified by gas chromatography–mass spectrometry analysis. Of these, the quantities of linalool, 4‐terpinenol, coumaran, methyl phenethyl ketone, and methyl ester cinnamic acid were 1.42, 0.37, 0.02, 3.12, and 4.59 μg g?1 of the wet soil, respectively. The herbicidal activity was varied among these qualified test compounds, in which methyl phenethyl ketone and methyl ester cinnamic acid were more herbicidal than coumaran, linalool, and 4‐terpinenol. A mixture of these compounds was also the least inhibitive against the growth of barnyardgrass, but exerted strong suppression against that of rice and monochoria. The present study demonstrates that barnyardgrass possesses strong phytotoxic properties and releases plant growth inhibitors into the soil to compete with rice and other paddy weeds in its vicinity by a chemical pathway. 相似文献