Maury Silt Loam Soil Research Articles

Bacteria-assisted removal of fluoroquinolones from wheat rhizospheres in an agricultural soil

Extensive fluoroquinolone antibiotics use results in their widespread occurrence in various environments including soil, which threatens the soil ecology and public health. The fate of fluoroquinolones in agricultural soil and the efficacy of enhanced degradation in the presence of an agricultural crops and antibiotic degrading bacteria could be better understood. The current study examined ciprofloxacin (CIP), enrofloxacin (ENR), and levofloxacin (LEV) biodegradation in a Maury Silt Loam soil in greenhouse conditions by bacterial-assisted removal of individual and mixed antibiotics in wheat rhizospheres. Fluoroquinolones were added at rates of 5, 50, and 100 mg kg−1. Three bacterial isolates were applied at 106 CFU g−1 soil individually and in consortium. Antibiotics appeared in wheat tissue, with more accumulation in roots than shoots. Low recoveries (<50%) of CIP, ENR, and LEV were observed at all levels and treatments in a bacteria and wheat-free control compared to the initial concentrations applied Contaminated soil with wheat had greater antibiotic recovery than the wheat-free control. Antibiotic recovery with bacterial inoculum was less than that of the indigenous bacteria. The least antibiotic recovery occurred with wheat and bacterial inoculum together. At concentrations of 5 and 50 mg kg−1, but not at 100 mg kg−1, CIP, ENR, and LEV were below detection limits in soil after 30 days through the combination of wheat and bacteria compared to the control. This synergistic removal of the fluoroquinolone antibiotics is proposed to be due to enhanced antibiotic bioavailability, which suggests it as an environment-friendly approach to biodegradation.

Evaluation of Irrigation Threshold and Duration for Tomato Grown in a Silt Loam Soil

Soil moisture-based, high-frequency, low-volume (pulsed) irrigation management strategies have saved water while maintaining yields of vegetables grown in coarse textured soils. However, little is known regarding the efficacy of soil moisture-based pulsed irrigation on finer textured soils. Therefore, five tensiometer-based, automated irrigation treatments were tested for tomato (Solanum lycopersicum) grown in a Maury silt loam soil in 2009 and 2010 in Lexington, KY. Irrigation treatments consisted of paired-tensiometer systems with on/off setpoints of −30/−10, −30/−25, −45/−10, and −45/40 kPa in both 2009 and 2010 and a single-tensiometer system with setpoints of −35 kPa in 2009 and −40 kPa in 2010. In 2009, the pulsed systems (−30/−25, −45/−40, and −35 kPa) irrigated more frequently but for a shorter duration than non-pulsed systems (−30/−10 and −45/−10 kPa). Soil moisture measurements in 2009 suggested that probes set at a depth of 6 inches were more closely matched to irrigation setpoints than those at 12 inches. In both years, the −45/−40 kPa setpoint treatment used the least amount of water while maintaining total marketable yields that were not significantly different from other treatments. Yields were significantly higher in 2009 than 2010, though atypical air temperatures in 2010 may have been the cause. Leaf water potential and relative water content were measured predawn and midday throughout the growing season in 2009 and 2010. Leaf water potential was not significantly affected by the treatments in either year, though leaf relative water content was affected in 2010. In this trial, an automated, soil moisture-based irrigation system maintained yields and saved water when compared with a non-pulsed irrigation system using similar irrigation setpoints for tomato grown in a silt loam soil.

Evaluation of MACRO model by short-term water and solute transport simulation in Maury silt loam soil

