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January 21-22, 2008 • Tunica, Mississippi · Delta & Pine Land · Helena Chemical Co. · HorizonAg · Pioneer Hi-Bred International Inc · RiceTec COTTON PRESENTATIONS Cropping Systems As Best Management Practices Presented by Dr. Donald J. Boquet Presented by Kenneth W. Paxton The traditional farming practice for cotton in the South for 200 years was to produce one summer crop per year following winter fallow. Because cotton residue provided scarce ground cover, this monoculture practice exposed the soil to long periods with little protection from the effects of winter and spring rainfall. Soil erosion was excessive and agricultural sediment became the primary pollutant of surface water causing the US EPA to declare many water bodies as impaired. Many cotton farmers now use conservation tillage and winter cover or grain crops to increase surface residue to reduce erosion and help improve surface water quality. Cover crops are good for water quality but are also good for soil quality and in the long term will be economic and beneficial, but in the short term, may not be. Year-round systems with summer crops of cotton, corn, soybean or grain sorghum and winter crops of wheat, rye or vetch are considered BMPs for surface water quality protection, since they reduce soil and nutrient losses into water bodies. Winter crops stabilize the soil and then eventually increase soil productivity by increasing soil organic matter and soil biological activity. Vetch also provides a large percentage of the N needed by cotton. Use of no till is one of the fastest ways to build organic matter in southern soils and combined with residue from winter crops provides a system with unparalleled benefits for soil and water quality. No-till and cover crop residue also conserve soil water, which can improve yields of the following summer crops. The year-round system of doublecropping wheat and soybean has been a common practice throughout the mid-South for 30 years. Acreage in doublecropping varies and is reliant on the perceived profitability and increased risk for the summer crop. In the case of cotton, the risk of doublecropping may be greater than with soybean because cotton is more reliant on early planting dates and longer growing seasons to maximize yield than soybean. In attempting to achieve the positive effects of these conservation systems on water quality, economics has been a major concern of farmers because these systems may increase production costs, reduce productivity andmay not provide short-termreturns to justify increased expenses. The LSU AgCenter has conducted research for many years on BMP cropping systems to evaluate the yield and economic benefits of these year-round diverse crop sequences. Some of these studies have evaluated irrigated systems that maintain ground cover through the use of crop residues, cover crops and no-till practices. The systems include winter wheat cover crop/cotton, doublecrop wheat/cotton, wheat/soybean, wheat/grain sorghum and doublecrop wheat/cotton rotated with corn, soybean or grain sorghum. Continuous monocropping/ winter fallow of each of the summer crops was included for comparison purposes, though these are not considered BMPs. Total commodity yield of the doublecrop systems was higher than any of themonocrop systems because of the added yield of wheat grain that averaged 65 bu/acre. Summer crop yields usually, but not always, sustained yield losses in double crop systems. For example, doublecrop cotton yield varied from a 3% yield increase to a 21% yield reduction and doublecrop soybean varied from a 12% increase to a 30% yield reduction. Sorghum yielded the same whether planted as a monocrop or doublecrop. Yields of soybean and corn were 10 to 16% higher in doublecrop rotational systems than in doublecrop systems without rotations, but cotton yields were the same with or without crop rotations. Compared with monocropping, doublecrop cotton yields lost an average 67 lb lint/ac each year and doublecrop soybean yields dropped an average of 5 bu/ac each year. Any yield reduction of the summer crop yields is a significant economic penalty because it represents a loss directly from the potential net returns. Although BMP systems were proven in the AgCenter research to be productive, the economics of each system relied greatly on the commodity prices received in a given year. In our studies, using enterprise budgets based on the yields and inputs for each system and annual prices, some of the most profitable systems were BMP systems (Figure1). Doublecrop cotton/ wheat produced annual net returns that ranged from $164.00 to $340.00 per acre from average yields of 65 bu wheat per acre and 1043 lb cotton lint per acre. The system of producing three crops in two years of corn-wheat-cotton averaged annual net returns that ranged from $86 to $221.00 per acre. In comparison, monocrop cotton averaged a net return of $112.00 to $167.00 per acre from average yields of 1110 lb lint per acre. The BMP systems of doublecrop cotton rotated with corn or grain sorghum produced annual net returns that ranged from$101.00 to $181.00 per acre -- approaching that ofmonocrop cotton but less than continuous doublecrop wheat/cotton. Continuous monocrop soybean, corn or sorghum yielded highly variable net returns that ranged from -$40.00 to $148.00 that were usually lower thanmonocrop cotton or BMP systems. Negative