Mitigation of nitrous oxide emissions from agricultural soil by 2-amino-4-chloro-6-methylpyrimidine

　　Agricultural soil is the largest anthropogenic source of nitrous oxide (N₂O), a greenhouse gas. Nitrification inhibitors have been used to increase fertilizer efficiency and to mitigate nitrogen leaching. They also decrease N₂O emissions from agricultural land. 2-chloro-6 (trichloromethyl) pyridine (nitrapyrin) is a strong nitrification inhibitor that has been used with liquid ammonia in the USA. However, it cannot be amended to solid fertilizer because of its low solubility and high volatility. To select an alternative nitrification inhibitor that is easy to handle and which will effectively mitigate N₂O emissions from the soil, 2-amino-4-chloro-6-methylpyrimidine (AM), sulfathiazole and 1-aryl-2-thiourea were compared. These chemicals can be amended into solid fertilizer.

　　The results of soil incubation experiments showed that AM mitigated N₂O emission from soil where nitrogen fertilizer had been applied. The effect of AM on reducing N₂O emissions was weaker than nitrapyrin but stronger than sulfathiazole and 1-aryl-2-thiourea (Table 1). Application of AM did not inhibit soil respiration. The side effects of AM on 7 bacterial species that contribute to agricultural production in the field were tested. AM proved to inhibit the growth of these bacteria to the same degree as other inhibitors (Table 2). These results show that AM selectively inhibits nitrification bacteria and that the side effects on other bacteria are minor. It was concluded that AM can be used to mitigate N₂O emissions from agricultural soil as an alternative to nitrapyrin. 

(T. Watanabe)

Table 1. Effect of nitrification inhibitors on mitigating N₂O emissions (Soil incubation experiment).

Table 2. Inhibitory effects of nitrification inhibitors on 7 bacteria useful in agriculture.  

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