Growth, Seed Yield, and Oil Content of Canola Grown under Saline Conditions
Due to health concerns regarding saturated fat in the human diet, canola (Brassica spp.) is becoming an increasingly important source of edible vegetable oil because of its low saturated fat content. This increased demand, and the need for crop diversification, will undoubtedly promote increased acreage of canola in the western USA, where some soils are or have the potential to become saline. Salt tolerance in two canola species (B. napus L. cv. Westar and B. campestris L. cv. Tobin) was determined in a 2-yr field plot study. Six salinity treatments were imposed on a Holtville silty clay (clayey over loamy, montmorillonitic [calcareous], hyperthermic Typic Torrifluvent) by irrigating with waters salinized with NaCl and CaCl2 (1:1 w/w). Electrical conductivities of the irrigation waters ranged from 1.2 to 9.7 dS m−1 the first year, and 1.2 to 11.5 dS m−1 the second year. Seed yield, vegetative growth, oil content, and protein content in the oil-free seed meal were measured. Relative seed yields of Westar and Tobin were unaffected by soil salinity up to ll.0 and 9.7 dS m−1 (electrical conductivity of the saturated soil extract: ECe), respectively. Each unit increase in salinity above the thresholds reduced the seed yield of Westar by 13.0% and Tobin by 14.3%. These results place both canola species in the salt-tolerant category. Increased salinity did not significantly affect the oil or protein content of the oil-free seed meal. Vegetative growth of both species was unaffected by soil salinity up to 10.0 dS m−1 and the growth decline above this threshold was 11.2% per unit increase in salinity.
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