returns occurred in some years, usually with monocrop systems and seldom with multicrop systems. Production risk was no greater with the diversity of crops in the BMP systems than with monocropping because these were irrigated studies, which prevented soil water deficient, the primary risk factor for these types of cropping systems in Louisiana. The BMP systems studied in the LSU AgCenter are highly productive and have potential to improve soil and water quality. Despite their value for environmental protection, farmers face limitations in fully implementing these systems because, with current inputs and variable commodity prices, not all systems will be economically competitive with monocrop cotton every year. Conservation programs that subsidize effective BMPs with public funding sources are needed for practices such as winter cover crops to promote implementation and attain their valuable environmental benefits, especially in combination with no till. These studies were conducted with no till, a viable economic practice because of the associated savings in fuel, equipment and labor costs. This research was funded in part by Cotton Incorporated, the Louisiana Cotton Support Committee and the Louisiana Soybean and Grain Research and Promotion Board. Management Of Crop Residues And Soil Compaction For Improved Soil Productivity And Profit Presented by Dr. Normie Buehring Historically, crop residue has been perceived as a problem that has to be destroyed either by fire or tillage. However, crop residues are a valuable resource not only for improving soil organic matter, soil tilth and water infiltration, but also recycle valuable fertilizer nutrients. Removal of corn or grain sorghum crop residue for any reason, including hay or ethanol production, removes valuable fertilizer nutrients from the field. The nutrient removal in the crop residue is correlated to the grain production. Thus, corn stalks baled from corn producing 100 bu/acre grain yield would remove slightly more than 100 lb/acre of K20 and about 15 lb/acre P205. The replacement cost for P205 and K20 removed in the corn residue is currently equal to about $0.30 per bushel of grain yield. Grain sorghum residue stalks baled from a 100 bu/acre grain yield would remove about 150 lb/acre of K20 and about 20 lb/acre of P205. The replacement cost for P205 and K20 removed in the grain sorghum residue would be $0.42 per bushel of grain yield. Therefore, removal of the crop residue by baling for hay or ethanol purposes would not only require extra fertilizer, but also fail to improve soil organic matter, especially on the lighter textured soils which often have organic matter of 1% or less. Improved soil organic matter enhances the soil tilth, water infiltration and soil productivity. Leaving crop residues on the soil surface where possible not only improves the organic matter and infiltration but also protects the soil from erosion caused by rain drop displacement of the soil particles. However, on land that is flat, raised beds are often necessary for seedling emergence and good early season growth. In this situation, without a soil compaction zone, a one-pass tillage-bedding implement operation would be all that is necessary. Basically, this implement is equipped with coulters or cutter blades and bedder sweeps that form a raised bed. The coulter/cutter blades cut the residue in front of the bedder sweep which allows the crop residue to flow through the implement without clogging and leaves some of the crop residue on the soil surface, helping minimize soil erosion. On soils that have a compaction zone, non-inversion under-the-row subsoiling (Terratill® Paratill®) may be required before bedding. These beds are often burned-down with a nonselective herbicide in the early spring and/or reshaped and harrowed prior to planting. With this production system, the row remains in place each year, which is known as a controlled traffic production system. In a controlled traffic system, all equipment wheel traffic, including harvest equipment, passes between the rows. This system does not compact the soil in the root zone where the crop is being grown. Soil compaction is known to reduce yield by impeding root growth, nutrient and water uptake, and overall plant growth. Research has shown that a controlled traffic system reduces soil compaction from approximately 90% in a conventional tillage system to approximately 30%. In summary, consider crop residues a valuable fertilizer nutrient and organic matter resource. Removal of crop residue will likely result in significant nutrient and soil organic matter losses. To minimize wheel track compaction effects, utilize implements with wheel tracks that run between the rows. For improved organic matter, soil tilth, water infiltration and reduced energy consumption utilize no-tillage or minimum one-pass reduced tillage stale seedbed production systems. Evaluation Of Surface Application Of Nitrogen Fertilizer Sources In A Conservation Tillage Cotton System Presented by Charles H. Burmester Surface application of nitrogen (N) fertilizer sources were evaluated for two seasons on cotton grown in a conservation tillage system. The tests were conducted at the Tennessee Valley Research and Extension Center in Belle MinaAlabama. Cotton was planted in late April each season into a heavy rye residue that was terminated approximately three weeks prior to cotton planting. The test area