Residual Atrazine Research Articles

Assessment of the ecological security of immobilized enzyme remediation process with biological indicators of soil health

This study used the enzymes extracted from an atrazine-degrading strain, Arthrobacter sp. DNS10, which had been immobilized by sodium alginate to rehabilitate atrazine-polluted soil. Meanwhile, a range of biological indices were selected to assess the ecological health of contaminated soils and the ecological security of this bioremediation method. The results showed that there was no atrazine detected in soil samples after 28 days in EN+AT (the soil containing atrazine and immobilized enzyme) treatment. However, the residual atrazine concentration of the sample in AT (the soil containing atrazine only) treatment was about 5.02 ± 0.93 mg kg(-1). These results suggest that the immobilized enzyme exhibits an excellent ability in atrazine degradation. Furthermore, the immobilized enzyme could relieve soil microbial biomass carbon and soil microbial respiration intensity to 772.33 ± 34.93 mg C kg(-1) and 5.01 ± 0.17 mg CO(2) g(-1) soil h(-1), respectively. The results of the polymerase chain reaction-degeneration gradient gel electrophoresis experiment indicated that the immobilized enzyme also could make the Shannon-Wiener index and evenness index of the soil sample increase from 1.02 and 0.74 to 1.51 and 0.84, respectively. These results indicated that the immobilized enzymes not only could relieve the impact from atrazine on the soil, but also revealed that the immobilized enzymes did no significant harm on the soil ecological health.

Biodegradation of s-triazine herbicide atrazine by Enterobacter cloacae and Burkholderia cepacia sp. from long-term treated sugarcane-cultivated soils in Kenya

In this study soils from sugarcane-cultivated fields were screened for bacterial species capable of atrazine (6-chloro-N2-ethyl-N4-isopropyl-1,3,5-triazine-2,4-diamine) degradation due to long exposure of the soils to this herbicide. To enrich for atrazine degraders, Minimal Salt Medium containing atrazine as the sole N source and glucose as the C source was inoculated with soils impacted with this herbicide and incubated. Bacterial growth was monitored by measuring optical density. The degradation of atrazine was followed by measuring residual atrazine in liquid cultures over a given time period by high performance liquid chromatography. Bacterial strains isolated from the enrichment cultures were characterized by biochemical tests and identified by 16S rRNA gene sequencing. Two bacterial strains coded ISL 8 and ISL 15 isolated from two different fields were shown to have 94 and 96% 16S rRNA gene sequence similarity to Burkholderia cepacia respectively. Another bacterial sp., ISL 14 was closely related to Enterobacter cloacae with a 96% 16S rRNA gene sequence similarity. There was not much difference between the extents of atrazine degradation by the enrichment cultures with communities (79–82% applied amount) from which pure strains were isolated and the pure strains themselves in liquid cultures that showed a degradation of 53–83% of applied amount. The study showed existence of bacterial strains in different sugarcane-cultivated fields which can use atrazine as a nitrogen source. The bacterial strains isolated can be used to enhance the degradation of atrazine in contaminated soils where atrazine is still considered to be recalcitrant.

