Evaluation of microirrigation levels for growth and productivity of avocado trees

Abstract

Avocado (Persea americana Mill. cv. Simmonds) is an important fruit among consumers in Puerto Rico and in the Hispanic community in the United States. During the last years, orchard establishment has increased considerably in Puerto Rico, where production of this fruit is third behind mango and oranges. Currently growers need to deal with lack of information on proper irrigation management in orchards under conditions observed in Puerto Rico. Typically, growers are encouraged to adopt an irrigation scheduling method to ensure tree establishment and adequate productivity, and thus to reduce problems associated with improper irrigation management. The Universities of Puerto Rico and Florida recommend the use of tensiometers to schedule irrigation for fruit trees. An avocado orchard was established during 2001 for evaluating the effect of soil water tension measured by tensiometers on growth and productivity of avocado trees under microirrigation. The predominant soil series at the experimental site is Coto clay, classified as Typic Eutrustox. Planting distance was 9.1 m x 9.1 m. Trees were submitted to two microirrigation treatments scheduled by using tensiometers installed at 30-cm and 45-cm depths. Trees were irrigated when tensiometer readings reached a low depletion level (10 to 15 kPa) or a high depletion level (40 to 45 kPa). A rainfed treatment was included as check. Variables measured were canopy volume, fruit weight and number, and irrigation applied. Canopy volume of trees growing under rainfed conditions was significantly lower than that of trees submitted to either 10 to 15 kPa or 40 to 45 kPa microirrigation treatment. Trees submitted to 40 to 45 kPa showed the maximum canopy volume, 148 m³/tree, which was not significantly different from that of trees submitted to 10 to 15 kPa. Only in 2005, trees irrigated at low depletion levels produced 68 fruits per tree, an amount which was significantly greater than that of the other two irrigation treatments. In general, avocado trees submitted to high depletion level significantly increased their growth and yield.