Submitted to: Journal of Environmental Quality
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/26/2002
Publication Date: 3/1/2003
Citation: Zvomuya, F., Rosen, C.J., Russelle, M.P., Gupta, S.C. 2003. Nitrate leaching and nitrogen recovery following application of polyolefin-coated urea to potato. Journal of Environmental Quality. 32:480-489. Interpretive Summary: Production of potatoes and other vegetable crops is often concentrated on sandy soils because yields and quality are usually better than on clay soils. Because sandy soils cannot hold much water, irrigation is used to supplement rainfall to prevent water stress in these shallow-rooted crops. Leaching of water and dissolved nutrients is a high risk on these soils. Once nutrients move below the root zone, it is no longer available to the crop. The cost of nitrogen fertilizer is low compared to potato value, so farmers typically apply more fertilizer to make sure that crop yields do not suffer from the leaching losses. However, there is additional concern about nitrate leaching, because this ion can easily contaminate underground drinking water supplies. New and effective techniques are needed to reduce the risk of nitrate leaching on sandy soils. Our research showed that special fertilizers that release nitrogen slowly can greatly improve nitrogen recovery in the crop and reduce leaching losses. These fertilizer are expensive now, so adoption of this technique may be limited until the economics are more favorable or until regulations require alternative practices.
Technical Abstract: High N fertilizer and irrigation amounts applied to potato (Solanum tuberosum L.) on coarse-textured soils often result in nitrate leaching and low recovery of applied fertilizer N. This 3-yr study compared the effects of two rates (140 and 280 kg N/ha) of a single polyolefin-coated urea (PCU) application versus split applications of urea on Russet Burbank potato yield and on nitrate leaching and N recovery efficiency (RE) on a loamy sand. Standard irrigation was applied in all years and excessive irrigation was used in another experiment in the third year. At the recommended rate of 280 kg N/ha, nitrate leaching during the growing season was 34 to 49% lower with PCU than three applications of urea. Under standard irrigation in the third year, leaching from five applications of urea (280 N kg/ha) was 38% higher than PCU. Under leaching conditions in the first year and excessive irrigation in the third year, PCU at 280 kg N/ha improved total and marketable tuber yields by 12 to 19% compared with three applications of urea. Fertilizer N RE estimated by the difference and 15N isotope methods at the 280 kg N/ha rate was, on average, higher with PCU (mean 50%) than urea (mean 43%). Fertilizer N RE values estimated by the isotope method (mean 51%) were greater than those estimated by the difference method (mean 47%). Results from this study indicate that PCU can reduce leaching and improve N recovery and tuber yield during seasons with high leaching.