Comparing theoretical irrigation requirement and actual irrigation for citrus in Florida

Florida ranks first in citrus production, with nearly 68% of all U.S. citrus growing in the season 2005-2006. Most of the citrus groves are located from central to south Florida, and agricultural irrigation permitting is regulated by three of Florida's five water management districts. Most of the permitting for citrus production in Highlands, Polk and Hillsborough counties is conducted by the Southwest Florida Water Management District (SWFWMD), and quantities are based on the District's AGMOD computer program. In 2003, the SWFWMD implemented new permit criteria so that permitted amounts were more representative of actual water use. This paper compares grower reported citrus irrigation water use in Highlands, Polk and Hillsborough counties from 1994 through 2005 with permitted and theoretical irrigation requirements calculated by a daily water balance. Two different sets of crop coefficients (K_c's) developed for citrus in Florida were compared in the daily soil water balance calculation of theoretical irrigation requirements. The percentage of irrigated area considered in this study ranged from 40 to 60% to simulate a range of grower practices. Meteorological data from two weather stations and additional rainfall information from 50 locations within the three counties was used in the water balance. Missing and error values in the meteorological historical record data were filled with weather generators. The multiannual average water consumption (including cold protection water use) from growers ranged from 243 (Hillsborough) to 406 mm (Highlands) and the multiannual average permitted irrigation requirement (without cold protection) ranged from 295 to 557 mm. The simulated gross irrigation requirements under different scenarios of location-K_c-wetted area were variable but mostly lower than the limits established by the district, except for some scenarios in Polk County, whose maximum simulated irrigation value reached 578 mm year⁻¹. In general, permitted limits recommended by the SWFWMD seem to be reasonable for the actual water use by growers in these counties.     

Evaluation of the sorption process for imidacloprid and diuron in eight agricultural soils from southern Europe using various kinetic models

Kinetic studies are of great concern for understanding the processes and parameters involved in the sorption of pollutants by soils. Sorption kinetics of imidacloprid and diuron in eight soils of different characteristics, with very low organic carbon content were investigated. Pseudosecond-order kinetic reactions closely correlate with the experimental kinetic (R(2) > 0.98) in all soils. The sorbed amount of diuron was higher than that for imidacloprid. The low OC content of these soils correlated neither with the sorbed amount nor with the kinetic parameters for both pesticides. Imidacloprid sorption was correlated with silt and sand content and cation exchange capacity (CEC); meanwhile for diuron, no correlation was found. Thus, sorption kinetics take place throughout different mechanisms related mainly to the chemical character of the pesticides. Sorption kinetic parameters determined using three of the four models selected (pseudosecond-order kinetic reactions, Elovich equation, and Weber-Morris models) have been shown to be worthy to distinguish the process controlling the sorption kinetic of both pesticides.     

Epidemiology of bovine anaplasmosis in dairy herds from Costa Rica

Bovine anaplasmosis is endemic and occurs in almost all areas of livestock production of Costa Rica. The aim of this study was to determine the seroprevalence and risk factors of anaplasmosis in dairy farms of Costa Rica by the recombinant truncated MSP-5 (rMSP-5) enzyme-linked immunosorbent assay (ELISA). Serum samples were obtained from 733 cattle from 20 commercial dairy herds of Costa Rica. The overall seroprevalence was 37.2% and herd seroprevalence ranged from 20.0 to 72.0%. The age-specific seroprevalence was 49.3% in young and 33.4% in adult animals. The main risk factors associated with seroprevalence were season of occurrence of clinical cases (rainy season) (OR=22.8), presence of tabanids (OR=9.5) and stable flies (OR=6.2), stable flies control measures (OR=3.2), non-use of ear tattoos (OR=2.8), interval of veterinary visit (≤ 60 days) (OR=2.7), altitude of the farms (<800 masl) (OR=2.6) and age (<2 years) (OR=1.8). The results indicated that exposure of cattle to Anaplasma marginale is common in dairy herds of Costa Rica and endemic instability situation probably is due to inadequate vector control.     

Susceptibility to and transmission of H5N1 and H7N1 highly pathogenic avian influenza viruses in bank voles (Myodes glareolus)

The study of influenza type A (IA) infections in wild mammals populations is a critical gap in our knowledge of how IA viruses evolve in novel hosts that could be in close contact with avian reservoir species and other wild animals. The aim of this study was to evaluate the susceptibility to infection, the nasal shedding and the transmissibility of the H7N1 and H5N1 highly pathogenic avian influenza (HPAI) viruses in the bank vole (Myodes glareolus), a wild rodent common throughout Europe and Asia. Two out of 24 H5N1-infected voles displayed evident respiratory distress, while H7N1-infected voles remained asymptomatic. Viable virus was isolated from nasal washes collected from animals infected with both HPAI viruses, and extra-pulmonary infection was confirmed in both experimental groups. Histopathological lesions were evident in the respiratory tract of infected animals, although immunohistochemistry positivity was only detected in lungs and trachea of two H7N1-infected voles. Both HPAI viruses were transmitted by direct contact, and seroconversion was confirmed in 50% and 12.5% of the asymptomatic sentinels in the H7N1 and H5N1 groups, respectively. Interestingly, viable virus was isolated from lungs and nasal washes collected from contact sentinels of both groups. The present study demonstrated that two non-rodent adapted HPAI viruses caused asymptomatic infection in bank voles, which shed high amounts of the viruses and were able to infect contact voles. Further investigations are needed to determine whether bank voles could be involved as silent hosts in the transmission of HPAI viruses to other mammals and domestic poultry.     

