Soil biochar amendment to improve nitrogen and water management

Authors: Gao, Suduan; Wang, Dong

Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/22/2020
Publication Date: 10/29/2020
Citation: Gao, S., Wang, D. 2020. Soil biochar amendment to improve nitrogen and water management. Fertilizer Research and Education Program Annual Conference. October 28-29, 2020 (virtual). p. 33-36.

Interpretive Summary: To address the issues associated with reactive nitrogen (N) from fertilizer application in agricultural fields this research evaluates if biochar can be part of the solution. Through both field and laboratory experiments, biochar demonstrated the ability to retain ammonium-N to certain degree but not much adsorption for nitrate, the source of leaching. Biochar incorporation significantly increased soil organic carbon (SOC) content in field studies but no significant improvement on crop yield and reduction in ammonia volatilization, nitrous oxide emissions, and nitrate leaching. Overall, biochar is highly effective to increase SOC and improve soil properties towards more productive soils. Biochar amendment can be adopted as a good agronomic practice but will largely depend on if biochar can be produced more economically as costs are high for commercial products today.

Technical Abstract: While enhancing crop production, nitrogen fertilizers have resulted in many detrimental effects on the environment (e.g., air quality from ammonia volatilization, groundwater pollution from nitrate (NO3-) leaching, and contribution to greenhouse gas emissions). Biochar has demonstrated the potential to mitigate some of the problems. The objectives of this research are to: 1) determine effects of soil amended with biochar produced from different feedstocks on adsorption capacity for ammonium (NH4+) and NO3-; and 2) determine effective amendment rate of biochar products and irrigation rates on crop response and N fate under field conditions. Laboratory experiments determined the adsorption capacity of seven biochar products from different feedstocks (almond shell, bamboo shoots, coconut shell, green waste, and softwood) or pyrolysis temperature ranging from ~500 to 900 oC for NH4+ and NO3- and pH effects. All biochar products exhibited some ability to adsorb NH4+, but not much for NO3-. The adsorption varies significantly among biochar types and pH with the maximum adsorption between pH 8-9, but data analysis indicates that its ability to retain N and reduce leaching is small. Results from two field experiments showed that biochar rate had little influence on vegetable yield (processing onions, garlic and tomatoes) or N losses via ammonia volatilization, nitrous oxide emission, or NO3- leaching. However, biochar amendment significantly increased SOC to improve soil properties towards more productive soils. The high cost of biochar production is the major hurdle for adoption as an agronomic practice. There are low cost pyrolysis techniques to produce biochar that can be explored in agricultural communities to replace the complete burning. For example, if orchard waste cannot be recycled due to disease concerns, biochar may be produced in situ and then incorporated into soil, which not only eliminates the air quality problems caused by burning but also enriching soil with organic carbon.