Bromide and Nitrogen-15 Tracers of Nitrate Leaching under Irrigated Corn in Central Nebraska
1996
Kessavalou, Anabayan | Doran, John W. | Powers, William L. | Kettler, Timothy A. | Qian, Jin H.
Nitrate leaching from agricultural fields into groundwater has caused environmental and health concerns. A study was conducted during 1992–1993 in the Central Platte Valley of Nebraska to assess the nitrate leaching potential under recommended center-pivot irrigation and fertilizer best management practices for continuous corn (Zea mays L.). At time of planting corn, potassium bromide (KBr) and double-labeled ¹⁵N ammonium nitrate (10 atom% ¹⁵NH₄¹⁵NO₃) tracers were applied at rates of 200 kg Br ha⁻¹ and 30 kg N ha⁻¹ to four 6.1 by 3.7 m plots that were representative of major soil types on the 32.1-ha field. Soil and plants sampled 7 wk after planting and at harvest in 1992, and in the spring of 1993, were analyzed for Br and N content and a mass balance was determined. At corn harvest, 41% (81.9 kg ha⁻¹) of the applied Br loss from the top 1.2 m of soil was attributed to leaching. Also, 54% (16.2 kg ha⁻¹) of the tracer applied was lost from the system; 41% (12.3 kg ha⁻¹) through leaching; and 13% (3.9 kg ha⁻¹) through denitrification and volatilization. By time of planting in the spring of 1993, 70% (139.3 kg ha⁻¹) of the applied Br and 46% (13.8 kg ha⁻¹) of the fertilizer N leached below 1.2 m. High negative correlations were found between soil clay and silt contents, and Br or NO₃ leaching. Despite use of best management practices for irrigation water and N applications, large amounts of nitrate can be lost through leaching under irrigated corn in this subhumid climate on fine- to medium-textured soils. Contribution of the Univ. of Nebraska Agric. Res. Div. Journal Series no. 11119.
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