Evaluation of soil moisture levels on growth and productivity of young citrus trees

A citrus orchard (Citrus sinensis [L] Osb. 'Rhode Red Valencia') was established at the Agricultural Experiment Substation of Isabela, Puerto Rico in 2001. The predominant soil series at the experimental site is Coto clay (Typic Eutrustox). One hundred-eight Rhode Red Valencia trees grafted on Cleopatra were planted at a distance 4.5 X 6.0 m. Irrigation water was applied at an average rate of 29.07 L/hr using microsprinklers installed on 1.3 cm polytubing line. The experimental plots were arranged in a randomized complete block design with four replications. Plots consisted of six trees; data were recorded on the four middle trees. Two irrigation treatments were scheduled by using tensiometers installed at 30 and 45 cm depth; trees were irrigated when tensiometer reached a low depletion level (10-15 kPa) or a high depletion level (30-35 kPa), there was also a rainfed treatment. Irrigation treatments did not affect orange tree growth or fruit yields during 2004. Tree canopy volume varied from 13.61 to 14.62 m3, producing an average of 42 fruits. During 2004, Valencia trees were harvested for the first time, therefore an irregular production is expected. Tough drip irrigation is a common practice for fruit orchards at the location; the experimental results obtained during 2004 showed that rainfall distribution was adequate to maintain growth. Older trees or those with a higher fruit load will probably require more frequent irrigations, mainly during the dry season.