Symbiotic and phenotypic characteristics of thirty rhiobial isolates obtained from root nodules of two cowpea (Vigna unguiculata L. Walp) cultivars that grow 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% NaCl 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.

Digesting animal manure anaerobically before applying it as fertilizer may be affected crop production differently compared to non-digested, particularly in desert soils. A pot experiment was carried out to evaluate three nondigested dry matter (NDM) and digested dry matter (DM) farmyard manures (cattle, poultry, and sheep) and their combinations with urea on the wheat crop cultivated in desert soil. Fertilizers were applied at rates corresponding to 50, 150, and 250 kg total nitrogen ha −1. During the growing period, seed germination percentage (SGP), plant height, plant tillering percentage (PTP), and deficiency symptoms were assessed. Furthermore, total biomass yield and relative yields of ear, straw, and root fractions were measured at harvest. Results showed that high application of DM reduced SGP significantly (P < 0.05), especially at the combination with urea. PTP was higher in non-digested manure treatments of sheep and poultry than DM, and also higher in digested cattle manure treatments than NDM, while it was zero in all urea treatments and control. Deficiency symptoms were seen in the treatments of low application rate as well as in all urea treatments and control. Plant height and biomass yield generally increased in NDM and DM treatments compared with urea treatments and the control. Beneficial of DM was seen in cattle and poultry manure (PM) treatments where they significantly (P < 0.05) yielded higher root, ears, and total biomass compared to NDM. However, non-digested sheep and PM yielded higher straw biomass than DM. The combination of non-digested and digested manure with urea gave the maximum biomass yield, especially in combination with digested PM.

Inoculation with Rhizobium meliloti and nitrogen fertilization on alfalfa increased the plant density, forage fresh yield and the protein content, and decreased the crude fibre content of alfalfa. Materials and methodsRhizobium meliloti strain ENRRI A12 was supplied by the National Centre for Research, Khartoum. Broth culture (400 ml of 1 × 10 9 cfu/ml) was aseptically added to 1kg of sterile fine charcoal adjusted to pH 6.7 and incubated in plastic bags at 26-28°C for 15 days. A series of pots were filled with Shambat clay soil with 17% silt, 31% sand and 48% clay; pH = 7.89, ECe = 1.10dS/m, SAR = 4.02; Na, Ca, Mg and K 5.83, 2.9, 1.3 and 0.26 mg/l, respectively, and N and P 0.04% and 0.011%, respectively. Ten seeds were sown in each pot and irrigated with tap water every 2 days. One week after sowing, urea was broadcast at the rate of 20, 40, 60, 80 and 100 kg N/ha and zero (control). The seedlings were thinned to six after emergence. Two weeks later the inoculum was injected around one triplicate set of seedlings at 5ml per plant, while another set was left uninoculated. Plants were harvested 10 weeks after transplanting.A field experiment was conducted at the University Farm in the semi-arid zone, with hot summers and a short rainy season in July-September with rainfall of 67.8 mm. Land prepared by deep ploughing, harrowing and levelling was ridged and divided into 5 × 3m plots. Seed at the rate of 50kg/ha coated with Rhizobium inoculum was broadcast randomly and irrigation water was applied immediately. Further irrigation was applied 5 days later and then every 11