received 20 and 30 pounds per acre of preplant N fertilizer in 2006 and 2007 respectively. At early squaring, all N fertilizer sources were surface applied. In 2006, 60 and 90 pounds per acre rates of N fertilizer were applied, while in 2007 N fertilizer rates were reduced to 50 and 80 pounds per acre because of an increase in preplant N fertilizer. The rye cover crop provided an almost solid cover over the soil when the N fertilizer sources were applied. In both seasons no rainfall occurred and no irrigation was applied for at least 7 days following fertilizer application. These conditions and warm temperatures each year provided ideal conditions for possible ammonia (NH3) volatilization losses after fertilizer application. In 2006 all N fertilizer sources tested were granular fertilizer products that were weighed and hand applied to all plots. In 2007, two liquid N fertilizers were added that were surface dribbled beside each row using a CO2 pressurized sprayer. Fertilizer sources tested in these experiments include: 1) ammonium nitrate, 2) urea, 3) urea + Agrotain (1 gallon per ton), 4) urea + 4.5% calcium thiosulfate, 5) urea + 7.0% calcium thiosulfate, 6) UAN, 7) UAN + Calcium Chloride, 8( UAN + Agrotain (1 gallon per ton), 9) GP 30-0-0. Cotton was irrigated and cotton yields were excellent both seasons. Lint yields ranged from 1200 to 1500 pounds per acre each season. Increasing N fertilizer rates increased cotton leaf- N and yields with all fertilizer sources tested in 2006 and 2007. In 2006, ammonium nitrate produced significantly higher cotton yields than urea. Cotton yields with ammonium nitrate, however, were not significantly different than yields produced with urea plus Agrotain or urea plus calcium thiosulfate. In 2007 cotton yields were slightly higher, but significant yield differences between ammonium nitrate and the granular urea fertilizers were not found. Cotton yields with the liquid N fertilizers were also not significantly different than yields with ammonium nitrate in 2007. This data indicates that although there appeared to be significant N loss from surface applied urea in 2006, these results were not repeated in 2007. Lower rainfall in 2007 may have kept the soil surface drier and reduced possible N volatilization losses after application. "From Spider Mites To Plant Bugs: Putting The Odds In Your Favor" Presented by Dr. Angus Catchot Introduction Over the last decade we have seen dramatic shifts in the relative status of insect pests in cotton throughout the mid-south region. Two of the most notable events have been successful implementation of boll weevil eradication and the introduction of transgenic B.t. technology. These two events have eliminated insecticide sprays targeted for boll weevil and tobacco budworm. Prior to 1995, boll weevil and tobacco budworm were major pests of cotton in the mid-south. Since that time their status as major pests has Page 9 • Eleventh Annual National Conservation Systems Cotton & Rice Conference Proceedings Book been greatly reduced. In fact, 1999 was the last year that Mississippi documented any losses associated with boll weevils. Since it’s introduction in 1996, producers throughout the mid-south region have readily adopted B.t. cotton. Most mid-south states have adoption levels of 85-95% over the last 5 years. While many acres still require at least one spray for cotton bollworm, the threat from tobacco budworm has been essentially removed, barring any future event of resistance. As with most biological systems, when one factor is removed, others quickly fill the void. The same is generally true for pests attacking row crops. With reduced sprays coupled with increasing insecticide resistance we have seen tarnished plant bugs quickly move from secondary pest status to the new number one pest of cotton in the mid-south region. Also, in the last three years producers in the mid-south have seen increased spider mites in cotton, particularly early in the season. Spider mites have been infesting cotton in the mid-south as far back as records have been kept but their status was one of occasional pest and infestations were largely limited to late in the season. Tarnished Plant Bug Prior to 2007, the record average number of insecticide applications made in the Mississippi delta region was 5.2 in 2004. In 2007, the number is estimated at 7-8. In a recent survey that represented 35% of the cotton acres in the MS delta, 45% of the acres surveyed received 10 or more applications for TPB while another 37% received between 7-10. In a more recent survey 22,000 acres represented had between 14-16 applications. Given the events in 2007, many producers want answers to two questions: (1) why were TPB populations so high in 2007 and (2)What can we do reduce our risk of being in this situation again? Both questions are valid and need to be addressed but unfortunately there are no “clear” answers. However, these topics have been discussed at length through the mid-south entomology working group and plausible explanations are available. Most believe one factor was the major increase in corn acres. In 2007, producers planted 980,000 acres of corn in MS, a 60% increase compared to 2006. While we know corn can serve as a host for TPB, it is a complex interaction not easily explained. Sampling corn for TPB often yields highly variable results, some fields have extremely high levels of TPB and others have none. The TPB