SUSTAINABLE ORGANIC CITRUS PRODUCTION USING IMPROVED AGROECOLOGICAL MANAGEMENT STRATEGIES

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: ACTIVE
• Funding Source: OTHER GRANTS
• Reporting Frequency: Annual
• Accession No.: 1032937
• Grant No.: 2024-51300-43188
• Cumulative Award Amt.: $1,999,997.00
• Proposal No.: 2024-03335
• Project Start Date: Sep 1, 2024
• Project End Date: Aug 31, 2028
• Grant Year: 2024
• Program Code: [113.A]- Organic Agriculture Research & Extension Initiative

Recipient Organization
UNIVERSITY OF FLORIDA
G022 MCCARTY HALL
GAINESVILLE,FL 32611

Performing Department
(N/A)

Non Technical Summary
The long-term goal of the project is to improve organic citrus production and sustainability through improved soil health, horticultural and pest management practices, and fruit yield. The critical needs for optimizing the efficiency of organic citrus production, include manipulation of horticultural practices, minimizing inputs while efficiently increasing fruit yields and productivity, pest and disease management, and better physiological responses of citrus trees. The project addresses two of the eight legislatively defined goals: 1) conducting advanced on-farm research and development that emphasizes observation of, experimentation with, and innovation for working organic farms, including research relating to production; and 2) examining optimal conservation, soil health, and environmental outcomes relating to organically produced agricultural products. As described in our methods, improving soil health through the use of cover crops and soil amendments in on-farm experiments in Florida and Texas will improve productivity and fruit yield for organic citrus producers through better pest and disease management while sustaining environmental quality. The project will use field days, refereed/extension publications, and social media to disseminate emerging and imminent findings on the project. Further, in-service training for extension agents will be conducted annually to build capacity and accelerate adoption of sustainable organic citriculture. Graduate students and postdoctoral fellows will also be mentored on the project and collaborate with organic citrus growers to develop the capacity of the next generation of organic agriculture researchers in the US.

Animal Health Component

100%

Research Effort Categories

Basic

0%

Applied

100%

Developmental

0%

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
102	0110	1060	100%

Knowledge Area
102 - Soil, Plant, Water, Nutrient Relationships;

Subject Of Investigation
0110 - Soil;

Field Of Science
1060 - Biology (whole systems);

Keywords

sustainable

organic

citrus

production

using

improved

agroecological

management

strategies

Goals / Objectives
We will seek to achieve the following objectives: 1) Determine the effect of organic soil amendments and cover crops on fruit yield and quality of organic citrus production systems, 2) Establish integrated pest management strategies in organic citrus production systems receiving soil amendments and cover crops, 3) Evaluate the microbial and non-microbial biostimulant to improve soil microbial biodiversity, plant growth, fruit yield and postharvest life in organic citrus production, 4) Increase the adoption of tools for promoting efficiency and production in organic citrus horticulture.

