Evaluaci.n del lavado de nitratos en un cultivo de tomate en riego por goteo y acolchado pl.stico.

English. The objective of this study was to evaluate nitrate leaching in tomato (Lycopersicon sculentum Mill) cropped with drip irrigation and plastic mulch, and following the management techniques of the medium Ebro valley. To achieve our goal we conducted in Valdeg.n (La Rioja), over a fine clayey soil, a field experiment in which tomato, cv. Brigade, was cultivated under two different management techniques: bare soil (S1), and plastic mulch (S2), and two different water doses of drip irrigation: R1 and R2, both estimated from the crop evapotranspiration (ETc) calculated for each soil management technique. Therefore, we had two treatments where the irrigation dose was adjusted to crop needs, S1R1 and S2R2, one treatment with water limitation, S2R1, and one treatment that received excess of water. To evaluate nitrate leached to 1 m depth, the drainage volume was multiplied by the nitrate concentration of the soil solution at that depth. Drainage was calculated by weekly measuring the water content of the soil profile and applying the water balance equation. The soil solution at 1 m depth was extracted by porous ceramic cups and was analysed for nitrate. Drainage and nitrate leaching were evaluated for three different crop periods: preplanting, postplanting, and cropping. Cumulative drainage accounted for 25% of total water applied for S1R1, 32% for S1R2, 30% for S2R1 and 32% for S2R2. Nitrate leaching was 63% of the initial plus the applied as fertilizer for S1R1, 91 for S2R1, 59 for S2R1 and 44 for S2R2. The larger water and nitrate losses took place during the periods of preplanting and postplanting.

Spanish; Castilian. El objetivo de este trabajo fue evaluar el lavado de nitrato en un cultivo de tomate (Lycopersicon sculentum Mill) en riego por goteo y acolchado pl.stico utilizando las pr.cticas agron.micas propias del valle medio del Ebro. Para ello se estableci. en la finca Valdeg.n del CIDA, La Rioja, y en un suelo arcilloso fino, un ensayo de tomate var. Brigade en el que se compararon dos sistemas de manejo del suelo: desnudo (S1) y acolchado pl.stico (S2) y riego por goteo con dos dosis de riego ajustadas a la evapotranspiraci.n del cultivo (ETc) de cada sistema R1 y R2, gener.ndose cuatro tratamientos, S1R1 y S2R2 con las dosis de riego ajustadas a sus necesidades y S1R2 y S2R1 con las dosis de riego ligeramente excedentaria y deficitaria respectivamente. Para cuantificar el lavado de nitrato a 1 m de profundidad, se multiplic. el volumen de drenaje por la concentraci.n de nitratos de la soluci.n del suelo a esa profundidad. El drenaje se estim. midiendo el contenido de agua en el perfil del suelo semanalmente y resolviendo la ecuaci.n de balance de agua del suelo. La soluci.n del suelo a 1 m se extrajo con c.psulas de cer.mica conectadas a ca.as de vac.o. Se calcularon el drenaje y las p.rdidas de nitrato en tres fases del cultivo: pretrasplante, postrasplante y cultivo. Los valores del drenaje sobre el total de agua aplicada, representaron el 24,9% en S1R1, 32,3% en S1R2, 29,6% en S2R1 y 31,6% en S2R2. Las p.rdidas de nitr.geno sobre el inicial m.s el aportado en la fertilizaci.n fueron del 62,8; 91,4; 59,0 y 43,5% respectivamente. Las mayores p.rdidas de agua y nitr.geno ocurren en las fases de pretrasplante y postrasplante.