Improve Irrigation Scheduling for Better Tree Response

By Davie Kadyampakeni

Citrus trees require water to be able to carry out the natural processes of growth, making food, and developing fruit and juice. To get the water from the soil, the fibrous roots do the extraneous work of absorbing the water and carrying it via the transpiration stream to the leaves. The water in the soil is made available through either irrigation or rainfall. In Florida, most of the rain falls from June to September, and growers need to water trees for the rest of the year.

Most citrus-producing soils of the state are very sandy with low water- and nutrient-holding capacities. Thus, good irrigation management is important to avoid overwatering or underwatering. Excessive water applications will leach most of the applied fertilizer and other chemicals, adding to the cost of production. Underwatering can lead to trees going thirsty for days, resulting in negative impacts such as wilting, flower abortion, fruit drop and severe defoliation.

Items to consider for irrigation management include the following:

1. Regularly check that all emitters or microjets are working in the grove. One problem in citrus irrigation is clogged emitters, especially where fertilizer is applied via fertigation. To avoid clogged emitters, routinely keep irrigation on for an additional 30 minutes following fertigation. This will flush the irrigation lines and avoid build-up of undissolved fertilizer.
2. Use weather data to decide when, how often and how much water to apply. The Florida Automated Weather Network irrigation scheduling tool is helpful. On the website, click on Tools and then Irrigation. Next, select Citrus Irrigation and then click on Citrus Microsprinkler Irrigation Scheduler. Specify the tree spacing, emitter discharge, and soil and root depths. This will give the user the amount of water to apply and how often. As a rule, when you receive ½ to 1 inch or more of rain, you can back off irrigation for a day or two.
3. Finally, base your decisions on how much water to apply based on soil moisture sensor information. Most sensors can provide information on available water and when one has to irrigate to make sure ample water is available in the root zone.

Davie Kadyampakeni is an assistant professor at the University of Florida Institute of Food and Agricultural Sciences Citrus Research and Education Center in Lake Alfred.

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