Terbuthylazine and other triazines in Italian water resources

The concern on the presence of pesticides in Italian water resources historically broke out around 1980 after severe episodes of ambient, raw water and drinking water contamination due to some herbicides, atrazine (ATR), its metabolites desethylatrazine (DEA) and deisopropylatrazine (DIA), simazine, cyanazine, bentazone, molinate, which affected mainly the maize, grain and rice producing floodplains and karst areas of the northern Regions. Due to the risks of human exposure, in the early 1990 the use of atrazine was banned in Italy and was replaced by terbuthylazine (TERB). In a few years, TERB became a chemical of concern, together with its main metabolite desethylterbuthylazine (DET), because of alerting detections in surface and groundwater resources. Up to now, the risk of contamination of water resources by TERB, DET, DEA and, in some extent ATR, is of relevance in Italy due to their present and past wide employment in agriculture, the discharges or seepages in particularly vulnerable areas, their unfavorable intrinsic properties, e.g. poor sorption and high persistence, their mobility by drift, leaching and runoff in vadose zones, aquifers and surface water. So, unsurprisingly, results from national monitoring of ambient water and raw water indicate that TERB, DET, DEA and residual ATR, despite its withdrawal, are detected at remarkable frequencies and, sometimes, at levels higher than pesticide quality standards under the Italian Decrees for the protection of surface water (specifically, raw waters doomed at the drinking water abstraction), groundwater and drinking water (tap water), that is 0.1–0.5μg/l for individual pesticides and for total pesticides, respectively, including relevant metabolites. On the other hand, in these last years, the control measures in drinking water production adopted by the waterworks Companies and the regional and central health Authorities, also in the view of the recent WHO approaches under the Water Safety Plans, ensure that levels of any pesticide residue (also involving TERB, DET, DEA, ATR) in finished tap water meet parametric values for pesticides. Therefore, in these last years, no derogation to the parametric values for drinking water has been required. The aim of this paper is to contribute to widen the knowledge on the water impact of these important water pollutants giving sound details on present usages, levels and frequencies of detection in water bodies in Italy, on their key chemiodynamic properties, e.g. soil half-lives (DT50) and soil to organic carbon partition (Koc) available in the open literature, particularly for TERB metabolites, and some details on legal provision adopted at the national level. In fact, a more effective protection of water supplies, particularly against TERB and DET, has been pursued in the late 2000s by the Italian Health Ministry through the adoption of consistent provisions aimed at mitigating emissions of TERB in routine agricultural activities, and by the Italian Ministry of the Environment through the adoption of specific Environmental Quality Standards for TERB and its metabolite DET, ATR, SIM for the protection of surface waters.

Emissions from open burning of used agricultural pesticide containers

Emissions from simulated open burning of used agricultural pesticide containers were sampled for polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDDs/PCDFs), polycyclic aromatic hydrocarbon compounds (PAHs), and particle matter (PM10 and PM2.5). Clean high density polyethylene (HDPE) containers, containers with trace pesticide, and triple-rinsed containers were burned separately in an open combustion facility and their emissions compared. Two common chlorinated pesticides were used: 2,4-dichlorophenoxyacetic acid (2,4-D) and 1-chloro-3-ethylamino-5-isopropylamino-2,4,6-triazine (atrazine). PCDD/PCDF emission factors ranged from 0.1 to 24ng toxic equivalents (TEQ)/kg C burned with a mean and median of 4.9 and 1.9ng TEQ/kgC burned, respectively. In a limited number of trials, the trace 2,4-D in the HDPE container led to a statistically significant increase in PCDD/PCDF formation compare to all other conditions. Residual atrazine did not lead to more PCDD/PCDF than the unrinsed 2,4-D container. Total (16 compounds) PAH emission factors varied from 1.5 to 6.7mg/kgC burned. These limited data suggest that rinsing the 2,4-D container prior to burning reduces both PCDD/PCDF and PAH emissions. Nine PM2.5 emission factors ranged from 9 to 35mg/gC burned and ten PM10 values ranged from 6 to 43mg/gC burned. Neither pesticide appeared to have any effect on PM concentration.

Research on Three Resistant Plants Remediating Atropine Contaminated Soil

Abstract This article examines the preliminary laboratory research on remediate atrazine contaminated soil and explores the degradation effect of resistant plants on atrazine contaminated soil, using sorghum hybird sudangrass, ryegrass and pennisetum. The findings turned out that the amount of remained atrazine in rhizosphere soil decreased gradually during the remediating procedure by sorghum hybird sudangrass and ryegrass with the degradation rates showing 75.10% and 74.20% respectively on the 40th day. Ryegrass shows slightly less effects than sorghum hybird sudangrass. Meanwhile, when remediate atrazine by pennisetum, according to the remediating data, atrazine was degraded fast in rhizosphere soil during the first 14 days, with 4.77 mg.kg-1 residual atrazine and a degradation rate of 85.70%. Therefore, remediation effects vary upon using different plants, the best choice being pennisetum, followed by sorghum hybird sudangrass and ryegrass.

