Off-target deposition of pesticidal spray material is both an economic loss to the grower and a potential environmental problem in southern Florida. This study evaluated the reduction in non-target deposition of copper resulting from different approaches to spraying row-ends in typical Indian River citrus (Citrus) production systems. Using copper as a model pesticide, applications were made in a commercial citrus grove in June and July 2001. Non-target deposition on the water surface within an adjacent drainage canal, as well as on surrounding ground surfaces, was measured using Teflon spray targets. Specific row-end spraying scenarios included: 1) leaving both banks of nozzles on while turning; 2) turning the outside-facing nozzles off (leaving tree-facing nozzles on); 3) turning both banks of nozzles off at the tree trunk; and 4) turning all nozzles off at the end of the foliage of the last tree within the row. Deposition directly onto surface water contained within drainage canals was reduced significantly when nozzles were turned off at the last tree within a row, or when the outside-facing nozzles-only were turned off through the turn. Likewise, deposition was reduced on ground surfaces adjacent to the sprayer under the same scenarios. No differences were observed on ground surfaces on the opposite side of the canal. Significant reductions in direct application of agrichemicals to surface waters within Indian River citrus production groves can be achieved by turning nozzles off when turning from one tree row into the next.
Nitrate-nitrogen (N) losses in surface drainage and runoff water from ornamental plant production areas can be considerable. In N-limited watersheds, discharge of N from production areas can have negative impacts on nontarget aquatic systems. This study monitored nitrate-N concentrations in production area drainage water originating from a foliage plant production area. Concentrations in drainage water were monitored during the transition from 100% reliance on fertigation using urea and nitrate-based soluble formulations (SF) to a nitrate-based controlled-release formulation (CRF). During the SF use period, nitrate-N concentrations ranged from 0.5 to 322.0 mg·L−1 with a median concentration of 31.2 mg·L−1. Conversely, nitrate-N concentrations during the controlled-release fertilization program ranged from 0 to 147.9 mg·L−1 with a median concentration of 0.9 mg·L−1. This project demonstrates that nitrate-N concentrations in drainage water during the CRF program were reduced by 94% to 97% at the 10th through 95th percentiles relative to the SF fertilization program. Nitrate-N concentrations in drainage water from foliage plant production areas can be reduced by using CRF fertilizer formulations relative to SF formulations/fertigation. Similar results should be expected for other similar containerized crops. Managers located within N-limited watersheds facing N water quality regulations should consider the use of CRF fertilizer formulations as a potential tool (in addition to appropriate application rates and irrigation management) for reducing production impacts on water quality.
Invasive species have disrupted thousands of acres of natural areas in Florida and appear to have a physiological competitive advantage over native species. The influence of light and temperature on germination was determined for the invasive Mexican petunia (Ruellia tweediana Griseb.) and native wild petunia (Ruellia caroliniensis Steud.). Seeds were collected and germinated in incubators with light or darkness at 15, 24, 33, and 30/20 °C. Light increased germination for each species, except at 15 °C (R. caroliniensis). For R. caroliniensis, highest germination (86% to 94%) occurred at 33 °C and 30/20 °C. Highest germination of R. tweediana (98% to 100%) occurred at 30/20 °C. Studies also were initiated to determine if R. tweediana has a competitive advantage over the native species when grown under wet and dry substrate conditions. Growth and development measurements after 8 weeks under controlled conditions revealed that R. tweediana grown in wet conditions had the greatest dry weight increase as compared to other treatments. Ruellia caroliniensis had higher specific leaf area when grown in wet or dry conditions, as compared to R. tweediana. Throughout the experiment, net CO2 assimilation of R. caroliniensis grown under dry or wet conditions was consistently lower than that of R. tweediana. Shoot nitrogen and phosphorus use efficiencies were generally greatest for R. tweediana plants grown in wet conditions. For shoot nutrient content, significant species × moisture interactions occurred for measured phosphorus (P) and calcium (Ca). When grown in wet conditions, R. tweediana had less shoot P and Ca as compared to dry conditions. For root nutrient content, species × moisture interactions were insignificant for each measured nutrient, with the exception of potassium (K). Potassium use efficiency of R. tweediana roots grown in wet conditions was higher than that of R. tweediana grown in dry conditions and R. caroliniensis grown in wet conditions.
