Dormant season fertigation promotes photosynthesis, growth, and flowering of ‘Blueshower’ rabbiteye blueberry in warm climates

Abstract

In the subtropical lowland of Taiwan with a warm winter climate, most rabbiteye blueberry cultivars (Vaccinium ashei) are semi-deciduous, and their leaves remain green through the winter. We investigated whether fertigation with nitrogen (N) and phosphorus (P) during the dormant season had any subsequent effects on vegetative growth and flowering of rabbiteye blueberry in this region. Potted 3-year-old ‘Blueshower’ plants were fertigated weekly from November 2012 to March 2013 with combinations of 100, 200, or 400 mg·L-1 N and 200 or 400 mg·L-1 P. Plants fertigated without N and P served as the control. Fertigation with any N and P treatment during the dormant season significantly increased photosynthesis (Pn) of overwintered leaves relative to the control, but had no effect on Pn of the new leaves. N at 100 mg·L-1 increased the total chlorophyll content in overwintered leaves more than two-fold compared to the control; total chlorophyll content in overwintered leaves increased with N rate, but was not affected by P rate. Dormant-season N and P fertigation advanced vegetative budburst. However, new shoot growth was negatively affected by dormant-season P fertigation. The number of flowers increased with N rate. We concluded that in the subtropical lowland with a warm winter climate, dormant-season fertigations, especially to supply N, can improve flowering and canopy development in the following spring.