This publication focuses on the evaluation of optimal nitrogen (N) rate for cotton in Florida. These updated recommendations assist growers in achieving economically viable yields while minimizing risks of both under- and overfertilization. Written by Hardeep Singh, Eajaz A. Dar, Ethan Carter, Michael Dukes, and Lakesh Sharma, and published by the UF/IFAS Department of Agronomy, January 2026.

Landscape plant palettes are changing due to water supply pressure. Turfgrass area is being replaced with alternative ground covers, other non-irrigated plants or hardscapes. Mechanisms range from incentive programs sometimes called “cash for grass” to outright bans on the use of turfgrass in “nonfunctional” areas or areas otherwise considered unnecessary. Despite evidence that shifts in landscape plants such as turf removal can save water, questions remain about the long-term impact of such programs as well as the high cost. This shift in plant palettes will need to be accompanied by development of new groundcovers. In addition, there is opportunity for turfgrass breeding and development for cultivars that require no irrigation in humid climates.

Periodic drought and shortage of potable water have led many municipalities in Florida to set limitations and restrictions on irrigation frequency for home lawns. These restrictions do not take into account turfgrass health and response and may be inappropriate across different species and cultivars; hence, there is a need to identify genotypes that could sustain quality and performance under reduced irrigation. A study was conducted at the University of Florida Plant Science Research and Education Unit in Citra, FL, to assess turfgrass response of 10 bermudagrass ( Cynodon spp.), nine zoysiagrass ( Zoysia spp.), and five seashore paspalum ( Paspalum vaginatum Swartz) cultivars to different irrigation regimes, consisting of non-irrigated control (Rainfed), soil moisture sensor (SENSOR)-based (up to 152 mm mo −1 ) , 8X per month (8XMO up to 152 mm mo −1 ), 4X per month (4XMO up to 76 mm mo −1 ), 2X per month (2XMO up to 38 mm mo −1 ), and 1X per month (1XMO up to 19 mm mo −1 ). Plots were evaluated for turfgrass quality and percent green cover using digital image analysis every 3 days over a 22-month period. Bermudagrass was able to sustain acceptable turfgrass quality during one of the growing seasons when irrigated 4XMO, showing substantial water savings compared to the other two species. SENSOR irrigation significantly reduced water consumption for all the three species and produced turfgrass quality similar to 8XMO irrigation. Results indicate that selecting the right cultivar for the area could help sustain turfgrass aesthetic and functionality.

Highlights Sod-based rotation was evaluated against conventional rotation. Sod-based rotations reduce NO3-N leaching by 39% in maize and 46% in peanuts. Sod-based rotations improve nitrogen use efficiency by 13% in maize. Sod-based rotations support both environmental protection and sustainable crop production. ABSTRACT. Excessive nitrate-nitrogen (NO3-N) loading from agricultural practices is a concern for areas like Florida, where total maximum daily load (TMDL) standards for nitrates are in place to protect water quality. Both organic and inorganic nitrogen fertilizers contribute to this issue, particularly in systems with conventional crop rotations. This study aimed to evaluate the effectiveness of rotational production, including sod-based rotations, as a best management practice (BMP) to reduce nitrate-nitrogen leaching and improve nitrogen use efficiency while maintaining crop productivity. A four-year field study (2019–2022) was conducted at the North Florida Research and Education Center-Suwannee Valley in Live Oak, FL. The nitrate-nitrogen systems included two conventional rotations: a maize (Zea mays) - peanut (Arachis hypogaea) rotation and a maize-carrot (Daucus carota)-peanut rotation. Additionally, there were two sod-based rotations: one involving two years of bahiagrass (Paspalum notatum) followed by maize and peanut, and another involving two years of bahiagrass followed by maize, carrot, and peanut. Results indicated that the sod-based rotations reduced nitrate-nitrogen leaching by 39% in maize and 46% in peanut compared to conventional rotations. Nitrogen use efficiency increased by 13% in maize under sod-based systems, though conventional rotations produced higher short-term crop yields over the four-year study period. Maize yields showed a normalized root mean square error (nRMSE) of 7.5 Keywords: Bahiagrass, BMP, Carrot, Leaching, Maize, Nitrogen balance, Peanut.

