Emission of NO2Gas Causing Damage to Plants in an Acid Soil under Conditions Favorable for Denitrification

Abstract

Nitrogen dioxide (<TEX>$NO_2$</TEX>) gas damage on vegetable crops commonly occurs in plastic film houses where relatively large amounts of <TEX>$NO_3{^-}$</TEX> are applied in acid soils. In acid soils, <TEX>$HNO_2$</TEX> can be formed from the <TEX>$NO_2{^-}$</TEX> accumulated during denitrification, and <TEX>$NO_2$</TEX> can be evolved from the chemical self-decomposition of <TEX>$HNO_2$</TEX>. In this study, <TEX>$NO_2$</TEX> gas production and its detrimental effects on plants were investigated in soils of various conditions to elucidate the mechanisms involved in the gas production. A silty loam soil was amended with <TEX>$NO_3{^-}$</TEX> (500 mg N <TEX>$kg^{-1}$</TEX>) and glucose, and pH and moisture of the soil were adjusted respectively to 5.0 and 34.6% water holding capacity (WHC) with 0.01 M phosphate buffer. The soil was placed in a 0.5-L glass jar with strawberry leaf or <TEX>$NO_2$</TEX> gas absorption badge in air space of the jar, and the jar was incubated at <TEX>$30^{\circ}C$</TEX>. After 4-5 days of incubation, dark burning was observed along the outside edge of strawberry leaf and <TEX>$NO_2$</TEX> production was confirmed in the air space of jar. However, when the soil was sterilized, <TEX>$NO_2$</TEX> emission was minimal and any visible damage was not found in strawberry leaf. In the soil where water or <TEX>$NO_3{^-}$</TEX> content was reduced to 17.3% WHC or 250 mg N <TEX>$kg^{-1}$</TEX>, <TEX>$NO_2$</TEX> production was greatly reduced and toxicity symptom was not found in strawberry leaf. Also in the soil where glucose was not amended, <TEX>$NO_2$</TEX> production was significantly reduced. In soil with pH of 6.5, <TEX>$NO_2$</TEX> was evolved to the level causing damage to strawberry leaf when the soil conditions were favorable for denitrification. However, compared to the soil of pH 5.0, the <TEX>$NO_2$</TEX> production and its damage to plants were much less serious in pH 6.5. Therefore, the production of <TEX>$NO_2$</TEX> damaging plants might be occurred in acid soils when the conditions are favorable for denitrification.