Biochar As an Approach to Reduce Nitrogen Losses From Soils: An Assessment of Three Different Studies.

Intensive farming systems apply high rates of nitrogen (N) fertilization to enhance crop productivity. A large fraction of these inputs is lost as gases or leached from the root zone to groundwater as nitrate (NO₃). Both forms of losses seriously impact the environment and threaten public health. Research has identified biochar as an approach to reduce N losses. Biochar has a high surface area and therefore, potential to retain minerals in soils. The objective of this study is to identify the conditions in which biochar prevents N losses. We will present a summary of three different studies investigating N transformations, N losses via leachate, nitrous oxide (N₂O) emissions and functional genes that encode enzymes responsible for nitrification and denitrification in bacteria. The first study investigated eight biochar materials in the cultivation of lettuce. The biochar materials induced distinct responses on the evaluated parameters and a correlation of N losses and ash content of biochars was observed. The second study examined the interaction of biochar and N fertilization levels.  Preliminary results show that biochar has the potential to prevent N losses at lower fertility levels but no interaction effects on plant production were observed. The third study investigated the performance of a locally produced walnut shell biochar in a 12-acre organic walnut orchard. Gas and soil samples were collected once a week or for seven days after major farming operations, such as irrigation or fertilization. The results for the first year of study show that there is large spatial variability within plots, especially for (N₂O) fluxes. However, decreases in N₂O emissions in biochar amended plots for some of irrigation or precipitation events were observed. These data also suggest that biochar can improve soil properties such as pH, aggregation and soil microorganisms.