Project Methods
Objective 1: Sub-objective 1a. We plan to conduct on-farm experiments assessing different soil amendments including compost and/or biochar with and without cover crops (legume and non-legume). These treatments will be focused on altering the agroecology of the organic farm. A total of 5 organic citrus farms will be used on the project. In Florida, four farms have Sugarbelle mandarin, Satsuma mandarin, Valencia and Navel sweet oranges while in Texas one organic farm has the Grapefruit. Typical layouts will take the form of replicated plots assuming selected treatment combinations as follows and replicated 4 to 5 times in a randomized complete block design: 1) Compost with legume cover crop; 2) Compost with non-legume cover crop; 3) Biochar with legume cover crop; 4) Biochar with non-legume cover crop; 5) No soil amendment with legume cover crop 6) No soil amendment with non-legume cover crop; and 7) No soil amendment.Measurements will include soil health dynamics including organic matter, organic carbon, soil texture, soil bulk density, soil cation exchange capacity, soil microbial activity, and soil nutrient content at the start of the project and annually thereafter using indices derived from Stott (2019). Leaf nutrient measurements will be done at the start and yearly thereafter.Sub-objective 1b. The aforementioned treatments will also be compared with two fertilizer sources, organic controlled-release fertilizer and organic conventional fertilizer (as subplots) to assess the efficiency of uptake in the presence or absence of soil amendment or CCs. Greenhouse gas emissions will be evaluated using the LICOR greenhouse gas analyzer for methane, nitrous oxide and carbon dioxide emissions (LI-7820). Fruit yield and canopy growth per amount of nitrogen applied will be estimated to determine the overall efficiency by the production system.Objective 2. Sub-objective 2a. Evaluate the populations of predators and parasitoids in citrus blocks with and without cover crops and compost. Methods: Assessments for predators and parasitoids will be made in trials established to evaluate effects of cover crops and compost treatments. We will sample for diversity and abundance of natural enemies in citrus trees in these trials and in control without cover crops and compost. Sampling in the treatment blocks and control will also help us determine the potential dispersal of natural enemies from the cover crops/compost blocks and any impact on their diversity and abundance to benefit the neighboring untreated blocks. We will employ visual observations, tap sampling, and suction sampling methods to evaluate the populations of predators and parasitoids in citrus trees (Qureshi et al. 2009, 2014, Qureshi and Stansly 2010, Monzo et al. 2015). We will also use potted-infested sentinel plants of citrus or orange jasmine (Murraya paniculata) to determine the diversity and abundance of predators colonizing trees in plots with and without cover crops. Potted plants will be placed in the plots with and without cover crops for a period of 5-7 days, and each plant will be observed visually for predators. These data will be recorded for each individual plant.Sub-objective 2b. Evaluate the release and establishment of commercially available predators and parasitoids through cover crops. Methods: We have already shown in the laboratory that three commercially available predators, two ladybeetles Adalia bipunctata and Hippodamia convergens and a lacewing Sympherobius barberi, are effective predators of ACP (Qureshi and Stansly 2011, Khan et al., 2016, 2020). Hippodamia convergens is a well-studied predator (Sivakoff et al., 2012). Tamarixia radiata is the primary parasitoid known to parasitize ACP nymphs and contribute to its mortality in citrus crops (Qureshi et al. 2009, Qureshi and Stansly 2019b). We will obtain A. bipunctata and S. barberi from commercial sources and T. radiata from the FDACS-DPI production facility. We will evaluate these releases in citrus blocks with and without cover crops and with and without compost. We will recover these natural enemies using sticky traps and suction samples. Cover crops and compost treatments improved tree growth and young shoots attractive to pests and beneficial organisms.Sub-objective 2c. Evaluate the biotic mortality of ACP in citrus blocks with and without a cover crop and compost. Methods: We will employ exclusion techniques to determine the biotic mortality in the populations of ACP in plots with and without cover crops and with and without compost (Qureshi and Stansly 2009). We will use natural pest infestation in the trees or infested sentinel plants described under sub-objective 2b. Cohorts of counted numbers of ACP nymphs developing on the young shoots will be protected from the natural enemies using the sleeve cages or left exposed to the natural enemies for a period of 7-10 days. At that point, they will be collected and examined under the stereomicroscope in the laboratory to determine: 1) mortality by predators and 2) parasitism in ACP nymphs (Qureshi et al. 2009). The reduction in the developing cohorts of ACP after exposure to the natural enemies will be adjusted using with reduction in the cohorts protected with sleeve cages using Abbott's formula (Abbott 1925, Khan et al. 2016). Assessment of parasitism in ACP nymphs will also be made by collecting these life stages and rearing to adults or examined under stereomicroscope to identify parasitized individuals and parasitoid species (McFarland and Hoy 2001, Qureshi et al. 2009, Chen and Stansly 2014). Percent parasitism (apparent parasitism) will be calculated by the number of parasitized nymphs and the number of hosts available in the sample (Stansly et al. 1997).Objective 3. To examine the effects of novel biostimulants on organic citriculture production.Organic citrus production can benefit from the use of biostimulants because these substances improve plant resilience to the different biotic and abiotic stresses, resulting in yield gap reduction between conventional and organic production. We will use different biostimulants such as humic acid, fulvic acid, seaweed extract, chitosan and plant-growth-promoting microbes. Selected biostimulants will be root applied (individually or in combination) at different growth/phenological stages i.e., flower initiation, fruit formation, fruit color change, and fruit full maturity. It will be a replicated study with 5 replications and 10 trees/replication. We will use commercially available products of our target biostimulants and will follow the label specific rate of application. Soil and tissue sampling will be done at four different growth stagesto determine soil health, microbial biodiversity, nutrient uptake, and physiological/biochemical attributes. Fruits will be harvested to determine fruit quality and postharvest attributes. Treatment plan will be as follows:1) Control (grower standard organic practices), 2) Humic acid (HA), 3) Fulvic acid (FA), 4) Seaweed extract (SWE), 5) Plant-growth-promoting-microbes (PGPM), T6: HA + FA, T7: FA + SWE, T8: HA + SWE, 9) Humic acid + fulvic acid + seaweed extract, 10) Humic acid + fulvic acid + seaweed extract + PGPMObjective 4. We will conduct grower workshops and field days once per year to show performance of treatments and obtain farmer feedback through surveys comparing the treatments proposed in this project. In addition, we will share results in Citrus Industry Magazines and at grower events such as Citrus Expo, Citrus Show and publish results in extension bulletins. We will document numbers of growers and acreage for organic citrus production from year one (ex-ante) and in years 2, 3 and 4 to determine level of adoption.