Are landscapes over-irrigated in Southwest Florida? A spatial�Ctemporal analysis of observed data

Monthly water billing records for eleven cities in Hillsborough County Florida were available from 2001 through 2007. Irrigation was estimated from total water use based on two different methods to estimate basic indoor water use and assumed impervious areas. Estimated irrigation use was compared with a calculated irrigation requirement by a water balance to test if homeowners were over-irrigating. Results showed that on average, the mean estimated irrigation was lower than the calculated irrigation requirements in most of the cities and years given the uncertainties in this analysis. The calculated irrigation ranged from 612 to 744 mm year⁻¹, whereas the average estimated irrigation ranged from 264 to 684 mm year⁻¹. However, there were some homeowners that greatly exceeded the calculated irrigation requirement. The estimated irrigation increased temporarily in areas under urban development, which was evidenced by built landscape expansion. Good correlation was found between the annual estimated irrigation and the annual calculated irrigation requirements, when the per capita method was used, but not between the annual estimated irrigation and the annual rainfall. Future conservation programs can use this methodology to identify users where substantial opportunity for water savings exists.     

Coffee agroecosystem performance under full sun, shade, conventional and organic management regimes in Central America

Changes in coffee economics are leading producers to reduce agrochemical use and increase the use of shade. Research is needed on how to balance the competition from shade trees with the provision of ecological services to the coffee. In 2000, long-term coffee experiments were established in Costa Rica and Nicaragua to compare coffee agroecosystem performance under full sun, legume and non-legume shade types, and intensive and moderate conventional and organic inputs. Coffee yield from intensive organic production was not significantly different from intensive conventional in Nicaragua, but in Costa Rica it was lower during three of the six harvests. Full sun coffee production over 6 years was greater than shaded coffee in Costa Rica (61.8 vs. 44.7 t ha^?1, P = 0.0002). In Nicaragua, full sun coffee production over 5 years (32.1 t ha^?1) was equal to coffee with shade that included Tabebuia rosea (Bertol.) DC., (27?C30 t ha^?1) and both were more productive (P = 0.03) than coffee shaded with Inga laurina (Sw.) Willd. (21.6 t ha^?1). Moderate input organic production was significantly lower than other managements under all shade types, except in the presence of Erythrina poepiggina (Walp.) O.F. Cook. Inga and Erythrina had greater basal area and nutrient recycling from prunings than other shade species. Intensive organic production increased soil pH and P, and had higher K compared to moderate conventional. Although legume shade trees potentially provide ecological services to associated coffee, this depends on management of the competition from those same trees.     

Phosphorus fractions and dynamics as affected by land-use changes in the Central Mexican highlands

Land-use change from forest to agriculture in the volcanic ash-derived soils of Mexico has increased over recent decades. It is likely that land uses and management practices, particularly fertilizer use have affected phosphorus (P) distribution and availability. The objective of this study was to evaluate the effects of land-use types (native forest and maize mono-cropping), and the related P addition, on the forms and distribution of soil P and their isotopic exchangeability. An Andisol, sampled from a cropping site, along with the contiguous area under native forest was treated with ³²P-labelled potassium phosphate (KH₂³²PO₄). The soil samples were extracted after incubation times of 7, 21, 35 and 49 days. Phosphorus content and ³²P recovery in fractions sequentially extracted were assessed for each incubation time. Total soil P was dominated by inorganic fractions (79 to 86%) in both land-use types. Resin-Pi, bicarbonate extractable inorganic P (Bic-Pi) and sodium hydroxide extractable inorganic P (NaOH_0.1-Pi) were all raised with P addition. However, the proportion of organic P fraction was reduced under cropped soil. The recovery of ³²P in soils with P addition indicates that resin-Pi, Bic-Pi and NaOH_0.1-Pi comprised nearly all the exchangeable P. In native soils with no P addition, more than 19% of the ³²P was recovered in Bic-Po and NaOH_0.1-Po forms. This finding indicates that organic P cycling is crucial when soil Pi reserves are presented in an inadequate amount. Ecologically based management has to be designed for replenishment and succeeding maintenance of soil organic P compounds to increase sustainable agricultural production.