[Effects of different fertilization patterns on soil enzyme activities in greenhouse vegetable field.] / ä¸åŒæ–½è‚¥æ¨¡å¼å¯¹è®¾æ–½èœç”°åœŸå£¤é ¶æ´»æ€§çš„å½±å“.

A fixed-site greenhouse vegetable fertilization experiment was carried out to study effects of 6 fertilization patterns on soil enzyme activities in Tianjin City, Northern China. The results showed that during the growing stages of tomato, activities of soil α-glucosidase, ß-xylosidase, ß-glucosidase, ß-cellobiosidase, chitinase and phosphatase in different treatments all increased first and then decreased, while soil urease activities increased first and then became flat. Compared with the chemical nitrogen fertilizer treatment, soil enzyme activities were much higher in treatments of combined application of organic materials with chemical fertilizers, and rose with the increasing input of pig manure and especially the application of straw. A significant positive correlation was found between soil enzyme activities, microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) contents at different growing stages of tomato. Under the condition of same nutrient input, the combined application of inorganic fertilizers with organic materials, especially a certain amount of corn straw, was capable of increasing soil enzyme activities and keeping soil fertility and sustainability in greenhouse vegetable production.

[Effect of the complex of casein phosphopeptide and amorphous calcium phosphate on reducing enamel demineralization and promoting remineralization].

OBJECTIVE: To investigate the effect of the complex of casein phosphopeptide and amorphous calcium phosphate (CPP-ACP) on the demineralization and remineralization of dental enamel in vitro. METHODS: Premolars extracted from patients receiving orthodontic treatment were cut into two slabs, which were embedded and polished. The slabs were randomly divided into non-acid etching group, acid etching group (immersed in 37.5% phosphoric acid for 2 minutes), experimental group A (immersed in 37.5% phosphoric acid for 2 minutes and wiped by CPP-ACP for 3 minutes, then immersed in distilled water for 7 days), experimental group B (immersed in 37.5% Phosphoric acid for 2 minutes and wiped by CPP-ACP for 3 minutes, then immersed in distilled water for 14 days), experimental group C (immersed in 37.5% phosphoric acid for 2 minutes and wiped by CPP-ACP for 3 minutes, then immersed in distilled water for 21 days), experimental group D (immersed in 37.5% phosphoric acid for 2 minutes and wiped by CPP-ACP for 3 minutes, then immersed in distilled water for 28 days), with 6 slabs in each group. The mineral content was determined by scanning electron microscope. RESULTS: There was a large amount of mineral deposited on enamel surface in experimental group A, B, C, D. The calcium content of experimental group D was higher than those of other 3 experimental groups. The calcium content of experimental group A, B, C, D (66.53 ± 0.63, 67.00 ± 0.49, 67.07 ± 0.24, 67.18 ± 0.50) was higher than that of acid etching group (65.74 ± 0.68) (P < 0.05). There was no significant difference of the calcium content among experimental group A, B, C, D (P > 0.05). CONCLUSIONS: CPP-ACP can reduce enamel demineralization and promote remineralization in vitro.