Modeling preferential flow has been a concern of many academic fields in the past 30 years all over the world and helps to prevent groundwater contamination. A dual-porosity model, MACRO, was evaluated for short-term (less than 2 days) simulation of water flow and non-reactive solute (chloride) transport through the profile of six plots in well-structured Maury silt loam soil. Water flow in micropores is calculated by the Richards&amp;rsquo; equation while simple gravity flow is assumed in the macropores. Solute transport in the micropores is calculated by the convection-dispersion equation (CDE) while the dispersion and diffusion in the CDE is neglected for the solute transport in the macropores. The applied water and chloride reached the bottom of the profile during the 2 and 1-hour(s) application periods in studies 2 and 3, respectively. There is a strong indication of macropore flow in this soil. Based on the statistical criteria, the model accurately simulated water flow and solute transport with depth and time in all plots. The mean values of three statistical parameters (coefficient of residual mass, model efficiency, and correlation coefficient) for water and chloride transport were &amp;ndash;0.0014, 0.791, 0.903 and 0.0333, 0.923, 0.956, respectively. Preliminary studies showed that the model could not simulate flow and transport well enough with the one-domain flow concept. In the two-domain flow, effective diffusion path-length, boundary hydraulic conductivity, and boundary soil water pressure were the three most important parameters that control flow and transport between the two domains. The effective diffusion path-length represented the structural development with depth in the Maury silt loam soil.

Early‐Maturing Soybean Cropping System: II. Growth and Development Responses to Environmental Conditions

AbstractProduction of early‐planted, early‐maturing soybean [Glycine max (L.) Merrill] cultivars has gained popularity in the southeastern USA in recent years, primarily as a drought‐avoidance mechanism. In seasons with adequate rainfall, however, early planting of such cultivars may not be essential for competitive yields. Our objective was to identify key environmental constraints to the growth and development of early‐maturing soybean in the southern region. Soybean cultivars from Maturity Groups (MG) 00 through IV were planted in late April, mid‐May, early June, and late June in 1990 through 1993 in 0.38‐m rows on a well‐drained Maury silt loam soil (fine, mixed, mesic Typic Paleudalf). Canopy closure, plant height, and plant mass per unit area were recorded at both R1 and R5. In addition, crop growth rate from R1 to R5 was calculated. Cool vegetative‐stage temperatures suppressed vegetative growth, particularly of early‐maturing cultivars and for early planting dates. Crop growth rate during pod‐set was not consistently associated with yield. Canopy closure at R1 of early‐maturing cultivars was more responsive to delayed planting than was that of later maturing cultivars. Across years and planting dates, canopy closure at R5 of MG 00 to I cultivars generally fell below 90%, while that of MG II to IV cultivars generally exceeded 90%. Early planting may be a disadvantage for early‐maturing cultivars in seasons with favorable rainfall patterns, particularly if canopy development is inhibited by cool temperatures during vegetative growth. If moisture is not limiting, delayed planting of early‐maturing cultivars may be advantageous.

Control of White Grubs in Turf Using Carbaryl Formulations, 1995

Abstract This test was conducted in turf-type tall fescue at the University of Kentucky Spindletop Farm, near Lexington. The turf was on a Maury silt loam soil (pH = 6.4) with negligible thatch. Plots (4 X 6 ft: 2 ft untreated borders) were arranged in a RCB with 4 replications. The turf was treated on 17 Aug, after egg hatch of JB and SMC. At that time, the population consisted mostly of 1 st and 2nd instars. Granular formulations were preweighed, mixed with dry sand, and applied evenly to the plots by gloved hand. Liquid applications were applied at a volume of 50 gal/acre using a low volume, CO2 sprayer equipped with 4 Spraying System 8004 Tee Jet nozzles that delivered 2109 g pressure per cm2. Each plot was syringed with about 1/8 inch of water within 5 min after application, and the whole site received about 3/4 inch of irrigation as soon as the last treatment was applied. Conditions at the time of treatment were 90°F with winds &amp;lt; 10 mph. The most recent precipitation before the treatment date was on 10 Aug, when 1.70 inches of rain fell. There was 0.44 and 0.17 inch of rain on the 18th and 19th of August, respectively; i.e., 1 and 2 DAT. Plots were sampled on 16 Sep. A motorized sod cutter was used to cut a 3 X 1.5 ft strip, about 3 inches deep, from the center of each plot. The sod was rolled back, broken apart, and all grubs were identified and counted.

