Riesgos de Contaminación de Suelo y Agua Determinados por Trazadores Isotópicos en Sistemas Agrícolas

MARIANA A. MELAJ; LUCRECIA AVILES; OLGA MARTÍN; HERNÁN E. ECHEVERRÍA; GUILLERMO STUDDERT; SILVIA C. LÓPEZ

Buenos Aires - Argentina

Simposio; Simposio sobre Energía Nuclear, Desafíos y Realidades en Latinoamérica; 2001

Comisión Nacional de Energía Atómica

Agricultural system sustainability involves the prevention of groundwater contamination due to fertilizer derived nitrates. Nitrogen (N) balance could prove an indicator for this contamination. Organic N, one of the balance constituents, is an indicator of soil organic matter variation. Zero tillage (SD) increases organic matter content in the upper layer, thus acting like a carbon dioxide sequestration system. The aim of the experiment was to obtain tillage and fertilization recommendations, avoiding soil and water contamination. Urea enriched with 15N was applied under two tillage systems (SD and conventional tillage (LC)) and different fertilization conditions. SD caused an increase of fertilizer derived N in the organic N soil fraction. In one growing season, the fertilizer recovered in crop and soil at 0 - 20 cm layer, varied between 66 and 82 %. Unrecovered fertilizer N (34 to 18 %) would be moved to deeper layers or would be lost as gaseous emissions. The use of 15N allowed us to quantify the applied fertilizer´s fate. In all the studied situations, N derived from fertilizer was found in the soil nitrate fraction (24 % average). This shows the importance of a correct fertilization to prevent water contamination. The other fractions were affected by the tillage system. Under SD, N derived from fertilizer in the ammonium fraction was lower (0,1 %). N derived from fertilizer in organic N fraction was increased (80 and 68 % under SD and LC, respectively). These results show that the use of appropriate tillage and fertilization practices, may prevent soil and water contamination contributing to the system´s sustainability.