A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized d...A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized design was established with three replications and five treatments, i.e., NO-3-N/NH4+-N of 100/0, 75/25, 50/50, 25/75 and 0/100. Results showed that 25% replacement of NO3--N by NH4+-N significantly (P = 0.05) improved fresh and dry weight, revealing that a proper percentage of NH4+-N was important for tomato nitrogen nutrition. This could increase the plant growth even though tomato was a crop that preferred nitrate nutrition. Also an increase in the proportion of NH4+-N in the nutrient solution led to a significant decrease (P = 0.05) in malate, citrate and fumarate. However, the 25% NH4+-N plus 75% NO3--N treatment had no significant effect (P = 0.05) on the 2-ketoglutarate, succinate or oxalic acid content, showing that only some organic acids in tomato plants were affected. Only pyruvate increased significantly (P = 0.05), and it only increased for 25% and 50% replacement of NO3--N by NH4+-N. Metabolism of these organic acids, especially malate, citrate and fumarate, should be further studied at the molecular level in vegetables applied with different nitrogen forms.展开更多
Laboratory-scale tests for magnesium ammonium phosphate（MAP）precipitation following urea hydrolysis of human urine were conducted using orthogonal experiment design.The effects of initial pH,temperature and the volu...Laboratory-scale tests for magnesium ammonium phosphate（MAP）precipitation following urea hydrolysis of human urine were conducted using orthogonal experiment design.The effects of initial pH,temperature and the volumetric ratios of stale urine to fresh urine,on urea hydrolysis in urine were studied to determine the final hydrolysis time to recover most nitrogen from separated human urine by MAP.With a volumetric ratio of stale to fresh urine>10% and at temperature≥20℃,urea hydrolysis could be completed in two days.Alkaline pH inhibited urea hydrolysis progress.The final pH values were all around 9.0 following urine hydrolysis,while the suspension pH might act as an indicator to detect the start and extent of urea hydrolysis.Over 95% of ammonium nitrogen and over 85% of phosphorus from hydrolyzed urine as MAP precipitate were obtained using MgCl;·6H;O and Na;HPO;·12H;O as precipitation agents at pH 8.5,molar ratio of Mg;:NH;-N:PO;-P at（1.2-1.3）:1:1,mixing speed of 120 r/min,and precipitation time and reaction time of 3 h and 15 min,respectively.The precipitate has a structure resembling pure MAP crystal.展开更多
基金Project supported by the National Natural Science Foundation of China (No. 30270790) and National Post-doctoral Foundation of China (No. 2003033494).
文摘A hydroponic experiment was conducted to study the effect of partial replacement of NO-3-N by NH4+-N on the seedling growth and organic acid content of tomato (Lycopersicon esculentum Mill.). A completely randomized design was established with three replications and five treatments, i.e., NO-3-N/NH4+-N of 100/0, 75/25, 50/50, 25/75 and 0/100. Results showed that 25% replacement of NO3--N by NH4+-N significantly (P = 0.05) improved fresh and dry weight, revealing that a proper percentage of NH4+-N was important for tomato nitrogen nutrition. This could increase the plant growth even though tomato was a crop that preferred nitrate nutrition. Also an increase in the proportion of NH4+-N in the nutrient solution led to a significant decrease (P = 0.05) in malate, citrate and fumarate. However, the 25% NH4+-N plus 75% NO3--N treatment had no significant effect (P = 0.05) on the 2-ketoglutarate, succinate or oxalic acid content, showing that only some organic acids in tomato plants were affected. Only pyruvate increased significantly (P = 0.05), and it only increased for 25% and 50% replacement of NO3--N by NH4+-N. Metabolism of these organic acids, especially malate, citrate and fumarate, should be further studied at the molecular level in vegetables applied with different nitrogen forms.
文摘Laboratory-scale tests for magnesium ammonium phosphate（MAP）precipitation following urea hydrolysis of human urine were conducted using orthogonal experiment design.The effects of initial pH,temperature and the volumetric ratios of stale urine to fresh urine,on urea hydrolysis in urine were studied to determine the final hydrolysis time to recover most nitrogen from separated human urine by MAP.With a volumetric ratio of stale to fresh urine>10% and at temperature≥20℃,urea hydrolysis could be completed in two days.Alkaline pH inhibited urea hydrolysis progress.The final pH values were all around 9.0 following urine hydrolysis,while the suspension pH might act as an indicator to detect the start and extent of urea hydrolysis.Over 95% of ammonium nitrogen and over 85% of phosphorus from hydrolyzed urine as MAP precipitate were obtained using MgCl;·6H;O and Na;HPO;·12H;O as precipitation agents at pH 8.5,molar ratio of Mg;:NH;-N:PO;-P at（1.2-1.3）:1:1,mixing speed of 120 r/min,and precipitation time and reaction time of 3 h and 15 min,respectively.The precipitate has a structure resembling pure MAP crystal.
