Nitrogen‐15 and Bromide Tracers of Nitrogen Fertilizer Movement in Irrigated Wheat Production

• Published in: Journal of environmental quality 2000-09, Vol.29 (5), p.1500-1508
• Main Authors: Ottman, M. J., Tickes, B. R., Husman, S. H.
• Format: Article
• Language: English
• Subjects: Agricultural and forest climatology and meteorology. Irrigation. Drainage; Agronomy. Soil science and plant productions; Biological and medical sciences; bromides; Crop production; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Irrigation. Drainage; Nitrogen; Soil and water pollution; Soil science; Triticum
• ISSN: 0047-2425; 1537-2537
• DOI: 10.2134/jeq2000.00472425002900050017x

In irrigated agricultural systems, NO3 leaching is believed to result from high fertilizer rates combined with the need to periodically leach salts from surface soil horizons. The purpose of this research is to estimate N fertilizer movement in the soil of commercial fields of flood‐irrigated wheat (Triticum spp.) while documenting best management practices (BMPs). Potassium bromide and 15N labeled ammonium sulfate were applied as tracers of N fertilizer movement to 1‐ × 1‐m microplots replicated 9 or 10 times in three commercial fields of flood‐irrigated wheat. The soil was sampled at harvest to a depth of 2.4 to 4.0 m. More fertilizer was applied at two out of three sites and more irrigation water was applied at all sites than recommended by BMPs. Bromide recovery in the soil and plant tissue at harvest was 29, 68, and 61% of that applied at the three sites. Most of the 15N measured in the soil profile was contained in the 0‐ to 0.3‐m increment of soil. Recovery on 15N in the soil and plant tissue at harvest was 54, 54, and 69% of that applied. The Br recovery data suggests that 32 ± 28% (standard deviation) of the 15N applied may have leached. The highest leaching potential was measured at the site that adhered to BMPs for N fertilizer management but had the most permeable soil. Nitrate leaching in flood‐irrigated wheat production seems inevitable even if BMPs for N fertilizer management are followed.