2/27/2024 - By Dr. Tom Reed

Irrigation management is important to maximize any fertilizer investment. When utilizing a technology like POLYON® controlled-release fertilizer (CRF) it is sensible to conduct practices to optimize that application.

Irrigation has a significant impact on fertilizer in the soil. Producers who apply too much water may not only waste that resource but also lose applied conventional fertilizer or nutrients that have been released from a CRF source. Consequently, this leaching of nutrients results in reduced yields and profits. This applies across cropping systems but is particularly relevant in Florida watermelon production.

Over-Irrigating

Watermelon requires considerable irrigation, particularly in warm seasons that lack rainfall, and because production is predominantly on sandy soils that have minimal nutrient-holding capacity. Growers should be cautious about protecting what nutrients are in the soil. Early in the season, before plants are well established, is an especially vulnerable time for nutrients to be carried away from the root zone by over-irrigating due to watermelons having approximately 3/4 of their roots in the top 12” of soil. Fertilizer moves with water applied, therefore, if the irrigation wetting zone is past 12” it is unlikely for much of those nutrients to be utilized with the limited plant roots at that depth.

Managing Irrigation

Shorter duration and higher frequency irrigations may result in less nutrient loss due to leaching and maintaining consistent nutrient levels in the root zone. To best manage water and nutrients it is important to know:

·         The crop growth stage and evapotranspiration

·         The root zone of the crop

·         Soil water-holding capacity

·         Proper drip tape placement

·         Emitter spacing

·         And flow rate

These factors will determine when to start and how long to run the irrigation system.

Irrigation Moisture Monitoring Methods

Soil moisture monitoring technology can assist growers in providing adequate moisture for the crop growing season, reducing the likelihood of leaching nutrients. Remember to always factor in the wetting pattern of the drip tape, root zone, and soil type to best place your soil moisture sensors. Placement should be beside an emitter, within the wetting pattern not between emitters, approximately half the distance of lateral water movement from the emitter, and between plants within a row.

Your Harrell’s Rep is Here to Help

Familiarizing oneself with the data and graphs being generated by soil moisture monitoring is essential to effectively manage irrigation at the correct times while monitoring rainfall events. Great irrigation management will increase your efficiency from a resource, economic, and environmental perspective.

Harrell's POLYON® blends are engineered to provide nutrients over time at a predictable rate under specified conditions. To find the right POLYON® CRF product for you, or if you have questions on proper irrigation maintenance and monitoring, reach out to your Harrell's Rep.