Network


Latest external collaboration on country level. Dive into details by clicking on the dots.

Hotspot


Dive into the research topics where John A. Guretzky is active.

Publication


Featured researches published by John A. Guretzky.


Ecological Applications | 1997

EVIDENCE FOR NATURAL BIOLOGICAL CONTROL: INSECTS DECREASE SURVIVAL AND GROWTH OF A NATIVE THISTLE

John A. Guretzky; Svat̂a M. Louda

Native thistles, in contrast to exotic species, are seldom noxious weeds. In this study, we evaluated one hypothesis for this difference: that the growth and fitness of native thistles are limited by natural enemies. Specifically, we tested the effect of insect foliage feeding on the survival and growth of large and small rosettes of tall thistle, Cirsium altissimum, using an insecticide exclusion experiment. Large juveniles were proportionally more damaged than were small ones. Insecticide reduced insect feeding, including overall intensity of plant damage and area removed or damaged on each of the two longest leaves, compared to controls treated only with water. As a result, both leaf growth and plant size increased significantly by the end of the growing season. Growth parameters showing major increases with the reduction in insect herbivory included upper rootcrown diameter, the total number of leaves, and the length of the two longest leaves on both large and small rosettes. Insecticide also reduced the mortality of large juveniles to half that of the controls. Thus, the study shows that the suite of naturally occurring, coevolved, foliage-feeding insects significantly reduces the growth and survival of rosettes of this native thistle under field conditions. The results provide strong support for the hypothesis underlying biological control of weeds programs.


Communications in Soil Science and Plant Analysis | 2011

Effect of Nitrogen Fertilizer Rate and Harvest Season on Forage Yield, Quality, and Macronutrient Concentrations in Midland Bermuda grass

Maru K. Kering; John A. Guretzky; Eddie Funderburg; Jagadeesh Mosali

Bermuda grass [Cynodon dactylon (L.) Pers.] is a major forage for grazing and hay production in the southern United States. The objectives of this study were to determine effects of nitrogen (N) fertilization rate (0, 112, 224, 336, and 448 kg ha−1), split spring and summer applications of N at the 224 and 448 kg ha−1 rates, and harvest periods (spring and summer) on forage yield, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), total digestible nutrients (TDN), and concentrations of phosphorus (P), potassium (K), magnesium (Mg), and calcium (Ca in Midland Bermuda grass. Data were collected from 2002 to 2008 as part of an ongoing, long-term soil fertility experiment in southern Oklahoma. Repeated measures analysis of these long-term data showed that forage yield responses to N rate varied with year and harvest time with up to 2.5-fold yield differences among years. Nitrogen fertilization increased CP, TDN, and macronutrient P and Mg and decreased ADF and NDF. Crude protein was increased by ≥50%, and ADF and NDF dropped by up to 25% with the greatest N rate. In general, split N applications did not affect forage yield but produced low-quality forage compared to single N application in spring. Split application of 448 kg N ha−1 gave forage with CP, TDN, ADF, and NDF similar to the Bermuda grass receiving 336 or 448 kg N ha−1 as a single application. Spring forage had better forage quality than summer harvests. While N fertilization increased forage Mg and P concentrations by more than 50% during both spring and summer, it had no effect or slight increased K and Ca concentrations. In the southern Great Plains, despite the weather-dependent variability in forage yield of Bermuda grass, N application increase forage quality.


Journal of Plant Nutrition | 2010

Fertilizer Rate Effects on Forage Yield Stability and Nutrient Uptake of Midland Bermudagrass

John A. Guretzky; Maru K. Kering; Jagadeesh Mosali; Eddie Funderburg; Jon T. Biermacher

Our objectives were to document effects of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates on forage yields and uptake of N, P, and K by Midland bermudagrass [Cynodon dactylon (L.) Pers.] on a Minco fine, sandy loam in southern Oklahoma. After six years of this long-term experiment, forage yield responses to fertilization were mixed and depended on year. Stability analysis indicated forage yields responded positively to N fertilization during favorable weather conditions but negatively during poor weather conditions. Application of 112 kg N ha−1 provided the best yield stability and mean annual forage yield among treatments, 11.5 Mg ha−1, across years. In years with near-average weather conditions, uptake of N, P, and K increased linearly with N application rate. Limited water holding capacity of the soil and high soil P and K may have contributed to the limited yield responses to fertilization in this semi-arid environment.


