To determine the best combinations of organic and mineral fertilizer applications under resource-limited conditions in the Sahel, West Africa, on-farm experiments for two years in the Fakara region of western Niger is...To determine the best combinations of organic and mineral fertilizer applications under resource-limited conditions in the Sahel, West Africa, on-farm experiments for two years in the Fakara region of western Niger is conducted. Ten treatments were tested; six of them received one of three organic fertilizers (none, millet husks, or manure), with or without mineral fertilizer; two grew millet/(dual-purpose) cowpea intercrops with mineral fertilizer in 1:1 or 4:4 row arrangement; one grew a millet/(spreading) cowpea intercrop with manure; and one grew a millet/hibiscus intercrop with millet husks. Manure increased total biomass by 127%- 147% (P 〈 0.001 ) and millet yield by 130%- 184% (P 〈 0.01 ). Mineral fertilizer increased total biomass by 27% (P 〈 0.01 ) and millet yield by 24% (P 〈 0.05) in 2008. The N balance was greatest and positive in the manure treatment (P 〈 0.001), followed by millet husks. Mineral fertilizer on the intercropped dual-purpose cowpea increased the agronomic N use efficiency of millet by 329%-483% (P 〈 0.01) compared with manure. The use of small quantities of mineral fertilizer on the intercropped dual-purpose cowpea, therefore, is a best combination for limited N-resources-farmers. Single manure, millet husks plus mineral fertilizer, or year-alternative-application are also recommendable depends on farmers accessibility to the resources.展开更多
Knowledge of plant responses to soil water availability is essential for the development of effcient irrigation strategies.However,notably different results have been obtained in the past on the responses of various p...Knowledge of plant responses to soil water availability is essential for the development of effcient irrigation strategies.However,notably different results have been obtained in the past on the responses of various physiological indices for different plants to soil water availability.In this study,the responses of various plant processes to soil water availability were compared with data from pot and field plot experiments conducted on maize(Zea mays L.).Consistent results were obtained between pot and field plot experiments for the responses of various relative plant indices to changes in the fraction of available soil water(FASW).A threshold value,where the relative plant indices began to decrease with soil drying,and a lower water limit,where the decline of relative plant indices changed to a very slow rate,were found.Evaporative demand not only influenced the transpiration rate over a daily scale but also determined the difference in transpirational response to soil water availability among the transient,daily and seasonal time scales.At the seasonal scale,cumulative transpiration decreased linearly with soil drying,but the decrease of transpiration from FASW = 1 in response to water deficits did not affect dry weight until FASW = 0.75.On the other hand,the decrease in dry weight was comparable with plant height and leaf area.Therefore,the plant responses to soil water availability were notably different among various plant indices of maize and were influenced by the weather conditions.展开更多
A sequencing batch reactor (SBR) seeded with activated sludge was established for landfill leachate treatment. Small bio-aggregates began to appear after 40-d operation, and gradually changed to mature aerobic granu...A sequencing batch reactor (SBR) seeded with activated sludge was established for landfill leachate treatment. Small bio-aggregates began to appear after 40-d operation, and gradually changed to mature aerobic granules, with a mean size of 0.36-0.60 ram. Their sludge volume index at 5 min (SVI5 rain), mixed liquor volatile suspended solids (MLVSS), and wet density were around 35 ml/g, 3.4 g/L, and 1.062 g/cm3, respectively. The settling velocities of the granules in distilled water ranged from 0.3 to 1.3 cm/s, which were faster than those in landfill leachate with a salt content of 1.4% (w/v), and also slightly faster than those predicted by Stokes' law for porous but impermeable particles. Microbial community evolution during the granulation process and stages under different nitrogen loading rates (NLRs) were monitored and analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), cloning, and sequencing of 16S ribosomal RNA (rRNA) fragments. Results revealed that some primary and dominant communities in inoculating activated sludge died out gradually; while a few common bacteria, inhabiting soils, municipal wastewater, or activated sludge systems, dominated in the SBR system throughout. In addition, some other dominant species, associated with the aerobic granulation process, were thought to play a significant role in the formation and growth of aerobic granular sludge. During the stable operation time under low NLR, a few species were present in abundance, and may have been responsible for the high organic removal efficiency at this time.展开更多
