Antibiotics in the aquatic environment - A review - Part II

http://abe.ufl.edu/Faculty/jjones/ABE_5646/Xtra%20files/The%20DSSAT%20Cropping%20System%20Model.pdf

The DSSAT cropping system model

A global perspective on the use, sales, exposure pathways, occurrence, fate and effects of veterinary antibiotics (VAs) in the environment

The U.S. Department of Energy (DOE) and the U.S. Department of Agriculture (USDA) are both strongly committed to expanding the role of biomass as an energy source. In particular, they support biomass fuels and products as a way to reduce the need for oil and gas imports; to support the growth of agriculture, forestry, and rural economies; and to foster major new domestic industries--biorefineries--making a variety of fuels, chemicals, and other products. As part of this effort, the Biomass R&D Technical Advisory Committee, a panel established by the Congress to guide the future direction of federally funded biomass R&D, envisioned a 30 percent replacement of the current U.S. petroleum consumption with biofuels by 2030. Biomass--all plant and plant-derived materials including animal manure, not just starch, sugar, oil crops already used for food and energy--has great potential to provide renewable energy for America's future. Biomass recently surpassed hydropower as the largest domestic source of renewable energy and currently provides over 3 percent of the total energy consumption in the United States. In addition to the many benefits common to renewable energy, biomass is particularly attractive because it is the only current renewable source of liquid transportation fuel. This, of course, makes it invaluable in reducing oil imports--one of our most pressing energy needs. A key question, however, is how large a role could biomass play in responding to the nation's energy demands. Assuming that economic and financial policies and advances in conversion technologies make biomass fuels and products more economically viable, could the biorefinery industry be large enough to have a significant impact on energy supply and oil imports? Any and all contributions are certainly needed, but would the biomass potential be sufficiently large to justify the necessary capital replacements in the fuels and automobile sectors? The purpose of this report is to determine whether the land resources of the United States are capable of producing a sustainable supply of biomass sufficient to displace 30 percent or more of the country's present petroleum consumption--the goal set by the Advisory Committee in their vision for biomass technologies. Accomplishing this goal would require approximately 1 billion dry tons of biomass feedstock per year.

/pdf/biomass-as-feedstock-for-a-bioenergy-and-bioproducts-3s9zwbb88u.pdf

Biomass as Feedstock for A Bioenergy and Bioproducts Industry: The Technical Feasibility of a Billion-Ton Annual Supply

Hydrologic analyses often involve the evaluation of soil water infiltration, conductivity, storage, and plant-water relationships. To define the hydrologic soil water effects requires estimating soil water characteristics for water potential and hydraulic conductivity using soil variables such as texture, organic matter (OM), and structure. Field or laboratory measurements are difficult, costly, and often impractical for many hydrologic analyses. Statistical correlations between soil texture, soil water potential, and hydraulic conductivity can provide estimates sufficiently accurate for many analyses and decisions. This study developed new soil water characteristic equations from the currently available USDA soil database using only the readily available variables of soil texture and OM. These equations are similar to those previously reported by Saxton et al. but include more variables and application range. They were combined with previously reported relationships for tensions and conductivities and the effects of density, gravel, and salinity to form a comprehensive predictive system of soil water characteristics for agricultural water management and hydrologic analyses. Verification was performed using independent data sets for a wide range of soil textures. The predictive system was programmed for a graphical computerized model to provide easy application and rapid solutions and is available at http://hydrolab.arsusda. gov/soilwater/Index.htm.

/pdf/soil-water-characteristic-estimates-by-texture-and-organic-56ntsbkyo4.pdf

Soil Water Characteristic Estimates by Texture and Organic Matter for Hydrologic Solutions

Regression models are presented for estimating soil-water-retention curves from particle-size distribution, percentage of organic matter, and bulk density. Models were developed from the measured soil-water-retention curves of artificially packed cores (7.6×7.6 cm) of 43 soil materials. These soil materials included 13 agricultural soils. Curves predicted with these models approximated reasonably well the measured water retention of 61 Missouri soils. Because conventional methods of obtaining retention curves are expensive and time consuming, these equations will be valuable for modeling salt and water flow in soils and for estimating available water capacities.

Estimating soil water retention characteristics from particle size distribution, organic matter percent, and bulk density

Antibiotics are commonly added to animal feed as supplements to promote growth of food animals. However, absorption of antibiotics in the animal gut is not complete and as a result substantial amounts of antibiotics are excreted in urine and feces that end up in manure. Manure is used worldwide not only as a source of plant nutrients but also as a source of organic matter to improve soil quality especially in organic and sustainable agriculture. Greenhouse studies were conducted to determine whether or not plants grown in manure-applied soil absorb antibiotics present in manure. The test crops were corn (Zea mays L.), green onion (Allium cepa L.), and cabbage (Brassica oleracea L. Capitata group). All three crops absorbed chlortetracycline but not tylosin. The concentrations of chlortetracycline in plant tissues were small (2-17 ng g -1 fresh weight), but these concentrations increased with increasing amount of antibiotics present in the manure. This study points out the potential human health risks associated with consumption of fresh vegetables grown in soil amended with antibiotic laden manures. The risks may be higher for people who are allergic to antibiotics and there is also the possibility of enhanced antimicrobial resistance as a result of human consumption of these vegetables.

