<p>Low commodity prices and environmental concerns have compelled cotton growers to increase production efficiency while decreasing inputs. Research evaluated weed interference, strip-tillage production, transgenic cultivars, and new herbicides to improve weed management in peanut and cotton. The rectangular hyperbola model described the effect of common ragweed density on percent peanut yield loss. With the asymptote constrained to 100% maximum yield loss, the I coefficient (yield loss per unit density as density approaches zero) was 68.3 + 12.2%. Common ragweed height was not affected by weed density or peanut canopy diameter. Weed height exceeded peanut height throughout the growing season, indicating that competition for light occurred between the two species. Common ragweed above-ground dry biomass per plant decreased as weed density increased, but total weed dry biomass per m crop row increased with weed density. Studies evaluated weed management using diclosulam and flumioxazin in strip-tillage and conventional-tillage peanut. Dimethenamid plus diclosulam or flumioxazin preemergence (PRE) controlled common lambsquarters, eclipta, and prickly sida at least 91%. Diclosulam and flumioxazin controlled Ipomoea morningglory species (59 to 91%) and bentazon plus acifluorfen postemergence (POST) provided >90% control. Dimethenamid plus diclosulam or flumioxazin PRE produced equivalent yields and net returns with no significant differences between the two PRE options. The tillage production system did not influence weed control of eight weeds, peanut yields, or net returns. Studies were conducted to evaluate weed management systems in non-transgenic, transgenic bromoxynil-resistant, and transgenic glyphosate-resistant cotton in strip- and conventional-tillage environments. Tillage did not affect the level of weed control provided by the herbicide systems evaluated. Excellent (>90%) control of common lambsquarters, Ipomoea species including entireleaf, ivyleaf, pitted, and tall morningglories; jimsonweed, prickly sida, and velvetleaf was achieved with programs containing bromoxynil, glyphosate, and pyrithiobac early postemergence (EPOST). Glyphosate systems controlled fall panicum, goosegrass, and large crabgrass more consistently than bromoxynil and pyrithiobac systems. Bromoxynil and pyrithiobac EPOST did not control sicklepod unless applied in mixture with MSMA and followed by (fb) a late postemergence-directed (LAYBY) treatment of prometryn plus MSMA. Herbicide systems that included glyphosate EPOST controlled sicklepod with or without a soil-applied herbicide treatment. The highest yielding systems included all the glyphosate systems and bromoxynil systems that included a soil-applied herbicide treatment. Non-transgenic systems that included a soil-applied herbicide treatment yielded less than soil-applied treatment plus glyphosate EPOST system. Net returns from glyphosate systems were generally higher than net returns from bromoxynil or pyrithiobac systems.<P>

<p>Purple and yellow nutsedge are herbaceous perennial weeds that are among the world?s worst pests. Nutsedge species are problematic due to their perennial nature, longevity of tubers, and prolific tuber production. Due to the relatively difficulty in reducing purple and yellow nutsedge populations, herbicide-management programs in cropping systems that target nutsedge species need to be developed. Field studies were conducted to evaluate potential reduction in purple and yellow nutsedge populations using sulfentrazone and glyphosate management programs and site-specific management in a tobacco and soybean rotation, as well as using sulfentrazone, glyphosate, and halosulfuron management programs in a soybean and corn rotation. All weed management systems reduced purple nutsedge densities similarly in the tobacco and soybean rotation. Sulfentrazone plus clomazone preplant incorporated (PPI) in tobacco or preemergence (PRE) in glyphosate-resistant (GR) soybean reduced yellow nutsedge densities 82 and 99%, respectively. Postemergence (POST) treatments of glyphosate in GR soybean did not increase yellow nutsedge reductions when sulfentrazone was applied in tobacco or GR soybean. Glyphosate applied on a site-specific basis POST with a light-activated hooded sprayer (LAS) reduced yellow nutsedge populations as effectively as glyphosate POST broadcast treatments in GR soybean. Weed management systems that included sulfentrazone PRE fb the LAS in GR soybean reduced POST herbicide use by at least 86%, compared to broadcast applications. Sulfentrazone plus clomazone PRE alone in GR soybean followed by (fb) nicosulfuron POST in GR corn reduced purple and yellow nutsedge populations by 48 and 85% relative to the nontreated control, respectively. Clomazone PRE in GR soybean fb sequential treatments of glyphosate POST in GR soybean and in GR corn, reduced purple and yellow nutsedge populations equivalent to soybean PRE herbicide programs and other GR corn POST management programs. Halosulfuron POST treatments reduced yellow nutsedge populations (> 90%) equivalent to glyphosate POST treatments in corn regardless of soybean PRE herbicide program. Greenhouse studies were conducted to evaluate cotton POST herbicides fb MSMA late postemergence (LPOST) for foliar and tuber reduction of yellow and purple nutsedge when applied to nutsedge foliage at two different application timings. CGA-3626222 treatments reduced purple and yellow nutsedge shoot and root/tuber dry weights equivalent to glyphosate POST fb MSMA LPOST. MSMA at 1120 and 2240 g ai/ha and glufosinate POST fb MSMA LPOST reduced purple and yellow nutsedge shoot dry weights, although reduction was greater at smaller nutsedge application heights. Less reduction was obtained with pyrithiobac POST fb MSMA LPOST. The addition of MSMA in mixture to other POST herbicides was of benefit for nutsedge growth reductions with pyrithiobac, but was seldom beneficial with other herbicides. These data initiated studies to evaluate the physiological behavior of CGA-362622 in purple and yellow nutsedge for possible reasons of control. Lab studies were conducted to evaluate absorption, translocation, and metabolism of 14C-CGA-362622 when foliar applied to purple and yellow nutsedge. Less than 53% of the herbicide was absorbed after 96 h. Both nutsedge species translocated appreciable herbicide (30%) out of the treated leaves. Translocation was both acropetal and basipetal, with at least 25% transported basipetally. Neither nutsedge species translocated over 4% of applied radioactivity to the tubers and roots. Most of the metabolites formed by the nutsedge species were more polar than 14C-CGA-362622 and averaged 69 and 61% of the radioactivity in purple and yellow nutsedge. The half-life of CGA-362622 was estimated at 4 h in both purple and yellow nutsedge.<P>

