Symbiotic and phenotypic characteristics of thirty rhiobial isolates obtained from root nodules of two cowpea （Vigna unguiculata L. Walp） cultivars that grown in different sites of Fezzan （Southern part of Libya） ...Symbiotic and phenotypic characteristics of thirty rhiobial isolates obtained from root nodules of two cowpea （Vigna unguiculata L. Walp） cultivars that grown in different sites of Fezzan （Southern part of Libya） were studied. Cultural characteristics and cross-nodulation with Arachis hypogega and Faidherbia albida showed that they were slow-growing rhizobia. Each isolate was found to coexist with non-symbiotic bacteria similar in their cultural characteristics to fast-growing rhizobia. All isolates formed symbiosis with the test plants, but different in their nitrogen-fixation efficiency. Numerical analysis of phenotypic characteristics showed that at boundary level of 70% average similarity, the isolates formed four distinguished groups and two isolates remained separate. Most isolates exhibited wide tolerance to acidity, alkalinity and extreme temperatures. They also resistant to some heavy metals such as mercury, copper, zinc, lead, cadmium and aluminum at low concentrations and antibiotics like polymyxin, colistin, bacitracin and nalidixic acid. Isolates displayed different response to salinity ranging from sensitive, which unable to grow in 1% NaCI to resistant and grow at 2% NaCl or above. Urea was hydrolyzed by most of them and carbohydrates utilizations were different. Sucrose and maltose were metabolized by most of the test isolates, whereas, monosaccharide and sugar alcohols were poorly utilized.展开更多
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
文摘Symbiotic and phenotypic characteristics of thirty rhiobial isolates obtained from root nodules of two cowpea （Vigna unguiculata L. Walp） cultivars that grown in different sites of Fezzan （Southern part of Libya） were studied. Cultural characteristics and cross-nodulation with Arachis hypogega and Faidherbia albida showed that they were slow-growing rhizobia. Each isolate was found to coexist with non-symbiotic bacteria similar in their cultural characteristics to fast-growing rhizobia. All isolates formed symbiosis with the test plants, but different in their nitrogen-fixation efficiency. Numerical analysis of phenotypic characteristics showed that at boundary level of 70% average similarity, the isolates formed four distinguished groups and two isolates remained separate. Most isolates exhibited wide tolerance to acidity, alkalinity and extreme temperatures. They also resistant to some heavy metals such as mercury, copper, zinc, lead, cadmium and aluminum at low concentrations and antibiotics like polymyxin, colistin, bacitracin and nalidixic acid. Isolates displayed different response to salinity ranging from sensitive, which unable to grow in 1% NaCI to resistant and grow at 2% NaCl or above. Urea was hydrolyzed by most of them and carbohydrates utilizations were different. Sucrose and maltose were metabolized by most of the test isolates, whereas, monosaccharide and sugar alcohols were poorly utilized.
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.