Antibiotic uptake by plants from soil fertilized with animal manure.

Since their discovery, antibiotics have been instrumental in treating infectious diseases that were previously known to kill humans and animals. However, their widespread use as an additive in animal feeds has raised concerns about the development of antibiotic‐resistant microorganisms. Increasingly, more microorganisms are becoming resistant to multiple antibiotics. A high proportion of the antibiotics added to animal feed is excreted in urine or manure. In some cases, as much as 90% of the antibiotic administered orally may pass through the animal unchanged. Once excreted in urine and manure, these antibiotics can enter surface and/or groundwater through nonpoint source pollution from manure‐applied lands. The literature shows that most of the antibiotics are strongly adsorbed in soils and are not readily degraded. An important environmental concern is the presence of antibiotics in sources of potable water. Except erythromycin and some sulfa drugs, most of the antibiotics found in surface waters have been only in minute quantities. In all cases, the amounts observed are in parts per billion ranges; 100‐ to 1000‐fold below minimum inhibitory concentration. Tetracyclines and penicillins, two of the most commonly used antibiotics in animal agriculture, have seldom been found in sources of potable water. There has been some reported presence of resistant bacteria in surface waters. This may have been from transport of resistant bacteria via animal or insect vectors, in airborne dusts, or simply water flow from some antibiotic‐rich setting such as manure lagoons. Direct toxic effects of antibiotics on plants and soil microflora and ‐fauna are unlikely because of the low concentrations at which antibiotics in manure are land‐applied. The indirect effects of antibiotics on the food web, however, cannot be discounted at this stage. Decrease in some components of the soil microbial populations due to manure‐applied antibiotics could cause loss of food sources for other soil organisms, which, in turn, could affect important soil microbial processes such as decomposition and mineralization. Also, repeated application of antibiotic‐laden manure can provide an environment in which selection of antibiotic‐resistant bacteria can occur. Prudent use of antibiotics to a bare minimum along with alternative methods that minimize development and proliferation of resistant bacteria need investigation.

Antibiotic Use in Agriculture and Its Impact on the Terrestrial Environment

Animal manure is applied to agricultural land as a means to provide crop nutrients. However, animal manure often contains antibiotics as a result of extensive therapeutic and subtherapeutic use in livestock production. The objective of this study was to evaluate plant uptake of a sulfonamide-class antibiotic, sulfamethazine, in corn (Zea mays L.), lettuce (Lactuca sativa L.), and potato (Solanum tuberosum L.) grown in a manure-amended soil. The treatments were 0, 50, and 100 microg sulfamethazine mL(-1) manure applied at a rate of 56 000 L ha(-1). Results from the 45-d greenhouse experiment showed that sulfamethazine was taken up by all three crops, with concentrations in plant tissue ranging from 0.1 to 1.2 mg kg(-1) dry weight. Sulfamethazine concentrations in plant tissue increased with corresponding increase of sulfamethazine in manure. Highest plant tissue concentrations were found in corn and lettuce, followed by potato. Total accumulation of sulfamethazine in plant tissue after 45 d of growth was less than 0.1% of the amount applied to soil in manure. These results raise potential human health concerns of consuming low levels of antibiotics from produce grown on manure-amended soils.

Sulfamethazine uptake by plants from manure-amended soil

Nitrogen management for irrigated potato (Solanum tuberosum L.)is important from both a production and environmental standpoint. Nitrogen deficiency can limit yield, while excessive N can leach to groundwater. The objective of this study was to investigate the effects of early-season N management on irrigated 'Russet Burbank' potato yield, N recovery, and NO 3 -N leaching. A 2-yr experiment was conducted on a Hubbard loamy sand (Udorthentic Haploborolls), using four N treatments and a 0 N control. Total N applied was 270 kg N ha -1 ; the portion applied at planting was 0, 45, 90, and 135 kg N ha -1 , with the remainder applied in equal quantities at emergence and hilling. In 1991, increasing the amount of N applied at planting did not affect total yield, but significantly increased the yield of non-marketable tubers. In 1992, total yield again was not affected, but the yield of smaller tubers significantly increased and the yield of larger tubers decreased as the proportion of N applied at planting increased. During 1991, when heavy leaching occurred, an average of only 33% of applied N was recovered by the crop. In contrast, during 1992, when fewer leaching events occurred, recovery of N averaged 56%. In both growing seasons, the amount of NO 3 -N leached increased linearly as the proportion of N applied at planting increased. The strategy of reducing N application at planting for irrigated Russet Burbank potato can reduce the potential for NO3-N leaching, increase N uptake, and improve marketable yield.

Satish C Gupta

Papers

Estimating soil water retention characteristics from particle size distribution, organic matter percent, and bulk density

Antibiotic uptake by plants from soil fertilized with animal manure.

Antibiotic Use in Agriculture and Its Impact on the Terrestrial Environment

Sulfamethazine uptake by plants from manure-amended soil

Potato yield response and nitrate leaching as influenced by nitrogen management