Enhancement of atrazine degradation by crude and immobilized enzymes in two agricultural soils

Contamination of soil, groundwater and surface water by atrazine is a worldwide concern. Arthrobacter sp. HB-5 is a high-efficiency atrazine degradation strain isolated by our laboratory. Crude enzyme extracted from HB-5 and immobilized enzyme made from crude enzyme on sodium alginate were introduced to atrazine-polluted soils to evaluate the degrading ability for practical use and to calculate the kinetics of atrazine degradation. Atrazine was applied at 10 mg/kg of soil. Brown soil or cinnamon soil samples with crude or immobilized enzyme were incubated at 25°C. Samples were collected every 24 h from 0 to 144 h to extract the residual atrazine and analyzed using gas chromatography. Results showed, at 144 h, that only about 10% of the initially applied amount of atrazine was left in the two soils, except in the control soil samples without crude or immobilized enzyme. Before 48 h of incubation, crude enzyme removed atrazine faster than the immobilized enzyme in each soil sample. However, after 120 h, degradation of atrazine reached a similar level with either treatment. Atrazine seemed to be removed more easily from cinnamon soil than from brown soil, and both crude and immobilized enzyme could be used. However, the immobilized enzyme is preferred for its stability.

Enhancement of Atrazine Removal by Free and Immobilized Arthrobacter Sp. HB-5 in Soil and Wastewater

In an attempt to remove atrazine in situ, high-efficiency atrazine–degrading Arthrobacter sp. strain HB-5 (HB-5) and HB-5 immobilized on sodium alginate were introduced into two atrazine-polluted soils that are representative of soils in North China. Soil and wastewater with and without (controls) HB-5 or immobilized HB-5 were incubated at 25°C after the addition of atrazine. Soil samples were collected after 0 d, 1 d, 3 d, 5 d, 7 d, 10 d, and 13 d, and wastewater samples were collected after 0 d, 1 d, 3 d, 7 d, 14 d, 21 d, and 28 d. The residual atrazine was extracted from each sample and detected using gas chromatography. The half-life of the atrazine in the in soil samples was less than 3 d, and less than 7 d in the wastewater samples, treated with HB-5 or with immobilized HB-5. The immobilized HB-5 appears to exhibit better self-protection than the free bacteria at different pHs, and its ability to degrade atrazine was less affected by different conditions. Thus, in practice, immobilized HB-5 is better suited to incubations longer than 7 days because of its good adaptability. Both HB-5 and immobilized HB-5 exhibited better degradation of atrazine under conditions similar to the optimal living conditions of HB-5 than under other conditions. A small part of atrazine was removed by adsorption of organic matters, too. This study demonstrates the usefulness of these microorganisms in the bioremediation of soil and water systems polluted with triazine herbicides.

Effect of dairy manure rate and the stabilization time of amended soils on atrazine degradation

The application rate of liquid cow manure (LCM) in the field and the stabilization time of amended soils before application of pre-plant herbicides are factors that determine their efficiency. This study includes evaluation of residual atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) in soil and amended soils with equivalent rate of 100,000; 200,000; and 300,000 L ha −1 of LCM and the effect of pre-incubation time of amended soils on atrazine degradation. The study was carried out under controlled conditions using an Andisol with previous historical application of atrazine. The respiratory activity and fluorescein diacetate (FDA) studies indicated that the time necessary for stabilization of amended soils is over 20–30 d. During the measurement of respiratory and FDA activity, no significant differences were observed when atrazine was applied. The half-life of atrazine ranged from 5 to 8 d and the relative distribution of degradation products seem to be affected by the application of LCM. The pre-incubation time of amended soil and LCM dose would not affect atrazine degradation rate, when the soil has a history of herbicide application. However, repeated applications of LCM in a long period of time could change the soil pH and increase the content of dissolved organic carbon (DOC) which could further contribute to a faster degradation of atrazine. Both effects would reduce the effectiveness of atrazine in weed control.

New approach to large‐volume injection in reversed‐phase high performance liquid chromatography: Determination of atrazine and hydroxyatrazine in soil samples

A well established method of direct injection of larger than conventional sample volumes ranging from 0.1 mL to 10 mL in HPLC is the injection valve method in which a loop of tubing is totally or partially filled with sample. Recent HPLC pumps have a flow-rate setting accuracy of +/- 1-2% over a flow-rate range from 0.1 mL/min to 10 mL/min and the flow stability is 0.2% or less. Quarternary low pressure gradient pumps are widely available and used, but all their hydraulic lines are seldom utilised. The idea of using one line of a common commercial HPLC quaternary low-pressure pump for direct on-column injection (pumping) of large sample volumes ranging from 1 mL to 100 mL was tested. This approach was evaluated during practical work on the development of an RP-HPLC method of determination of residual atrazine and hydroxyatrazine. In lysimetric environmental experiments hydroxyatrazine was formed in situ in a soil column by hydrolysis of atrazine. The results proved the applicability of this approach not only in experiments with model mixtures of analytes at microg/L levels in solutions. Analysis of 20 mL of soil leachates and extracts of soil samples containing atrazine and hydroxyatrazine at the 10 microg/kg level (in dry soil) revealed that good figures-of-merit were preserved, even in the presence of a large excess of humic substances.