increase is more likely attributed to several factors working together. In 2007 we saw unusually warm weather extended over a 3-week period during the month of March. Entomologists with USDA-ARS in Stoneville, MS reported extremely high levels of TPB reproduction occurring. Next we went through and early drought period that caused a reduction in wild hosts about the time cotton was beginning to square and corn and group IV soybeans were flowering and being irrigated. TPB simply utilized these hosts to sustain the large populations that reproduced in March and we saw continued emigration out of these alternate crops into a cotton crop that was reduced in acres by 46%. What can we do to reduce our risk of being in this situation again? With very few new insecticides available to control TPB, entomologist are beginning to reach deep into the bag to make producers aware of management practices that could help reduce the number of insecticide sprays. Several methods include: treating only when threshold numbers are present, reducing the “edge effect” next to corn, manage broad leaf weeds in ditch banks, equip sprayers with correct nozzles for insecticides, utilize nectariless cotton when available, increase GPA, etc. Spider Mites Over the last three years, the frequency of spider mite treatments has greatly increased in the mid-south. Since treating spider mites is extremely expensive, producers are looking for ways to better manage this pest. Many have speculated as to why mite problems are increasing. Some believe that it is due to the switch from Temik to insecticide seed treatments. Preliminary data, from Mississippi State University shows that the risk of spider mites is slightly greater with a seed treatment, but the results are highly variable. While there are numerous factors likely involved, the single biggest factor is likely extended periods of drought during the growing season the last several years, which is favorable for spider mite development and reproduction. A factor associated with early season spider mite infestations seems to be wild hosts either within or near fields. Delayed weed burndown greatly increases the risk for early season infestations of spider mites. If spider mites happen to be present on winter annuals and burndown is delayed, mites simply move off dying weeds onto the crop. Growers should try and have weeds dead at least 3 weeks prior to planting. Recent host plant work has found henbit to be one of the major early season hosts for spider mites. Other weeds include; honeyvine milkweed, vervain, white clover, and coneflower. Summary The first step in being able to reduce risk from a pest is a basic understanding of the biology and association of the pest with that crop and the environment. With some basic understanding of these concepts we can start removing requirements or introducing obstacles so that these pests are less likely to reach an economic threshold. An attempt has been made to introduce several of the factors that often play key roles in the likelihood of these pests reaching economic status in a given year. Furthermore, many of the concepts mentioned are cultural in nature, and require very little input on the part of the producer to implement, and enable the producer to minimize insecticidal inputs. Recognizing Potential Cotton Pest Problems In AMulti-Crop Environment Presented by Dr. B. Rogers Leonard Introduction The recent increase in grain prices has motivated many producers to broaden their cropping systems to include combinations of wheat, field corn, soybean, grain sorghum, and cotton. Many southern arthropod pests infest more than one of these plant hosts and crop diversification has the potential to increase overall pest pressure and influence the costs of plant production strategies. This report will briefly illustrate examples of pests that may be influenced by crop diversity on individual farms and in local areas. In addition, several suggestions for common sense management tactics will be discussed. Arthropod (Insects and Spider Mites) Pests and Cropping System Interactions In many cases, the initial infestations of cotton pests do not occur across the entire field and are discovered as localized problems in specific areas. Usually these areas are associated with field borders and may be adjacent to a number of landscapes such as crops, fallow fields, pastures, woodland, WRP-CRP fields, and wetlands. There is only one arthropod pest, boll weevil, which is specific to cotton and not found attacking other crops. Infestations of other pests in cotton fields usually originate from populations in other native host areas or crop fields and immigrate to cotton fields. This event usually occurs as the result of cotton plants becoming more attractive as hosts for those specific pests than those plants where the population first originated. Examples of cotton arthropod pests that are found in other crops are common. Thrips often develop on native winter and spring grasses or grain crops such as wheat. As wheat plants mature, high numbers of thrips migrate into adjacent cotton fields and attack seedlings. Tarnished plant bugs are often found infesting native vegetation, field corn, soybeans, and even grain sorghum fields. As these crops become unfavorable hosts, populations can migrate to adjacent cotton fields for an extended period. The corn earworm or bollworm prefers corn plants during the silking stage of