2010 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 in the 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-resistant crops, cover crops, row spacing, and conservation tillage. A broad range of techniques will used to assess biology and management of weed species and impact of 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 to understand the traits that lead to weediness and devise effective control measures.
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 seeds/seedlings. Even though stand establishment was reduced, the plots receiving starter fertilizer produced 4% higher lint yield than the plots without starter fertilizer. This was the second straight year that starter fertilizer has given a statistically significant yield increase. Research on morphology of barnyardgrass and junglerice biotypes from several southern states is in progress. 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 are progressing (MSU collaboration). Aminomethylphosphonic Acid (AMPA), a metabolite of glyphosate, was detected in Roundup Ready (RR) soybean. Additional studies to investigate 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 Root System Conductance. Water movement through a cotton plants root system can be altered by the variety grown or the level of nitrogen fertilization. ARS scientists in Stoneville, Mississippi, have demonstrated that the root hydraulic conductance of a diverse group of cotton genotypes varied in response to differing levels of nitrogen fertilization in 2009. Root hydraulic conductance is thought to be associated with aquaporin (water channel) proteins that are involved in water transport throughout the plant. If these results are confirmed in 2010, then they could indicate ways to manipulate water use and nitrogen use efficiencies in cotton.
Aminomethylphosphonic Acid (AMPA) Effects on Soybean Physiology. AMPA, a metabolite of glyphosate is formed in glyphosate-treated soybean plants and is known to cause ‘yellow flashes’, but its mode of action is different from that of glyphosate. ARS scientists at Stoneville, Mississippi, have investigated physiological effects of AMPA on glyphosate-resistant (GR) and glyphosate-sensitive (GS) soybean. AMPA applied to soybean at 0.1 and 1.0 kg/ha injured soybean. Visual plant injury was observed on young leaves within 3 days after treatment (DAT) and plants recovered by 28 DAT in both soybean types. AMPA at 1.0 kg/ha decreased significantly chlorophyll content, photosynthesis, and root respiration in both soybean types. AMPA had no effect on nodulation and nitrate reductase activity at 10 DAT, and plant height and shoot dry weight at 28 DAT in GR and GS soybean. The fact that AMPA decreases chlorophyll content prior to reducing photosynthesis rate suggests that AMPA might interfere in chlorophyll biosynthesis in soybean. These data suggest that exposure to relatively high rates of AMPA may impair chlorophyll synthesis and photosynthesis. However, the probability of soybean exposure to greater than 10% of use rate is unlikely under field conditions.
Cogongrass. Cogongrass an invasive weed species continues to spread and establish in the southeastern U.S. ARS scientists at Stoneville, MS, have determined that cogongrass will grow and reproduce in every soil type, habitat, and physiographic region of Mississippi, except areas with permanently saturated and continually flooded soils. Research also determined that only plant height and leaf length and width were related to soil nutrients. Other morphological characteristics among cogongrass accessions were genetic traits and were not affected by edaphic characters.
Soybean. The first year’s research on Planting Date vs. Plant Populations vs. Row Type and Plant Bed Type vs. Plant Population vs. Maturity Group were successfully completed and planted for a second year. An experiment on Plant Populations vs. Row Type vs. Maturity Group was conducted for the second year in a row. Initial results indicate yields are unaffected by planting in twin-row configuration vs. a single row or increases in planting rates above 20 seed m-1.
Cotton Planting Dates. Early planting (April) compared to normal planting (May) increases irrigated cotton yields. ARS scientists at Stoneville, Mississippi, have demonstrated that early planting increased lint yield by 13% under irrigated conditions in 2 of 4 years but not under dryland conditions. Early planting decreased dryland lint yield by 35% in 1 of the 4 years but not under irrigated conditions. Fiber from the normal planted cotton was 5% stronger than from the early planted cotton. Both early planting and dryland conditions had a propensity to increase the short fiber content. These results indicate that early planting cotton need irrigation to achieve its yield benefits and Mississippi Delta cotton producers should not adopt an early planting production strategy for dryland.
