Brian J. Boman

Fertigation versus conventional fertilization of flatwoods grapefruit

A four-year field experiment was conducted to compare conventional fertilization by broadcasting granular material with a combination broadcast/fertigation program. The experiment was conducted on mature ’Ruby Red’ grapefruit trees in a south Florida Flatwoods grove. The conventional fertilization (CONV) consisted of broadcast applications 3 times per year (Feb/Mar, May/Jun, Oct/Nov). The combination treatment (COMB) had a broadcast application of 33% of the annual N and K20 in Feb/Mar followed by the remainder applied as fertigation at 2-week intervals beginning in April. The CONV plots received 33% of the annual N and K20 (plus minor elements) during an application in late winter plus additional applications, each with a third of the annual N and K20 in the May/June and Oct/Nov time periods. During the four-year period, the COMB trees out-produced the CONV trees in 3 of the 4 years. The 4-year cumulative fresh fruit yield advantage of the COMB trees averaged 4150 kg ha−1 (108 boxes ha−1) per year advantage over the CONV program. The cumulative total soluble solids (TSS) produced over four years with the COMB trees averaged 10.9 Mg ha−1 versus 10.1 Mg ha−1 for the CONV treatment. The production increases by the COMB treatment over the CONV program represent 8% and 9% advantages for the TSS and fruit yield, respectively. The combination dry + fertigation treatment provided a higher fertilizer use efficiency (greater production for similar application rates) than the conventional dry broadcast applications alone.

Characterization of selected organo-nitrogen herbicides in south florida canals: Exposure and risk assessments

Much uncertainty exists regarding the discharge characteristics of terrestrial-use herbicides into aquatic systems. This study evaluated the temporal distribution and concentrations of five commonly used herbicides (atrazine, bromacil, metolachlor, norflurazon, and simazine) in a typical South Florida watershed. Surface water samples were collected weekly over a 3-yr period from four canals and Ten Mile Creek. These systems received drainage water from a variety of land-uses, including residential, pastures, and citrus production. Herbicides were extracted and analyzed by GC-MS/SIM. Atrazine was most frequently detected (87% of samples) in the canal serving the residentially developed sub-basin, with median and maximum concentrations of 0.43 and 6.67 μg L(-1), respectively. Norflurazon was most frequently detected (90-95% of samples) in the systems serving agricultural production areas, with median and maximum concentrations ranging from 0.37-0.63 μg L(-1) and 1.98-6.97 μg L(-1), respectively. Bromacil was detected in 14-36% of samples with median and maximum concentrations ranging from 0.50-0.67 μg L(-1) and 2.31-4.96 μg L(-1), respectively. Metolachlor was detected in 1.8-10% of the samples, with median and maximum concentrations ranging from 0.16-0.2 μgL(-1) and 0.17-1.55 μg L(-1), respectively. Simazine was detected in 10-35% of the samples, with median and maximum concentrations ranging from 0.18-0.28 μg L(-1) and 0.37-1.35 μg L(-1), respectively. Bromacil+norflurazon was the most commonly detected (240 samples of 1060 total) binary combination of herbicides; whereas bromacil+norflurazon+simazine was the most frequently detected tertiary combination (58 samples). While detectable concentrations were present for significant periods of time, risks of acute toxicity were relatively low; affecting <1% of the potentially affected fraction (PAF) of plant species based on 90th centile exposure concentrations and 10th centile effects concentrations from species sensitivity distributions.

Distribution Patterns of Microirrigation Spinner and Spray Emitters

Several microirrigation spinner and spray emitters were evaluated to determine their distribution patterns and the relationship between their operating pressure and the resulting discharge flow rate. Eleven types of spray emitters were evaluated along with five spinner types. Emitter flow rate, pattern distribution and uniformity were measured for each type of emitter at pressures of 103, 138, and 172 kPa (15, 20, and 25 psi). The spinner types of emitters had higher uniformity of water application than spray types under the no-wind conditions. Most spray emitters had 50 to 75% of the wetted area receiving insignificant water applications while 10 to 15% of the wetted area received more than three times the average application. Spinner emitters, however, had 30 to 80% of the wetted area receiving applications in the range of 50 to 150% of the average. None of the spinner models had areas of application greater than four times the mean application depth of the emitter.

An overview on the organic pollution around the Qinghai-Tibet plateau: The thought-provoking situation

The Qinghai-Tibet Plateau plays an important role in the ecological safety and human health of the surroundings due to its unique geographical position and function. Therefore, it is necessary to study the pollution status and potential risk in this area. This study summarizes the distribution of different organic pollutants in biota and environmental media of the Qinghai-Tibet Plateau. Moreover, it also pays attention to the potential health risks of these organic pollutants. Organochlorine pesticides (OCPs), polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and polybrominated diphenyl ethers (PBDEs) were the most frequently detected in different matrices. In general, the carcinogenic risks of organic pollutants were ranked in the very-low to moderate range for both children and adults. The carcinogenic risks of organic pollutants in fish, food, and water for children were 1-2 times higher than those for adults, while risks of organic pollutants in soil/sediment and in air for children were generally 10.6-16.5 and 2.6-2.8 times higher than those for adults, respectively. The maximal hazard quotient for non-carcinogenic risk was 0.95 (potential risk for children posed by organic pollutants in yak milk of Ruoergai), almost reaching an unacceptable level. Therefore, the potential health risks could not be neglected, especially for children who were more likely to be affected by the pollutants.

