COMPARING N-NO₃^- LOSSES THROUGH leaching MEASURED IN the FIELD AND ESTIMATED USING A NITROGEN BALANCE

Virginia Aparicio^1*, José Luis Costa¹, Hernán Sainz Rozas^1-2; Daniel Gimenez³ y Fernando García⁴

¹ Instituto Nacional de Tecnología Agropecuaria INTA. Balcarce. Ruta 226, Km. 73.5, Buenos Aires, Argentina.

²Consejo Nacional de Investigaciones Científicas y Técnicas.

³ Departments of Environmental Sciences, Rutgers State Univ., New Brunswick, NJ

⁴ IPNI Latinoamérica-Cono Sur. Av. Santa Fe 910. (B1641ABO) Acassuso - Buenos Aires – Argentina

^* Correo Electrónico: vaparicio@balcarce.inta.gov.ar

Abstract

The nitrogen (N) balance method is a valuable tool to estimate nitrogen losses but the sum of errors incurred when each of the balance pools are determined could lead to incorrect estimates of the amount of the nitrate leaching. The aim of this study was to compare the estimated N- NO₃^-  losses using a simplified N balance and data of N- NO₃^- losses made in the field over five growing seasons with varied rainfall. The trial was carried out on a Typic Argiudoll soil. In each growing season the leached nitrogen was measured and the balance of this nutrient was carried out on the corn crop. The average value of Nl (over the years) for the doses 100 and 200 kg N ha^-1 was 28 and 38 kg N ha^-1, meaning that the average over-estimation of Nl calculated using Nne² for the above-mentioned doses was 25 and 49 kg N ha^-1, respectively. The nitrogen balance over-estimates the losses through leaching which occur in the field. The greatest over-estimation took place in those years where annual rainfall was far below the historical average and when most nitrogen was available.

Key words: nitrate, balance, mesuarement