文摘To determine the best combinations of organic and mineral fertilizer applications under resource-limited conditions in the Sahel, West Africa, on-farm experiments for two years in the Fakara region of western Niger is conducted. Ten treatments were tested; six of them received one of three organic fertilizers (none, millet husks, or manure), with or without mineral fertilizer; two grew millet/(dual-purpose) cowpea intercrops with mineral fertilizer in 1:1 or 4:4 row arrangement; one grew a millet/(spreading) cowpea intercrop with manure; and one grew a millet/hibiscus intercrop with millet husks. Manure increased total biomass by 127%- 147% (P 〈 0.001 ) and millet yield by 130%- 184% (P 〈 0.01 ). Mineral fertilizer increased total biomass by 27% (P 〈 0.01 ) and millet yield by 24% (P 〈 0.05) in 2008. The N balance was greatest and positive in the manure treatment (P 〈 0.001), followed by millet husks. Mineral fertilizer on the intercropped dual-purpose cowpea increased the agronomic N use efficiency of millet by 329%-483% (P 〈 0.01) compared with manure. The use of small quantities of mineral fertilizer on the intercropped dual-purpose cowpea, therefore, is a best combination for limited N-resources-farmers. Single manure, millet husks plus mineral fertilizer, or year-alternative-application are also recommendable depends on farmers accessibility to the resources.
基金Supported by the CAS/SAFEA International Partnership Program for Creative Research Teamsthe Knowledge Innovation Program of the Chinese Academy of Sciences (No.KSCX1-YW-09-07)the National Natural Science Foundationof China (No.40671083)
文摘Knowledge of plant responses to soil water availability is essential for the development of effcient irrigation strategies.However,notably different results have been obtained in the past on the responses of various physiological indices for different plants to soil water availability.In this study,the responses of various plant processes to soil water availability were compared with data from pot and field plot experiments conducted on maize(Zea mays L.).Consistent results were obtained between pot and field plot experiments for the responses of various relative plant indices to changes in the fraction of available soil water(FASW).A threshold value,where the relative plant indices began to decrease with soil drying,and a lower water limit,where the decline of relative plant indices changed to a very slow rate,were found.Evaporative demand not only influenced the transpiration rate over a daily scale but also determined the difference in transpirational response to soil water availability among the transient,daily and seasonal time scales.At the seasonal scale,cumulative transpiration decreased linearly with soil drying,but the decrease of transpiration from FASW = 1 in response to water deficits did not affect dry weight until FASW = 0.75.On the other hand,the decrease in dry weight was comparable with plant height and leaf area.Therefore,the plant responses to soil water availability were notably different among various plant indices of maize and were influenced by the weather conditions.
基金Project supported by the National Water Pollution Control and Man-agement Project of China (No. 2009ZX07314-002)the Tianjin Science and Technology Development Program (No. 06YFGZSH06700)the Science and Technology Planning Project of Tianjin Binhai New Area, China (No. 2010-Bk130067)
文摘A sequencing batch reactor (SBR) seeded with activated sludge was established for landfill leachate treatment. Small bio-aggregates began to appear after 40-d operation, and gradually changed to mature aerobic granules, with a mean size of 0.36-0.60 ram. Their sludge volume index at 5 min (SVI5 rain), mixed liquor volatile suspended solids (MLVSS), and wet density were around 35 ml/g, 3.4 g/L, and 1.062 g/cm3, respectively. The settling velocities of the granules in distilled water ranged from 0.3 to 1.3 cm/s, which were faster than those in landfill leachate with a salt content of 1.4% (w/v), and also slightly faster than those predicted by Stokes' law for porous but impermeable particles. Microbial community evolution during the granulation process and stages under different nitrogen loading rates (NLRs) were monitored and analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), cloning, and sequencing of 16S ribosomal RNA (rRNA) fragments. Results revealed that some primary and dominant communities in inoculating activated sludge died out gradually; while a few common bacteria, inhabiting soils, municipal wastewater, or activated sludge systems, dominated in the SBR system throughout. In addition, some other dominant species, associated with the aerobic granulation process, were thought to play a significant role in the formation and growth of aerobic granular sludge. During the stable operation time under low NLR, a few species were present in abundance, and may have been responsible for the high organic removal efficiency at this time.