Irrigation of grapevines with saline water at different growth stages - 1.Effects on soil, vegetative growth, and yield

Mature field-grown grapevines, Colombard on Ramsey rootstock, grown in a se mi-arid climate were irrigated with saline water during any one of 4 growth stages within the season: pre-flowering, during berry development, during berry ripening, and post-harvest. At other times, plots were irrigated with river water (EC 0.5 dS/m) as was the control throughout the season. Saline water (EC 3.5 dS/m) with a high sodium absorption ratio was produced by ad dition of sodium chloride brine. Soil cation exchange capacity was 14 cmol( c)/kg, and at the end of the trial, the soil exchangeable sodium percentage in the control was 6%, in the treatment salinised pre-flowering 13%, durin g berry development 20%, during berry ripening 20%, and post-harvest 19%. T reatments were applied for 6 consecutive seasons. Vines were highly product ive, with the average yield in the control equal to 62 t/ha of grapes. Sali ne irrigation caused significant, but small, declines in yield in 3 seasons , in pruning weights in 2 seasons, and in berry weights in 4 seasons. Effec ts on growth, once established, often persisted unchanged through one or mo re subsequent seasons of saline irrigation. The growth stage shown to be mo st sensitive to saline irrigation was berry development; saline irrigation during berry development reduced the yield by 7% and during berry ripening by 3%, and pre-flowering it reduced the berry weight by 1%, during berry de velopment by 6%, and during berry ripening by 4%. The amounts of irrigation applied in each of the 4 growth stages were not equal, and hence, treatmen ts did not receive equal additions of salt. Normalising data to remove this effect showed that the rate of yield decline per unit dS/m increase in the seasonal average salinity during berry development, 7%/dS.m, was 3-fold gr eater than the 2%/dS.m during berry ripening. We conclude that this scion/r ootstock combination, grown under these conditions, can maintain high produ ctivity despite 'slugs' of saline irrigation.