Enhancing cell survival of atrazine degrading Rhodococcus erythropolis NI86/21 cells encapsulated in alginate beads

To develop a method to produce beads with encapsulated Rhodococcus erythropolis NI86/21 with high cell density, extended shelf life, ease of handling and good atrazine degradation capabilities in both liquid and in agricultural soil. Our findings show that the supplementary recovery step in nutrient broth media shortly after cell encapsulation facilitates cell survival in both wet and dry beads upon extended storage at 4 degrees C. Air drying has little or no impact on encapsulated R. erythropolis cell's ability to degrade atrazine in liquid or soil. Bead storage for periods extending up to 12 months at 4 degrees C did not affect the capacity of R. erythropolis encapsulated cells to degrade atrazine in either BMN or nonsterile soil extracts. Bentonite-amended beads formulated with 1% skim milk and exposed to the supplementary growth step, outperformed all other bead formats. These beads provided adequate numbers of vigorous R. erythropolis cells in either liquid or soil media to degrade atrazine. Supplementary growth in nutrient broth media immediately following cell encapsulation greatly enhances R. erythropolis cells survival in both wet and dry beads upon extended storage at 4 degrees C. Wet and dried beads have similar capacity for atrazine degradation, and their usefulness and appeal in agronomic practise will only be known after bioassay evaluation and successful demonstration at field scale using incurred residues. R. erythropolis NI86/21 encapsulated cells have the potential to reduce residual atrazine in soil, thereby minimizing the likelihood of off-site transport to ground or river water and reduce the loss of crops because of phytotoxicity of residual herbicide. Owing to their ease of handling, storage and possible compatibilities with pre-existing mechanical equipment, dried bead formats are ideally suited for agricultural and remediational applications.

Increase of the detoxification potential of basidiomycetes by induction of laccase biosynthesis

The effect of oxidoreductase inducers guaiacol and syringaldazine on the ability of Coriolus hirsutus, Coriolopsis fulvocinerea, Cerrena maxima, and cocultivated Coriolus hirsutus/Cerrena maxima to degrade atrazine in submerged cultures was studied. All the basidiomycetes reduced atrazine concentration with and without syringaldazine or guaiacol. The degree of atrazine degradation was higher in induced cultures (77-98% vs. 68-94% without induction). Of the four cultures, the highest detoxifying potential was observed in Coriolopsis fulvocinerea with and without an inducer (98% with guaiacol), and the lowest was in Cerrena maxima. Inducers decreased the residual atrazine concentration differently in the different cultures. A long-term increase of laccase production was observed in both induced and uninduced cultures, whereas the activity of Mn-peroxidase decreased. The results indicate that laccase plays a larger role in atrazine biodegradation than Mn-peroxidase.

Study of atrazine fate in silty loamy soils of the Paris Basin via a combination of isotopic and pyrolytic methods

The fate of organic micro-pollutants in soil largely depends on their interactions with soil organic matter (SOM). Indeed, the intensity and nature of such interactions are major factors in the control of micro-pollutant bioavailability, and hence degradation and micro-pollutant mobility in the environment [Khan and Hamilton, 1980 ; Calderbank, 1989 ; Dec et al., 1990, 1997 ; Barriuso and Koshinen, 1996]. Residual micro-pollutants, i.e. the remaining micro-pollutants and their various transformation products (metabolites), occur in soil both in the water phase and associated with the solid phase. A part of these associated molecules, termed bound residues (BRs), cannot be released via extraction with water or organic solvents like methanol. SOM plays a major role in BR formation [e.g. Loiseau et al., 2000] and different types of interaction (like covalent bonds and trapping in organo-mineral aggregates) can be implied [Hsu and Bartha, 1976 ; Schiavon et al., 1977 ; Bollag et al., 1992 ; Dec and Bollag, 1997 ; Steinberg et al., 1987; Providenti et al., 1993]. The present study is concerned with the fate of atrazine in three silty loamy soils from the Paris Basin. Atrazine is largely used (ca. 5000 T/year in France) as herbicide for maize cropping and may cause important pollution problems through transfer to water resources.