<p>Transgenic, glyphosate-resistant (GR) cotton has been available to U.S. growers since 1997. Despitewide-spread acceptance, there have been performance complaints by growers citing lower boll retention in GRvarieties than in conventional varieties. Field and greenhouse studies confirmed grower observations,demonstrating a glyphosate-associated decrease in boll retention compared to non-treated GR or conventionalplants. Late (beyond the 5 leaf stage) foliar applications were the most injurious, presumably because plantswere entering early reproductive stages. Boll ?cavitation,? (dessicated bolls attached to plants) also observed bygrowers following glyphosate treatment, resulted from abnormal abscission zone formation and was related tovariety.<p>14C-glyphosate absorption per square centimeter was greater when applied to stem tissue than leaf tissue, but overallabsorption is likely greater when applied foliarly, due to a greater total surface area. Because glyphosatetypically moves from source tissue to sink tissue, up to 3.7% of applied 14C-glyphosate was translocated toreproductive tissues.<p>Seedling development in both GR and conventional cotton was inhibited by root-absorbed glyphosate.Root tissues were more sensitive to glyphosate than cotyledons or hypocotyls, as was demonstrated byinhibition of lateral root formation and shikimic acid accumulation. CP4-EPSPS content was significantly lowerin GR seedling roots than cotyledons, accounting for glyphosate sensitivity.<p>Further studies compared the accumulation of shikimic acid in response to glyphosate in reproductiveand vegetative tissues in GR and conventional cotton. Shikimic acid accumulation per mM of glyphosate, wasgreater in reproductive than vegetative leaf tissue in both GR and conventional cotton, suggesting thatreproductive tissue is innately more sensitive to glyphosate than vegetative tissue. The quantity of theglyphosate-resistant CP4-EPSPS enzyme was significantly less in stamens than in vegetative leaf tissues.Several morphological differences were apparent in flowers of glyphosate-treated GR cotton.<p>Glyphosate applications inhibited stamen elongation, resulting in anthers not extending to the tip of the stigma,thereby limiting pollen deposition to the lower, less receptive portion of the stigma. Total pollen deposition on the stigma was less in glyphosate-treated GR cotton than non-treated GR or conventional cotton. Microscopicanalysis of pollen revealed that glyphosate arrested maturation in at least 3 pollen developmental stages. Atanthesis, pollen grains from glyphosate-treated GR plants were collapsed, highly vacuolated, and had 60% lowerviability (ability to germinate) than pollen from non-treated GR or conventional plants. Retained bolls fromglyphosate-treated plants had fewer seeds than those from non-treated GR or conventional plants. Hand crossesbetween glyphosate-treated plants demonstrated that the number of seeds per boll was decreased when the maleparent, but not the female parent, was glyphosate treated. Hand pollinations using pollen from treated plants,although overcoming the increased anther-stigma distance, did not restore the normal number of seeds per boll.Treatment of GA onto glyphosate-treated GR plants did not remediate glyphosate effects on pollen viability andfloral morphology. Therefore, presumably, several of the bolls that were shed due to glyphosate-treatments,contained an insufficient number of fertilized ovules and are thus shed.<p>This research proposes that boll shed due to glyphosate in GR cotton is due to insufficient levels ofCP4-EPSPS in stamens, which are highly sensitive to glyphosate. As glyphosate accumulates in reproductivestructures, stamen elongation and pollen development are inhibited, resulting in poor fertilization of ovules.Because fewer ovules are fertilized, bolls are either shed or contain fewer seeds if retained. Growers shouldlimit glyphosate contact with GR cotton, especially during the reproductive stages in order to minimize thepotential for glyphosate-induced boll shed.<P>

