Modelizaci.n de la distribuci.n de sales en un suelo con cultivo de tomate bajo riego localizado.

Spanish; Castilian. Se realiza una simulaci.n de la distribuci.n de la salinidad en suelos agr.colas de regad.o, utilizando para ello un modelo de transporte de multicomponentes en medio poroso variablemente saturado, NSATCHEM-2D (Simunek y Su.rez, 1993b). Este modelo se ha utilizado para simular la distribuci.n de sales en un cultivo de tomates de la isla de Fuerteventura. El suelo de cultivo es un Calcisol l.ptico, el sistema de riego es localizado de alta frecuencia (goteo) con aguas de pozo que presentan un alto riesgo de salinizaci.n del suelo (CE = 7840 micro S/cm) y el cultivo, se ha dicho, es tomate de la variedad Daniela. El modelo simula que a los 100 d.as de implantado el cultivo se produce una fuerte acumulaci.n salina en los primeros 10 cm del suelo a unos 35 cm de distancia del gotero, llegando a alcanzar la soluci.n ed.fica m.s de 300 dS/m en los primeros 2 cm superficiales y descendiendo r.pidamente con la profundidad. La distribuci.n de isol.neas de conductividad el.ctrica al finalizar el cultivo (270 d.as), muestra una distribuci.n m.s homog.nea de la salinidad que la obtenida para los 100 d.as de cultivo y adem.s la zona de m.xima acumulaci.n de sales aparece mucho m.s cerca del punto de goteo (18-20 cm). Seg.n el modelo, la m.xima acumulaci.n de sales en la superficie del suelo tiene lugar, en la simulaci.n de 100 d.as, en una franja situada entre 30 y 40 cm de distancia al gotero mientras que al final del cultivo (270 d.as), la zona de acumulaci.n salina se desplaza hacia el gotero, en una franja situada entre 15 y 25 cm del punto de goteo, debido a las menores dimensiones del bulbo h.drico. El modelo tambi.n predice un desplazamiento de la zona de acumulaci.n de sales hacia el punto de goteo, y que esta franja se sit.a a unos 8-11 cm (depende de la .poca) alejada de la zona, donde la humedad en la superficie del suelo alcanza el punto de marchitamiento.(...).

English. The distribution of salinity in irrigated agricultural land was simulated using a multicomponent transfer model in variably saturated porous medium, UNSATCHEM-2D (Simunek and Suarez, 1993b). The necessary inputs for the model UNSATCHEM-2D are the concentration of the major ions (calcium, magnesium, sodium, potassium, sulfates, chlorides and nitrates), alkalinity (carbonates and bicarbonates), concentrations in adsorbed and solid phases, water content (field capacity and wilting point), bulk density and partial CO2 pressure. The absorption of water by the roots depends on the hydric potential difference between inside and outside the roots. The osmotic potential values are obtained by the model by using the osmotic coefficients and the modified equation of van.t Hoff, the absorption of solutes by the plant roots being considered negligible. This model was used to simulate the distribution of salts in a tomato crop on the island of Fuerteventura. The soil involved is a leptic Calcisol, the irrigation system is localized high-frequency (drip) with well-water that presents a high risk of soil salinization (CE = 7840 dS/cm) and the crop, as stated above, is tomato of the Daniela variety. 100 days after crop planting a marked accumulation of salts was simulated in the first 10 cm of the soil to a distance of 35 cm from the point of irrigation, the soil solution reaching more than 300 dS/m in the first 2 cm at the surface and quickly descending with depth. The model showed that distribution of electrical conductivity isolines at the end of the cropping period (270 days) was more homogeneous than that obtained 100 days after planting and, moreover, the zone of maximum accumulation of salts was much closer to the point of irrigation (18-20 cm). The maximum accumulation of salts at the soil surface takes place, in the 100-day simulation, in a strip situated between 30 and 40 cm from the irrigation point while, at crop end (270 days), the zone of salt accumulation is found to be closer to the point of irrigation, in a strip located between 15 and 25 cm from the watering point, due to the smaller dimensions of the water bulb.(...).