Progress 09/01/24 to 08/31/25

Outputs
Target Audience:Our target audience is the commercial organic citrus and tree cropgrowers in need of new ways of managing their organic cropping systems with regard to fertilization, integrated pest management, and horticultural management. We are also targeting suppliers of soil amendments to help us improve soil health in soils depleted of soil fertility. Changes/Problems:The major change was the delay in recruiting two graduate students, one in Entomology at UF, and the other in Horticulture at Texas A&M Kingsville. Those two students should start this Fall or early Spring 2026. Some of the treatments were modified to suit farmer interests, but did not deviate much from the planned scope of work. What opportunities for training and professional development has the project provided?Dr. Kadyampakeni presented a the Citrus and Specialty Crops Expo on "The 5 Rs of Citrus Sustainability" highlighting the prudence of water management, nutrient rate, nutrient timing, nutrient source, and nutrient placement in citrus production systems including organic production. Commercial growers received continuing education units (CEUs) from this Expo. How have the results been disseminated to communities of interest?We have shared some of the results through citrus industry magazine articles and through workshops and slides for the benefits of our growers. Information on soil amendments, cover crops, and biostimulants have been the major items included in these talks. What do you plan to do during the next reporting period to accomplish the goals?We are planning to continue conducting workshops and disseminating information in magazines so our growers have information on emerging trends and results. We also plan to hire two additional graduate students to train the next generation of researchers in Entomology and Horticulture for organic citrus production. In the next reporting period, we also plan to collect more data from field studies to show the impacts of our treatments in improving and sustaining organic citrus production and improving soil health.

