Nitrapyrin, terrazole, atrazine and simazine influence on denitrification and corn growth

Abstract

In modern agriculture, long‐term soil fertility and crop productivity are maintained by a combination of inorganic fertilizers and pesticide inputs which, in turn, create environmental and health concerns. Therefore, studies were initiated to evaluate two commonly used herbicides (atrazine and simazine) and two biological nitrification inhibitors (nitrapyrin and terrazole) applied with NO₃‐N source fertilizer for their effects on denitrification and on corn (Zea mays L.) growth and yields. Each chemical applied at the rate of 10, 50, or 100 mg a.i. L^‐1 suppressed denitrification of NO₃ ^‐ in a liquid medium inoculated with a Tifton loamy sand in a laboratory study. Nitrapyrin and terrazole selectively suppressed NO₃ ^‐ or NO₂ ^‐ or both reduction while atrazine and simazine suppressed NO₂ ^‐ or N₂O or both reduction. In greenhouse pot culture studies, chemical application resulted in higher percent N recovery relative to the control. When atrazine or simazine was part of the chemical treatment, concentrations of NO₃ ^‐ and NO₂ ^‐ in corn (Zea mays L.) plants increased, and plant growth was restricted due to NO₂ ^‐ toxicity. During two consecutive years of field studies using split‐banded applications of N fertilization with nitrapyrin and terrazole, corn ear yields increased 78% and 25% in the first and second year, respectively. With atrazine and simazine, however, yields increased significantly in the first season only. Mixing either herbicide with nitrapyrin or terrazole had no effect on yields during both seasons.

Chemical Names: atrazine = [2‐chloro‐4‐ethylamino‐6‐isopropylamino‐s‐triazine]; simazine = [2‐chloro‐4,6‐bis(ethylamino)‐s‐triazine]; nitrapyrin = [2‐chloro‐6‐(trichloromethyl)pyridine]; terrazole = [ethoxy‐3‐trichloromethyl‐1,2,4‐thiadiazole].