development. As corn plants mature beyond this stage of development, this pest moves into cotton fields that are usually are in their reproductive stages of plant development. The fall armyworm is a migratory pest that feeds on a wide range of native and crop hosts. During the late summer as those hosts mature and are no longer attractive, populations of fall armyworm often move into cotton fields and cause injury. Spider mites are active during the early spring on numerous plant hosts including corn and soybean which allows populations to increase. During favorable environmental conditions, spider mites can infest cotton fields during the early-, mid-, and late-season. The same complex of stink bugs that infests soybean also will feed on cotton. Many southern producers are producing MG IV soybeans that are harvested during August and early September. Late-season stink bugs problems have become common in many agroecosystems that include combinations of cotton andMG IV soybean. This brief list certainly does intend to include all possible arthropod pests that can be found in multi-crop environments, but should provide enough examples to justify the importance of the potential interactions and effects on cotton IPM strategies. Considerations for Pest Management Tactics Producers and scientists have recognized for many years that crop production practices and the local environment within and around cotton fields can have significant effects on the development of pest problems, and require an adjustment in pest management strategies. More costly pest problems do not always occur in each and every instance, but producers and agricultural consultants should be aware of the potential for these effects, and be prepared to modify their pest control tactics. Several suggestions for managing cotton pests in fields associated with multi-crop landscapes are listed below. • Establish field plans for crops well-in-advance of planting after considering the implications of emigrating pests. Provide this information to your agricultural consultant for review and obtain his suggestions to minimize pest problems. • Producers should attempt to plant the same crop across an entire field or in groups of fields. This strategy will minimize the number and length of border areas between cotton fields and other crops that may provide a source of emigrating arthropod pests. • Effective control of late-winter and early-spring vegetation across all fields on a farm can reduce overwintering pest populations before the crop is planted. Producers should use tillage or herbicide combinations to completely destroy all weeds in fields. Welltimed herbicide use strategies can reduce alternate host availability, suppress pest population development, or delay emigration into adjacent cotton fields. • If a pest problem is identified in an adjacent field, increase the frequency of scouting cotton fields along the border areas. Early detection of pests and the timely application of the appropriate control tactics can be important to reduce the overall seasonal injury potential and costs of pest management. Do not apply preventative treatments and use established action thresholds for applications of pesticides. • Crops such as wheat and field corn are usually actively growing at the time cotton is being planted. Recognize the potential of thrips immigrating to adjacent cotton fields. Producers should consider using a soil insecticide such as Temik 15G or insecticide-treated seed to reduce the impact of thrips injury to cotton seedlings. As wheat matures, high numbers of thrips may migrate to adjacent cotton fields. If this immigration occurs after the residual efficacy of the insecticide has decayed, supplemental foliar insecticide applications may be necessary. • If pest populations are detected in localized areas along cotton field borders, apply pesticide treatments only to those areas of fields where infestations are located, especially during the early to mid-season. Treating only isolated portions of fields reduces control costs without sacrificing yields. • During the mid-to-late season, producers and agricultural consultants should monitor all crops on a farm. Allowing pest populations to increase in one crop, even if that crop is already mature and no economic injury is occurring, can provide a source of infestation to adjacent fields. Usually late-season emigrating populations are very heavy and may persist for an extended period. This may result in multiple pesticide applications at frequent intervals. • Be aware of differences in pesticide labels among different crops. Although the same pest may infest and injure several crops, pesticides are not universally labeled across all crops. Using non-labeled pesticides is illegal and could cause crop phytotoxicity and yield loss to occur. • Destroy all post-harvest crop residue and weedy vegetation to eliminate overwintering quarters for pests and subsequently build populations during the fall. • Double-cropping cotton after winter wheat should be given special consideration due to the delay in planting, crop development, and eventual harvest. The double-cropped fields remain attractive to arthropod pests after most other local cotton fields have reached harvest maturity. An “island” effect is created in which many of the pests in that area funnel into the attractive double-cropped fields. In some instances, persistent and high populations can occur