2011 Annual Report
1a.Objectives (from AD-416)
Assess biological and ecological characteristics of weeds that contribute to their invasive and adaptive potential in an effort to provide more effective weed control tactics. Determine specific morphological and physiological characteristics of herbicide-resistant weed biotypes (e.g., horseweed, and invasive (e.g., cogongrass), native and non-native (e.g., pitted morningglory, purple-nutsedge, johnsongrass) weed species and causes for their variable control with herbicides. Develop and/or refine effective, economical, environmentally safe, and sustainable weed management systems for cotton, soybean, and corn by integrating chemical, cultural, and herbicide-resistant cultivars with a greater emphasis on conservation tillage practices. Determine ecological changes that occur inthe weed populations as a consequence of cultural practices and herbicide changes, including weed species shifts, changes in seed bank dynamics, and the development of herbicide resistance. Investigate mechanism of resistance in glyphosate-resistant horseweed. Assess risks associated with glyphosate-resistant cropping systems on soil microbial ecology, soybean diseases, and nitrogen fixation/assimilation.
1b.Approach (from AD-416)
Sustainable integrated weed management systems will be developed by integrating chemical, cultural, and mechanical control methods to exploit the benefits of each practice to minimize herbicide inputs and to maximize weed control and yield. Focus will be on use of conservation tillage, cover crops, crop rotation, narrow row spacing, competitive cultivars, and herbicide-resistant crops to reduce herbicide use and risks. Research will evaluate changes in the distribution and type of weed species and seed bank dynamics as a consequence of changes in production practices, such as herbicide-rsistant crops, cover crops, row spacing, and conservation tillage. A broad range of techniques will be used to assess biology and management of weed species and impact on herbicide-resistant cropping systems on weed populations and species shifts and resistance. Investigations will include biological and ecological aspects of a number of pernicious, noxious, and invasive weeds tounderstand the traits that lead to weediness and devise effective control measures.
All the experiments outlined in the project plan were completed successfully. The results from the agronomic, physiological, and crop culture studies gave insight to physiological mechanisms leading to lint yield and fiber quality differences among diverse cotton varieties. Early cotton planting increased yields under irrigated environment and decreased yields under dryland conditions compared to the normal planting date. Variety, planting date, and irrigation regimes all impacted multiple fiber traits. In particular, both early planting and dryland conditions increased short fiber content. Genotypic variation was detected in leaf photosynthesis, leaf chlorophyll concentration, dry matter partitioning, and canopy light interception. These differences are similar to previously reported differences in lint yield, yield components, and fiber quality among the cotton genotypes. Starter fertilizer reduced cotton stand counts relative to the plots not receiving any starter fertilizer, probably due to some toxicity from free ammonia near the seed/seedlings. Even though stand establishment reduced, the plots receiving starter fertilizer produced 4% higher lint yield than the plots without starter fertilizer. Twin-row soybean had a slight yield advantage over single-row plantings. Making a switch to twin-row from single-row system is a personal preference. Producers with large farm can readily recover the cost of planter and reap the potential economic benefits than producers with a small farm. Research on morphology of barnyardgrass and junglerice biotypes from several southern states was completed. The Mid South Area Office/Delta Council call for research on narrow-row cotton production vs. traditional wide-row cotton production was completed and two research articles were published. Studies on mechanisms of glyphosate-resistance in Palmer amaranth were completed (MSU collaboration). Aminomethylphosphonic Acid (AMPA), a metabolite of glyphosate, was detected in Roundup Ready (RR) soybean. Additional studies to investigage AMPA effects on soybean physiology were completed and manuscript submitted. Book - Weeds of the Midwestern United States and Central Canada (University of Georgia Press, Athens, GA) the second most comprehensive book on weed identification, distribution, and toxic properties was published in 2010.
Cotton varieties and seeding rates. Cotton producers are increasing interest in possibly utilizing lower seeding rates due to the increased costs of the seed. ARS scientists at Stoneville, MS, have demonstrated that both obsolete and modern cotton varieties demonstrated improved yields at lower seeding rates (19,500 plants/acre) than the higher, more traditional, seeding rates (39,000). The key is that the plants in the lower population density must be uniformly distributed. Breeding efforts over the past 30 years have not altered the way varieties respond to different population densities for lint yield. Fiber quality traits were only minimally affected by the different seeding rates. If improved planting equipment is combined with high quality seed and good weather conditions to ensure uniform seedling emergence, then the data suggest that producers could still achieve comparable, if not improved, lint yields by utilizing reduced seeding rates, which would in turn also reduce their seed input costs.
Comparison of single-row vs. twin-soybean production in the Mid South. Twin-row soybean production is being rapidly adopted by Mid South farmers with nearly 80% of the area’s hectares being grown this way using the established Early Soybean Production System developed earlier. An ARS researcher at Stoneville, MS, completed two experiments in 2010, one to examine possible yield differences between Maturity Group (MG) IV and V varieties grown in both single- and twin-rows at seeding rates of 200,000, 300,000, 400,000 and 500,000 seeds per hectare, and another to study the effects of April, May, and June plantings on yield of an MG IV cultivar grown in both single- and twin-rows at similar seeding rates. Both experiments were planted on a sandy loam soil and a clay soil and irrigated. Twin-row plantings yielded more mainly because more plants survived in the twin-rows than in single-rows. The MG IV yielded more than the MG V on both soils and delayed planting until June resulted in decreased yields on both soils. Seeding rates above 300,000 seeds per hectare did not increase yields in either single- or twin-rows with either Maturity Group or planting date. These data support the transition to twin-row planting of soybean in the Mid South especially for large hectarage producers.
