The effect of incorporating biosolids on soil quality after cotton crop management

pilot sewage sludge (also known as “biosolids”, BS) application of 7,000 kg/ha (dry weight) was performed in the area of Lamia prefecture, central Greece, in two fields cultivated with Cotton. BS was very rich in organic matter (75%) and had high concentrations of nutrients, with all heavy metals below the limits set for use in agricultural soils. Soil samplings before BS applications and after cotton cultivation for 1 and 2 years for the first and second pilot respectively, revealed the positive effect of BS use to soil quality. Soil organic matter increased from 0.9 and 0.8% to 3.8 and 3.3% respectively. Soil P content increased only to the pilot sampled one year after BS applications. BS increased significant the concentration of Mg, Mn and Fe at both pilots farms. Heavy metals in the soil was kept in acceptable levels at both pilots after BS use except Cr that exceeds the upper limits set by Common Ministerial Decision at both pilots. In conclusion, the results of the study underline the positive effect of BS in soil quality if we could control toxic heavy metals concentrations in the soils by analyzing and organizing proper application rates for each soil case separately.