and require numerous and costly pesticide applications to obtain satisfactory control. The same concerns also exist for any late-planted cotton fields. Summary Southern agriculture will continue to evolve with annual fluctuations in the value of all available crops. Successful producers will capitalize on the profitability and stability of multi-cropping systems. This change to multi-crop production systems will also influence the diversity and severity of arthropod pest problems. A “common-sense” approach to pest management strategies is necessary to optimize farm income from cotton, as well as other crops.Agricultural consultants and producers are forewarned to recognize the direct relationships of cotton pest problems and specific plant hosts in multi-crop production systems and to adjust their pest control tactics accordingly. Performance Of New Cotton Varieties In The North Delta Presented by Dr. Chris Main The release of cotton varieties with the latest biotechnology traits has researchers and p roducers scrambling to find varieties that perform as well as first generation biotechnolog y trait varieties. Beyond obvious yield goal, intangible benefits of these new technologies are driving their adoption. The increased flexibility for weed management and the ability t o use a natural refuge with Roundup Ready Flex and two gene Bt traits has producers look ing towards these new varieties for time savings and reductions in input costs. In this pres entation we investigate the performance of recently released cotton varieties in the North Delta states of Arkansas, Missouri, and Tennessee.
Table 1. Top ten varieties in Arkansas and Tennessee OVT’s for 2005, 2006, and 2007.
Table 2. Top ten varieties in Missouri OVT’s for 2005, 2006, and 2007.
While yields for these new cotton varieties have lacked stability, fiber quality is typicall y equal to or better than the first generation biotech cotton varieties. To better understand p erformance of these new varieties the presentation will focus on yield stability models and fiber quality evaluations for several of the more popular cotton varieties grown in the North Delta region. Net Return Comparison Of No Tillage And Minimum Tillage Cotton-Corn Rotations Presented by Dr. Steven W. Martin Crop rotations have been shown to have agronomic benefits. An increasingly common crop rotation in the Mid–South is cotton rotated with corn. Many previous studies have focused on tillage systems or crop rotations. Few have evaluated a combination of the two (crop rotations and tillage) especially from an economics perspective. Field studies were conducted at Stoneville, MS for the period 2001-2006. Treatments included no-till continuous cotton, minimum till continuous cotton, one year corn followed by two years cotton no till, one year corn followed by two years cotton minimum till, one year corn-one year cotton no till and one year corn-one year cotton minimum till. Results revealed that cotton yields were increased in all four systems rotated with corn. Lower risk was associated with minimum till cotton. Gross returns were higher in a monoculture minimum till cotton system. Net returns were larger in a system that included minimum tillage and a corn rotation. The highest net returns and lowest risk were obtained from a minimum till system of cotton rotated with corn every other year. For those producers required to use a no-till system, a one year corn-two year cotton rotation provided the highest net returns and least risk. Accumulation Of Nitrates In Soil Profiles Due To Over-Fertilized With Urea In Optimum Irrigated And Dry Land Cotton Production Systems Presented by Dr. J. Scott McConnell Nitrogen (N) fertilizer use in cotton (Gossypium hirsutum L.) production has come under scrutiny as a potential source of nitrate contamination of streams and ground water. This study was conducted to determine the distribution of nitrate-N in soil cropped to continuous cotton, and to evaluate fertilization practices and irrigation methods that might exacerbate the accumulation of nitrate--N in the soil profile. Long-term N-fertilization studies in side-by-side irrigation blocks at the Southeast Branch Experiment Station at Rohwer, Arkansas, the McConnell - Mitchell Plots, were utilized to determine nitrate-N accumulation and depletion. The soil at the study site was an Hebert silt loam (fine-silty, mixed, thermic Aeric Ochraqualfs). This test, the oldest continuous test inArkansas, was established in 1982. The two irrigation methods reported are furrow flow irrigation (FI) and high-frequency center pivot (HFCP). The two irrigation methods were compared to a dry land (DL) control. Nitrogen treatments were tested within each irrigation block and ranged from 0 to 150 lb N/acre in 30-lb N/acre increments. Nitrogen treatments were first applied in 1982 and continued through1999. Nitrogen treatments were discontinued from 2000 through 2003, then resumed in 2004. Soil samples were taken in the early spring (2000 and 2004) prior to N-fertilization to a depth of 5.0 ft in 0.5-in increments from three replicates of each N-treatment within each irrigation block. The samples were air-dried, ground, and analyzed for nitrate-N. The distribution of soil nitrate-N in the FI block indicated significant differences due to sample depth and N treatment in both 2000 and 2004. Soil nitrate-N was lowest in the surface 1.0 ft, and greatest soil nitrate-N was