Effect of temperature, moisture content and soil surface area on the biological degradation of biosolids added to soil

The objective is to develop and apply an organic matter degradation model (OMDM) that predicts changes in the biological degradation of organic matter added to soils as a function of soil temperature, moisture content and mineral surface area using data from field and laboratory measurements.;A one year long laboratory study was conducted to determine biosolids microbial degradation rates (21 °C and 20% moisture content) for soils from eight different fields Biosolids microbial degradation rates were also determined for the eight soils under field condition (10 °C and 10% moisture content) by applying a degradation rate model (DRM). The total mineral surface areas for 27 soil samples were also determined. Regression analysis revealed that the degradation rate was positively associated with mineral soil surface area (R2=0.85) and that the biosolids application rate is not significantly associated with the biosolids degradation rate (p value =0.35>0.01).;The OMDM determines a decomposition rate of 1.04 yr -1 at 30 °C, 20% moisture content, and 10 m2/g soil and provides correction factors for changes in soil temperature, moisture, and mineral surface area. The model predicted in changes of the biological degradation rate of biosolids added to soils with mineral surface areas that varies from 1 to 10 m2/g soil under laboratory and field conditions. A comparison of the measured and simulated degradation rates for eight different soils produced R2 = 0.87 for field data. The model was also able to predict the degradation rate of biosolids for 19 additional soils under field conditions (R2=0.89). The model was also applied to agricultural plant litter. The estimated degradation rates are 0.45 yr -1 corn stover, 0.35 yr-1 oats, 0.26 yr-1 wheat, and 0.13 yr-1 millet at 30 °C, 20% moisture content and 10 m2/g. This study demonstrates that the effects of environmental conditions and soil mineral surface area have a significant impact on degradation rates of organic matter and must be considered when assessing degradation rates for organic matter added to soil. Higher temperatures and moisture content and finer soils are related to larger degradation rates.