Highlights Passive wick lysimeter performance was tested against soil water balance and simulation models under high and perched water table conditions. Passive wick lysimeters overestimated deep drainage as compared to soil water balance and simulation models. Lysimeter data inflated NO3-N leachate estimates, questioning the reliability in similar field conditions. The out-row placed lysimeters recorded higher drainage volumes than in-row placed. Abstract. Understanding soil water and nutrient dynamics is pivotal for agricultural and environmental research, particularly the accurate measurement of nutrient leaching. This study critically compares the performance of passive-wick drainage lysimeters to the soil water balance approach and simulation models such as DSSAT (Decision Support System for Agrotechnology Transfer) and HYDRUS-1D (1-dimensional) in estimating deep drainage and nitrate-nitrogen (NO 3 -N) leaching under field conditions marked by high and perched water tables and coarse sandy soils. The study was conducted at the North Florida Research and Education Center, Live Oak, FL, over four years (2019–2022). Forty passive-wick drainage lysimeters, with 25 in-row and 15 out-row placements, were installed 61 cm below the soil surface to record deep drainage measurements. The results showed lysimeters exhibited poor correlation (R 2 = 0.04) with soil water balance estimates during the crop growing season, alongside a Root Mean Square Error (RMSE) of 7.9 liters, indicating substantial measurement discrepancies. The average deep percolation from the lysimeter was 2221 mm (SD = 1490 mm), which was 841% higher than the soil water balance method, 741% higher than the DSSAT simulated deep drainage, and 774% higher than the HYDRUS-1D simulation. Keywords: Deep percolation, Drainage lysimeter, DSSAT, HYDRUS-1D, Nitrate leaching.

This Net Irrigation Requirements for Florida Turfgrass Lawns series explains the process of estimating net irrigation requirements for Florida turfgrasses. The process used here gives a long-term (30-year) historical analysis of turfgrass monthly net irrigation requirements. This article shows the calculation of evapotranspiration for selected sites throughout the state (plus one in Alabama, to cover the west side of the Florida Panhandle). Written by Consuelo C. Romero, Bernard Cardenas, and Michael D. Dukes, and published by the UF/IFAS Department of Agricultural and Biological Engineering, revised August 2024.

The purpose of this document is to provide background information to all stakeholders—including scientists, legislators, local governments, landscape managers, Extension agents, Master Gardener Volunteers, homeowners, and the general public—on the underlying issues of fertilizer use, with an emphasis on an urban setting, and to outline the current state of the science on urban fertilizers and water quality in Florida. This information is presented in response to 12 frequently asked questions (FAQs) that also include discussion of several technological and regulatory solutions that have been adopted around the state. Written by Michael D. Dukes, Lisa Krimsky, Mary Lusk, Laurie Trenholm, Bryan Unruh, Michelle Atkinson, Rao Mylavarapu, and Bernard Cardenas, and published by the UF/IFAS Department of Agricultural and Biological Engineering, revised August 2024.

Optimizing irrigation and nitrogen (N) fertilizer management in irrigated potato crops grown on sandy soils in subtropical regions such as in northeastern Florida, USA is essential to sustain a high yield and to minimize leaching. N applications in this region typically occur at approximately 25–30 days prior to planting (Npre), at emergence (Neme), and at tuber initiation (Nti). However, recent studies suggest that applying N near planting (Npl) enhances fertilizer N use efficiency (FNUE). We combined experimentation with modeling to assess irrigation and N management options for potato in northeastern Florida. We first aimed to evaluate the DSSAT/CSM-SUBSTOR-Potato model using two-year irrigated field experiments conducted on sandy soils with variable N rates and application timings. CSM-SUBSTOR-Potato accurately simulated aboveground plus tuber dry weight [Relative root mean squared error (RRMSE) = 26.4%, Willmott’s index (d) = 0.98] and N accumulation (RRMSE = 28.6%, d = 0.97). Soil moisture and mineral N were captured well overall, but they were often underestimated due to a water table influence that is currently not considered in DSSAT. Subsequently, CSM-SUBSTOR-Potato was applied to simulate tuber yield, N leaching, and FNUE under scenarios of irrigation scheduling and N-fertilizer application (rate/timing) strategies, focusing on Npre versus Npl aiming to improve resource use efficiency. The simulations indicated that a target of 60% and 70% of the available soil water can be safely used as an irrigation strategy to achieve a high yield, while reducing irrigation water applied and N leached to the environment. Overall Npl increased crop N uptake by 10%, tuber yield by 7%, reduced N leached by 13%, and consequently increasing FNUE by 9%, compared to Npre across the irrigation treatments. Thus, Npl should be preferred in sandy soils and climate-risky subtropical environments, along with Neme and Nti as key timings to synchronize N supply with potato growth.

