Doctor of Philosophy / Department of Agricultural Economics / Jeffrey M. Peterson / Technological changes have always been subject to numerous debates and studies to establish if and how much they benefit society. Glyphosate resistant soybean can be seen as such a technological improvement that has generated numerous studies attempting to measure the welfare gains. There are obvious gains from adopting the technology from a production efficiency standpoint, as it significantly decreases production cost and simplifies weed control management. However, with some consumers being reluctant to embrace such a change, especially in Europe, it is not obvious that overall welfare gains are positive. This study attempts to address some shortcomings perceived in recent economic literature, namely the disregard of consumers’ demand responses and the lack of analysis over time. A partial equilibrium model is created where supply and demand functions are estimated based on observed prices and quantities, the adoption rate of the new technology, and production information such as yield and harvested areas. The model developed considers 6 different regions, namely the U.S., Europe, China, Argentina, Brazil and the rest of the world, and develops for each one of them a supply function and three demand functions for soybean grain, meal and oil. Once those are calibrated, the gains for the different players in the industry are computed. The findings are that the gains are proportionally allocated to the different consumers based on the share of the demand for the specific country. Price supports in the U.S. in the early years provide, proportionally to the adoption rate, more gains to the consumers. Producers gain or lose from the technology depending on whether they have adopted it or not. Countries like the U.S. or Argentina, who were the earlier adopters, definitely see an increase in their producer surplus from the adoption of the technology. Countries such as Brazil, which have delayed adopting the technology for political reasons, have faced a significant loss due to lower prices without the benefits of enjoying a cost-saving production technology. The innovator’s gain increases over time as the adoption rate rises. From a country perspective, the U.S. is without doubt the country that has benefited the most from the technology. The main reasons are that the U.S. has the largest acreage of soybean that is grown using the Glyphosate resistant technology. The U.S. consumer base for soybean products is the largest and the monopoly is a U.S.-based company. Therefore some of the gain captured abroad by the monopoly funnels into the U.S. This study finds that, from 2002 to 2005, even if the European consumer completely stopped purchasing soybean, the U.S. as a whole would still benefit from the technology. For the earlier period 1998-2005, the study finds that if Europe had decreased its demand from 35% to 48%, there would have been a possibility for the U.S. as a whole to have been made worse off by the technology.

Glyphosate, a non-selective herbicide, is antagonized by salts in the spray carrier and responds to surfactant type and concentration. Glyphosate antagonism by dissolved salts such as calcium and magnesium was verified with natural water carriers and with carriers to which salts were added. Salt antagonism of glyphosate occurred from the formation of complexes that were less absorptive than the formulated isopropylamine glyphosate. Absorption of various salts of glyphosate varied as follows: isopropylamine > acid > ammonium > sodium > calcium. Ammonium sulphate increased the absorption of glyphosate both in distilled water carriers and in water carriers containing calcium chloride. Absorption and retention of glyphosate generally increased as surfactant (nonylphenol ethoxylate) hydrophilic/lipophilic balance (HLB) increased. The optimal HLB for glyphosate absorption was lower when ammonium sulphate was added to the spray carrier. An experimental adjuvant (trade name: Power-Up) that contained nonionic surfactant and ammonium sulphate, increased glyphosate efficacy more than the currently registered South African adjuvants. This could be as a result of increased foliar absorption and/or retention on foliage. The use of acid containing adjuvants was not essential for adequate glyphosate efficacy. Visual assessment of spray droplet residuals on leaves indicated that the appearance of spray droplet residuals was linked to glyphosate efficacy. Thick, amorphous and grainy spray droplet residuals on the leaf surface was an indicator of poor efficacy, whilst thinner, smoother residuals in close contact with the leaf surface was linked to increased efficacy. / Thesis (PhD (Agronomy))--University of Pretoria, 2005. / Plant Production and Soil Science / unrestricted

The effects of sublethal drift rates and carryover of glyphosate and dicamba into the next generation of seed potato cultivars Atlantic and Dakota Pearl are unknown. The objective of this research is to determine the impact of sublethal glyphosate and dicamba rates on mother and daughter chipping potato plants. Field studies were conducted in 2018 and 2019 in Oakes, ND. Herbicides were sprayed at the tuber initiation stage and consisted of dicamba (0, 20, and 99 g ae ha-1) and glyphosate (0, 40, and 197% g ae ha-1). During the year of application (2018), the combination of glyphosate at 197 g ha-1 and dicamba at 99 g ha-1 resulted in a 40% yield reduction compared to the non-treated in both cultivars. In 2019, the daughter tubers from mother tubers that were treated with glyphosate (23%) experienced a 16% reduction in marketable yield in both cultivars.

