Atrazine and Cyanazine Interception and Retention on Crop Residue

The effect of several variables on herbicide interception and retention by crop residue was investigated. Variables considered include residue type and amount, amount of rain, time of rainfall occurrence, and herbicide formulation. Experiments were conducted in the greenhouse using corn (Zea mays), soybean (glycine max), and wheat (Triticum aestivum) residue. Simulated rainfall was applied using a modified potsprayer. Herbicide concentration in washoff water was determined using the pyridine-alkali colorimeteric technique for chloro-s-triazine herbicides. As the percent ground cover increased, the amount of herbicide reaching the soil surface at application decreased. With normal residue levels attained in South Dakota, 60% or more of the applied herbicide may be intercepted. Generally, cyanazine {2-[ [4-chloro-6- (ethylamino),1,3,5-triazin-2-yl]amino]-2- methylpropanenitrile} was more easily removed from residue with rainfall than was atrazine [6-chloro-N-ethyl-N\u27- (l-methylethyl)-1,3,5-triazine-2,4-diamine]. The wettable powder formulation of atrazine and the dry flowable formulation of cyanazine were most easily removed. Of the total applied herbicide, 50% of the atrazine and 75% of the cyanazine was removed with 25 mm of rainfall. With a 25 mm rainfall, atrazine removal decreased by 25% and cyanazine removal decreased by 8% fourteen days after application. Both cyanazine and atrazine were most easily removed from corn residue. compared to soybean or wheat residue. A theoretical model was developed f or each herbicide and formulation tested. These models can be used to predict the level of herbicide reaching the soil surface under wheat residue with various rainfall conditions

Reduced Tillage Effects on Weed Control, Soil Properties, and Dominant Weed Species in Southeastern South Dakota

In recent years, farmers have made dramatic changes in their tillage practices. The conventional plow-disk-drag system allows farmers to control weeds, remove crop residue, and prepare the soil for planting. The development of 2,4-D [(2,4-dichlorophenoxy) acetic acid] in the 1940’s and of additional herbicides since then has greatly reduced the need for tillage to control weeds. Improvements in planting equipment allow farmers to use crop residue to their benefit. Farmers using tillage systems which leave residue on the soil surface can realize savings of time, labor, and equipment together with increased moisture and soil conservation while. maintaining yields equal to conventional tillage. As tillage is decreased, several potential problems become apparent. Incorporation of fertilizer becomes more difficult nitrogen requirements may increase. Soil is slower to warm in the spring end may become more compacted without tillage to loosen the soil. Weed pressure may increase and weed species may change which reduced tillage. Crop residue can intercept herbicides applied and methods of herbicide application may have to be changed for optimum control. Crop diseases and insects may become more troublesome. An evaluation of potential benefits and problems associated with reduced tillage systems in southeastern South Dakota would be beneficial to farmers. The objectives of this research were to determine (1) whether presently available herbicides can effectively control weeds in reduced tillage systems planted in a corn-bean rotation, (2) the effect of reduced tillage systems on residual soil fertility and other soil properties, and (3) the potential for weed species shifts with reduced tillage systems in southeastern South Dakota

Detrital Zircon Provenance of Mesoproterozoic to Cambrian Arenites in the Western United States and Northwestern Mexico