found from 1.5 to 2.5 ft, although not all differences were significant in 2000. Differences in soil nitrate-N in the FI block after suspending N treatments for four years were similar to those found in 2000, although the soil nitrate-N was generally depleted in 2004 compared to 2000. The primary zone of nitrate-N accumulation was within the argillic horizon both years. Soil nitrate-N was found to increase irregularly with increasing N rates both years. The distribution of soil nitrate-N in the DL block was dependent on the interaction of sample depth with N treatment in 2000 and 2004. Soil nitrate-N was minimal in the three lowest N treatments (0-, 30-, and 60-lb N/acre) in 2000. The 90 lb N/acre treatment had substantial accumulations of soil nitrate-N in the surface 2.0 ft that declined with depth in 2000. Greatest amounts of soil nitrate-N were found in conjunction with the 120- and 150-lb N/acre treatments at depths of 0.5 to 2.5 ft in 2000. These depths extend approximately midway through the argillic horizon. Soil nitrate-N was minimal in the four lowest N treatments (0-, 30-, 60-, and 90-lb N/acre) in 2004. This indicates that discontinuing the N treatments for four years, in combination with continuous cropping depleted the soil of some of the excess nitrate-N. The upper 2.0 ft of 120- and 150 lb N/acre treatments were also found to be depleted of excess soil nitrate-N in 2004. Observationally, this depth coincides with the approximate depth of rooting of the cotton crop most years. The distribution of soil nitrate-N in the HFCP irrigated block was dependent on the interaction of sample depth with N treatment in 2000 and 2004. No significant difference was observed in the soil nitrate-N of the 0- to 120-lb N/acre treatments in 2000. The 150 lb N/acre treatment produced soil nitrate-N concentrations that significantly differed with both other depths within the treatment and with other N treatments in 2000. Differences in soil nitrate-N were too small to be of practical importance in 2004. Differences in soil nitrate-N between the two sampling years were evident only in the 150 lb N/acre treatment, and indicate that the nitrate-N was depleted from the soil. These results indicate that accumulation of nitrate-N in soils cropped to cotton was a potential environmental problem only in the DL block when N treatments exceeded crop requirements. Further, reserving N fertilization for more than four years may be required to deplete excess soil nitrate-N. Where Do Seed Treatments Fit In Cotton Disease Management? Presented by Dr. Boyd Padgett In the past, in-furrow applied fungicides and nematicides were the most effective method for managing cotton seedling diseases and nematodes. However, with the advent of new seed treatment fungicides and nematicides, producers now have the option of using a complete package on the seed for their seedling disease and nematode problems. This option is attractive to producers because of the added convenience, but questions remain about the effectiveness of these treatments relative to the in-furrow applied products. Seed treatments for managing seedling diseases have been available for many years, but treatments for managing some nematodes are a recent advance in seed treatment technology. While seed treatments may seem attractive, there are advantages and disadvantages that need to be considered before ditching your hopper boxes. Pros of Seed Treatments Convenience is an attractive advantage of seed treatments. Treatments are applied by seedsmen prior to sale; therefore, the need to calibrate equipment and load hopper boxes is eliminated thus saving the grower valuable time. Producers can use this time for planting or additional field operation. In addition, there is no opportunity for equipment failure or maintenance. If hopper boxes are not needed the expenses associated with these boxes can be used for other expenses. In the past, clogged delivery tubes resulted in non-treated areas in the field and increased disease and reduced yields. Safety is another advantage of seed treatments. The amount of pesticide exposure is minimized with seed treatments. Farm labor is directly exposed to in-furrow applied fungicides and nematicides, but seed treatments are delivered to the farm already on the seed. Rates of in-furrow applied fungicides or nematicides range from a few fluid ounces to several quarts or a few ounces to several pounds, compared to a fraction of an ounce or fluid ounce needed for most seed treatments. Therefore, exposure of farm labor to fungicides and nematicides is minimized. In addition to safety for labor, overall pesticide load in the environment is less for seed treatments relative to in-furrow applied products. In-furrow applied products are deposited on the seed and the surrounding soil, but seed treatments are confined to the seed surface making this attractive to the Environmental Protection Agency. As environmental awareness and stewardship increases, seed treatments may be the option of choice. Cons of Seed Treatments Efficacy of seed treatments may not be as effective as in-furrow applied products. Since seed treatments are limited to product on the seed coat, the amount of available product is usually less for seed treatments than for in-furrow applied products. This reduction in quantity could result in lower efficacy in scenarios where disease pressure is high. In fields infested with nematodes, more