Competition between soybean and cowpea rhizobia and bradyrhizobia in nodulating soybean.

The competitive interactions among four strains that nodulate soybean and cowpea rhizobia were studied in soybean plants grown under pot and field conditions. All the possible combination between the four strains; Bradyrhizobium japonicum USDA 110, Rhizobium fredii USDA 191, Rhizobium spp. [Arachis] strain 1 and Bradyrhizobium spp. [Vigna] strain 2 were studied to obtain single, double, triple and quadruple inocula. Developed plants were examined after 45 and 90 days from planting to record number, dry weight and nitrogenase activity of the root nodules as well as the dry weight and N-content of shoots. Nodule occupancy by the tested strains was also determined by agglutination and double gel diffusion techniques. Data showed that dual inoculation with R. fredii USDA 191 and B. Japonicum USDA 110 showed maximal effects on all tested parameters and provided soybean plants with 75% of its N-requirements. However, no nodules were developed on soybean roots inoculated with Rhizobium spp. [Arachis] strain 1 in single or combined inocula, Bradyrhizobium spp. [Vigna] strain 2 formed effective nodules in both cases

Reducing the heavy metals toxicity in sludge amended soil using VA mycorrhizae

A pot experiment was conducted to evaluate the role of VA mycorrhizae as a biological agent in reducing the toxicity of heavy metals. A newly reclaimed soil from Ismailia Governorate was supplemented with sewage sludge from two sources at five different rates 0.0, 0.5, 1.0, 2.0 and 4.0%. One half of each treatment was inoculated with VA mycorrhizae. Application of sewage sludge up to 2% increased faba bean growth, nodule number and weight and phosphorus and nitrogen contents. Inoculation with VA mycorrhizae also induced significant increase in these parameters as compared with the uninoculated treatments. Plant Zn, Mn, Cu, Ni, Cd, Pb, and Co contents were increased with the application of sewage sludge. In the sewage sludge treated soil where the heavy metals were present in high concentrations, inoculation with VA mycorrhizae reduced the concentration of heavy metals. This indicates the role of VA mycorrhizae in reducing the hazardous effect of heavy metals when present in high levels in the media of growing plants

Bio-indicators of soil fertility in sugar cane rotation

The relationship between soil biological activity and soil fertility was studied under sugar cane rotation to find out whether or not the biological activity of the soil can be used as an index to soil fertilityThe results showed differences in soil enzyme activities [dehydrogenase, invertase, phosphatase and urease] at the different locations according to soil fertility levelA significant positive correlation between the enzyme activities and organic matter content was foundOn the other hand, a significant positive correlation was found between the enzyme activities and the microbial populations as well as CO2 evolution playing an important role in the release of essential nutrients for plantTherefore, enzyme activities can be used as an index to soil fertility level

Bio-indicators of soil fertility in rice rotation

The relationship between enzyme activities and some soil properties under rice rotation at two governorates was studied to find out whether or not the enzyme activities can be taken as a bioindicator to soil fertility. The results indicated that there are clear differences in soil enzyme activities [dehydrogenase, phosphatase, invertase and urease] at the different localities of the two governorates according to its soil fertility level. Significant positive correlation was established between the activities of dehydrogenase and urease and total bacterial counts, total fungi, phosphate-dissolving bacteria [PDB], ureolytic microorganisms and CO2 evolution. Phosphatase activity was positively correlated with total baccarat counts, total fungi and CO2 evolution but not correlated with PDB and ureolytic organisms. On the other hand, positive correlations were detected between invertase activity and each of total fungi, PDB, ureolytic organisms and evolved CO2

Bio-indicators of soil fertility in cotton rotation

The correlation assessment of the bioindicators and classical chemical indicators of soil fertility can help in testing the practical application of the bioindicators as alternative approach for soil fertility evaluations. The relationship between enzyme activities and some soil properties under the cotton rotation at three governorates was studied to find out whether or not the enzyme activities can be taken as bioindicator to soil fertility. The results showed that there were differences in soil enzyme activities [dehydrogenase, invertase, phosphatase and urease] at the different sites within the three governorates according to its soil fertility level. Also, a significant positive correlation was found between the enzyme activities and soil organic matter content and clay fraction%. Significant positive correlations were also established between the activity of each of the studied enzyme and the microbial population, which are the functions of the essential nutrients of the soil