Two long-term no-till corn production studies, representing dierent soil texture, consistently sh... more Two long-term no-till corn production studies, representing dierent soil texture, consistently showed higher leaching of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] to groundwater in a silt loam soil than in a sandy loam soil. A laboratory leaching study was initiated using intact soil cores from the two sites to determine whether the soil texture could account for the observed dierences. Six intact soil cores (16 cm dia by 20 cm high) were collected from a four-year old no-till corn plots at each of the two locations (ca. 25 km apart). All cores were mounted in funnels and the saturated hydraulic conductivity K sat was measured. Three cores (from each soil texture) with the lowest K sat were mixed and repacked. All cores were surface treated with 1X7 kgaiha À1 [ringÀ 14 C] atrazine, subjected to simulated rainfall at a constant 12 mm h À1 intensity until nearly 3 pore volume of leachate was collected and analyzed for a total of 14 C. On an average, nearly 40% more of atrazine was leached through the intact silt loam than the sandy loam soil cores. For both the intact and repacked cores, the initial atrazine leaching rates were higher in the silt loam than the sandy loam soils, indicating that macropore¯ow was a more prominent mechanism for atrazine leaching in the silt loam soil. A predominance of macropore¯ow in the silt loam soil, possibly due to greater aggregate stability, may account for the observed leaching patterns for both ®eld and laboratory studies. Ó
This study was conducted to evaluate the eect of hairy vetch cover crop residue on runo losses of... more This study was conducted to evaluate the eect of hairy vetch cover crop residue on runo losses of atrazine and metolachlor under both no-till corn ®eld plots and from a laboratory runo system. A 2-year ®eld study was conducted in which losses of atrazine and metolachlor from vetch and non-vetch ®eld plots were determined from the ®rst runo event after application (5 and 25 days after application in 1997 and 1998, respectively). A laboratory study was conducted using soil chambers, designed to simulate ®eld soil, water, vegetation, and herbicide treatment conditions, subjected to simulated rain events of 5, 6, 20 and 21 days after application, similar to the rainfall pattern observed in the ®eld study. Atrazine losses ranged from 1.2 to 7.2% and 0.01 to 0.08% and metolachlor losses ranged from 0.7 to 3.1% and 0.01 to 0.1% of the amount applied for the 1997 and 1998 runo events, respectively. In the laboratory study, atrazine runo losses ranged from 6.7 to 22.7% and 4.2 to 8.5% and metolachlor losses ranged from 3.6 to 9.8% and 1.1 to 4.7% of the amount applied for the 5±6 and 20±21 day events, respectively. The lower losses from the ®eld study were due to smaller rainfall amounts and a series of small rains prior to the runo event that likely washed herbicides o crop residue and into soil where adsorption could occur. Runo losses of both herbicides were slightly higher from non-vetch than vetch ®eld plots. Losses from the laboratory study were related to runo volume rather than vegetation type. Ó
The interaction of conventional tillage (CT) and no-tillage (NT) crop production practices with r... more The interaction of conventional tillage (CT) and no-tillage (NT) crop production practices with rainfall on the movement of three herbicides into shallow groundwater was evaluated over 4 yr.
Climate and soil conditions in South Florida along with an extensive canal system facilitate move... more Climate and soil conditions in South Florida along with an extensive canal system facilitate movement of agricultural pesticides into surface waters. In a two-year study (2002)(2003)(2004) of the currently used pesticides in South Florida, atrazine, endosulfan, metolachlor, chlorpyrifos, and chlorothalonil were the most frequently detected in the canals and in Biscayne Bay, with average concentrations of 16, 11, 9.0, 2.6, and 6.0 ng/L, respectively. Concentrations of atrazine and chlorpyrifos were highest near corn production. Chlorothalonil and endosulfan concentrations were highest near vegetable production, with no clear trend for metolachlor, which is used on multiple crops. Concentration data were used to calculate an aquatic life hazard potential for the planting period (November) versus the harvest period (March). This analysis indicated that a higher hazard potential occurs during harvest, primarily from the use of endosulfan. These data will also serve to document canal conditions prior to implementation of the Comprehensive Everglades Restoration Plan (CERP).
Abstract High levels of cover-crop residue can suppress weed emergence and also can intercept pre... more Abstract High levels of cover-crop residue can suppress weed emergence and also can intercept preemergence herbicides and potentially reduce their effectiveness. This research was conducted in continuous no-tillage corn to compare the effect of residue from a hairy ...
