The impact of biochar addition on nutrient leaching and soil properties from tillage soil amended with pig manure

The application of pig manure to a tillage soil can result in pollution of surface and groundwater bodies. Countries in the European Union are required to comply with the Water Framework Directive, which states that all countries should attain at least "good status " surface and ground water quality by 2015. Amendment of soil with biochar has previously been shown to reduce nutrient leaching and improve soil properties. The objectives of this laboratory study were to investigate if the application of two types of biochar at a rate of 18 t ha-1 (a) reduced leaching of carbon (C), nitrogen (N) and phosphorus (P) from a low P Index tillage soil amended with pig manure and (b) affected the soil properties before and after pig manure application. Three treatments were examined as follows: (a) non-amended soil (the study control), (b) soil mixed with biochar from the separated solid fraction of anaerobically digested pig manure, and (c) of soil mixed with biochar from Sitka Spruce. Columns, filled with sieved soil (<2 mm) and biochar (<2 mm), were incubated for 30 weeks at 10 °C and 75% relative humidity and leached with 160 mL distilled water per week. Pig manure, equivalent to 170 kg N ha -1 and 36 kg P ha-1, was applied to half of the columns in each treatment after 10 weeks of incubation. Amendment with pig manure biochar increased the Morgan's P content of the soil, while leaching of P and C also increased, indicating the unsuitability of pig manure biochar as an amendment to soils which may be used as pig manure spreadlands. However, the addition of wood biochar increased soil water, C and organic matter contents, while reducing nitrate and organic C leaching. The addition of wood-derived biochar to tillage soil which will receive pig manure may be justifiable, as it reduces nutrient leaching from the soil, sequesters C and may allow for higher application rates of pig manure. © Springer International Publishing Switzerland 2014.