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Urea is the predominant ammonium-forming nitrogen (N) source applied in delayed-flood rice because of its high N content (46%) and relatively low cost. Nitrogen applied prior to flooding can be lost by multiple mechanisms such as ammonia volatilization or nitrification/denitrification. In recent years, technological advancements have provided alternative enhanced efficiency fertilizer additives with potential to be incorporated in rice production to reduce N losses. Research was conducted at the Mississippi State University Delta Research and Extension Center from 2018 to 2020 to determine the effects of broadcast applications of nitrapyrin at two specific growth stages to enhance fertilizer-N recovery efficiency, determine optimal application methods of nitrapyrin with urea, determine the effects of nitrapyrin mixed with different herbicides for weed control, and to evaluate nitrapyrin efficacy alone and in conjunction with N-(n-butyl) thiophosphoric triamide (NBPT) to reduce ammonia volatilization. In the current research, there was no effect on grain yield responses from the addition of nitrapyrin regardless of soil textures or application timing. Broadcast applications of nitrapyrin did not improve fertilizer-N recovery efficiency regardless of soil texture or application timing. Differences in rice grain yield were not observed with respect to nitrapyrin application method or NBPT combination for clay and silt loam textures. Barnyardgrass control was unaffected with nitrapyrin applied with different herbicides. Lastly, nitrapyrin was ineffective at reducing ammonia volatilization and resulted in a similar trend to urea alone. Efficacy from nitrapyrin plus NBPT was not different from NBPT alone at reducing N losses. Nitrapyrin efficacy can be influenced by soil texture, application timing, or application method. Implementing nitrapyrin as an enhanced efficiency fertilizer additive to mitigate N losses is inconsistent, and rice grain yields will vary based on environmental and soil conditions.

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