U-Pb isotopic dating of detrital zircon from supracrustal Proterozoic and Cambrian arenites from the western United States and northern Mexico reveal three main age groups, 1.90 to 1.62 Ga, 1.45 to 1.40 Ga, and 1.2 to 1.0 Ga. Small amounts of zircons with ages of 3.1 to 2.5 Ga, 1.57 Ga, 1.32 Ga, 1.26 Ga, 0.7 Ga, and 0.5 Ga are also present. Detrital zircons ranging in age from 1.90 to 1.62 Ga and from 1.45 to 1.40 Ga are considered to have been derived from Proterozoic crystalline basement rocks of these known ages, and probably in part from reworked Proterozoic supracrustal sedimentary rocks, of the western United States. The 1.2 to 1.0 Ga detrital zircon ages from California, Arizona, and Sonora are characterized by distinct spikes (1.11 Ga, in particular) in the age-probability plots. These spikes are interpreted to indicate the influx of zircon from major silicic volcanic fields. Igneous rocks such as the Pikes Peak Granite (1.093 Ga) of Colorado, and the Aibo Granite (1.110 Ga) of Sonora, Mexico, may represent the deeply eroded roots of such volcanic fields. Samples from farther north along the Cordilleran margin that contain abundant 1.2–1.0 Ga detrital zircons do not show spikes in the age distribution, but rather ages spread out across the entire 1.2–1.0 Ga range. These age spectra resemble those for detrital zircons from the Grenville province, which is considered their source. Less common detrital zircons had a variety of sources. Zircons ranging in age from 3.36 to 2.31 Ga were apparently derived from inland parts of the North American continent from Wyoming to Canada. Zircons of about 1.577 Ga are highly unusual and may have had an exotic source; they may have come from Australia and been deposited in North America when Australia and North America were juxtaposed as part of the hypothetical Rodinian supercontinent. Detrital zircon of ∼1.320 Ga apparently had the same source as that for tuff (1.320 Ga) in the Pioneer Shale of the Apache Group in Arizona. Detrital zircons of about 1.26 Ga in the Apache Group and Troy Quartzite appear to be related to local, approximately coeval volcanic fields. Zircons of about 0.7 Ga may have had a source in igneous rocks related to rifting of the Proterozoic supercontinent of Rodinia, and 0.5 Ga zircons a source in relatively small areas of granitic rocks of this known, or inferred, age in Oklahoma, Texas, New Mexico, and Colorado

Mechanisms of the Age-Related Power Reduction in the Knee Extensor Muscles of Men and Women

The mechanisms for the loss in limb muscle power output in old (60-79 years) and very old adults (≥80 years) and whether these mechanisms differ between older men and women are not well-understood. The aims of the thesis are to 1) compare peak power output of the knee extensor muscles between young, old, and very old adults and 2) determine the physiological mechanisms for the age-related loss of power in men compared with women. 31 young (22.9±3.0 years, 16 men), 83 old (70.4±4.9 years, 44 men), and 16 very old adults (85.8±4.2 years, 7 men) performed maximal isokinetic contractions at 15 different velocities (0-450°/s) to identify peak power output across the torque-velocity relationship. Voluntary activation (VA) and contractile properties were assessed with transcranial magnetic stimulation and electrical stimulation of the femoral nerve. Old and very old men and women generated less power than young across all velocities (p\u3c0.01). Compared with young men (673±163 W), peak power output was ~42% lower in old (399±119 W, p \u3c0.01) and ~67% lower in very old (225±51 W, p\u3c0.01). For women, peak power output was ~49% lower in old (223±45 W, p\u3c0.01) and ~60% lower in very old (170±40 W) compared with young (428±79 W, p\u3c0.01). Factors within the muscle were the most highly associated variables with peak power for both sexes including; lean thigh tissue mass (men: R^2 =0.53, p\u3c0.01; women: R^2=0.34, p\u3c0.01), potentiated twitch amplitude (men: R^2=0.60, p\u3c0.01; women: R^2=0.55, p\u3c0.01), and rate of twitch torque development (men: R^2=0.69, p\u3c0.01; women: R^2=0.57, p\u3c0.01). In contrast, VA was weakly associated with peak power output for women (R^2=0.13, p=0.01) and not associated at all for men (R^2=0.03, p=0.18). Muscle activation (% peak EMG amplitude) of the vastus lateralis during the maximal power contraction was not associated with peak power output for men (R^2=0.01, p=0.37) or women (R^2=0.00, p=0.88). These data suggest that the age-related loss in power of the knee extensor muscles is due primarily to factors within the muscle for both men and women, and that impaired neural activation may play a minor role in the loss in power output for women

Genetic Analysis of Frost Tolerance in Rapeseed/Canola (Brassica Napus L.)

