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Use of saline irrigation water on Fraser River delta soils Stewart, John

Abstract

Two field plots in the Ladner area, one supporting pasture species and the other inter-tilled crops, were irrigated by sprinkler with water containing more than 13,000 parts per million of ocean salts. Eight acre inches of water were applied annually, in three equal applications, the trial being conducted for a period of two to three years. Soil samples, obtained at appropriate intervals during the course of the irrigation trials, were studied in the laboratory to determine the effects of the treatment on their physical and chemical properties. Plant yields were recorded and tissues chemically analysed to reveal alterations, if any, in the uptake of mineral elements. Analyses revealed that, as a result of irrigation, marked increases occurred in respect to salt content of the soil and osmotic pressures in the soil solution. Subsequent dormant-season rains were observed to remove a large portion of the accumulated salt, but sufficient salt residue remained in the cultivated soil after two year's irrigations to affect injuriously the growth of a non-irrigated silage crop. The exchangeable sodium percentage of the soil was increased only slightly in the pasture field, but to a dangerous level in the cultivated field. Exchangeable magnesium was increased and calcium decreased in both soils. The effects on soil calcium are considered to be important, since the soils are already low in available calcium, and a further deficiency of this element for plant growth is therefore threatened. Studies of soil structure revealed no destructive changes which could be definitely ascribed to irrigation with saline water. Calcium uptake by the plants was generally depressed by the treatment, and of the tissues studied, all, with the exception of the grasses, showed accumulation of sodium Pea and silage corn yields were reduced by irrigation, sugar beet yield was unaffected, and pasture grass yield was increased eight-fold. The quality of all crops was impaired by the treatment. The author is convinced that the continued use of this highly saline water, except in very special circumstances, will cause reduced crop yields and lead ultimately to serious and permanent impairment in the physical and chemical properties of the soils.

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