Space-time variability of soil salinity in irrigated vineyards of South AfricaReportar como inadecuado

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(2009) Mark abstract Salts present in the soil and surface waters of the Western Cape Province of South Africa represent a limitation to farming activities. Therefore the management of salinity in the landscape, which includes measuring, mapping and monitoring of its behaviour on a regional scale, is the subject of this investigation. Four sites were actively investigated in this study. These are the Robertson experimental farm, Goedemoed farm near Robertson, Broodkraal farm near Piketberg and the Glenrosa farm near Paarl. Regular point measurements and soil samples were taken to study the behaviour of salinity in irrigated soils over several irrigation seasons. The quality of the irrigation water was adjusted to six different levels of salinity, between 30 mS m-1 and 500 mS m-1. At the Broodkraal and Glenrosa farms, large scale investigations were conducted to estimate salinity over larger areas. Broodkraal farm was a large newly established table grape enterprise offering the opportunity to study the initial change in soil salinity when irrigated with saline water. At the Glenrosa farm, there was an opportunity to characterize the soil even before irrigated vineyards were established. Suction cup measurements were taken with self-designed and patented lysimeters and used to follow the seasonal soil water salinity changes through the root zone under different salinity regimes. These results were used to characterize an average salt depth trend, which was found to be best represented by a linear function, and its evolution over time. A method was proposed to reduce the number of samples necessary to determine this salt depth trend and to estimate the quality of the soil water that drains below the rooting zone. One of the important findings was that an ECe threshold for vines of 100 mS m-1 was more suitable than the conventional 150 mS m-1 and that the sensitivity of the vines to levels beyond this threshold increased with the number of years of exposure. The detailed surveys at the Broodkraal and Glenrosa Farms helped the modelling of the regional salinity behaviour. This study allowed gaining a comprehensive understanding of the soil salinity dynamics in an irrigated landscape using saline water.

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Autor: Willem de Clercq



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