Frost can be detrimental to canola (Brassica napus L.) production. Depending on the severity, the entire field can be killed. Having frost tolerance in canola would benefit growers by allowing them to plant early, utilize early season moisture, and avoid high heat during flowering. However, frost tolerance in canola has not been well studied. A protocol was developed that determined 14 day old seedlings should be acclimated at 4°C for 7 days before being exposed to overnight frost (-4°C) in a small freezing chamber. However, when a larger chamber was used for freezing, the protocol was optimized to -8°C instead. A greenhouse study was conducted on a diverse collection of 231 genotypes and genome-wide association scan (GWAS) was conducted to identify potential genes that were related to frost tolerance or abiotic stress tolerance. Thirty-eight significant single nucleotide polymorphism (SNP) markers were selected based on 10,000 bootstraps and 0.1 percent tail of the empirical distribution. The markers were located on chromosomes A01, A02, A03, A04, A07, A08, A09, A10, C03, C05, C06, C07, and C09. Stepwise regression highlighted a QTL located on chromosomes A02. Another GWAS was done on 147 canola germplasm lines phenotyped under natural conditions. Thirty-eight significant SNPs identified from this study were located on chromosomes A05, A07, A09, C01, C02, C03, C04, C05, C06, C07, and C09. Stepwise regression identified a QTL located on chromosome C04. A protocol was developed to measure the freezing induced electrolyte leakage from leaves of rapeseed/canola. A total of 157 germplasm lines were evaluated for freezing induced (-12°C for 2 h) electrolyte leakage. Thirty-six significant SNPs located on chromosomes A01, A02, A03, A04, A05, A06, A07, A08, A09, A10, C01, C02, C04, C05, C06, C07, and C09 were identified. Stepwise regression identified 10 QTL located on chromosomes A01, A02, A04, A06, A07, C02, C05, C07, C09, and one that could not be assigned. All GWAS studies identified potential genes of interest that were related to frost tolerance, abiotic stress, and transcription factors.Northern Canola Growers Associatio

Status of mineral resource information for the Fort Apache Indian Reservation, Arizona

Ill. Administrative Report BIA-77. Maps. Includes bibliographic references. "This report was prepared for the Bureau of Indian Affairs (BIA) by the U.S. Geological Survey (USGS) and the Bureau of Mines (USBM) under an agreement to compile and summarize available information on the geology, mineral resources, and potentials for mineral development of certain Indian lands. Source material included published and unpublished reports and personal communications. No fieldwork was done." 57 pages (PDF version)

Geologic Map of the Horseshoe Dam 7.5' Quadrangle, Maricopa County, Arizona

The Horseshoe Dam quadrangle straddles part of the lower Verde River valley of central Arizona, a north-trending, west-tilted half-graben along the southern edge of the Transition Zone tectonic province (Spencer and Reynolds, 1989). The graben is filled with Miocene sedimentary and volcanic rocks. Elevations in the quadrangle range from 2000' to 4500', and the area is thickly vegetated with upper Sonoran desert flora. The north-facing slopes are generally choked with dense patches of brush, but the south-facing slopes are relatively open. The area can be reached via the Horseshoe Dam road, a graded gravel road accessible to all vehicles, and a number of primitive jeep trails on the west side of Verde River. Most of the country east of Verde River is either roadless or part of the Mazatzal Wilderness area.Documents in the AZGS Document Repository collection are made available by the Arizona Geological Survey (AZGS) and the University Libraries at the University of Arizona. For more information about items in this collection, please contact [email protected]

Neural and Muscular Contributions to the Age-Related Loss in Power of the Knee Extensors in Men and Women

The mechanisms for the loss in limb muscle power in old (60-79 years) and very old (≥80 years) adults and whether the mechanisms differ between men and women are not well-understood. We compared maximal power of the knee extensor muscles between young, old, and very old men and women and identified the neural and muscular factors contributing to the age-related loss of power. 31 young (22.9±3.0 years, 15 women), 83 old (70.4±4.9 years, 39 women), and 16 very old adults (85.8±4.2 years, 9 women) performed maximal isokinetic contractions at 14 different velocities (30- 450°/s) to identify peak power. Voluntary activation (VA) and contractile properties were assessed with transcranial magnetic stimulation to the motor cortex and electrical stimulation of the femoral nerve. The age-related loss in power was ∼6.5 W·year-1 for men (R2=0.62, p\u3c0.001), which was a greater rate of decline (p=0.002) than the ∼4.2 W·year-1 for women (R2=0.77, p\u3c0.001). Contractile properties were the most closely associated variables with power output for both sexes, such as the rate of torque development of the potentiated twitch (men: R2=0.69, p\u3c0.001; women: R2=0.57, p\u3c0.001). VA was weakly associated with power in women (R2=0.13, p=0.012) but not men (p=0.191), whereas neuromuscular activation (EMG amplitude) during the maximal power contraction was not associated with power in men (p=0.347) or women (p=0.106). These data suggest that the age-related loss in power of the knee extensor muscles is due primarily to factors within the muscle for both sexes, although neural factors may play a minor role in older women