Control of White Grubs with Halofenozide (RH 0345) and Imidacloprid (MERIT), 1996

Abstract This test was conducted on mature, low-maintenance Kentucky bluegrass turf at the University of Kentucky Spindletop Farm, near Lexington. The turf was on a Maury silt loam soil (pH = 6.4) with negligible thatch. Plots (6X6 ft) were arranged in a RCB design with 4 replicates. The turf was treated on 29 Aug, when soil populations consisted of primarily 2nd instars, with some 3rd instars. Conditions during application were 84°F with winds &amp;lt; 10 mph. The whole site received ½ inch irrigation as soon as the last treatment was applied. There was no additional water on the site until 7 Sept, when it rained 0.82 inch. Granular formulations were preweighed, mixed with dry sand, and applied by gloved hand. Plots were sampled on 17 Sep by cutting a 3 X 1.5 foot strip, about 3 inches deep, from the center of each plot with a motorized sod cutter. Sod was rolled back, broken apart, and examined for grubs which were counted and identified.

Effects of Timing on Efficacy of Halofenozide (RH034S) and Imidacloprid (Merit) Against White Grubs, 1996

Abstract This test was conducted on mature, low-maintenance Kentucky bluegrass turf at the University of Kentucky Spindletop Farm, near Lexington. The turf was on a Maury silt loam soil (Ph = 6.4) with negligible thatch. Plots (6 X 6 ft) were arranged in a RCB design with 4 replicates. Treatments were applied once a month in Jun, Jul, and Aug. Granular formulations were preweighed, mixed with dry sand, and applied by gloved hand. Liquid applications were applied at 50 gpa using a low volume, CO2 sprayer equipped with 4 Spraying System 8004 Tee Jet nozzles that delivered 2109 g pressure per cm2. The whole site received 1/2 inch irrigation as soon as the last treatment was applied. Conditions during application were 85, 86 and 89°F, respectively, with winds &amp;lt; 10 mph for all applications. The site received natural rainfall between treatments as well as post-treatment irrigation after all applications. Plots were sampled on 17 Sep by cutting a 3 X 1.5 foot strip, about 3 inches deep, from the center of each plot with a motorized sod cutter. Sod was rolled back, broken apart, and examined for grubs which were counted and identified.

Irrigation Effects on Efficacy of Halofenozide (RH 0345) Against White Grubs, 1995

Abstract This test was conducted in turf-type tall fescue at the University of Kentucky Spindletop Farm, near Lexington. The turf was on a Maury silt loam soil (pH = 6.4) with negligible thatch. Plots (4X6 ft; 2 ft untreated borders) were arranged in a RCB with 4 replications. Plots that received post-treatment irrigation were treated on 27 Jul, during flight of JB. The population in the soil consisted mostly of eggs, with some 1st instars. Granular formulations were preweighed, mixed with dry sand, and applied evenly to the plots by gloved hand. Liquid applications were applied at 50 gpa using a low volume, CO2 sprayer equipped with 4 Spraying System 8004 Tee Jet nozzles that delivered 2109 g pressure per cm2. Treated and untreated check plots were syringed with 1/8 inch of water within 5 min after application, and the whole site received 3/4 inch of irrigation as the last treatment was applied. Conditions at the time of treatment on 27 Jul were 88°F with winds &amp;lt; 10 mph. The non-irrigated plots were treated in the same manner on 31 Jul, except that no syringing or post-treatment irrigation was applied. Conditions at the time of treatment were 92°F, with negligible wind. There was 0.23 inch of rain on 26 Jul, the day before the irrigated plots were treated. There was no additional rain until 1.78 inch fell on 5 Aug. All plots were sampled on 14 Sep. A motorized sod cutter was used to cut a 3 X 1.5 ft strip, about 3” deep, from the center of each plot. The sod was rolled back, broken apart, and all grubs were identified and counted.

