Integrated waste management for rural development in Egypt.

Rural areas generate a large amount of plant and animal residues that can be recycled and utilized instead of relocation and/or burning. This will lead to increasing the benefits from agricultural sector in rural communities and ensuring a better environment. To increase the economic output and environmental benefits of recycling agricultural residues, integrated system should be considered, e.g., energy--compost-recycled water system; composting--co-composting system; food-feed compost system, ensilage of crop residues. The present work was a pilot study for optimizing integrated systems for bioconversion agricultural residues completed by establishing a Training Center for Recycling Agricultural Residues (TCRAR) thereby ensuring the dissemination of the technical, environmental, and socioeconomic aspects to farmers, live stock producers, extensions service staff, and private sector. Three integrated subsystems for bioconversion of agricultural residues were developed. They were based on (i) energy--manure-recycled water system, (ii) composting and co-composting system, and (iii) food-feed/compost system.

Survival and efficiency of cowpea rhizobia on pelleted and non-pelleted peanut seeds, treated with fungicides.

Peanut seeds were either normally inoculated with the legume inoculant Okadin, containing cowpea rhizobia, or pelleted and treated with each of the fungicides Brassical, Thiram, Orthocide 75, Falisan, Vitavax 75, and Agrosan. The seeds were then incubated at room (+/- 25 degrees C) or refrigeration temperatures (+/- 5 degrees C). Survival tests were made after 2 and 10 days. Treated seeds were also planted in pots containing Nile silt for testing the efficiency of rhizobia as affected by the fungicide and the pelleting treatments. Pelleting of peanut seeds enhanced the survival of rhizobia whether seeds were incubated at room or refrigeration temperature. Protection was more pronounced when seeds were kept at low temperature. This was true of the fungicides Brassical, Orthocide 75, Vitavax 75, Thiram, and Agrosan. Falisan, however, did not help the rhizobia to survive. All the fungicides tested reduced the number of rhizobia to nil within 10 days when the seeds were normally inoculated and then treated and incubated at room temperature. The numbers of rhizobia were appreciably reduced when incubated at refrigeration temperature. Pelleting tended to prevent the harmful effect of the fungicides. This was clearly demonstrated with a tendency of an increase in the total nitrogen of the plants. On the contrary, normally inoculated and treated seeds grew into plants with reduced amounts of total nitrogen fixed.

The correlation between the efficiency of rhizobia and nitrate reductase and dehydrogenase activities of cowpea nodules.

Cowpea seeds variety Fettriat were planted in Nile silt soil and inoculated with 5 strains of cowpea rhizobia. After 50 and 80 days, the plants were uprooted, analysed for dry weight, total nitrogen, fresh weight of nodules, nitrate reductase activity in the leaves, and nitrate reductase and dehydrogenase activities in the nodule homogenate in the presence or absence of succinate, citrate, and ethyl alcohol. The data were analysed to establish the correlation coefficients between total nitrogen and other characteristics. A significant positive correlation existed between total nitrogen and fresh weight of nodules in both cuts (after 50 and 80 days). The correlation was significant between total nitrogen and dry weight of the plants in the first cut, but was non-significant in the second one. Nitrate reductase activity in leaves and nodule homogenates in the presence of different hydrogen donors were positively correlated in the first cut and negatively correlated in the second one. Nitrate reductase activity in the leaves was much less than that in the nodule homogenates. A negative correlation was noticed between phenol content of the nodules and total nitrogen. In the first cut, while the correlation between total nitrogen and dehydrogenase activity in the presence of citrate or absence of any hydrogen donors was positive, it was negative with ethanol and succinate. In the second cut, however, all the dehydrogenase activities were negatively correlated with total nitrogen.

Certain environmental factors affecting rhizobia and symbiotic systems.

The interrelation between rhizobia and certain fungi, bacteria, actinomycetes, nematodes, and seed-coat diffusates of Phaseolus vulgaris were investigated. The effect of pesticides, i.e. fungicides, herbicides, and nematocides on growth of rhizobia, and the symbiotic systems between rhizobia and their respective host is reported. Degradation of certain herbicides and insecticides is shown. The movement of rhizobia in soil as affected by water tension, tolerance of salts, and soil temperatures are discussed. Environmental factors may affect the successful establishment of an effective symbiosis between rhizobia and their hosts at any or all the three stages. They may 1) affect occurrence, growth, and survival of root nodule bacteria, 2) modify nodule formation, or 3) affect the function of the formed nodules (VINCENT 1962). The environmental aspect considered here include the antagonistic factors against rhizobia, the pesticides, and some ecological aspects of rhizobia in soil, e.g., the movement and salts and heat tolerance. These aspects were investigated by Egyptian workers over the period 1948-1972. Comprehensive reviews on the effect of environmental factors on rhizobia were reported by VINCENT (1962) and NUTMAN (1972).

The stimulatory effect of kojic acid on the production of aflatoxin by isolates of Aspergillus flavus Link.

Kojic acid at the levels of 0.01, 0.1, and 1.0% (w/v) was incorporated in the growth media of Aspergillus flavus. In the presence of 0.01% of kojic acid, isolates I, II, and III produced 157, 113, and 135% aflatoxin, respectively, as compared to the control. At the highest level of kojic acid, i.e. 1%, aflatoxin production was inhibited to 74% in isolate I, but was little affected in isolate II (104%) and strongly inhibited in isolate III (54%). Kojic acid, at a concentration of 0.1%, was still stimulatory to isolate II, while it was inhibitory to isolates I and III. The dry weight of mycelia of the three isolates was not affected by kojic acid addition.