Yield response of bananas to trickle irrigation

Abstract

Supplementary trickle irrigation applied twice a week by single microtube at replacement rates of 0 (control), 20, 40, 60, 80, 100 and 120% of Class A pan evaporation (El from 1970 to 1976 increased bunch weight significantly (P= 0.02) above 40% E. Treatment 60% E gave a bunch weight of 27.6 kg compared with 25.7 for the control. The control, 20 and 40% treatments did not affect hand number from 1970 to 1976 while all other treatments increased hand number by 0.3 hands each year. Means of treatments over all years for fingers showed an annual increase of 4.6,4.0,5.8 and 5.0 fingers for 60,80,100 and 12O0Io treatments, respectively. Gravimetric sampling in 1974 showed the control plot had a lower water potential than other plots. There was little change in water potential in any of the other treatments. There was a significant linear decrease in water potential with increase in radius from the emitter. Root distribution studies showed that about 70% of the root systems in all treatments were concentrated in the upper 40 cm of soil. Forty per cent of the total root system was confined to a square, 60 x 60 cm, close to the base of the plant. Thus trickle irrigation with an emitter positioned near the base of the plant and a slow flow rate (3 litres/h) would reach most of the root system. Four out of the six years of the experiment were very wet (greater than 1700 mm rainfall). Only 29% of the total water over the 6 years in the 60% E treatment was provided by trickle irrigation. This experiment showed that 60% of Class A pan evaporation can be used as a reliable guide for the trickle irrigation of bananas on the East coast of Australia with free draining soils.