Bromide and Nitrogen‐15 Tracers of Nitrate Leaching under Irrigated Corn in Central Nebraska

Abstract

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 ISN ammonium nitrate (I0 atom% ISNH415NO3) tracers were applied at rates of 200 kg Br ha-i and 30 kg N ha-i to four 6.1 by 3.7 m plots that were representative of major soil types on the 32.l-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-I) of the applied Br loss from the top 1.2 m of soil was attributed to leaching. Also, 54% (16.2 kg ha-i) of the tracer ap plied was lost from the system; 41% (12.3 kg ha-I) through leaching; and 13% (3.9 kg ha-i) through denitrification and volatilization. By time of planting in the spring of 1993, 70% (139.3 kg ha-I) of the applied Br and 46% (13.8 kg ha-i) 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.

In situ validation of fungal N translocation to cereal rye mulches under no-till soybean production

“…The sharp reductions in extractable soil inorganic 15 N observed in both experiments (Fig. 7) were immobilized via the intense microbial competition for N in the low N environment, or leached below the sampling depth (Kessavalou et al 1996;Dou et al 2007). …”

Soil N and salinity leaching after the autumn irrigation and its impact on groundwater in Hetao Irrigation District, China

“…For annual crops, the N uptake efficiency is <50%, even when following good management practices (Ju and Zhang, 2003;Gillian et al, 1985) and about 30-50% of applied N fertilizer is leached into groundwater (Zhang, 1987). Using best management practices and near optimum N rates, the amount of NO 3 -N leaching has been estimated to be 41% for irrigated maize (Kessavalou et al, 1996), 32 AE 28% (standard deviation) for irrigated wheat (Ottman et al, 2000) and 27.9% for irrigated Orchardgrass (Watts et al, 1991). In addition, when compared to solely rain-fed fields, the amounts of leached NO 3 -N have been found to be 17 and 53% higher in low and high volume irrigated fields, respectively (Timmons and Dylla, 1981).…”

Nitrogen Fertilizer Rate and Crop Management Effects on Nitrate Leaching from an Agricultural Field in Central Pennsylvania

“…In earlier studies [16], we found that the average apparent recovery of N fertilizer by corn grain at the EON rate was 55%, so the 40% lost in leachate in the current study appears to be realistic. Other studies have reported that 41% of applied fertilizer N was lost as leachate in irrigated corn [17] and that 50% of fertilizer N applied to corn was available for leaching, denitrification, and/or NH 3 volatilization [18]. …”