Asymmetrical Distribution and Dissipation of Band‐Applied Atrazine in Soil

AbstractMovement of herbicides, particularly atrazine [2‐chloro‐N‐ethyl‐N′‐(1‐methylethyl)‐1,3,5‐triazine‐2,4‐diamine], is of great interest, as farming systems are designed to protect water quality. The effects of time and precipitation on the distribution of atrazine banded over corn (Zea mays L.) rows were measured for 2 yr in a ridge‐tillage corn‐soybean [Glycine max (L.) Merr.] rotation. The soil was a Zimmerman fine sand (mixed, frigid Lamellic Udipsamment). During the growing season, soil atrazine was determined at 0.1‐m horizontal intervals perpendicular to the row to a depth of 0.3 m. Within the first 22 days after treatment (DAT), atrazine concentrations decreased 65% in the application zone and had not leached below 0.075 m. A 60‐mm rain between 22 and 29 DAT first moved atrazine into the 0.075‐ to 0.15‐m depth increment. By 60 DAT and 240 mm of accumulated rain, atrazine concentrations had decreased by an estimated 90% in the zone of application. Atrazine movement appeared to be greater on the windward side of the row. An estimated 98% of applied atrazine was dissipated by the end of the first growing season and by the end of the second year, detections of residual atrazine were very limited and confined to the zone directly below the treated area. Significant horizontal movement of atrazine was never observed. Atrazine was not detected in soil samples below 0.6 m to a depth of 2.4 m.

Water quality in a sand plain after conversion from dryland to irrigation: tillage and cropping systems compared

Groundwater quality is perceived to be vulnerable under irrigated sandy soil because of increased agrichemical loading. Flushes of NO 3–N and deteriorated groundwater quality may also result from accelerated mineralization when converting from dryland to irrigated production. Groundwater quality under a corn ( Zea mays L.)–soybean [ Glycine max (L.) Merr.] cropping system with banded herbicide (atrazine, alachlor, metribuzin) in ridge-till compared to continuous corn with broadcast applied herbicide (atrazine, alachlor) in a mulch-till cropping system was studied from 1991 to 1995 in southeastern ND, USA. Nitrogen application rate and method differed between the ridge-till and mulch-till systems. Residual soil NO 3–N in the upper 90 cm of soil, at the end of the growing season, was similar in ridge-till and mulch-till corn and ca. 32% less in ridge-till soybean. Low-to-moderate levels (20–59 kg ha −1) of residual NO 3–N in both cropping systems during the fall-to-late-spring period indicate a similar potential for deep percolation of NO 3–N, independently of the cropping system. Nitrate–N concentration in the upper 30 cm of groundwater increased after irrigation was initiated in 1991, and then decreased in both cropping systems to within 4 mg l −1 of the initial concentration. The source of this rise in NO 3–N concentration was most likely from increased mineralization of soil N with the advent of irrigation, above-normal precipitation, and residual NO 3–N from previous dryland agriculture. Residual herbicide was retained shallow enough in the soil so that cultivation in the mulch-till corn moved enough herbicide from the furrow to the row area, for the row area to contain ca. 76% of the total residual atrazine and 84% of the residual alachlor 11 weeks after application. Metribuzin was seldom detected below the 15 cm soil depth. Alachlor and metribuzin were not detected in groundwater, and atrazine was detected at <0.41 μg l −1 in four out of 130 samples in the upper 30 cm of groundwater. Under an irrigated corn and soybean rotation on a sand plain, groundwater quality was not impaired by herbicides and NO 3–N concentrations were only temporarily elevated and finally returned to pre-irrigation levels.

Atrazine degradation in saline wastewater by Pseudomonas sp strain ADP

Wastewater from atrazine manufacturing plants contains large amounts of residual atrazine and atrazine synthesis products, which must be removed before disposal. One of the obstacles to biological treatment of these wastewaters is their high salt content, eg, up to 4% NaCl (w/v). To enable biological treatment, bacteria capable of atrazine mineralization must be adapted to high-salinity conditions. A recently isolated atrazine-degrading bacterium, Pseudomonas sp strain ADP, originally isolated from contaminated soils was adapted to biodegradation of atrazine at salt concentrations relevant to atrazine manufacturing wastewater. The adaptation mechanism was based on the ability of the bacterium to produce trehalose as its main osmolyte. Trehalose accumulation was confirmed by natural-abundance 1H NMR spectral analysis. The bacterium synthesized trehalose de novo in the cells, but could not utilize trehalose added to the growth medium. Interestingly, the bacterium could not produce glycine betaine (a common compatible solute), but addition of 1 mM of glycine betaine to the medium induced salt tolerance. Osmoregulated Pseudomonas sp strain ADP, feeding on citrate decreased the concentration of atrazine in non-sterile authentic wastewater from 25 ppm to below 1 ppm in less than 2 days. The results of our study suggest that salt-adapted Pseudomonas sp strain ADP can be used for atrazine degradation in salt-containing wastewater.

