As the fertigation system is computer-controlled, and
based on the continuous EC measurements, it is designed
to accommodate changes in dilution of the leachate collection
tanks such as the introduction of rainfall, as long as
the tanks do not overflow. During the present experiment,
an undetermined amount of rain water was allowed to collect
in the leachate collection tanks, although none of the
tanks overflowed. Rainfall of 78, 83 and 0 mm in July,
August and September, respectively, was below long-term
averages of 90, 93, and 90 mm for the same months. The
prevailing temperature was cooler than normal during Period
I and warmer during Period II particularly in September.
The cool Period I may account in part for reduced
release of nutrients from CRF and hence lower performance
especially of dogwood and ninebark, the two most
rapidly growing species.