Soil Nitrogen Dynamics As Affected By Biochars Co-Applied with Different Nitrogen Sources.

Despite evidence suggesting that biochars have capability to retain plant nutrients (particularly N) and, consequently, reduce the risks of nutrient transport, research on the co-application of biochar with organic residuals or inorganic fertilizer is limited. The objective of this study was to evaluate the effectiveness of two biochar sources [pine biochar (PB), and grass biochar (GB) generated at temperatures of 800 and 400 °C, respectively] in controlling N liability in soils amended with different N sources. A 112-day static laboratory incubation and a leaching study were conducted with two biochars co-applied with three N sources: ammonium nitrate, a Class B cake biosolids, and a Class AA pelletized biosolids. Biochar and N sources were applied at an equivalent rate of 1% and 180 kg N ha^-1 (dry soil mass basis), respectively. Total soil N concentration was unaffected by biochar treatment, but soil C concentration increased by 21% over the control (no biochar or N fertilizer) treatments. Grass biochar addition decreased extractable nitrate-N (NO₃-N) by 23 to 33% in Class AA pelletized and Class B cake biosolids, respectively, but had no effect in ammonium nitrate treatments. Biochar had no effect on extractable soil ammonium-N (NH₄-N) with any N source, but reduced cumulative leachate NH₄-N mass by 27%.There were no significant biochar effects on cumulative leachate inorganic N loads for treatments receiving biosolids. Both biochar type and fertilizer source affected the effectiveness of biochar in controlling the release and leaching of N from soils receiving N.