Effet de l’herbicide atrazine sur la respiration et l’ammonification de l’azote organique dans un sol agricole au cours d’une incubation

The importance of soil microflora and fauna in the breakdown of organic matter and nutrient release for plant growth is well recognized. However, the use of pesticides can affect soil bioactivity in a variety of ways. A long-term incubation laboratory experiment was performed to study the impact of the herbicide atrazine (commercial formulation) on soil respiration and arginine ammonification. The incubation time was lower than the half-life time for atrazine: this allows the presence of significant amounts of residual atrazine in soil throughout the incubation period. Atrazine induced a marked stimulation of cumulative CO2 evolution and the results were analyzed to fit a first-order degradation model for soil organic carbon. In the presence of various atrazine application rates (from 1 to 5 times the agricultural rate), the soil mineralizable carbon content was found to be 1.7 and 1.4 times higher than that of untreated soil. During the incubation, a marked temporal variability occurred in the arginine ammonification rate. Atrazine induced a decrease in ammonification rate, in comparison to the one obtained for the untreated soil. The ammonification rate varied little for atrazine applications greater than three times the agricultural rate, and for incubation times greater than 40 d. The characterization of the relation between the soil CO2 production rate (for 1 or 2 wk) and the ammonification rate (for 3 h) was obtained as a function of incubation time intervals by applying linear regression functions. Results showed that these variables are not significantly related. Key words: Bioactivity, atrazine, respiration, arginine ammonification, agricultural soil

Atrazine persistence and phytotoxicity on wheat as affected by nitrogen and rotation-induced changes in soil properties

Wheat growing in a rotation experiment on an alkaline black earth was severely damaged by atrazine residues, whereas wheat in an adjacent experiment on a slightly acid red clay, was undamaged. Atrazine at 1.8 kg a.i, ha-1 had been applied to both sites nine months before wheat sowing. Nitrogen fertilizer had also been applied as split-plot treatments to the previous crop in each rotation sequence. There were four rotations, each comprising grain sorghum with either lucerne, an annual grain legume, long fallow, or continuous cereal growing.There were significant rotation effects on soil organic matter, pH, mineral nitrogen and residual atrazine. Organic carbon was highest, and soil pH and atrazine were lowest in the lucerne rotation, while the opposite occurred in the long fallow treatment. Atrazine concentration was positively correlated with pH and negatively correlated with organic carbon. The numbers of dead plants on the black earth were positively correlated with atrazine levels, but mortality was lowered by increasing mineral nitrogen at any particular level of atrazine.Wheat yields varied from zero in two continuous cereal plots to over 3.0 t ha-1 in a long fallow plot, and were highly correlated with mineral nitrogen levels. At any level of nitrogen, however, wheat yields were depressed by increasing levels of atrazine. The very large yield response to nitrogen, whether from soil or fertilizer, resulted from its dual beneficial effect of lowering plant mortality and improving the nitrogen status of the surviving plants.These results show that in a wheat crop following atrazine-treated sorghum, significant atrazine damage may occur on soils of pH &gt; 64, that atrazine persistence and phytotoxicity will increase as the pH increases, but that phytotoxicity will decrease as soil nitrogen fertility increases. Lucerne rotations will lower atrazine persistence by decreasing soil pH and increasing organic matter, and will lower phytotoxicity by raising soil nitrogen.