Pesticides are a growing concern around the world as they are widely increasing in use and not as highly regulated as some health and environmental hazards. As agricultural, home, and other pesticide applications continue to rise, the need for analytical testing and removal of these pesticides from our rivers, streams, and other runoffs is becoming more and more significant. Glyphosate, an active ingredient in the herbicide Roundup, is an amine compound that has a maximum contamination level of 700 ppb. This work studied the use of water soluble Iron (II) tetrasolfophthalocyanine in amine detection that could be further applied to glyphosate. Also included in this study is a glimpse of removal possibilities combining phthalocyanines with traditional adsorption media for enhanced extraction and capacity.

Glyphosate (N-(phosphonomethyl)glycine)-containing herbicides are a common and highly effective method to terminate alfalfa (Medicago sativa) stands. With the development and use of glyphosate-resistant (Roundup Ready®) alfalfa, this tool is no longer an option. The purpose of this research was to determine the optimal strategy to rotate from glyphosate-resistant alfalfa into silage corn (Zea mays). Studies were conducted in 2012 and 2013 at sites near Cache Junction and Cornish, Utah to determine the effect of tillage type and timing [fall conventional till (FCT), spring conventional till (SCT), fall strip-till (FST), spring strip-till (SST), and no-till (NT)], 2,4-D plus dicamba herbicide timing (fall, spring, in-crop, and a control), and N rate (0, 56, 112, and 224 kg N ha-1) on soil penetration resistance (PR), alfalfa re-growth, and corn emergence rate index (ERI), silage yield, quality, and economic return. The fall, spring, and in-crop herbicide timings across all tillage treatments reduced alfalfa stem count and biomass by at least 95% and 98%, respectively. Tillage reduced PR compared to NT to or near the depth of tillage. The ERI was significantly higher under FCT, SCT, and SST and when herbicides were applied in fall or spring. Silage yield, quality, and economic return were the highest when spring herbicide timing was used with all tillage types and timings and the fall herbicide timing under conventional tillage. Increasing N rates increased crude protein, milk ha-1, and dry matter yield. However, optimal yield and quality can be obtained with no additional N fertilizer. First-year silage corn yield, quality, and economic return can be optimized under fall or spring conventional till, strip-till, and no-till at the spring herbicide timing along with the fall herbicide timing for conventional tillage with no additional N fertilizer.

A rapid primary herbicide screening experiment was conducted to determine if synergism or antagonism occurs with imazapyr(Arsenal&#174;) plus triclopyr ester (Garlon 4®) and imazapyr plus glyphosate(Accord®) mixtures applied to woody weed seedlings. Using a booth sprayer, 66 herbicide treatments were applied to greenhouse grown black cherry (Prunus serotina), winged elm (Ulmus alata), sweetgum (Liquidambar styraciflua), red maple (Acer rubrum), black locust (Robinia psuedoacacia), loblolly pine (Pinus taeda), water oak (Quercus nigra) and cabbage palmetto (Sabel palmetto). The seedlings were rapidly screened and percent mortality, height and dry weight measurements were obtained five months after treatment. The sweetgum, red maple and black locust experienced unacceptable mortality in the control treatments, and were excluded from further analysis. A determination of synergistic or antagonistic interactions was made using response surface analysis, the nonlinear blending method, the isobologram method, and the Colby method. Imazapyr plus triclopyr ester mixtures were found to be synergistic on black cherry (p < 0.05), with antagonism occurring at high rates of both herbicides. Imazapyr plus triclopyr ester was additive on the remaining species. The imazapyr plus glyphosate mixtures were found to be additive for all tested species. / Master of Science

Onarm research was conducted in 2011 and 2012 to determine the postemergence and residual control by dicamba of glyphosate-resistant (GR) Palmer amaranth (Amaranthus palmeri S. Wats.). Preemergence dicamba at 0, 0.28, 0.56, and 1.1 kg ae ha-1 and 0.07 kg ae ha-1 flumioxazin was applied at 30, 15 and 0 days prior to planting. Postemergence dicamba at 0.28, 0.56, and 1.1 kg ae ha-1 with and without 0.84 kg ae ha-1 glyphosate was applied to 5, 10 and 15 cm Palmer amaranth. In addition, a greenhouse experiment was conducted in 2012 to evaluate and confirm the optimum rate for control of Palmer amaranth with a new formulation of dicamba (BAS 18322H). In the greenhouse, dicamba at 0.14, 0.28, 0.56, 1.1, and 2.2 kg ae ha-1 was applied to 5, 10, and 15 cm Palmer amaranth.

