View Poster Application

Calibrating Prescribed Flush Cycles

Extension Education

Mark Warren
Agriculture Agent
UF/ IFAS Extension


Drip fertigation systems, when properly managed, provide opportunities for increased use efficiencies for both water and crop nutrients. In the Suwannee Valley region of Northeast Florida, drip fertigation in combination with plastic mulch is used on a variety of high value horticultural crops. Among these crops, the region produces approximately 11,000 acres of spring watermelons; over half of the acres grown in Florida. Using soil moisture probes and weekly petiole sap tests, extensive efforts are made to help optimize efficiencies and to minimize potential environmental impacts relating to the use of crop nutrients.

One component of the 4R Nutrient Stewardship Program addresses fertilizer placement. Without proper and uniform placement, fertilizer efficiencies can be greatly diminished.

In drip fertigation systems, where soluble fertilizers are injected into the irrigation system during operation, placement is controlled by the management of irrigation water used to deliver the fertilizer. The less water used; the higher in the root profile the nutrients can be maintained. For this reason, fertilizers are typically injected at the end of an irrigation cycle. At the end of an injection event, proper flush times are the required to ensure that the fertilizer is pushed out of the system while the system is still at operating pressure.

Failure to properly flush a system at the end of an injection event can result in ununiformly applied fertilizer, clogging and emitter failure, and reduced crop performance. This project has demonstrated that proper system calibration is a required and justifiable activity. Standard estimated flush times used widely across the region, prior to this service, were shown to be significantly deficient in properly placing important crop nutrients.

In Levy County, over the previous two-year period (2021-22), 71 producer fields were evaluated with 87% being found significantly out of calibration. According to a season end grower survey, farmers estimate that services such as flush time calibration and petiole sap testing represented a $200/ acre value. Of the 1,785 acres in Levy County currently being managed with the support of this program, this  represents a $357,000 annual benefit.

Poster has NOT been presented at any previous NACAA AM/PIC

This poster is being submitted for judging. It will be displayed at the AM/PIC if not selected as a State winner. The abstract will be published in the proceedings.

Click to view Poster

Authors: Mark Warren
  1. Warren, M. Extension Agent I., NACAA/ FACAA, Florida, 32110