Abstract
espanolPara evaluar la eficiencia de riego en condiciones de limi-tacion de agua, se ensayaron cuatro tratamientos dife-rentes de riego subsuperficial en melocotoneros (Prunuspersica L.) en un clima mediterraneo semiarido cerca de Lleida (NE Peninsula Iberica). Los tratamientos consistieron en inyeccion de aire presurizado, irrigacion deficitaria, irrigacion completa (control) y una adicion de cascarilla de arroz alrededor de la tuberia para mejorar la porosidad. Debido a que el ultimo tratamiento mejoro las condiciones fisicas y mejoro el crecimiento de los arboles, se realizo un estudio micromorfologico para comprender este comportamiento. El suelo fue un Xeric Torriorthent, con textura franca, afectado por salinidad y con un bajo contenido de materia organica. Se tomo un bloque no perturbado (30 cm de lado) de cada tra-tamiento, y se hicieron dos secciones delgadas verticales, 5 × 13 cm, incluyendo el tubo subterraneo. Se anadio un colorante fluorescente a la resina de poliester para obtener imagenes UV de la porosidad. Se caracterizo la porosidad y se obtuvo la distribucion del tamano de poro para cada tratamiento. Los tipos de poros de los cuatro tratamientos mostraron diferencias evidentes en las secciones delgadas. Los tratamientos de riego completos y con deficit se caracterizan por una estructura de bloques subangulares poco desarrollada y una estructura intraa-gregados vesicular. El riego deficitario con inyeccion de aire produce, en su parte superior, una estructura similar a las de riego completo y con deficit. En el entorno y por debajo de la tuberia, donde el efecto del aire presurizado fue mayor, la estructura es apedial, con vesiculas (bur-bujas), de 200 – 500 μm de tamano. La porosidad del suelo con cascarilla de arroz es el doble que los otros tres tratamientos. La fraccion de 15 – 30 μm se duplica, mientras que las fracciones mayores triplican las del resto de los tratamientos. Contiene muchos excrementos ovales de acaros (probablemente Oribatidae), de 50 – 100 μm de tamano, asociados a tejidos de cascarilla de arroz medianamente descompuestos. Podemos concluir que las enmiendas alrededor de las tuberias de riego que promueven la actividad faunistica son muy efectivas para transportar agua al suelo, opuesto al aire presurizado que solo aumenta la porosidad vesicular (no conectada). EnglishIn order to assess the irrigation efficiency under water-limiting conditions, four different treat-ments of subsurface irrigation of peach trees in a semi-arid Mediterranean climate near Lleida (NE Iberian Peninsula) were tested. The treatments included pressurized air injection, deficit irriga-tion, full irrigation (as control) and an addition of rice husk around the pipe to improve porosity. Because the latter treatment improved physical conditions and resulted in better tree growth, a micromorphological study was conducted in order to understand the reason for this behaviour. The experiment was carried out in a commercial peach orchard (Prunus persica L.). The soil was a Xeric Torriorthent, with a loam texture, affected by salinity and with low organic matter content. One undisturbed block (30 cm each side) was taken from each treatment, and two vertical thin sections, 5 × 13 cm, including the subsurface pipe, were made. A fluorescent dye was added to the polyester resin to obtain UV light images of the porosity. The pore parameters and the pore size distribution were obtained for each treatment. Strong changes in the pore types of the four treat-ments are evident in the thin sections. Full and deficit irrigation treatments are characterised by a weakly developed subangular blocky structure, with a vesicular intra-aggregate structure. Deficit irrigation with air injection produced, in its upper part, a structure similar to the full and deficit irri-gation treatments. In the surroundings and below the pipe, where the effect of pressurized air was higher, the soil structure is apedal, with vesicles (bubbles), 200 – 500 μm in size. Porosity of the soil modified with rice husk is greater than that of the other three treatments: the 15 – 30 μm porosity fraction is double, and the larger fractions three times that of the other treatments. It contains many oval excrements of mites (probably Oribati-dae), 50 – 100 μm in size, associated with moder-ately decomposed rice husk tissues. We conclude that the modifications around the irrigation pipes that promoted faunal activity are very effective in conveying water to the soil in comparison to that of pressurized air, which only increases vesicular (non connected) porosity.
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