An Investigation Into the Short-Term Effects of Biochar on Nitrate Leaching From Artificial Columns of Sand

Leaching of NO3 has been shown to be a major problem in coarse-textured sandy soils. It has been suggested that biochar application to sandy soils could reduce leaching of NO3. However, how biochar could be used to provide short-term NO3 leaching reduction in sandy soils has received little research attention. Therefore, the aim of this study was to determine if and how biochar could be used to reduce NO3 leaching from artificial columns of sand (sandy soil). To achieve this, a simple assay was developed in a controlled temperature room to assess the short-term impacts of biochar on NO3 leaching from a column containing sand. The capacity to pick-up variations in NO3 leaching pattern from the sand columns based on the concentrations of the NO3 solutions used to perfuse the sand columns, as well as, the rate at which these solutions were perfused through the sand columns using this approach was initially established. A pulse chase experiment showed that the NO3 was very mobile, and once the supply was removed, the column of sand rapidly lost the NO3. The exception appears to the inclusion of biochar where this process is slowed down, but eventually the sand column lost all the NO3. When oak biochar produced through high temperature pyrolysis (500-600 oC) by a commercial producer (Humko, d.o.o., Bled Sheenjek, Slovenija) was applied to the sand columns at a rate of 10% (w/w), the pattern of NO3 leaching was modified. Biochar appeared to delay NO3 leaching from the sand. The extent of this delay, and how it may influence NO3 availability in the soil for plant uptake requires further research.