The chloride status of the irrigated sultana vine and its relation to vine health

Abstract

The chloride content of petioles from the middle leaves of shoots (which is higher than that of corresponding leaves) gives the best estimate of the chloride status of an irrigated sultana vine from bud burst until the middle of January. After this date, foliar samples may not give a reliable indication of the vine chloride status. The physiological age of the portion sampled and the normal seasonal chloride accumulation must be considered in interpreting foliar chloride values. A sample of the annual wood taken in winter may also give a suitable estimate. On an undrained loam which bears vines showing various degrees of salt injury, there is a close relation between petiole chloride, severity of the salt symptoms, and vine health. Vines with petiole chloride levels (dry basis) of 0.8 per cent. in early December showed slight burning of basal leaf margins, while chloride levels above 1.9 per cent. in early December or 2.5 per cent. in early January were accompanied by severe burning of the basal leaves, considerable restriction of growth, and very low fruit yields. On two other sites healthy vines with no obvious salt injury had petiole chloride contents of 1.7 per cent. in December in one case, and 2.0 per cent. in the other. Therefore a general petiole chloride level indicative of excessive salinity could not be established. To investigate whether local variations in vine health may be attributed to salt, adjacent healthy 'vines should be sampled in the same way for comparison, especially on those sites where leaf symptoms are absent. The leaf symptoms, as used in this study, may be assumed indicative of excess soil salts. On the sites examined there is no relation between total sulphur or boron content of petioles or leaves and the leaf burn symptoms described. In contrast to chloride values, both the total sulphur and boron contents of leaves are higher than those of petioles.