Impacts
What was accomplished under these goals? Five field experiments on using cover crops, organic amendments and biostimulants and IPM under way. One experiment is evaluating the impact of legume cover crops, cow pea and sunn hemp, and compost along with using orange peel powder on how this improves the performance of Navel oranges, soil health and long-term agricultural sustainability. We will also evaluate how the timing of termination of the cover crops affects overall soil health and crop performance. The treatments cover about 10 acres of organic citrus farm land. We are also tracking how the modified agroecology helps mitigate pest pressure for the Asian citrus psyllid and mites, and other opportunistic pests. Some measurements include Leaf Area Index (LAI), Tree Growth, Leaf Area Index (LAI), Photosynthetic Activity, Photosynthetic Activity, Leaf Area Index (LAI), Soil Organic Matter, Soil Texture, Soil Organic Matter, Soil Texture, Ground Cover Observations and soil microbial activity. Specific objectives of the first experiment include: Evaluate how different cover crop termination timings influence soil health parameters, including organic matter content, microbial activity, and nutrient availability in HLB-affected citrus groves. Assess the impact of cover crop termination timing on citrus tree growth, canopy development and productivity. Asses the effect of cover crop termination timing on weed suppression using the cover crop weed index. The second experiment evaluates the impacts of composting and different cover crop combinations (cow pea and sunn hemp) and the control (no cover cropping nor composting), affect overall sustainability of organic citrus production. Here we are also evaluating the impact of integrated pest management in managing several pests of citrus. We are sampling soil, leaves and tree size characteristics over time to document treatment impacts over time. Specific objectives here include: Evaluate the effects of cover cropping and soil amendments on soil health parameters. Assess the impact of cover cropping and soil amendments on citrus tree growth, canopy development and productivity. Quantify changes in remote sensing signals and vegetation indices in relation to soil and citrus canopy improvements. The third experiment evaluates the impact of organic biochar with and without beneficial microbes (e.g. Agrobacteria spp) and how that improves citrus growth, nutrient availability and fruit yield over time. The specific objectives of this experiment include: To evaluate the long-term impact of bacteria-inoculated biochar on citrus growth, yield, and nutrient uptake under field conditions. To monitor changes in soil physical, chemical, and biological properties over time in biochar-amended sandy soils. The fourth experiment was initiated to evaluate the impact of selected organic nutrient sources on citrus growth and health under organic production systems. Five fertility treatments (Fish Hydrolysate (control), soy hydrolysate, Chilean Nitrate, and combined soy hydrolysate, Chilean Nitrate are being tested for their effectiveness in supporting early organic citrus establishment, improving nutrient uptake, and enhancing overall plant vigor. The trial is established using uniform citrus plantings under standardized organic-compliant practices. Treatments are being applied according to manufacturer recommendations, and plant performance is monitored through physiological, nutritional, and growth parameters. Specific objectives for the fourth experiment: Evaluate the effectiveness of organic nutrient sources on early citrus growth, vigor, and nutrient uptake. Compare individual vs. combined applications of soy hydrolysate and Chilean nitrate to determine potential synergistic effects. Assess the impact of organic inputs on soil health and microbial activity, supporting long-term sustainability in citrus orchards. Provide science-based recommendations for organic fertility management to growers interested in transitioning to or improving organic citrus production. Establish baseline data for future long-term studies on yield, fruit quality, and economic viability in organic citrus systems. This fifth study aims to investigate the impact of integrating perennial peanut (Arachis glabrata) with selected annual cover crop mixtures on soil microbial biodiversity, nutrient bioavailability, and overall soil health in organic citrus orchards. As organic citrus growers face challenges related to nutrient cycling, soil fertility, and sustainable weed management, cover cropping offers a promising ecological approach to improving long-term soil function and productivity. Perennial peanut, a low-growing legume, is known for its nitrogen-fixing capabilities, weed suppression, and compatibility with tree crops. By combining it with diverse annual cover crops, this study seeks to enhance organic matter inputs, microbial activity, and nutrient cycling dynamics. Treatments are established under certified organic practices and monitored through soil sampling, microbial community analysis (e.g., metagenomics, PLFA), and nutrient profiling. Specific objectives for the fifth experiment include: Evaluate the effect of perennial peanut alone and in combination with annual cover crops on soil microbial biodiversity and community structure in organic citrus orchards. Assess improvements in nutrient bioavailability, particularly nitrogen and key micronutrients, resulting from legume-driven and mixed-species cover crop systems. Determine the impact of cover cropping strategies on soil health indicators, including organic matter content, aggregation, pH, and enzymatic activity. Compare weed suppression potential and ground cover efficiency between perennial peanut monocultures and mixtures with annual species. Provide practical, science-based recommendations for integrating perennial and annual cover crops in organic citrus production to enhance soil function, reduce external input needs, and promote agroecosystem sustainability. Two graduate students recruited to work on the project. Jose Prieto Fajardo joined the University of Florida and is pursuing a PhD in Soil, Water and Ecosystem Sciences in Fall 2024 under the supervision of Dr. Davie Kadyampakeni. His research topic is "Impacts of Cover Crops and Soil Amendments on Soil Health and Tree Performance of Organic Citrus in Florida." The research will lead to the development of guidelines for soil amendments, cover crop usage and termination along with weed management in organic citrus production systems. Jose has also developed his Individual Development Plan highlighting the goals of his graduate program and aligning with his advisor's mentoring plan. Another PhD student, Oluwafemi Adesina, joined the University of Florida's Horticultural Sciences Department under the mentorship of Dr. Muhammad Shahid at North Florida Research and Education Center. He is now working on his research topic addressing the challenges and opportunities for organic satsuma mandarin production in north Florida. Two more graduate students will be recruited this fall. Dr. Qureshi, an Entomologist, and Dr. Cabrera, a Horticulturalist, will each recruit a graduate student this fall to implement aspects of the project in Florida and Texas. One postdoctoral associate working on the project. Dr. Shankar Shrestha will work part-time on the project to support some measurements on soil health in Florida and Texas. One paper published on using orange peel powder in organic citrus production systems. Dr. Kadyampakeni submitted a paper on preliminary work on using orange peel powder in organic citrus production system. The paper was accepted in Nutrient Cycling and Agroecosystems and will be in print in the next reporting cycle. One paper will be presented at the ASA/CSSA/SSSA Tri-Society meetings in November 2025.

Publications