. In addition, bactericides, Current vegetable production systems use polyethylene (plastic) inse... more . In addition, bactericides, Current vegetable production systems use polyethylene (plastic) insecticides, and fungicides required to protect vegetamulch and require multiple applications of agrochemicals. During rain events, runoff from vegetable production is enhanced because 50 to ble crops are known to have adverse effects on finfish, 75% of the field is covered with an impervious surface. This study shellfish, and other aquatic organisms at environmenwas conducted to quantify off-site movement of soil and pesticides tally relevant levels with runoff from tomato (Lycopersicon esculentum Mill.) plots con- Pait et al., 1992; Hetzer et al., 1999 Hetzer et al., , 2000. taining polyethylene mulch and a vegetative mulch, hairy vetch (Vicia Tomatoes are one of the most economically important villosa Roth). Side-by-side field plots were instrumented with autovegetables grown in the USA. The U.S. tomato industry mated flow meters and samplers to measure and collect runoff, which includes both the fresh market and processing tomato was filtered, extracted, and analyzed to determine soil and pesticide industries, which have average annual yields of 3.5 billoss. Seasonal losses of two to four times more water and at least lion pounds (ca. 1.6 billion kg) and 9.8 million tons (ca. 8.9 three times as much sediment were observed from plots with polyethylene mulch (55.4 to 146 L m Ϫ2 and 247 to 535 g m Ϫ2 , respectively) versus million Mg) valued at $1.1 billion and $529 million, plots with hairy vetch residue (13.7 to 75.7 L m Ϫ2 and 32.8 to 118 g respectively (Davis et al., 1998). Fresh-market vegetable m Ϫ2 , respectively). Geometric means (Ϯstandard deviation) of total production generally requires polyethylene (plastic) pesticide loads for chlorothalonil (tetrachloroisophthalonitrile) and mulch to primarily control weeds and to preserve soil ␣and -endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydromoisture. Use of this impervious mulch on 50 to 75% 6,9-methano-2,4,3-benzodioxathiepin 3-oxide) for a runoff event were of the field may cause large amounts of water to run 19, 6, and 9 times greater from polyethylene (800 Ϯ 4.6, 17.6 Ϯ 3.9, off the fields with an intense pulse of agrochemicals and and 39.1 Ϯ 4.9 g m Ϫ2 , respectively) than from hairy vetch mulch plots sediments during rain events. Research from McCall et (42 Ϯ 6.0, 2.8 Ϯ 5.0, and 4.3 Ϯ 4.6 g m Ϫ2 , respectively) due to greater al. (1988) and Wan and El-Swaify (1999) have shown concentrations and larger runoff volumes. The increased runoff volume, soil loss, and off-site loading of pesticides measured in runoff
Two long-term no-till corn production studies, representing dierent soil texture, consistently sh... more Two long-term no-till corn production studies, representing dierent soil texture, consistently showed higher leaching of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] to groundwater in a silt loam soil than in a sandy loam soil. A laboratory leaching study was initiated using intact soil cores from the two sites to determine whether the soil texture could account for the observed dierences. Six intact soil cores (16 cm dia by 20 cm high) were collected from a four-year old no-till corn plots at each of the two locations (ca. 25 km apart). All cores were mounted in funnels and the saturated hydraulic conductivity K sat was measured. Three cores (from each soil texture) with the lowest K sat were mixed and repacked. All cores were surface treated with 1X7 kgaiha À1 [ringÀ 14 C] atrazine, subjected to simulated rainfall at a constant 12 mm h À1 intensity until nearly 3 pore volume of leachate was collected and analyzed for a total of 14 C. On an average, nearly 40% more of atrazine was leached through the intact silt loam than the sandy loam soil cores. For both the intact and repacked cores, the initial atrazine leaching rates were higher in the silt loam than the sandy loam soils, indicating that macropore¯ow was a more prominent mechanism for atrazine leaching in the silt loam soil. A predominance of macropore¯ow in the silt loam soil, possibly due to greater aggregate stability, may account for the observed leaching patterns for both ®eld and laboratory studies. Ó
This study was conducted to evaluate the eect of hairy vetch cover crop residue on runo losses of... more This study was conducted to evaluate the eect of hairy vetch cover crop residue on runo losses of atrazine and metolachlor under both no-till corn ®eld plots and from a laboratory runo system. A 2-year ®eld study was conducted in which losses of atrazine and metolachlor from vetch and non-vetch ®eld plots were determined from the ®rst runo event after application (5 and 25 days after application in 1997 and 1998, respectively). A laboratory study was conducted using soil chambers, designed to simulate ®eld soil, water, vegetation, and herbicide treatment conditions, subjected to simulated rain events of 5, 6, 20 and 21 days after application, similar to the rainfall pattern observed in the ®eld study. Atrazine losses ranged from 1.2 to 7.2% and 0.01 to 0.08% and metolachlor losses ranged from 0.7 to 3.1% and 0.01 to 0.1% of the amount applied for the 1997 and 1998 runo events, respectively. In the laboratory study, atrazine runo losses ranged from 6.7 to 22.7% and 4.2 to 8.5% and metolachlor losses ranged from 3.6 to 9.8% and 1.1 to 4.7% of the amount applied for the 5±6 and 20±21 day events, respectively. The lower losses from the ®eld study were due to smaller rainfall amounts and a series of small rains prior to the runo event that likely washed herbicides o crop residue and into soil where adsorption could occur. Runo losses of both herbicides were slightly higher from non-vetch than vetch ®eld plots. Losses from the laboratory study were related to runo volume rather than vegetation type. Ó
The interaction of conventional tillage (CT) and no-tillage (NT) crop production practices with r... more The interaction of conventional tillage (CT) and no-tillage (NT) crop production practices with rainfall on the movement of three herbicides into shallow groundwater was evaluated over 4 yr.