Control of Japanese Beetle and Masked Chafer Grubs with Halofenozide (RH-0345), 1995

Abstract This test was con ducted in turf-type tall fescue at the University of Kentucky Spindletop Farm, near Lexington. The turf was on a Maury silt loam soil (pH = 6.4) with negligible thatch. Plots (4X6 ft; 2 ft untreated borders) were arranged in a RCB, with 4 replications. The turf was treated on 27 Jul, during flight of JB. The soil population consisted mostly of eggs, with some 1st instars. Granular formulations were preweighed, mixed with dry sand, and applied by gloved hand. Liquid applications were applied at 50 gal/acre using a low volume, CO2 sprayer equipped with 4 Spraying System 8004 Tee Jet nozzles that delivered 2109 g pressure per cm2. Each plot was syringed with about 1/8 inch of water within 5 min after application, and the whole site received 3/4 inch irrigation as soon as the last treatment was applied. Conditions during application were 88°F with winds &amp;lt; 10 mph. There was 0.23 inch of rainfall on 26 Jul. the day before the test. There was no additional rain until 5 Aug, when 1.78 inch fell. Plots were sampled on 12 Sep by cutting a 3 X 1.5 foot strip, aboul 3 inches deep, from the center of each plot with a motorized sod cutter. Sod was rolled back, broken apart, and examined for grubs which were counted and identified.

Control of White Grubs with Halofenozide (RH-0345), 1995

Abstract This test was conducted in turf-type tall fescue at the University of Kentucky Spindletop Farm, near Lexington. The turf was on a Maury silt loam soil (pH = 6.4) with negligible thatch. Plots (4X6 ft; 2 ft untreated borders) were arranged in a RCB, with 4 replications. The turf was treated on 27 Jul, during flight of JB. The soil population consisted mostly of eggs, with some 1 st instars. Granular formulations were preweighed, mixed with dry sand, and applied by gloved hand. Liquid applications were applied at 50 gal/acre using a low volume, CO2 sprayer equipped with 4 Spraying System 8004 Tee Jet nozzles that delivered 2109 g pressure per cm2. Each plot was syringed with about 1/8 inch of water within 5 min after application, and the whole site received 3/4 inch irrigation as soon as the last treatment was applied. Conditions during application were 88°F with winds &amp;lt; 10 mph. There was 0.23 inch of rainfall on 26 Jul, the day before the test. There was no additional rain until 5 Aug, when 1.78 inch fell. Plots were sampled on 14 Sep. A 3 X 1.5 ft strip, about 3” deep, was cut from the center of each plot with a motorized sod cutter. The sod was rolled back and broken apart, and all grubs present were counted and identified.

Efficacy of Various Insecticides for Control of White Grubs, 1995

Abstract This test was conducted in turf-type tall fescue at the University of Kentucky Spindletop Farm, near Lexington. The turf was on a Maury silt loam soil (pH = 6.4) with negligible thatch. Plots (4X6 ft; 2 ft untreated borders) were arranged in a RCB, with 4 replications. The turf was treated on 27 Jul, during flight of JB. The soil population consisted mostly of eggs, with some 1st instars. Granular formulations were preweighed, mixed with dry sand, and applied by gloved hand. Liquid applications were applied at 50 gal/acre using a low volume, CO2 sprayer equipped with 4 Spraying System 8004 Tee Jet nozzles that delivered 2109 g pressure per cm2. Each plot was syringed with about 1/8 inch of water within 5 min after application, and the whole site received 3/4 inch irrigation as soon as the last treatment was applied. Conditions during application were 88°F with winds &amp;lt; 10 mph. There was 0.23 inch of rainfall on 26 Jul, the day before the test. There was no additional rain until 5 Aug, when 1.78 inch fell. The curative application of Dylox 6.2G was made on 17 Aug, with 3/4 inch of irrigation immediately after treatment. All plots were sampled on 16 Sep. A motorized sod cutter was used to cut a 3 X 1.5 ft strip, about 3 inches deep, from the center of each plot. The sod was rolled back, broken apart, and examined for grubs, which were counted and identified.