5.Significant Activities that Support Special Target Populations
Scientist has participated in activities targeting minority, historically under-served operators/stakeholders. Scientist is a co-principal investigator on a Capacity Building Grant 2010 proposal submitted with Alcorn State University.
Burke, I.C., Reddy, K.N., Bryson, C.T. 2009. Pitted and Hybrid Morningglory Accessions Have Variable Tolerance to Glyphosate. Weed Technology. 23:592-598.
Reddy, K.N., Bellaloui, N., Zablotowicz, R.M. 2010. Glyphosate Effect on Shikimate, Nitrate Reductase Activity, Yield, and Seed Composition in Corn. Journal of Agriculture and Food Chemistry. 58:3646-3650.
Pettigrew, W.T., Molin, W.T., Stetina, S.R. 2009. Impact of Varying Planting Dates and Tillage Systems on Cotton Growth and Lint Yield Production. Agronomy Journal. 101:1131-1138.
Pettigrew, W.T. 2010. Effects of Foliar Fertilizer and Mepiquat Penteborate on Early Planted Cotton Growth and Lint Production. Crop Management. doi:10.1094/CM-2010-0215-01-RS.
Nandula, V.K., Poston, D.H., Reddy, K.N., Whiting, K. 2009. Response of Soybean to Halosulfuron Herbicide. International Journal of Agronomy. 2009(754510):1-7.
Reddy, K.N., Bryson, C.T. 2009. In-Crop and Autumn-Applied Glyphosate Reduced Purple Nutsedge (Cyperus rotundus)Density in No-Till Glyphosate-Resistant Corn and Soybean. Weed Technology 23:384-390.
Reddy, K.N., Boykin Jr, J.C. 2010. Weed Control and Yield Comparisons of Twin-and Single-row Glyphosate Resistant Cotton Production Systems. Weed Technology. 24:95-101.
Reddy, K.N., Norsworthy, J.K. 2010. Glyphosate-Resistant Crop Production Systems: Impact on Weed Species Shifts. In: Nandula, V.K., editor. Glyphosate Resistance in Crops and Weeds: History, Development, and Management. Eds. Vijay K. Nandula. Glyphosate Resistance in Crops and Weeds: History, Development, and Management. John Wiley & Sons, Inc., New York, New York. pp. 165-184.
Bryson, C.T., Defelice, M.S. 2010. Weeds of the Midwestern United States and Central Canada. University of Georgia Press, pp. 1-427.
Bruns, H.A., Abbas, H.K. 2010. Additional potassium did not decrease aflatoxin or fumonisin nor increase corn yields. Crop Management. doi: 10.1094/CM-2010-0216-01-RS.
Bruns, H.A., Abbas, H.K. 2010. Comparisons of herbicide treated and cultivated herbicide-resistant corn. International Journal of Agronomy. doi:10.1155/2010/798127.
Bryson, C.T., Rothrock, P.E. 2010. Carex Oklahomensis (Cyperaceae) New to Alabama, Georgia, and Louisiana, and Additional Records for Mississippi. Journal of Botanical Research Institute of Texas. 4:349-350.
Bellaloui, N., Reddy, K.N., Zablotowicz, R.M., Abbas, H.K., Abel, C.A. 2009. Effects of Glyphosate Application on Seed Iron and Root Ferric (III) Reductase in Soybean Cultivars. Journal of Agriculture and Food Chemistry. 57:9569-9574
Bruns, H.A., Abbas, H.K. Aflatoxin Contamination in Corn Differs Among Inoculation Techniques. Plant Health Progress, Published on-line - DOI:10.1094/PHP-2010-0601-01-RS.
Nandula, V.K., Poston, D.H., Reddy, K.N. 2010. Seed Germination Differences Between Glyphosate-Resistant and -Susceptible Italian Ryegrass Populations. Seed Technology Journal. 31(2):123-133.