Research in Europe and the United States showed that interplot competition in variety trials can result in distortion of yield and misleading conclusions from yield comparisons. Field trials were conducted at Swift Current and Saskatoon in 1993 and 1994 to find out if interplot competition occurs in the wheat growing region of Saskatchewan. Four spring wheat (<i>Triticum aestivum</i> L.) cultivars, Biggar, Oslo, Genesis and Glenlea, were grown in four-row plots in a diallel competition treatment design, with the competition treatments applied randomly to each of eight replications in a randomized complete block design. Generally, yield was distorted from pure stand yield when adjacent plots differed for height ($-$0.34% cm$\sp{-1}).$ Plots with Biggar or Oslo flanked by a tall cultivar, Genesis or Glenlea, yielded less than when flanked by themselves, and the reverse occurred when the tall cultivars were flanked by the short cultivars. Interplot competition also affected spike density in the same fashion, did not significantly affect height, and was inconclusive with regards to kernel weight. Simulation indicated that a correlation between height and yield would not affect the covariance adjustment with average height difference. Sixty-five historical data sets were tested to see if an adjustment for interplot competition with average height difference as a covariate would be effective. The negative relationship between yield and the height covariate was significant for 25 of the data sets. At Saskatoon in 1995, row directions were compared and interplot competition was significant in the north/south rows and not significant in the east/west rows. An experiment at Regina and Swift Current in 1995 indicated that less interplot competition occurred when plots were separated by spring planted winter wheat than when plots were 23 cm apart. It was concluded that when plots differ for height, yield distortion can occur in the Saskatchewan wheat growing region.

Thesis (M.S.)--Wisconsin. / Includes bibliographical references (leaves 250-277).

Inaug.-diss.--Jena. / Lebenslauf.

Master of Agribusiness / Department of Agricultural Economics / Jeffery R. Williams / Production agriculture is constantly evolving to become more efficient and productive. Crop residue serves as a valuable source of nutrients for the soil, but it is increasingly abundant with today’s enhanced crop genetics. If new technology can effectively provide a way to micro-manage crop residue levels within a field, the benefits will go beyond soil health. Surplus crop residue can be collected for secondary income while leaving the optimum amounts in the field to maintain the environment and soil health as well as promote future crop growth. The main objective of this study is to create a budget model that will determine the economic impact of crop residue removal on a controlled basis. The goals are to determine crop residue removal practices that are sustainable for the long-term, while also enhancing soil quality and increasing grain yield in future years. A sub-objective is to build a business case for producers to invest in variable crop residue management. The hypothesis presented in this study is that the increased complexity and price of a variable rate system is offset by more supplemental profits, increased crop yields, and better management of soil health and nutrients. The negative perceptions of crop residue removal include the fear of soil erosion or loss of soil organic matter. By developing a budget model that is easy to use, takes advantage of existing field data for inputs, and allows producers the ability to look at their operations on a sub-field level, this study aims to provide the necessary motivation to invest in new technology that will increase their productivity. By entering their site-specific crop residue return rate data into a budget model, along with prices and costs related to combine and auxiliary equipment, corn and corn stover, transportation and logistics, and nutrient replacement, they will come up with a return per acre for both constant rate and variable rate collection. The budget model determines whether it is economically viable to harvest crop residue from a continuous corn rotation at a variable rate across a field, rather than at a constant rate, using a producer’s own specific field data. To validate the concept, data from a joint study between John Deere and Iowa State is entered into the model. Prescriptions for corn stover return rates are provided from the study for pre-defined grid areas. Prescriptions are derived from a combination of data including grain yield, soil loss due to wind and water erosion, climate, topography, and soil sample data at time of planting (Nelson, et al. 2004). The average corn stover removal percentage was less for variable rate collection than constant rate collection, 26.05% to 31.85%. However, the assumption that grain yield and corn stover yield are positively correlated did not prove to be true in this case study. The variable rate plots had a lower average grain yield of 158.84 bushel/acre, compared to 160.46 for the constant rate plots, but they had more total corn stover available and therefore a higher return rate of 3.70 tons/acre, compared to 3.05 for the constant rate plots. This case study illustrates that less corn stover can be returned to the field through constant or variable rate collection while sustaining higher grain yields than a conventional harvest that would return all of the corn stover to the field. This case study demonstrates that variable rate collection can be more expensive than constant rate, but not in every situation. Every unique field site will require a specific crop residue management recommendation that is determined by both economic and environmental factors.

No description available.

4 pp. / Lesquerella (Lesquerella fendleri) is a member of the mustard family and is native to the southwestern United States and northern Mexico. The oil in lesquerella seeds has superior performance compared to castor, soybean, and rapeseed methyl esters in reducing wear and damage in fuel injected diesel engines. Lesquerella can also be used as an ingredient for a number of other bioproducts such as lubricants, motor oils, plastics, inks, and adhesives. The hydroxylated oil in lesquerella is similar to castor oil but does not contain the deadly poison ricin. Therefore, lesquerella is a safer alternative to castor in the United States and can be handled both at the farm level and the oilseed processing level with industry standard equipment and technology. This article provide information to growers in planting, water and nutrient management, pest management, and harvesting of lesquerella as a potential alternative crop.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1983. / Typescript. Vita. Description based on print version record. Includes bibliographical references (leaves 244-249).