Amount and Quality of Chicory Herbage Ingested by Grazing Cattle

Ingestive behavior of cattle (Bos taurus L.) grazing chicory (Cichorium intybus L.) has not been elucidated. Adult Angus cows were utilized to measure ingestive behavior over a range of allowances (2.53–5.17 kg cow−1 h−1) on vegetative chicory (cv. Grasslands Puna) growing on a Maury silt loam (fine, mixed, mesic, Typic Paleudalf) soil. A change‐over design employing difference procedures was used with tethered animals to evaluate allowance effects on forage quality of available, consumed and residual herbage as well as rate of biting and dry matter intake. Pre‐ and post‐grazing herbage mass and quality were determined in three 10‐cm strata above a 5‐cm stubble. Cattle consumed about 66% of the available herbage at each allowance level during a 1‐h grazing meal. In vitro dry matter disappearance (IVDMD) ranged from 719 to 746 g kg−1 across the three canopy strata prior to and after grazing. Nitrogen concentration increased from 26 to 47 g kg−1 from the lower to upper canopy stratum. Herbage intake rate increased from 1.7 kg h−1 at the lowest allowance to 3.6 kg h‐~ at the highest, in response to a linear increase in intake per bite. Biting rate was unaffected by herbage allowance. High dry matter intake per feeding station and a relatively low number of feeding stations visited per meal suggest that chicory was not grazed in distinct horizons. Together with high intake rates, the high and uniform quality of chicory canopies indicate that this species could be useful for livestock having high nutrient and dry matter intake requirements.

Corn Yield Response to Cover Crops and N Rates Under Long-Term Conventional and No-Tillage Management

ABSTRACT A more sustainable agroecosystem may be obtained by combining cover crops with conservation tillage in grain crop production systems. This study was conducted in 1993 and 1994 on a Maury silt loam (Typic Paleudalfs) soil, at Lexington, Kentucky. The objectives were to evaluate: the effects of hairy vetch (Viciavillosa Roth) and rye (Secale cereale L.) cover crop on corn (Zeamays L.) yields under no-tillage (NT) and conventional tillage (CT) management; corn yield response to N fertilizer rates under different cover crops and tillage systems; and the effects of two cover crops on selected soil chemical properties. The results showed that corn grain yields were significantly higher under hairy vetch cover crop than under rye cover crop, 7.73 and 7.08 Mg ha−1, respectively. At least 40 to 60 kg ha −1 more N was estimated to have been added to the agroecosystem by hairy vetch as compared to rye cover crop. Higher corn yields under NT, 7.62 Mg ha −1 as compared to 7.18 Mg ha−1 for CT, indicated a more...

Soluble calcium fertilizer effects on early growth and nutrition of burley tobacco

Abstract During production of burley tobacco (Nicotiana tabacum L.), initial soil pH needs to be 6.6 in order to maintain pH at midseason in the range of 5.8 to 6.2 to control manganese (Mn) toxicity, molybdenum (Mo) deficiency, and to enhance overall nutrient availability in soil. A field experiment was conducted at Lexington, Kentucky, during 2 years to determine the effects of rate of soluble calcium (Ca) (as gypsum‐CaSO4) on early growth and chemical composition of burley tobacco. On Maury silt loam soil (Typic Paleudalf; pH 6.6), plant dry weight and concentrations of potassium (K), Ca, and magnesium (Mg) 40 days after transplanting increased with rate of Ca fertilization up to 380 kg Ca/ha. Further increases in Ca fertilization decreased dry weight and K but had no effect on plant Ca or Mg concentrations. Generally, the effect of Ca on growth and nutrient accumulation was greatest in the presence of supplemental irrigation, K fertilization, and use of a nitrate (NO3) source of N. Plant Ca concentrat...

Effect of strip band and in‐row placement of phosphorus and potassium fertilizer on growth, yield, and efficiency of potassium use by burley tobacco

Abstract A replicated field experiment was conducted at Lexington, Kentucky on Maury silt loam soil (Typic Paleudalf) using burley tobacco (Nicotiana tabacum L. cv. KY 14). The purpose of the study was to determine the response of burley to placement (banding) of N‐P‐K fertilizer in or near the row. The experimental soil used tested low in potassium (K). Treatments consisted of various application rates of grade 6–24–32 (N‐P2O5‐K2O) fertilizer applied either broadcast, in 40 cm wide bands directly under and parallel to the row, in 10 cm wide bands applied 50 cm apart and perpendicular to rows, or in two drill bands each 10 cm to the side of the row. Additional nitrogen fertilizer (NH4NO3) was applied to all plots to provide a uniform rate of 265 kg N/ha. Results indicated that plant response increased as rate of 6–24–32 fertilizer increased and response was greater in all band treatments than the broadcast control. As contrasted to broadcast applications, in‐row placement of fertilizer in 40‐cm wide bands...