The purpose of this publication is to familiarize irrigation managers, contractors, Extension agents, homeowners, and other interested persons with programming guidelines for an irrigation timer in Florida. Written by Michael D. Dukes, Bernard Cardenas, and Dorota Z. Haman, and published by the UF/IFAS Department of Agricultural and Biological Engineering, revised July 2024.

Originating from environmental or humans sources, too much nitrogen (N) and/or phosphorus (P) in water bodies can degrade water quality. In an attempt to reduce the contribution of human sources of N and P to local waters, urban fertilizer ordinances have been adopted in at least 35 counties in Florida and 97 additional Florida municipalities. Despite this work, the efficacy of fertilizer ordinances are debated by end users. The purpose of this publication is to summarize a peer-reviewed, scientific article that investigated impacts of fertilizer on long-term water quality trends in Florida lakes (Smidt et al. 2022) and is intended to be used by UF/IFAS Extension faculty and/or regulatory officials considering adopting or modifying an urban fertilizer ordinance. We encourage green industry professionals and concerned community members to share the effectiveness of fertilizer ordinances.

This publication aims to provide basic information about rain sensors when incorporated into automatic irrigation systems. Written by Michael D. Dukes and Bernard Cardenas, and published by the UF/IFAS Department of Agricultural and Biological Engineering, revised July 2024.

This 9-page fact sheet was developed to help Extension agents, water-conservation managers, and homeowners estimate the economic benefits of residential outdoor water conservation. It provides guidance for reporting benefits, including lowered utility bills for homeowners, reduced water-delivery costs for utilities, and increased water supply. This publication also offers an example of an impact statement.­ Written by Tatiana Borisova, Laura A. Warner, Jennison Searcy, Anil Kumar Chaudhary, and Michael Dukes, and published by the UF Department of Food and Resource Economics, February 2017. FE1009/FE1009: Estimating Benefits of Residential Outdoor Water Conservation: A Step-by-Step Guide (ufl.edu)

Water quality and quantity are important issues. The frequently asked questions (FAQs) in this publication, based on extensive UF/IFAS research, address common concerns related to water, irrigation, fertilizers, best management practices (BMPs), landscapes, and landscape maintenance. Written by Michael D. Dukes, Bernard Cardenas, Laurie E. Trenholm, Ed Gilman, Chris J. Martinez, John L. Cisar, Thomas H. Yeager, Amy Shober, and Geoffrey Denny, and published by the UF/IFAS Department of Agricultural and Biological Engineering, revised September 2024.

The Net Irrigation Requirements for Florida Turfgrass Lawns series explains the process of estimating net irrigation requirements for Florida turfgrasses. The process used here gives a long-term (30-year) historical analysis of turfgrass monthly net irrigation requirements. This article explains how the weather data were gathered and checked for quality. Written by Consuelo C. Romero, Bernard Cardenas, and Michael D. Dukes, and published by the UF/IFAS Department of Agricultural and Biological Engineering, revised August 2024.

