The Use of Bio-Fortified Sewage Sludge for Ameliorating Soils in Arid and Semi-Arid Regions

Desert soils in arid and semi-arid regions are poor in organic matter and nutrient elements which is the second factor after water for developing these soils. Organic matter is important to improve the biological, chemical and physical properties of sandy soils as well as a source of nutrients elements for growing plants. As a result of sewage sludge contains macro- and micro-nutrients and bulky of daily generation rates, we can re-use it in agricultural practices with extreme caution to minimize inauspicious health and environmental impacts. During the last few decades numerous microorganisms have been shown to exert beneficial effects as a biological agent in controlling certain soil borne diseases and reducing the toxicity of heavy metals such as mycorrhizal fungi and pseudomonas bacteria. A study was carried out to assess the role of biofertilizers and gamma radiation to reduce pathogenic microorganisms and eliminate heavy metals uptake by cowpea plants grown in sludge amended sandy soil from semi-arid region. A pot experiment was conducted to evaluate the role of biofertilizers (arbuscular mycorrhizal fungi and Pseudomonas fluorescens) as a biological agent to reduce the heavy metals uptake by cowpea plants grown in sludge amended sandy soil as compared with effect of the pretreated sludge (as the rate of 4%) with (10 kGy) gamma radiation or (20%) lime. Obtained results showed that biofertilizers treatments reduced the heavy metals uptake by cowpea plants. Although the addition of lime reduced the heavy metals uptake, the growth parameters of the plant were negatively affected. Generally, the greatest values of growth parameters and yield of cowpea were observed under biofertilizers (arbuscular mycorrhizal fungi + Pseudomonas fluorescens) and gamma radiation (10 kGy) under sludge application (4%)