Sources of irrigation water in South Florida typically contain high levels of dissolved carbonates and bicarbonates. Repeated application of high alkalinity water can cause substrate-solution pH to rise, thereby altering nutrient availability, and possibly leading to the development of nutrient disorders and a reduction in plant growth. The objectives of the current study were to determine the effects of neutralizing alkalinity of irrigation water on the nutritional status and growth of Thryallis (Galphimia glauca Cav.). Plants were grown in 11.4-L containers in a 5 peat: 4 pine bark: 1sand (v:v:v) mix. Treatments were prepared with water collected from a commercial nursery with inherent calcium carbonate levels in excess of 260 mg·L-1 and pH above 7.3. Treatments consisted of 0% (control), 40%, or 80% alkalinity neutralized with sulfuric acid. At harvest, 51 weeks after initiating treatments, foliar levels of Fe were 28% greater, Mn 55% greater, and Zn 27% greater in the 80% than 0% neutralized alkalinity treatment. Growth indices and leaf greenness averaged over the course of the study were significantly greater in the 40% than in the 0% or 80% alkalinity neutralized treatments. Over the course of the study, leachate pH averaged 7.5, 6.8, and 5.3; and electrical conductivity (EC) averaged 1.4, 1.9, and 2.2 dS·m-1 in the 0%, 40%, and 80% alkalinity neutralized treatments, respectively.
Reset/replant problems and/or failure are recognized as a problem in fruit tree production throughout the world. Problems in establishing or reestablishing fruit trees have been documented in apple, peach, grape, and citrus. Research to date has not identified a single casual agent responsible for reset failure, but rather there is evidence that such problems are related to a complex interaction of biotic and abiotic factors. In this study, we compared abiotic factors related to soil texture and soil nutrients in healthy and reset failure areas of a commercial citrus grove in Florida. A significant difference in soil texture was found in healthy sand, silt, and clay (94%, 4%, and 2%, respectively) vs. failed (99% sand and <1% silt and clay) reset areas in the citrus grove block. Mehlich III extractions were performed on soil samples and levels of Ca, Cu, Fe, K, Mg, Mn, P, and Zn in the extract solution were significantly higher in healthy compared to failed reset areas of the citrus grove block. These data are consistent with what has been observed in other fruit crops where soil texture, which directly relates to soil hydrologic conditions, and soil nutrient levels have been identified as contributing factors related reset/replant failure in fruit tree crops.
Parts I and II of this series revealed substantial opportunities for improving spraying of Indian River citrus (Citrus spp.). In this segment of our work we develop guidelines for growers to select the spray parameters providing an optimal balance between efficiency and efficacy while minimizing environmental contamination.
It is proposed that these guidelines could be codified in a simple expert system to make them easier to use. We propose that understanding limiting conditions may be the key to choosing spray options. Wind is a major factor influencing spray deposition and offtarget drift. Based on weather records, wind speeds below 5 mph (8.0 km·h-1) are only routinely observed from 2000 HR until 0800 HR, making night spraying a good choice for low-volume applications. The importance of adjusting sprayer set-up for individual groves is demonstrated, with economic estimates of the cost of failing to make these adjustments. Routine use of careful sprayer adjustments is also likely to reduce off-target drift. Improvements in equipment and spray chemicals are also discussed. Use of non-orchard buffer areas and/or windbreaks appear to offer considerable opportunity for reducing off-site spray movement.
Foliar application of spray materials is an integral component of commercial citrus production. An intensive assessment of spray application practices has been stimulated by low fruit value and increased concern about potential surface water contamination in the Indian River citrus region of Florida. Many publications report research results regarding distribution of spray materials within orchards and off-target deposition, but interpretation is challenging because so many factors influence spray results, and integrating this information into practical recommendations is difficult. Canopy geometry and density are prominent factors contributing to variable deposition and spray drift. Environmental factors such as temperature, relative humidity, wind speed, and wind direction also greatly influence spray deposition and drift, and substantial changes can occur within seconds. In addition the physical and/or mechanical set up of the sprayer interact significantly with the other factors. A better understanding of these interactions should help growers optimize spray effectiveness and efficiency while reducing potential off-target effects.
Enrichment of surface water with nitrate-nitrogen (NO3-N) is a significant problem throughout the world. In support of developing a method for removing NO3-N from water using denitrification, this project characterized runoff events at two nurseries in southern Florida to provide information needed for designing capacity. Specifically, estimates of runoff rates and volumes, NO3-N concentrations and loadings were profiled during intensively sampled fertigation events at a foliage plant nursery and a bedding plant nursery. Discharge volumes and rates varied with event, ranging from 2,487 to 20,935 L and 59.2 to 126 L·min−1, respectively, per event. NO3-N concentrations ranged from 0.7 to 386.4 mg·L−1, and event loadings ranged from 51 to 3024 g, indicating that significant losses may be realized. This project provided valuable hydraulic and chemical loading information needed for the development and design of bioremediation tools for the horticultural industry.
