Acetylene (C
2H
2) is often employed to assess soil total denitrification (N
2O + N
2) due to its ease of implementation. However, this technique underestimates soil denitrification in soils with low nutrient contents, particularly those supporting grain yields. To our knowledge, there are limited studies that have specifically investigated the impact of C
2H
2 on nutrient-rich vegetable soils, especially concerning the emissions of N
2 and N
2O and the nitrogenous gas product ratio (i.e., N
2O/(N
2O + N
2)). In this study, we conducted both anoxic and oxic incubations at various C
2H
2 concentrations (0%, 0.01%, and 10%,
v/
v) and utilized a robotized sampling and analysis system to quantify soil N
2, N
2O, and CO
2 emissions. Our findings revealed that the cumulative N
2O production in soil treated with 10%C
2H
2 was significantly lower than that in soil treated with 0.01%C
2H
2 and soil without C
2H
2. Contrarily, high concentrations of C
2H
2 (10%,
v/
v) led to increased N
2 production. Similar trends were observed under oxic conditions, where 10%C
2H
2 concentration did not enhance N
2O production but markedly increased N
2 and CO
2 emissions. Moreover, the N
2O/(N
2O + N
2) product ratio was notably higher in soils treated with 0%C
2H
2 compared to the 10%C
2H
2 treatment under anoxic conditions. These findings indicate that high concentrations of acetylene could facilitate the reduction of N
2O to N
2 and lead to underestimated soil total denitrification in vegetable soil, regardless of anoxic or oxic conditions. This discovery underscores the drawbacks when employing high concentrations of acetylene to evaluate actual total denitrification in intensive greenhouse vegetable soils, highlighting the necessity for further investigation into alternative methodologies.
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