galls were noticed on seedlings originating from seed treated with nematicides compared to seedlings where in-furrow nematicides were used. Residual activity of seed treatments is usually less than that provided by in-furrow applied products. This is due, in part, to the reduction in the amount of product available. The efficacy of seed treatments do not provide the extended residual activity provided by in-furrow treatments. Cost of seed treatments can rival that of those for in-furrow applied products. Where do seed treatments fit? While the efficacy of seed treatments may be less and cost as much as in-furrow applied products, seed treatments have a fit in the Mid-South. Using seed treatments can save producers valuable time during the early spring when the weather can be unpredictable. Seed treatments should not be used in fields where seedling disease and/or nematode problems are severe. In addition, seed treatments would not be the best option when planting during inclement weather. However, seed treatments are effective when used in fields where low to moderate disease or nematode pressure exists or during short periods (several days) of inclement weather. Cotton And Corn Rotation Under Reduced Tillage Management: Impacts On Soil Properties, Weed Control, And Yield Presented by Dr. Krishna N. Reddy Historically, cotton has been grown inmonoculture under conventional tillage systemin the lower Mississippi Delta region. Profit margins in cotton production have declined in recent years due to high production costs, low commodity prices, and stagnant yields. There is a need to find profitable crop production systems that increase crop yields without greatly increasing production costs. There has been a renewed interest in producing cotton in a rotation system to overcome chemical and biological factors associated with a yield plateau that occur in cotton monoculture.When crops are rotated, the change in herbicides and practices may often improve control of problem weeds, soil properties, and crop yields. Reduced tillage system minimize input cost due to fewer tillage operations. Transgenic crops resistant to glyphosate introduced during the past decade have provided farmers flexibility to manage weeds and freedom to choose a rotational crop for the following year without restrictions. This study examines cotton and corn production in a rotation under a reduced tillage system. The specific objectives of this study were to compare soil properties, weed control, yields, and net return fromcontinuous and rotated cotton-corn production systems.Weed control and yields from glyphosate-resistant (GR) and non-GR cultivars were measured and compared over the 6-yr period.An important aspect of this research was to determine whether rotation of cotton with corn would increase crop yields and profit under reduced tillage systems in the lower Mississippi River alluvial flood plain region. A6-yr rotation studywas conducted from2000 to 2005 on aDundee silt loamat Stoneville, MS. There were four rotation systems (continuous cotton, continuous corn, cotton-corn, and corn-cotton) for each conventional and GR cultivar arranged in a randomized complete block design with four replications. Each treatment consisted of eight rows spaced 40-inch apart and 150-feet long.After the fall of 2000, the experimental area received no tillage operations except the beds were conditioned: re-hipped after harvest and flattened before planting. Glyphosate-based program in GR cultivars and non-glyphosate-based program in conventional cultivars were used for weed control. Crops were irrigated on an as-needed basis each year. Soil organic matter in surface 5-cm soil at planting was higher in corn grown continuously and in rotation compared to continuous cotton system. Overall, soil pH and other fertility parameters were similar in all rotation systems. Control of ten dominant weed species (grass and broadleaf) in cotton and corn was >93%, regardless of herbicide program and weed control was sufficient to support cotton and corn production. Control of browntopmillet and hyssop spurge slightly reduced (83 to 85%) in rotated non-GR cotton after 6 years. Control of yellow nutsedge (55%) was reduced in continuous non-GR cotton; this apparent weed species shift toward yellow nutsedge was mitigated by breaking the cotton monocrop with corn. Plant populations of both conventional and GR cotton rotated with corn were similar to that of continuous cotton suggesting cotton stand establishment was not affected by corn residues from the previous year. Cotton yield increased every year following rotation with corn by 10 to 32%in the conventional cultivar and by 14 to 19%in the GR cultivar compared to continuous cotton. Similarly, corn yield increased by 5 to 13%in the conventional cultivar and by 1 to11%in the GR cultivar when rotated with cotton. These results indicate that a rotational system can increase yield in both cotton and corn over a mono-cropping system without increasing production costs. This 6-yr study under reduced tillage demonstrated that a switch to cotton-corn rotation system is agronomically feasible, economically beneficial, and potentially sustainable option for farmers in the lower Mississippi Delta region. منبع:سایت پنبه آمریکا ان شاءالله به زودی چکیده مقاله به فارسی ارائه می گردد | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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