Increasing Warm-Season Native Grass Biomass Using Fire, Herbicide, and Nitrogen Applications

The North American Great Plains tallgrass prairie was once a system of native cool and warm season grasses, which have been degraded by non-native invasive plants. Native grass restoration is highly desirable to improve ecosystem functions and productivity. In this two-year study, the impact of fire, herbicide, and nitrogen on productivity and the presence of invasive species [primarily the cool season grass, smooth brome (Bromus inermis Leyss.)] and native warm season native grass species [big bluestem (Andropogon gerardii Vitman), sideoats and blue grama (Bouteloua curtipendula (Michx.) Torr.), and B. gracilis (Willd. Ex Kunth) Lag. ex Griffiths] were investigated. Spring fire or a glyphosate application increased warm season grass biomass and decreased cool season grass biomass at peak warm season growth (August) during the treatment year. A second consecutive year of fire or herbicide further increased warm season grass biomass. If left untreated in the second year, cool season grasses tended to increase when sampled in August. Long-term management implementation is needed to suppress the tenacious cool season species and encourage the reestablishment of warm season grass populations

Transport of Agrichemicals by Wind Eroded Sediments to Nontarget Areas

Water and wind erosion are the primary mechanisms by which surface soil is removed from agricultural fields. Wind erosion accounts for as much or more soil loss (tons/acre/year) than does water erosion. Sediments moved by wind may carry agrichemicals from agricultural fields to nontarget areas. Nontarget areas may include road ditches, shelterbelts, and waterways. The objective of this study was to determine if agrichemical movement via wind blown sediment is a potential pollutant of surface and/or groundwater. Samples of sediment that had been deposited in ditches on top of snow were collected during winters of 1994 and 1995 near or around Brookings, SD. Soil samples from adjacent fields (top 1 inch) were also collected. Soil and sediment samples were extracted and alachlor, atrazine, and atrazine metabolites, desethylatrazine and desisopropylatrazine were quantified. Alachlor was detected in about 30% of soil and sediment samples in both years with an average concentration of 2.2 ppb in soil and 5.44 ppb in sediment in 1995. In 1994, atrazine, desethylatrazine, and desisopropylatrazine were detected in 70%, 100%, and 50% of the sediment samples and 70%, 90%, and 60% of the soil samples, respectively. In 1995, atrazine, desethylatrazine, and desisopropylatrazine were detected in 73%, 27%, and 9% of the sediment samples at average concentrations of 8.9, 0.89, and 56.4 ppb, respectively. Atrazine, desethylatrazine, and desisopropylatrazine were detected in 70%, 40%, and 10% of the soil samples in 1995 at average concentrations of 11.9, 2.0, and 0.9 ppb, respectively. Herbicides were detected in most of the sediment samples. This suggests that wind erosion may be a transport mechanism by which herbicides are deposited into nontarget areas

The Influence of Biochar Production on Herbicide Sorption Characteristics

Biochar is the by-product of a thermal process conducted under low oxygen or oxygen-free conditions (pyrolysis) to convert vegetative biomass to biofuel (Jha et al., 2010). There are a wide variety of end-products that can be manufactured depending on processing parameters and initial feedstocks (Bridgewater, 2003). The pyrolytic process parameters such as temperature, heating rate, and pressure can change the recovery amounts of each end-product, energy values of the bio-oils, and the physico-chemical properties of biochar (Yaman, 2004)

Adsorption and Desorption of Atrazine, Hydroxyatrazine, and S-Glutathione Atrazine on Two Soils

Adsorption and desorption isotherms for atrazine and two metabolites, hydroxyatrazine (HA) and S-glutathione atrazine (GSHA), were determined by batch equilibration on Plano and Waukegan silt loam soils at two soil pH levels (Plano, 6.1 and 4.5; Waukegan, 6.1 and 4.0). Freundlich adsorption isotherms were not affected by soil type except for GSHA at pH 4.0 to 4.5. When averaged over both soils, the order of adsorption at pH 6.1 was atrazine (Kf = 3.7) \u3c GSHA (Kf = 7.3) \u3c\u3c HA (Kf = 25) and at pH 4.0–4.5 was atrazine (Kf = 6.1) \u3c\u3c HA (Kf = 58) ≤ GSHA (Kf: Plano = 35; Waukegan = 78). The average slope of the adsorption isotherms (1/nads) was 0.81. The slopes of all desorption isotherms (1/ndes) were less than their respective 1/nads, indicating hysteresis. Atrazine desorbed into soil solution (1/ndes \u3e 0.0). With the exception of GSHA which desorbed from the pH 6.1 Plano silt loam (1/ndes = 0.15), desorption of HA and GSHA from other treatments was negligible (1/ndes = 0.0). Consequently, leaching of HA and GSHA in these and similar soils is not likely, due to high adsorption and low desorption

Characterization of Alachlor and Atrazine Desorption from Soils

Herbicide desorption isotherms may be affected by the amount of nondesorbable herbicide present in soil. Nondesorbable alachlor (as determined after methanol extraction) generally increased on a Waukegan silt loam (Typic Hapludolls) and a Ves clay loam (Udic Haplustolls) during five 0.01 M CaCl₂ desorptions. Atrazine was totally extracted with methanol from the Waukegan soil after one desorption using 0.01 M CaCl₂. However, after five desorptions with 0.01 M CaCl₂ an average of 5.5 and 15.5% of the total recovered atrazine from two atrazine application rates was methanol nondesorbable from the Waukegan and Ves soils, respectively. Freundlich desorption isotherms adjusted for nondesorbable herbicide accounted for as much as 71% of the difference between adsorption and desorption isotherms. Only a portion of the hysteresis observed can be attributable to nondesorbable herbicide

