Abstract
Orange [Citrus sinensis (L.) Osb.] is a crop of great economic importance in the world and in Puerto Rico despite the negative impact caused by the presence of Huanglongbing disease. To maintain profitability, growers must optimize management practices. Important practices include proper use of supplemental irrigation, using improved rootstocks and cultivars, and effective disease control. To assess the response of 'Rhode Red Valencia‘ trees to supplemental microirrigation, an experiment was conducted in Adjuntas, Puerto Rico, at an orchard originally established in 2007 under microirrigation. From 2011 to 2013, the adult orange trees were submitted to three treatments. In two of the treatments, microirrigation was scheduled using tensiometers at soil water tension between 10 and 15 kPa and between 30 and 35 kPa. A third treatment, without microirrigation (rainfed), was included as a check. Water stress periods were evident from January through June during the years 2008 to 2014. Microirrigation treatments did not have a significant effect on number of fruits, fruit weight and canopy volume during 2011 to 2013. Hence, under the conditions of this experiment, supplemental irrigation was not necessary for an adequate production of 'Rhode Red Valencia‘.
Highlights
Citrus trees can fall into water stress, especially during active growth
Soil water tension remained lower than 15 kPa and lower than 35 kPa for the maximum threshold for each microirrigation treatment (Figure 1)
Tensiometers readings were reflecting a low need for irrigation events required by trees under the climatic conditions registered at Adjuntas, Puerto Rico
Summary
Citrus trees can fall into water stress, especially during active growth. When a tree loses water faster than the soil can provide it, the tree becomes stressed due to drought and wind. Excessive irrigation or rain can cause stress. This stress may happen because lack of oxygen in the tree root system increases hydrogen ions that can damage the root and impede the absorption of water from the soil (Parsons and Wheaton, 1995). Several days of water stress can reduce stem and leaf enlargement and result in a lighter green color of the leaf. Longer periods of stress can cause leaves to dry, starting from the apex, and the abscission of flowers and fruits. Exposure of trees to stress during several years can reduce their size while reducing their long-term performance potential
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