Glufosinate effects on nitrogen nutrition, growth, yield, and seed composition in glufosinate-resistant and glufosinate-sensitive soybean. When glufosinate is applied to glufosinate-resistant crops, drift to non-glufosinate-resistant crops may cause injury, disrupt nitrogen metabolism, and reduce yields. Herbicide drift complaints from ground or aerial applications are common in the Mississippi Delta. ARS scientists at Crop Production Systems Research Unit and Crop Genetics Research Unit, Stoneville, Mississippi, have conducted a 2-yr field study to determine effects of glufosinate on plant injury, chlorophyll content, nodulation, nitrogenase activity, leaf nitrogen, yield, and seed composition in glufosinate-resistant and –susceptible soybean. Glufosinate-sensitive (glyphosate-resistant and conventional) soybean exposed to glufosinate drift may exhibit transient injury (speckling, necrosis, and chlorosis) and soybean can recover from injury over time. Glufosinate had no effect on yield; increased leaf nitrogen at R4 growth stage, seed protein, and oleic acid; and decreased oil content, linoleic, and linolenic acid in glufosinate-sensitive soybean. In glufosinate-resistant soybean, chlorophyll content, nitrogenase activity, root respiration, plant biomass, soybean yield were not affected while seed nitrogen and protein were increased and seed oil content decreased. These results indicate that Glufosinate-sensitive soybean exposed to glufosinate drift may exhibit transient injury but soybean could recover over time without a yield penalty. Glufosinate altered seed composition in all soybean types. These data demonstrate that glufosinate drift injury is not a concern to soybean producers.
Pettigrew, W.T. 2010. Impact of varying planting dates and irrigation regimes on cotton growth and lint yield production. Agronomy Journal. 102:1379-1387.
Freeland, Jr, T.B., Pettigrew, W.T., Thaxton, P., Andrews, G.L. 2011. Agrometeorology and cotton production. World Meteorological Organization. 10(1):1-128. http://www.wamis.org/agm/gamp/GAMP_Chap10.pdf.
Reddy, K.N., Ding, W., Zablotowicz, R.M., Thomson, S.J., Huang, Y., Krutz, L.J. 2010. Biological responses to glyphosate drift from aerial application in non-glyphosate-resistant corn. Pest Management Science. 66:1148-1154.
Ding, W., Reddy, K.N., Krutz, L.J., Thomson, S.J., Huang, Y., Zablotowicz, R.M. 2011. Biological response of soybean and cotton to aerial glyphosate drift. Journal of Crop Improvement. 25:291-302.
Boykin Jr, J.C., Reddy, K.N. 2010. The effects of narrow-row and twin-row cotton on fFiber properties. Journal of Cotton Science. 14:205-211.
Ding, W., Reddy, K.N., Zablotowicz, R.M., Bellaloui, N., Bruns, H.A. 2011. Physiological responses of glyphosate-resistant and glyphosate-sensitive soybean to aminomethylphosphonic acid, a metabolite of glyphosate. Chemosphere. 83:593-598.
Bruns, H.A. 2011. Comparisons of single-row and twin-row soybean production in the Mid South. Agronomy Journal. 103:702-708.
Bruns, H.A. 2011. Planting date, rate and twin-row vs single-row soybean in the mid south. Agronomy Journal. 103:1308-1313.
Bryson, C.T., Carter, R. 2010. Spread growth and reproductive potential for brown flatsedge (Cyperus fuscus). Journal of Invasive Plant Science and Management. 3:240-245.
Bryson, C.T., Krutz, L.J., Ervin, G., Reddy, K.N., Byrd, J.D. 2010. Ecotype variability and edaphic characteristics for cogongrass (Imperata cylindrica) populations in Mississippi. Journal of Invasive Plant Science and Management. 3:199-207.
Bellaloui, N., Reddy, K.N., Abel, C.A., Gillen, A.M. 2010. Nitrogen metabolism and seed composition as influenced by foliar boron application in soybean. Plant and Soil. 336:143-155.
Locke, M.A., Weaver, M.A., Zablotowicz, R.M., Steinriede Jr, R.W., Bryson, C.T., Cullum, R.F. 2011. Constructed wetlands as a component of the agricultural landscape: Mitigation of herbicides in simulated runoff from upland drainage areas. Chemosphere. 83:1532-1538. DOI:10.1016/j.chemosphere.2011.01.034.
Bellaloui, N., Bruns, H.A., Gillen, A.M., Abbas, H.K., Zablotowicz, R.M., Mengistu, A., Paris, R.L. 2010. Soybean seed protein oil fatty acids and mineral composition as influenced by soybean-corn rotation. Journal of Agricultural Science. 1(3):102-109.