Leafy Spurge - A Review

Leafy spurge (Euphorbia esula L.) is a perennial herbaceous weed that infests millions of acres of range and pasture in the northern Great Plains. It outcompetes grasses and lowers land productivity because cattle will not graze infested areas even if spurge makes up only 10% of the vegetative biomass. This presentation will cover the history, taxonomy, and phenology of leafy spurge. A discussion of chemical, mechanical, and biocontrol techniques that aid in leafy spurge management will also be included

Reproduction of Soybean Cyst Nematode Populations on Field Pennycress, Henbit, and Purple Deadnettle Weed Hosts

Several weeds serve as alternative soybean cyst nematode (SCN) hosts. Still, the relative reproductive capacity of SCN HG types (Heterodera glycines type) on weed hosts relative to soybean is not well understood. This study examined the reproduction of three South Dakota endemic SCN populations—PSCN-1 (HG 0), PSCN-2 (HG 2.5.7), and PSCN-3 (HG 7)—on purple deadnettle, field pennycress, and henbit. The Relative Female Index (RFI) was calculated to compare SCN reproduction relative to the susceptible soybean check. Weed hosts, HG types, and their interactions influenced SCN reproduction. Henbit (RFI = 51.8) and purple deadnettle (RFI = 47.6) roots had a similar high RFI, whereas field pennycress (RFI = 23.04) had a lower RFI. Similarly, SCN populations PSCN-1 and PSCN-3 had a similar RFI of 36.9 and 37.2, respectively, while the population PSCN-2 had a higher RFI of 44.9 across weed hosts. A significant interaction between PSCN-1 and purple deadnettle was observed where the RFI was the highest (RFI = 53.3). These results indicate that these weed hosts support endemic SCN populations, and the HG type influenced reproductive success, further complicating SCN management. Hence, SCN presents a significant challenge in the new prospect of incorporating field pennycress host as an oilseed cover crop in the Midwest’s corn–soybean production system

Imapct of Biochar Application on Soil Properties and Herbacide Sorption

Biochars are the byproduct of anaerobic combustion (pyrolysis) of organic materials. Three biochars (switchgrass, cornstover, and Ponderosa pine woodchip) were created by burning the materials under anaerobic conditions for four hours at maximum temperatures of 850 o C (fast pyrolysis). Biochar samples were sorted by size (\u3c 2 mm, 2-4 mm, and \u3e 4 mm) and electrical conductivity (EC) and pH characteristics were determined in 1:5 (w/v) water and 0.01M CaCl2 . Each biochar type and size was added at 1 and 10% (w/w), to two South Dakota soils, Barnes (loamy) or Maddock (loamy fine sand). Atrazine sorption and changes in soil pH and EC were measured in slurry experiments (1:2 w/v). Biochar pH values were higher than soil pH values; however, the addition of biochar had minimal influence on soil pH. Biochar size affected soil EC values; the smallest sized chars at the 10% addition increased the soil EC. Atrazine sorption from solution increased from about 35% in soil only to almost 99% with each biochar treatment. Targeted biochar addition to soil may be warranted. If atrazine carryover is suspected, addition of biochar may reduce unwanted affects; however, higher sorption may require higher application rates to provide weed control similar to that of nonamended soil

Mob vs. Rotational Grazing: Impact on Forage Use and Artemisia absinthium

Short duration (≤24 h), high stocking density grazing systems (e.g., mob grazing) mimics historic prairie grazing patterns of American bison (Bison bison), and should minimize selective grazing. We compared mob [125 cow-calf pairs on either 0.65 ha for 12 h; or 1.3 ha for 24 h] vs. rotational [25 cow-calf pairs on 8.1 ha for 20 days starting in mid-May with or without 2,4-D application prior to grazing; and 15 days starting mid-April (no herbicide)] grazing systems based on forage utilization and impact to Artemisia absinthium (absinth wormwood) in a tall grass pasture of Eastern South Dakota. Grass height and density, and Artemisia absinthium patch volume were quantified pre- and post-grazing at sampling points along multiple transects. Mob grazing had >75% forage utilization, whereas rotational grazing averaged 50% (all consumption). Within a grazing season, three grazing systems suppressed Artemisia absinthium patches with rotation/spray (100% decrease) > mob (65 ± 10% decrease) > mid-May rotation (41 ± 16% decrease), whereas Artemisia absinthium patches in the mid-April rotation followed by summer rest dramatically increased in size. Artemisia absinthium patches <19,000 cm3 were browsed, whereas larger patches were trampled in mob-grazed areas, but avoided in rotational grazing. All Artemisia absinthium patches had regrowth the year following any grazing event

Alachlor Movement Through Intact Soil Columns Taken From Two Tillage Systems

Intact soil columns were evaluated as a screening technique to determine the effect of tillage on herbicide movement through soil. Alachlor was applied at 3.3 kg ai ha-1 to intact surface 0- to 10-cm and subsurface 10- to 20-cm soil columns (15-cm diam) taken from long-term no-till and conventional tillage plots and leached with 11.6 pore volumes (7 L; 39 cm) of water at a rate that did not create ponding. Leachate was collected in 0.07 pore volume fractions. Twice as much alachlor leached from surface no-till than from surface conventional tillage columns. The differences in leaching patterns from the surface soil can be attributed to the effect of tillage on soil physical and chemical properties. Using intact soil columns in the laboratory can be a useful rapid screening technique to evaluate tillage impacts on herbicide movement