Biochar alters nitrogen transformations but has minimal effects on nitrous oxide emissions in an organically managed lettuce mesocosm

Abstract

We investigated the effect of biochar type on plant performance and soil nitrogen (N) transformations in mesocosms representing an organic lettuce (Lactuca sativa) production system. Five biochar materials were added to a silt loam soil: Douglas fir wood pyrolyzed at 410 °C (W410), Douglas fir wood pyrolyzed at 510 °C (W510), pine chip pyrolyzed at 550 °C (PC), hogwaste wood pyrolyzed between 600 and 700 °C (SWC), and walnut shell gasified at 900 °C (WS). Soil pH and cation exchange capacity were significantly increased by WS biochar only. Gross mineralization increased in response to biochar materials with high H/C ratio (i.e., W410, W510, and SWC), which can be favorable for organic farming systems challenged by insufficient N mineralization during plant growth. Net nitrification was increased by W510, PC, and WS without correlating with the abundance of ammonia oxidizing gene (amoA). Increases in N transformation rates did not translate into increases in plant productivity or leaf N content. WS biochar increased the abundance of amoA and nitrite reductase gene (nirK), while SWC biochar decreased the abundance of amoA and nitrous oxide gene (nosZ). Decreases in N 2 O emissions were only observed in soil amended with W510 for 3 days out of the 42-day growing season without affecting total cumulative N 2 O fluxes. This suggests that effects of biochar on decreasing N 2 O emissions may be transient, which compromise biochar's potential to be used as a N 2 O mitigation strategy in organic systems. Overall, our results confirm that different biochar materials can distinctively affect soil properties and N turnover.

Gas entrapment and microbial N2O reduction reduce N2O emissions from a biochar-amended sandy clay loam soil

“…the number of expressed nitrous oxide reductase genes per expressed nitrite reductase genes, was significantly higher in biochar microcosms. These results are in good agreement with other studies in which functional denitrification genes141677 and their mRNA1516 have been quantified and suggest that biochar addition enhances microbial N 2 O reduction. As reported in several studies nitrous oxide reductases are highly pH sensitive and are impaired due to post-transcriptional effects at pH values below 6.1257879.…”

Effects of bio‐based residue amendments on greenhouse gas emission from agricultural soil are stronger than effects of soil type with different microbial community composition

“…Therefore, not all bio‐based residues are suitable soil additives. Although some residues may contribute to soil carbon (paper pulp C : N ratio: 518.3) and nutrients as in this study and others (e.g., Galvez et al ., ; Kirkby et al ., ; Pereire et al ., ), the positive effects may be offset by detrimental effects on crop growth.…”

“…Therefore, the consequences of bio-based residue input in agricultural lands have thus led to the need for a comprehensive organic amendment strategy to attenuate GHG emission, while maintaining the soil carbon storage capacity, quality, and fertility (Paustian et al, 2016). Previous work investigated the response of soil microorganisms to nutrient amendments through addition of specific residues in a particular soil type, or in relation to specific microbial guilds mediating greenhouse gas turnover in agricultural soils as case studies (e.g., Jia & Conrad, 2009;Bannert et al, 2011;Ho et al, 2011Ho et al, , 2013Harter et al, 2014;Bastida et al, 2015;Pereire et al, 2015;Stempfhuber et al, 2016). Case studies are informative, but the nonuniformity of the methodologies used and variable experimental duration complicate cross-study comparisons (Pan et al, 2010;Shade et al, 2016).…”

Vegetable yields and soil biochemical properties as influenced by fertilization in Southern China

“…AOB genes and transcripts were quantified by using the BACT1369 F and PROK1492 R primers for amplification (Pereira et al, 2015). AOA genes and transcripts were quantified by using the crenamoA23 F and crenamoA616 R primers for amplification (Tourna et al, 2008).…”