Influence of Soil Amendments on Soil Water Holding Capacity and Nutrient Leaching.

Management practices including the application of soil amendments significantly influences soil water holding capacity, plant available water content, and nutrient leaching. Although the influence of amendments on various soil properties is well known, still there is lot of information, such as influence on plant available water content, lacking. Animal wastes such as poultry litter (PL) have been in use as soil amendments for a long time. In recent years, biochar (BC) as a soil amendment has become popular due to the many reported advantages such as increase in crop yield, decrease in nutrient loss and C sequestration. The objectives of the present study were to determine the influence of PL and a pine wood BC (produced at 550^oC) on water holding properties and nutrient leaching/ movement of a Norwood sandy loam soil. Results showed that the addition of PL and BC had a significant impact on the soil water content; however, addition of PL or BC or PL +BC to soil either decreased plant available soil water content (Field capacity – permanent wilting point) or had no difference compared with the control. Also, addition of PL or BC didn’t show any impact on water loss through evaporation compared with control. Unsaturated hydraulic conductivity decreased by the addition of either PL or BC. On the other hand, addition of PL (2.5, 5 and 10 % on weight basis) significantly increased leaching of nutrients from the soil and was proportional to the amount of PL added. Major nutrients leached from PL amended soil were K, Na, S, Ca, and P. Addition of equal amount of BC, as PL, to the soil column decreased leaching of Al, As, B, Cu, Fe, Ni, Se and Zn while no effect/ increase in Ca, Mg and P. Similarly, BC addition significantly decreased leaching of dissolved organic C (DOC) from both unamended soil (~80%) and PL amended soil (~34 %). Overall, addition of BC and PL didn’t show any beneficial effect on plant available soil moisture content; addition of BC along with PL to the soils can help in minimizing nutrient and DOC leaching and runoff from the fields.