Removing polybrominated diphenyl ethers in pure water using Fe/Pd bimetallic nanoparticles

Polybrominated diphenyl ethers (PBDEs) have been widely used as fire-retardants. Due to their high production volume, widespread usage, and environmental persistence, PBDEs have become ubiquitous contaminants in various environments.Nanoscale zero-valent iron (ZVI) is an effective reductant for many halogenated organic compounds. To enhance the degradation efficiency, ZVI/Palladium bimetallic nanoparticles (nZVI/Pd) were synthesized in this study to degrade decabromodiphenyl ether (BDE209) in water. Approximately 90% of BDE209 was rapidly removed by nZVI/Pd within 80 min, whereas about 25% of BDE209 was removed by nZVI. Degradation of BDE209 by nZVI/Pd fits pseudo-first-order kinetics. An increase in pH led to sharply decrease the rate of BDE209 degradation. The degradation rate constant in the treatment with initial pH at 9.0 was more than 6.8 × higher than that under pH 5.0. The degradation intermediates of BDE209 by nZVI/Pd were identified and the degradation pathways were hypothesized. Results from this study suggest that nZVI/Pd may be an effective tool for treating polybrominated diphenyl ethers (PBDEs) in water.

Inorganic pollution around the Qinghai-Tibet Plateau: An overview of the current observations

The Qinghai-Tibet Plateau is the highest geographical unit in the world. Thus, it serves an important role in evaluating long-term ecologic conditions and environmental status and changes over time. This study summarizes major and trace element concentrations in biota and in water and soil. It also pays attention to gaseous pollutant and particle concentrations in air around the Qinghai-Tibet Plateau. The degree of soil heavy metal contamination and the water heavy metal hazard index were respectively evaluated. The contamination degrees of two sampling areas around the Qinghai-Tibet Plateau reached extremely high levels with soil mCd (modified degree of contamination) values exceeding 20. Surprisingly, over 54% of sampling areas showed moderate or more serious soil contamination degree (mCd>1.5). Moreover, the hazard indexes of two important rivers were 1.56 and 7.59, reaching unacceptable level. The potential risk might be beyond our expectation. Therefore, it should be an urgent and top priority to identify and confirm possible pollution sources around the Qinghai-Tibet Plateau. Then, it is imperative to implement feasible and effective environmental quality control strategies.

Current Status of Microsprinkler Irrigation in the United States

Microsprinkler irrigation is often the preferred method of irrigation for tree and vine crops since it provides a greater degree of freeze protection than drip irrigation and provides water and energy savings over sprinkler and flood irrigation methods. With chemigation, microirrigation also provides an economical method of applying fertilizer and other agricultural chemicals on a timely basis. However, microsprinkler systems generally require more maintenance than drip or overhead systems, and they require a higher level of management expertise than sprinkler or flood irrigation methods. This article discusses the current status of design, operation, and maintenance of microsprinkler systems and the benefits and limitations of these systems for several agricultural crops. Types and characteristics of available microsprinklers are discussed in relation to appropriate application considering crops, soils, and management philosophy. Topics include uniformity, clogging, insect problems, wetting patterns, emitter maintenance, chemigation, system evaluation, management for both young and mature trees, crop response, and freeze protection.

Nontarget deposition and losses of oxamyl in surface runoff from flatwoods citrus production areas

Pesticide export from citrus production areas is a concern in the Indian River Lagoon drainage basin (Florida, USA). These studies evaluated nontarget deposition and losses of the insecticide oxamyl from typical flatwoods citrus production areas in South Florida. Deposition was estimated with the use of Teflon spray targets placed across nontarget water furrows during spray applications. After oxamyl applications, surface water runoff events were generated with an overhead irrigation system to simulate relatively low intensity rainfall. Results indicated that 0.3 to 20.0% of the applied active ingredient landed on nontarget water furrow surfaces and that the majority of oxamyl loss occurs in runoff events shortly following application. Mean concentrations were greater during the first runoff events, ranging from 34.7 to 47.0 microg/L. Total losses during the first several hours of each set of runoff events ranged from 0.1 to 3.8% of the total active ingredient applied. Similar losses can be expected when rainfall occurs shortly after application for other pesticides with similar chemical properties and application methods.

The Indian River Citrus BMP Development and Implementation Process

The Total Maximum Daily Load (TMDL) program requirements of the federal Clean Water Act are requiring states to develop new initiatives for managing agricultural nonpoint sources. On the east coast of Florida, the citrus industry is taking the lead in developing and implementing watershed-based BMP programs to reduce impacts to off-site impacts of agricultural operations. The process began In 1998, when growers took the initiative to begin the development of Best Management Practices (BMPs) for Indian River Area citrus groves. By adopting and enacting the BMPs, growers hoped to minimize the effects of regulation, legislation, and litigation concerning the EPA’s establishment of total maximum daily loads for the Indian River Lagoon and St. Lucie estuary. The BMP process has produced an extensive BMP manual, a series of workshops and onfarm demonstrations, a public education campaign, and an extensive agricultural worker training program. This paper explains the project and presents some lessons learned about developing consensus among the diverse interests involved in developing BMPs.

Citrus Best Management Practices

Agricultural best management practices (BMPs) are practical, cost-effective actions that agricultural producers can take to reduce the amount of pesticides, fertilizers, sediment, and other pollutants entering water resources. BMPs are designed to benefit water quality while maintaining or even enhancing agricultural production. Implementing BMPs benefits both the farmer and the environment and demonstrates agriculture’s commitment to water resource protection and is a key component of agriculture’s environmental stewardship role.