148 research outputs found
Estrategias de muestreo para la determinación de las propiedades hidráulicas del suelo en dos unidades cartográficas
Cuando se usan los mapas de suelos para estimar las propiedades
hidráulicas del suelo, éstos presentan diversas limitaciones debidas a
varios factores, entre los cuales podemos citar, la falta de información
a cerca de su variabilidad espacial a escala detallada (finca). En estos
casos se hace necesario el muestreo adicional de estas propiedades
para obtener una mejor estimación de su variabilidad espacial de cara
la planificación y ejecución del riego. Con el objetivo de conocer los
requerimientos de muestreo de la conductividad hidráulica saturada y
la sorptividad (el horizonte Ap y sobre la superficie del suelo) fueron
muestreadas dos unidades cartográficas de suelos a escala 1:25000
del área de influencia del canal Segarra-Garrigues, en Cataluña (NE
de España) a través de un muestreo anidado. Los semivariogramas
muestran un patrón de variabilidad acorde al tamaño modal de las
fincas del área (a nivel de serie) con manejo homogéneo de la superficie del suelo. La sorptividad es la propiedad menos afectada por
este factor (manejo del suelo). La distancia optima de muestreo y el
número de muestras necesarias para obtener un buen resultado en la
estimación de la Ks
en el horizonte Ap es impracticable en ambas unidades. Para el resto de las propiedades la distancia de muestreo está
dentro del tamaño modal de las fincas (100 m). Únicamente se puede
obtener una buena estimación de la Ks
y la sorptividad en el orden
de magnitud del logaritmo de los datos obtenidos con un número de muestras considerablemente baja
Soil porosity changes in orchards with subsurface irrigation: quantification and interpretation
In order to assess the irrigation efficiency under
water-limiting conditions, four different treatments 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 irrigation, 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 treatments 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 irrigation 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 Oribatidae), 50 – 100 µm in size, associated with moderately 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.info:eu-repo/semantics/publishedVersio
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