Effect of irrigation on yield, berry weight, and sugar content of blackcurrants

Blackcurrant bushes (cv. Magnus) planted on a free-draining Lismore stony silt loam were used to study the yield responses to four irrigation regimes, using one unirrigated and three irrigated treatments. Irrigation treatments were applied each time gravimetric soil samples (0–150 mm deep) taken 300mm from the hedgerow fell to 10,15,or20%soil moisture (s.m.) content. In the first two years, the 15 and 20% s.m. treatments produced yields 150-220% higher than both the unirrigated and infrequently irrigated 10% s.m. treatments. As the unirrigated and 10% s.m. treatment bushes developed with time, the annual yield differences decreased to a level where, by the fifth harvest, the 15 and 20% s.m. treatment yields respectively were only 15% and 37% higher than the unirrigated treatment yield. Average berry weight increased with irrigation frequency during the first three seasons. However, differences in berry weight decreased gradually with timeandby the 1986/87 season showed no significant differences ...