The potential of biochar to prevent nitrogen (N) losses and improve plant performance were studied across various levels of N input for two growing seasons in mesocosms simulating an organic lettuce production system. A silt loam soil was amended with pine chip (PC) and walnut shell (WS) biochar (10tha-1) in combination with five organic N fertilization rates (0, 56, 112, 168, and 225kgNha-1). The N output through harvest, leachate, and N2O emissions were measured to assess N utilization and environmental losses of biochar-amended soils. For both biochars, only at the 100% N fertilization rate was lettuce biomass production improved with significant increases in N use efficiency (NUE); however, only PC biochar decreased N losses via leaching (at 100% N fertilization rate) and seasonal N2O emissions (at 50% N fertilization rate). Thus, due to increases in plant biomass and decreases in N losses, PC biochar significantly decreased the ratio of N lost over N exported in biomass. Findings from this study suggest that both WS and PC biochars can improve organic lettuce production but only at 225kgNha-1. Decreases in N losses via leachate and N2O emissions vary with fertilization level and biochar type.
Keywords: Amendments; Leachate; Nitrogen use efficiency, nitrous oxide; Organic farming; Vegetable crops.
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