Liming agents (LAs) in irrigation water, typically associated with carbonates and bicarbonates of calcium (Ca) and magnesium (Mg), contribute to water alkalinity. Repeated application of LA to container crops can cause media-solution pH to rise overtime, that uncorrected, can lead to a nutrient availability imbalance that may be suboptimal for plant-growth due to nutrient disorder(s). To correct high levels of LA in irrigation water, growers can inject acid into their irrigation system to neutralize alkalinity. Therefore, a 52-week study was conducted using irrigation water, substrate, and plants from a commercial nursery in Florida that has a history of poor water quality and plant production problems related to high alkalinity irrigation water. The objectives of the study were to assess substrate pH, electrical conductivity (EC), and nutrients, and plant nutrition and growth for thyrallis (Galphimia gracilis Bartl.) to irrigation water acidification. Treatments consisted of irrigation water acidified with sulfuric acid (H2SO4) to neutralize 0% (control), 40%, or 80% of calcium carbonates (CaCO3) yielding a CaCO3 (meq·L−1)/pH levels of 5 [High Alkalinity (H-A)]/7.37, 3 [Medium Alkalinity (M-A)]//6.37, and 1 [Low Alkalinity (L-A)]//4.79, respectively. Substrate analysis by the 1:2 dilution method at the end of the study was significant (P < 0.05) for pH 6.2, 5.2, and 4.7 for the H-A, M-A, and L-A treatments, respectively, and for nutrients Ca, Mn, and Zn. Foliar nutrient levels were statistically significant (P < 0.05) for alkalinity treatment for Fe, K, Mn, P, and Zn. Alkalinity treatment was significant (P < 0.05) for growth, leaf greenness (by SPAD), and quality (by survey) with the M-A treatment producing more biomass, having greener leaves, and the highest aesthetic quality value than the H-A or L-A treatments. A qualitative survey of root systems at harvest showed that the M-A and L-A treatment root systems were greater than the H-A treatment based on visual side-wall root development. These data demonstrate that irrigation water acidification does alter substrate pH and nutrients and plant tissue nutrient levels and growth over a long-term production cycle typical for nursery crops.
Anaerobic soil disinfestation (ASD) is considered a promising sustainable alternative to chemical soil fumigation (CSF), and has been shown to be effective against soilborne diseases, plant-parasitic nematodes, and weeds in several crop production systems. Nevertheless, limited information is available on the effects of ASD on crop yield and quality. Therefore, a field study was conducted on fresh-market tomato (Solanum lycopersicum L.) in two different locations in Florida (Immokalee and Citra), to evaluate and compare the ASD and CSF performances on weed and nematodes control, and on fruit yield and quality. In Immokalee, Pic-Clor 60 (1,3-dichloropropene + chloropicrin) was used as the CSF, whereas in Citra, the CSF was Paldin™ [dimethyl disulfide (DMDS) + chloropicrin]. Anaerobic soil disinfestation treatments were applied using a mix of composted poultry litter (CPL) at the rate of 22 Mg·ha−1, and two rates of molasses [13.9 (ASD1) and 27.7 m3·ha−1 (ASD2)] as a carbon (C) source. In both locations, soil subjected to ASD reached highly anaerobic conditions, and cumulative soil anaerobiosis was 167% and 116% higher in ASD2 plots than in ASD1 plots, in Immokalee and Citra, respectively. In Immokalee, the CSF provided the most significant weed control, but ASD treatments also suppressed weeds enough to prevent an impact on yield. In Citra, all treatments, including the CSF, provided poor weed control relative to the Immokalee site. In both locations, the application of ASD provided a level of root-knot nematode (Meloidogyne sp.) control equivalent to, or more effective than the CSF. In Immokalee, ASD2 and ASD1 plots provided 26.7% and 19.7% higher total marketable yield as compared with CSF plots, respectively. However, in Citra, total marketable yield was unaffected by soil treatments. Tomato fruit quality parameters were not influenced by soil treatments, except for fruit firmness in Immokalee, which was significantly higher in fruits from ASD treatments than in those from CSF soil. Fruit mineral content was similar or higher in ASD plots as compared with CSF. In fresh-market tomato, ASD applied using a mixture of CPL and molasses may be a sustainable alternative to CSF for maintaining or even improving marketable yield and fruit quality.