Climate and soil conditions in South Florida along with an extensive canal system facilitate move... more Climate and soil conditions in South Florida along with an extensive canal system facilitate movement of agricultural pesticides into surface waters. In a two-year study (2002)(2003)(2004) of the currently used pesticides in South Florida, atrazine, endosulfan, metolachlor, chlorpyrifos, and chlorothalonil were the most frequently detected in the canals and in Biscayne Bay, with average concentrations of 16, 11, 9.0, 2.6, and 6.0 ng/L, respectively. Concentrations of atrazine and chlorpyrifos were highest near corn production. Chlorothalonil and endosulfan concentrations were highest near vegetable production, with no clear trend for metolachlor, which is used on multiple crops. Concentration data were used to calculate an aquatic life hazard potential for the planting period (November) versus the harvest period (March). This analysis indicated that a higher hazard potential occurs during harvest, primarily from the use of endosulfan. These data will also serve to document canal conditions prior to implementation of the Comprehensive Everglades Restoration Plan (CERP).
Abstract High levels of cover-crop residue can suppress weed emergence and also can intercept pre... more Abstract High levels of cover-crop residue can suppress weed emergence and also can intercept preemergence herbicides and potentially reduce their effectiveness. This research was conducted in continuous no-tillage corn to compare the effect of residue from a hairy ...
. In addition, bactericides, Current vegetable production systems use polyethylene (plastic) inse... more . In addition, bactericides, Current vegetable production systems use polyethylene (plastic) insecticides, and fungicides required to protect vegetamulch and require multiple applications of agrochemicals. During rain events, runoff from vegetable production is enhanced because 50 to ble crops are known to have adverse effects on finfish, 75% of the field is covered with an impervious surface. This study shellfish, and other aquatic organisms at environmenwas conducted to quantify off-site movement of soil and pesticides tally relevant levels with runoff from tomato (Lycopersicon esculentum Mill.) plots con- Pait et al., 1992; Hetzer et al., 1999 Hetzer et al., , 2000. taining polyethylene mulch and a vegetative mulch, hairy vetch (Vicia Tomatoes are one of the most economically important villosa Roth). Side-by-side field plots were instrumented with autovegetables grown in the USA. The U.S. tomato industry mated flow meters and samplers to measure and collect runoff, which includes both the fresh market and processing tomato was filtered, extracted, and analyzed to determine soil and pesticide industries, which have average annual yields of 3.5 billoss. Seasonal losses of two to four times more water and at least lion pounds (ca. 1.6 billion kg) and 9.8 million tons (ca. 8.9 three times as much sediment were observed from plots with polyethylene mulch (55.4 to 146 L m Ϫ2 and 247 to 535 g m Ϫ2 , respectively) versus million Mg) valued at $1.1 billion and $529 million, plots with hairy vetch residue (13.7 to 75.7 L m Ϫ2 and 32.8 to 118 g respectively (Davis et al., 1998). Fresh-market vegetable m Ϫ2 , respectively). Geometric means (Ϯstandard deviation) of total production generally requires polyethylene (plastic) pesticide loads for chlorothalonil (tetrachloroisophthalonitrile) and mulch to primarily control weeds and to preserve soil ␣and -endosulfan (6,7,8,9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydromoisture. Use of this impervious mulch on 50 to 75% 6,9-methano-2,4,3-benzodioxathiepin 3-oxide) for a runoff event were of the field may cause large amounts of water to run 19, 6, and 9 times greater from polyethylene (800 Ϯ 4.6, 17.6 Ϯ 3.9, off the fields with an intense pulse of agrochemicals and and 39.1 Ϯ 4.9 g m Ϫ2 , respectively) than from hairy vetch mulch plots sediments during rain events. Research from McCall et (42 Ϯ 6.0, 2.8 Ϯ 5.0, and 4.3 Ϯ 4.6 g m Ϫ2 , respectively) due to greater al. (1988) and Wan and El-Swaify (1999) have shown concentrations and larger runoff volumes. The increased runoff volume, soil loss, and off-site loading of pesticides measured in runoff
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