The introduction of glyphosate-resistant (GR) crops in the late 1990s changed the way producers used herbicides to control weeds. Since the introduction of GR crops producers have relied on glyphosate alone for weed control instead of utilizing multiple modes of action for weed control. This over-reliance resulted in several weed species developing resistance to glyphosate. This has resulted in organizations from the public and private sector questioning the sustainability of GR cropping systems. Researchers from Illinois, Indiana, Iowa, Mississippi, Nebraska, and North Carolina established 156 onarm trials to determine the sustainability of GR cropping systems. The objectives of this study were: to determine the economics of a university weed resistance best management practice (BMP) versus a producers’ normal production practice; to evaluate when a producer that is risk neutral (profit maximizing) or risk averse should adopt a weed resistance BMP; and to compare the influences of using a university weed resistance BMP to a producer’s normal production practice on the 27 most common weed species in Mississippi. In all instances, the university weed resistance BMP utilized multiple modes of action in conjunction with glyphosate. A university weed resistance BMP can provide the same level of control on 27 of the most common weeds in Mississippi that a producer has become accustomed to with a glyphosate alone system, while delaying or controlling GR weeds. A university weed resistance BMP resulted in an increase in weed control cost, but similar yields and economic returns when compared to a producer’s normal production practice. Rotating a GR crop with a different GR crop resulted in higher economic returns when compared to a continuous GR cropping system or a GR crop followed by a non-GR crop rotation. Producers are often reluctant to adopt a weed resistance BMP because of the perceived increased cost for weed control. A risk neutral or risk averse producer should adopt a weed resistance BMP and feel confident that their decision will provide weed control equivalent to a glyphosate alone weed control program before resistance developed, delay or control GR weeds and be economically sound.

A survey was conducted by phone to nearly 1,200 growers in six states (Illinois, Indiana, Iowa, Mississippi, Nebraska, and North Carolina) in 2005. The survey measured producers’ cropping history, perception of glyphosate-resistant (GR) weeds, past and present weed pressure, tillage practices, and herbicide use as affected by the adoption of GR crops. The objectives of this study were to determine the effect of GR crop use on producers’ tillage practices; changes in herbicide use patterns after adoption of a GR crop; effect of grower awareness of GR weeds on sources of information growers’ use; and growers’ perceptions on resistance management based on knowledge of GR weeds in their farming operation. The adoption of GR cropping systems contributed to large increases in the percentage of growers using no-till and reduced-till systems. Tillage intensity declined more in continuous GR cotton and GR soybean (45 and 23%, respectively) than in rotations that included GR corn or non-GR crops. Tillage intensity declined more in the states of Mississippi and North Carolina than in the other states, with 33% of the growers in these states shifting to more conservative tillage practices after the adoption of a GR crop. This was in part due to the lower amount of conservation tillage adoption in these states prior to GR crop availability. With respect to herbicide use patterns, frequently used herbicides for fall applications were 2,4-D and glyphosate; these herbicides were often used for preplant, burndown weed control in the spring. As expected, crop rotations using GR crops had a high percentage of respondents that made one to three POST applications of glyphosate per year. Overall, glyphosate use has continued to increase, with concomitant decreases in utilization of other herbicides. Concerning grower awareness of GR weeds and perceptions of resistance management in 2005, the majority of the growers (88%) were aware of a weed’s potential to develop resistance to glyphosate, while 44% were aware of state-specific, documented cases of glyphosate weed resistance. Growers that have had experience with GR weeds were more knowledgeable about resistance management practices that could be used to mitigate them.

With the adoption of the Xtend® technology growers began to report reduced control levels of weedy grasses when applying tank-mixes of glyphosate and dicamba. Therefore, research was conducted at the Delta Research and Extension Center in Stoneville, MS from 2019 to 2021 to examine influence of herbicide mixtures with dicamba, as well as carrier volume and nozzle type. Results indicated barnyardgrass control 14 and 28 DAT was greatest with glyphosate alone. Control was not different when DGA or BAPMA dicamba or 2,4-D choline were mixed with glyphosate. At 28 DAT, barnyardgrass control was 15 to 18% lower with herbicide mixtures compared with glyphosate alone. Barnyardgrass control with glyphosate plus dicamba was not decreased by drift-reducing nozzles. Carrier volume of > 94 L ha-1 provided greater control of barnyardgrass compared to 47 L ha-1. These results indicate potential of reduced barnyardgrass control with glyphosate plus dicamba.