Forage and Grazinglands | 2008

Nitrogen Fertilizer Rate and Weather Dictate Nutritive Value of Fall Stockpiled Bermudagrass

John A. Guretzky; Jeff Ball; Billy Cook

Stockpiled bermudagrass [Cynodon dactylon (L.) Pers. ‘Midland’] as a standing forage may meet nutritional needs of beef cows during winter. Our objective was to evaluate accumulation and nutritive value of fall stockpiled bermudagrass in response to N fertilization rate, N application date, and harvest date. Research was conducted near Burneyville, OK from 2000 to 2003. Fertilization rates included 0, 50, 100, and 150 lb N per acre applied on 15 August, 1 September, 15 September, 1 October, and 15 October. Forage accumulation was measured 10 days after the first killing frost; thereafter, crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), and total digestible nutrients (TDN) were assessed biweekly from 6 December to 20 February. An exceptionally hot and dry summer resulted in negligible forage production and unrepresentative forage quality in 2000. Forage accumulated linearly in 2001 and 2002 and quadratically in 2003 with N fertilization rate (P ≤ 0.05). The dry matter averaged 56% TDN and 6.0, 6.9, 7.9, and 8.7% CP when N was applied at 0, 50, 100, and 150 lb/acre, respectively. The fertilized bermudagrass stands would have met CP and TDN requirements of mid-gestation beef cows had they been maintained on this forage.


Journal of Environmental Quality | 2015

Patch burning: implications on water erosion and soil properties.

Altıngül Özaslan Parlak; Mehmet Parlak; Humberto Blanco-Canqui; Walter H. Schacht; John A. Guretzky; Martha Mamo

Patch burning can be a potential management tool to create grassland heterogeneity and enhance forage productivity and plant biodiversity, but its impacts on soil and environment have not been widely documented. In summer 2013, we studied the effect of time after patch burning (4 mo after burning [recently burned patches], 16 mo after burning [older burned patches], and unburned patches [control]) on vegetative cover, water erosion, and soil properties on a patch-burn experiment established in 2011 on a Yutan silty clay loam near Mead, NE. The recently burned patches had 29 ± 8.0% (mean ± SD) more bare ground, 21 ± 1.4% less canopy cover, and 40 ± 11% less litter cover than older burned and unburned patches. Bare ground and canopy cover did not differ between the older burned and unburned patches, indicating that vegetation recovered. Runoff depth from the older burned and recently burned patches was 2.8 times (19.6 ± 4.1 vs. 7.1 ± 3.0 mm [mean ± SD]) greater than the unburned patches. The recently burned patches had 4.5 times greater sediment loss (293 ± 89 vs. 65 ± 56 g m) and 3.8 times greater sediment-associated organic C loss (9.2 ± 2.0 vs. 2.4 ± 1.9 g m) than the older burned and unburned patches. The recently burned patches had increased daytime soil temperature but no differences in soil compaction and structural properties, dissolved nutrients, soil C, and total N concentration relative to older burned and unburned patches. Overall, recently burned patches can have reduced canopy and litter cover and increased water erosion, but soil properties may not differ from older burn or unburned patches under the conditions of this study.


Plant and Soil | 2011

Switchgrass for forage and bioenergy: harvest and nitrogen rate effects on biomass yields and nutrient composition

John A. Guretzky; Jon T. Biermacher; Billy Cook; Maru K. Kering; Jagadeesh Mosali


Bioenergy Research | 2012

Biomass Yield and Nutrient Removal Rates of Perennial Grasses under Nitrogen Fertilization

Maru K. Kering; Twain J. Butler; Jon T. Biermacher; John A. Guretzky


Crop Science | 2006

Species Diversity and Functional Composition of Pastures that Vary in Landscape Position and Grazing Management

John A. Guretzky; Kenneth J. Moore; E. Charles Brummer; C. Lee Burras


Bioenergy Research | 2012

Biomass Yield and Nutrient Responses of Switchgrass to Phosphorus Application

Maru K. Kering; Jon T. Biermacher; Twain J. Butler; Jagadeesh Mosali; John A. Guretzky


Bioenergy Research | 2013

Effect of Potassium and Nitrogen Fertilizer on Switchgrass Productivity and Nutrient Removal Rates under Two Harvest Systems on a Low Potassium Soil

Maru K. Kering; Twain J. Butler; Jon T. Biermacher; Jagadeesh Mosali; John A. Guretzky

Collaboration


Dive into the John A. Guretzky's collaboration.

Top Co-Authors

Avatar

Maru K. Kering

Virginia State University

View shared research outputs
Top Co-Authors

Avatar

Walter H. Schacht

University of Nebraska–Lincoln

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Terry J. Klopfenstein

University of Nebraska–Lincoln

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Laura K. Snell

University of Nebraska–Lincoln

View shared research outputs
Top Co-Authors

Avatar

Martha Mamo

University of Nebraska–Lincoln

View shared research outputs
Top Co-Authors

Avatar
Top Co-Authors

Avatar

Andrea K. Watson

University of Nebraska–Lincoln

View shared research outputs
Researchain Logo
Decentralizing Knowledge