Farm-scale decisions are key determinants of water quality and water use on a regional scale. This paper evaluates farm-scale economic–environmental tradeoffs associated with row crop land management decisions as well as land use decisions in a 15-county area of the Suwannee River Basin in North Florida. Discussions with stakeholders through a participatory modeling process identified the farm-scale land management and land use choices relevant for the study region. Land management choices included three fertilizer and irrigation management systems, and land use choices included a combination of corn, carrot, and peanut crop rotations. Farm-scale nitrate leaching and crop yield outcomes were simulated using the Soil & Water Assessment Tool (SWAT), and annualized net returns were simulated using Simetar Excel Add-In based on Extension production budgets and USDA crop and input price history. We show that the impacts from farmers’ crop rotation choices outweigh the impacts from the irrigation and fertilizer management system choices. This difference in impacts can lead to a rebound in nutrient leaching if water policy regulates land management but not the land use. Nitrate leaching abatement cost were found to be comparable with the costs for other, non-agricultural pollution reduction projects in the region.

The Net Irrigation Requirements for Florida Turfgrass Lawns series explains the process of estimating net irrigation requirements for Florida turfgrasses. The process used here gives a long-term (30-year) historical analysis of turfgrass monthly net irrigation requirements. This article outlines the results of the net irrigation estimation. Written by Consuelo C. Romero, Bernard Cardenas, and Michael D. Dukes, and published by the UF/IFAS Department of Agricultural and Biological Engineering, revised August 2024.

AE459, a 12-page fact sheet by Lincoln Zotarelli, Michael D. Dukes, Consuelo C. Romero, Kati W. Migliaccio, and Kelly T. Morgan, provides a step-by-step calculation of the reference evapotranspiration (FAO-56 method) for a given location from the available weather data. Includes references. Published by the UF Department of Agricultural and Biological Engineering, February 2010.

Improving irrigation efficiency can contribute greatly to reducing production costs of vegetables, making the industry more competitive and sustainable. Through proper irrigation, average vegetable yields can be maintained (or increased) while minimizing environmental impacts caused by excess applied water and subsequent agrichemical leaching. Recent technological advances have made soil water sensors available for efficient and automatic operation of irrigation systems. Automatic soil water sensor-based irrigation seeks to maintain a desired soil water range in the root zone that is optimal for plant growth. This document is AE354, one of a series of the Department of Agricultural and Biological Engineering, UF/IFAS Extension. Original publication date June 2005. AE354/AE354: Automatic Irrigation Based on Soil Moisture for Vegetable Crops (ufl.edu)

The Upper Floridan aquifer underlying the Suwannee River Basin in Florida has experienced increased groundwater pumping and nitrate leaching over the last half century resulting in violation of water quantity and quality standards, largely due to row crop production. Increasingly carrot is being added as a winter cash crop to the traditional corn-peanut rotation in the region which may further increase pumping and nitrogen leaching. Establishing carrot nitrogen and irrigation best management practices is therefore critical to help growers meet yield goals while minimizing groundwater quantity and quality impacts. In this study, a carrot cultivation field experiment was conducted to evaluate the effects of a range of irrigation and nitrogen fertilizer practices on irrigation demand, nitrogen uptake and carrot crop growth and yield. Results showed that soil moisture sensor-based irrigation reduced the amount of water used for carrot cultivation by approximately 30% over the calendar-based irrigation without statistically significant reductions in yield, and fertilization rates above 224 kg ha−1 showed no statistically significant increase in yield. A field-scale SWAT carrot model was calibrated using the field experiment data and validated using previously published experimental results. The carrot parameters were then incorporated into a watershed-scale SWAT model of the Santa Fe River Basin, a tributary of the Suwannee River, and used to assess groundwater recharge and nitrate leaching impacts of adding carrot into corn-peanut rotations across all row crop lands in the watershed. Modeling results showed that adding carrot cultivation to the rotation will increase irrigation by 32–43% and decrease net groundwater recharge from row crop land by 9–28%. Moreover, it will increase nitrate leaching from row crop land by 60–100%. These results indicate that adding carrot cultivation to the conventional corn-peanut rotation will make water quantity and quality standards in the region more difficult to achieve.

This publication discusses turfgrass and landscape irrigation recommendations from UF/IFAS. Written by Michael D. Dukes and Bernard Cardenas, and published by the UF/IFAS Department of Agricultural and Biological Engineering, revised July 2024.