Micromorphological Characteristics of Long‐Term No‐Till and Conventionally Tilled Soils

AbstractConservation tillage practices have been shown to affect a number of soil physical properties, but less is known about their effect on the size, shape, and arrangement of soil constituents. To evaluate soil structural differences between tillage treatments, six paired conventionally tilled and no‐tilled plots of Maury silt loam soil (fine, mixed, mesic Typic Paleudalf) were analyzed. Oriented undisturbed samples (16 by 9.5 by 5.5 cm) were taken from each plot at depths of 0 to 5, 10 to 15, and 20 to 25 cm. The samples were impregnated with polyester resin and two vertical thin sections were prepared from each sample. The micromorphic features were described, and the size (equivalent spherical diameter), shape, and orientation of pores and aggregates were measured using an interactive image analysis system. The no‐tilled plots had platy structure near the surface and interconnection of fine pores (50–100 µm) throughout the profile. Eartbworm channels with excrement infillings were abundant in the no‐till plots at all depths, but absent in conventionally tilled plots. The conventionally‐tilled soil was composed of granular and fragmented structural units with no evidence of earthworm activity. The no‐till plots contained about 11% pore area &gt;50 µm, compared with about 16% for conventional tillage management. However, the no‐till plots have an average pore size (0.18–0.26‐mm diam.) that is greater than the conventionally tilled plots (0.12–0.17‐mm diam.). The finer aggregate size of the conventionally tilled plots (0.25–0.39‐mm diam.) compared with the no‐till plots (0.41–1.08‐mm diam.) is probably due to plowing and disking.

Control of Green June Beetle Grubs During Egg Hatch Resolves Problem of Grubs Dying on Turf Surface, 1993

Abstract This study was conducted in a mature, low-maintenance stand of Kentucky bluegrass in Lexington, KY. The turf was on a Maury silt loam soil (fine-silty, mixed, mesic Typic Paleudalf)- Thatch accumulation was negligible. Plots (10 × 10 ft) were established in a RCB with five replications. There were 2 ft untreated boundaries between plots. The turf was mown weekly to 3 inch height, with the clippings left on the plot surface. Treatments were applied 28 Jul, about 2 wk after peak adult flight activity. Conditions at the time of treatment were sunny, 92°F, with 5-10 mph winds. Granular treatments were diluted with dry sand and applied to the plots by gloved hand. The wettable powder formulation was mixed with water and applied with a Solo backback sprayer using 1 gal of spray per plot. All treatments were immediately irrigated with 0.25 inch of water, using a water truck and hose with a shower-type nozzle. The grub population at the time of treatment consisted of eggs and first instars. Effectiveness of treatments was assessed 61-62 DAT using an insecticide flush method. Triumph 4E (isazophos) was applied at the labeled rate (2 lb (AI)/acre) on 27 Sep, using a Solo backback sprayer that delivered 0.5 gal spray/plot. The flush spray was immediately syringed with 0.25 inch of water as before. Grub populations were assessed at dawn of the following 2 d. A frame (3.3 × 3.3 ft) made from PVC pipe was placed in the center of each plot, and dead green June beetle grubs within the sample area were counted and removed. Counts for the two samples were pooled and analyzed by ANOVA followed by Fisher’s protected LSD to separate treatment means.

