Search

The use of sewage sludge in agriculture is known to be environmentally friendly as it is a practical way of recycling municipal waste. A short-term experiment was carried out to study the changes in soil chemical and microbiological properties influenced through the addition of sewage sludge along with saline irrigation under a pearl millet-wheat crop rotation. There were three irrigation (canal water (0.35 dS m-1), 8 and 10 dS m-1 electrical conductivity saline water) and five fertilizer treatments (control-F1, sewage sludge (5 t ha-1)-F2, sewage sludge (5 t ha-1) +50% recommended dose of fertilizer (RDF)-F3, sewage sludge (5 t ha-1)+75% RDF-F4 and RDF-F5). The results showed that soil organic carbon, and available nitrogen, and phosphorus were reduced significantly under saline conditions but there was an increase in available potassium with the increasing salinity levels of the irrigation water. A significant reduction in soil microbial biomass carbon and enzyme activities was caused by 8 and 10 dS m-1 as compared to 0.35 dS m-1 at different growth stages of crops. Treatment F4 attained the highest soil microbial activity at each crop growth stage by a significant margin among all of the fertilizer treatments, which is associated with a substantial build-up of organic carbon and available NPK in the soil. Soil microbial activities followed a particular trend: at 35 and 75 days after sowing>harvest>sowing in pearl millet and wheat, respectively. Sewage sludge dumping is a major problem in India, and the present study suggests that by applying sewage sludge, soil biological health is improved; therefore its use in agriculture is recommended to farmers. [ABSTRACT FROM AUTHOR]

Cultivated soils in high water conditions can be a source of methane (CH4). Despite the significant introduction of lead (Pb) into soils with fertilizers or sewage sludge, there are few reports concerning its impact on methane production in arable soils. The main premise of the study was to characterize the response of methanogenesis after soil contamination with Pb. For this reason, the effect of Pb on CH4 production in three different mineral arable soils was investigated. Lead, in the chloride form, was added at two concentrations, which were established based on the Sewage Sludge Directive (300 and 1 500 mg kg-1). Additionally, two types of controls were used - water and CaCl2 with chloride ions. It was observed that the process could be slowed down at the lower dose and that methane production was totally inhibited at the higher dose. Additionally, the inhibitory effect of the chloride ions on the process was also observed in the control samples. Despite the inhibition of methanogenesis in the soil, which has a positive effect on reducing the amount of the gas released, this process cannot be analysed individually. Other reactions in the soil should also be taken into consideration, and these changes which occur under the influence of the various factors should be investigated further. [ABSTRACT FROM AUTHOR]