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
0%
Research Effort Categories
Basic
0%
Applied
100%
Developmental
0%
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.