Major nutrient balances in small-scale vegetable farming systems in peri-urban areas in China

Balances of major nutrients such as nitrogen (N), phosphorus (P), and potassium (K) in small-scale farming systems are of critical importance to nutrient management and sustainable agricultural development. Mass balances of N, P, and K and some of their influencing factors were studied for two years from July 2003 to July 2005 on small-scale vegetable-farming systems in two contrasting peri-urban areas (Nanjing and Wuxi) of the Yangtze river delta region of China. This balance approach considered organic fertilizer inputs (cow manure, pig manure, and human biosolids), inorganic fertilizer inputs (urea, composite fertilizer, and phosphates), irrigation water, and atmospheric deposition; and considered outputs by vegetables. Input via organic fertilizers was significant for all element balances in the Nanjing area. Inorganic and organic fertilizer, particularly inorganic fertilizer, contributed major nutrient inputs to the system in the Wuxi area. Compared with nutrient output by vegetables, there were significant surpluses of N and P on two vegetable farm systems. Furthermore, N surplus in the Nanjing area was higher than that in the Wuxi area with an inverse relationship to P surplus. In contrast, the general trend of K balances was negative on both sites; hence, the nutrient use efficiency was significantly lower for N and P than K. The nutrient imbalance may be attributed to the differences between fertilizer types and management modes driven by social economic status differences among farmer households. The large N and P net excess creates an environmental threat because of potential losses to ground or surface waters, whereas negative K balance creates soil fertility risks. The results highlight researchers’ and farmers’ need to develop rational fertilization technology to optimize nutrient management on vegetable farmlands to promote sustainable agricultural development in peri-urban areas.     

低能离子注入诱变酿酒酵母菌胞外代谢产物的差异性分析

基于代谢组学方法研究低能离子束诱变重组菌株N6076与原始菌株Kh08在不同发酵时期的差异性胞外代谢产物,并通过网络药理学探讨了相关代谢通路.结果表明,不同时期两种菌株的胞外代谢产物存在明显差异,鉴定出VIP>1的15种代谢差异物,其中吲哚3-丙酸不仅作为共同的代谢产物,而且其差异性也最为显著.基于网络药理学的差异代谢...     

食源性沙门菌流行趋势及耐药性研究进展

沙门菌病是主要的食源性疾病,构成了全球范围内主要的公共卫生问题,我国由沙门菌引起的食源性疾病也占首位.研究发现,肉制品可能是人类沙门菌病主要的传染源,且近年来在全球范围内,肉制品中耐药性沙门菌的检出率居高不下,这使临床医生治疗时可选择的药物受到限制.随着家禽肉类食品的日益全球化,沙门菌病的控制可能会面临更严峻的挑战,因...     

Metabolic and endocrine changes in response to endotoxin administration with or without oral arginine supplementation

This study was performed to investigate blood metabolite, tumor necrosis factor-alpha, and hormone responses to intravenous administration of lipopolysaccharides (2 microg of endotoxin of Escherichia coli 026:B6/kg body weight at times of feeding) in veal calves orally supplemented with arginine (0.25 g/kg of body weight twice daily for 4 d; group GrA) compared with calves not supplemented with arginine (group GrC). Arginine supplementation alone caused a significant rise of plasma arginine, urea, and insulin concentrations, whereas glucagon concentrations tended to increase, but there were no significant group differences. Concentrations of triglycerides, NEFA, glucose, protein, albumin, growth hormone, insulin-like growth factor-I, 3.5.3'-triiodothyronine, and thyroxine were not affected by arginine supplementation. Lipopolysaccharide administration alone caused a rise of tumor necrosis-factor-a, lactate, and cortisol concentrations and concentrations of tumor necrosis-factor-a after 1 h, and of triglycerides and urea after 6 h were higher, whereas of glucose after 3 h were lower in GrA than in GrC. Concentrations of NEFA, glucose, protein, albumin, insulin, growth hormone, insulin-like growth factor-I, 3.5.3'-triiodothyronine, and thyroxine were not affected by lipopolysaccharide administration. In conclusion, arginine supplementation had selective effects on plasma metabolites and hormones, but barely modified lipopolysaccharide effects. Effects of lipopolysaccharides in the postprandial state were different from what is usually seen in the fasted state.