Reducing Soil Erosion and Agricultural Chemical Losses with Conservation Tillage

AbstractAs nonpoint source pollution of water becomes more evident, more concern is being focused on the effects of agricultural practices on water quality. This study evaluated the effects of conventional tillage (CT), chisel‐plow tillage (CP), and no tillage (NT) on the quality of runoff water from a Maury silt loam soil (fine, mixed, mesic Typic Paleudalf) near Lexington, KY. The mean runoff rate, total runoff volume, mean sediment concentration, and total soil losses were significantly less for NT than for CP and CT. Concentration of NO−3, NH+3, and PO3−4 in the runoff water from NT were greater than from CP or CT. Concentration of atrazine [6‐chloro‐N‐ethyl‐N′‐(I‐methylethyl)‐1,3, 5‐triazine‐2,4‐diamine] in the runoff water tended to be higher from CP than from NT or CT. Total losses of NO−3, NH+4, PO3−4, and atrazine in runoff water were generally in the order CT &gt; CP &gt; NT. The sum of all chemicals lost was less than 3% of the total amount of each applied.

Ontrol of Japanese Beetle and Southern Masked Chafer Grubs, 1992

Abstract CThis study was conducted in a 2-yr old stand of tall fescue at Elkhorn Springs Sod Farm, near Frankfort, KY. The turf was on a Maury silt loam soil (fine-silty, mixed, mesic Typic Paleudalf). Soil texture was 23% clay, 74% silt, and 3% sand, with 8.8% organic matter and pH = 6.4 Thatch accumulation was negligible. Plots (7 x 10 ft) were established in a RCB with five replications, with 2 ft untreated boundaries between plots. The turf was mown to 3" height before treatment, with the clippings raked and removed. Treatments were applied on 18 Aug. Liquid formulations were applied with a high pressure CO2 sprayer that delivered 2 gal of spray per 1000 ft2. Granular treatments were diluted with dry sand and applied to the plots by gloved hand. Nematode treatments were applied last, after which all plots were irrigated with about 0.5 inch of water, beginning 5-10 min after the final treatment was applied. Conditions at the time of application were sunny, 78°F, 57% relative humidity, and 5 mph winds. The soil was moist due to the 0.45 of rain that had fallen in the previous 4 d. The grub population at the time of treatment consisted of a mixture of 2nd and 3rd instars of each species. Treatment effectiveness was assessed 29-30 DAT by cutting a strip (25 X 18 inches, 2.5 inches deep) from the center of each plot with a motorized sod cutter. The sod strips were broken apart and examined for living grubs in the field. Data were analyzed by ANOVA followed by Fisher's protected LSD test to separate treatment means.

EFFECT OF DITHIOPYR, SEED PLACEMENT. AND SOIL ORGANIC MATTER CONTENT ON GROWTH OF TOLERANT AND SUSCEPTIBLE WEEDS

Dithiopyr (Dimension, Monsanto) is a turfgrass herbicide currently under evaluation for use in ornamentals. Granular herbicide depth and seed placement were evaluated in greenhouse studies with tolerant or susceptible weeds. Dithiopyr was applied preemergence to weeds at the rate of 2.24 kg/ha to Maury silt loam soil. Weed seeds were planted routinely at 0.64 cm depth. Dithiopyr placed at the soil surface or 0.64 cm in depth caused the greatest injury to seedlings, followed by dithiopyr at 1.28 cm depth. Dithiopyr at 2.54 and 3.81 cm below the surface had no effect upon seedling growth. When seeding depth was investigated, seed placed at 0.64, 1.28 or 1.91 cm below the surface showed greatest seedling injury when dithiopyr was routinely applied at 0.64 cm depth. Seed placement on the soil surface resulted in the least injury to weeds. Peat moss was added to Maury silt loam soil and to sand to investigate the influence of organic matter upon activity. Soil with 2% peat resulted in the least injury to selected weed seedlings while sand, and sand plus up to 3% peat showed greatest injury. Sand amended with 5 and 6% peat also resulted in less injury to weed seedlings. Ivy leaf morningglory and KY 31 fescue were most tolerant of dithiopyr while barnyardgrass and large crabgrass were most sensitive. Dithiopyr uptake, translocation and metabolism studies will be conducted with susceptible and tolerant weed and woody ornamental species.