ARS | Publication request: Fertilizer management effects on nitrate leaching and indirect nitrous oxide emissions in irrigated potato production

Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 23, 2011
Publication Date: July 1, 2011
Citation: Venterea, R.T., Hyatt, C., Rosen, C. 2011. Fertilizer management effects on nitrate leaching and indirect nitrous oxide emissions in irrigated potato production. Journal of Environmental Quality. 40(4):1103-1112.

Interpretive Summary: Potato is the fourth most-consumed food crop in the world, after rice, wheat, and corn, and is the leading vegetable crop in the U.S. Potato is also a nitrogen (N) intensive crop with high potential to result in the leaching of the nitrate (NO3-) into groundwater and surface waters, which can lead to eutrophication and other undesirable ecological consequences. The high leaching potential also represents a potential source of so-called “indirect” emissions of the potent greenhouse gas nitrous oxide (N2O), which can occur when NO3- is transformed to N2O after it leaves the fertilized field. Best management practices (BMPs) for potato production attempt to minimize N losses by better matching the timing of soil N availability with crop N demand. The objective of this study was to measure the amount of NO3- leaching and indirect N2O emissions in an irrigated potato cropping system managed using three different BMPs, consisting of multiple applications of a conventional soluble fertilizer applied over the course of the growing season, and two different polymer-coated urea products, each applied in a single application prior to planting. Over three consecutive growing seasons, annual rates of fertilizer-induced NO3- leaching ranged from 0.6 to 8 % of the amount of applied fertilizer N. Indirect N2O emissions were estimated to be 10 to 30% of direct N2O emissions occurring within the field, based on previous measurements from the same experiment. The PCU treatments did not increase NO3- leaching or indirect N2O emissions compared with the CSA treatment. These results indicate that the additional labor and expense associated with multiple split applications can be avoided though the use of single pre-plant PCU applications, while maintaining yields and preserving the same level of environmental impact. This information will be useful to potato producers and environmental policy-makers and regulators interested in minimizing the environmental impact of potato production, particularly in coarse-textured soils and when grown under irrigation where potential for N leaching is greatest.

Technical Abstract: Potato is a nitrogen (N) intensive crop with high potential for nitrate (NO3-) losses, particularly when irrigated. The high leaching potential also represents a potential source of indirect nitrous oxide (N2O) emissions resulting from the transformation of NO3- to N2O after it leaves the fertilized field. Best management practices (BMPs) for potato production attempt to minimize N losses by better temporal matching of soil N availability with crop N demand. The objective of this study was to quantify NO3- leaching and indirect N2O emissions in an irrigated potato cropping system managed using three different BMPs, consisting of (i) conventional split application (CSA) of soluble fertilizer and (ii, iii) single pre-plant applications of two different polymer-coated urea products (PCU-1 and PCU-2), each applied at 270 kg N ha-1. Over three consecutive growing seasons, rates of NO3- leaching were quantified using porous cup sampling and water balance modeling. Indirect N2O emissions were estimated using published emissions factors. Annual rates of fertilizer-induced NO3- leaching ranged from 0.6 to 8 % of the amount of applied N. Indirect N2O emissions were estimated to be 10 to 30% of direct N2O emissions based on previous measurements from the same experiment. The PCU treatments did not increase NO3- leaching or indirect N2O emissions compared with the CSA treatment. These results indicate that the additional labor and expense associated with multiple split applications can be avoided though the use of single pre-plant PCU applications, while maintaining yields and preserving the same level of environmental impact.