COMPARISON OF CROP ROTATIONS FOR SORGHUM PRODUCTION IN SOUTHERN ALBERTA

Grain sorghum (Sorghum bicolor L. Moench.) was evaluated in six rotations under rainfed conditions at the Lethbridge Research Station from 1978 to 1984. The rotations included continuous sorghum, sorghum-fallow, sorghum-barley, sorghum-spring wheat-fallow, sorghum-fallow-spring wheat and sorghum-fallow-winter wheat. The highest total production was achieved with the sorghum-barley rotation. This was followed by the continuous sorghum and sorghum-fallow-winter wheat rotations. The 3-yr rotations were not significantly different from each other but the sorghum-fallow-winter wheat rotation appeared to be the best. The 2-yr rotation, sorghum-fallow, was the least productive. Variability in yields was adequately accounted for by variability in annual rainfall. Water use efficiencies were 1.30 and 1.35 kg m−3 for sorghum and wheat grown on fallow and 1.11 and 1.12 kg m−3 when seeded into stubble. Therefore, it was concluded that sorghum was no more drought-resistant than wheat. Bioassay of soils from the crop rotation study indicated that residual atrazine toxicity should not be a significant limitation to wheat grown in rotation with sorghum. Economically, sorghum was at a disadvantage despite comparable yields in wheat because of its lower price. It was concluded that the inclusion of sorghum in crop rotations in southern Alberta cannot currently be recommended.Key words: Spring wheat, winter wheat, atrazine, adaptation

Response of Barley, Spring Wheat, and Oats to Atrazine1

Frequent inquiries about the response of small grains to atrazine (2‐chloro‐4.ethylamino‐6‐isopropylamino‐s‐triazinc) have been made, but research in this area has been very limited. If atrazine carryover is expected, harley (Hordeum vulgate L. emend Bowden) and spring wheat (Triticum aestivum L. em Thell) might be more suitable small grains to grow if they produced more grain and straw in residual atrazine than oats (Avena sativa L.). The objectives of this research were to evaluate the response of barley and spring wheat to atrazlne, to compare the response of these two small grains to the response of oats, and to test for genotyplc differences for grain yield response to atrazine in barley and spring wheat.Atrazine applications of 0, 1.12, 2.24, 3.36, and 4.48 kg/ha were applied postemergence to corn (Zea mays L.) in 1975, and the small grains were sown during the spring of 1976. This procedure was repeated in 1976 and 1977. The soil was a silt loam (Typic Arguidoll, finesilty, mixed, mesic) with 3.5 to 4.0% organic matter.Grain and straw yields of all genotypes were reduced by atrazine carryover, and species differences were evident. Barley produced higher grain and straw yields in residual atrazine than spring wheat in both 1976 and 1977. Oats, which were not included in 1976 comparisons, also had higher grain and straw yields than spring wheat in 1977. Oats did not yield as much grain and straw as barley in high levels of residual atrazine in 1977, but on the basis of tolerance (yield in soil containing atrazine/yield in soil with no atrazine), there was little difference between barley and oats. However, barley was significantly more tolerant of atrazine than spring wheat on the basis of seedling dry matter production in a greenhouse test. Variation among genotypes for response to atrazine in the 2 years of testing was limited in both barley and spring wheat.The results of this research indicate that if small grains are grown in soil with an anticipated atrazine carryover problem, barley would be preferable to oats. and both harley and oats would be preferable to spring wheat.

Colorimetry and High Performance Liquid Chromatography of Atrazine Residues in Soil: Comparison of Methods

Abstract The colorimetric method for determining residual atrazine levels in soil is compared with reverse phase high performance liquid chromatography (HPLC). The soil samples are extracted with water-acetonitrile (10 + 90) and the filtrate is partitioned with methylene chloride. For the colorimetric analysis the organic phase is filtered through activity V alumina, collected, and evaporated to dryness. The residue is dissolved first in ethyl ether, and then in water as the ether is removed. The atrazine solution is buffered (citric acid, pH 7.0) and heated with added pyridine. When the reaction is complete, the product is complexed with ethylcyanoacetate, and the solution absorbance is measured at 550 nm. The complex obeys Beer’s law and has a sensitivity of 230 ng for a 1% full scale deflection at 1 AUFS. For the HPLC method, the methylene chloride extract is dried, the chromatographic solvent is quantitatively added (either chloroform or methanol), and the solution is analyzed with a UV detector at 254 nm. Minimum amount detectable for a 1% full scale deflection is 5 ng at 0.01 AUFS. Soil background interferences were investigated for both methods, and buffering the pyridine-triazine reaction solution was the most efficient method for removing the background for colorimetry. The recovery efficiencies for the colorimetric and HPLC methods were 45.5 ± 3.8% and 94.4 ± 3.4%, respectively.