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Long-term crop rotation studies were established at the Delta Research and Extension Center near Stoneville, MS to evaluate the contributions of rotations involving cotton, corn, and soybean with respect to both yield and profitability. The most up-to-date technology has been used that incorporates the latest advances in biotechnology, herbicides, cultural practices, irrigation, and fertility. The five cropping sequences include 1) corn-cotton, 2) corn- cotton-cotton, 3) corn-soybean, 4) soybean-corn-cotton, and 5) soybean-corn-cotton-cotton with a continuous cotton system as the basis for comparison. Each crop has been grown each year giving a total of 15 'treatments' in the study with four replications. Crop yields, nutrient uptake, and nutrient removal are calculated annually based on harvests made with commercial harvesters adapted for plot harvest. The value of the crop being grown has been calculated based on loan rate (LR) or the average price received by producers (NASS), whichever is higher. The economic impact of crop rotations is evident in most years just from the yield standpoint. As the cost of inputs continues to increase the more important crop rotation becomes. In the first few years where cotton prices were low and producers sold into the loan, cotton's value was high relative to corn and soybean. However, in the last few years grain prices have increased dramatically while cotton prices have remained lower or constant. As the grain prices increased the crop value greatly increased. When taking into consideration the cost of production for each crop, cotton production costs greatly exceed corn or soybean production cost even with high fertilizer and seed costs. [ABSTRACT FROM AUTHOR]

Long-term crop rotation studies were established at the Delta Research and Extension Center near Stoneville, MS to evaluate the contributions of rotations involving cotton, corn, and soybean. The most up-to-date technology has been used that incorporates the latest advances in biotechnology, herbicides, cultural practices, irrigation, and fertility. The five cropping sequences include 1) corn-cotton, 2) corn-cotton-cotton, 3) corn-soybean, 4) soybean-corn-cotton, and 5) soybean-corn-cotton-cotton with a continuous cotton system as the basis for comparison. Each crop in a rotation system has been grown each year giving a total of 15 'treatments' in the study with each replicated four times. The cropping sequences will reach the same point after 12 years and will repeat the cycles. Crop yields, nutrient uptake, and nutrient removal are calculated annually based on harvests made with commercial harvesters adapted for plot harvest. Continuous cotton yields have been lower than any other system that included cotton and thus has the overall lowest nutrient removal. Corn yields have ranged from 185 to 223 bu/acre depending upon the year. Soybean yields have ranged from 52 to 81 bu/acre over the first five years with water tending to be the most limiting factor. Timely irrigation is needed for consistent high yields. Nutrient removal has been strongly related to the crops being grown. Soybean removed the largest percentage of nitrogen (N) and potassium (K) while corn removed more phosphorus (P) from the system. With respect to soybean production, most of the N being removed is available to the plants through symbiotic fixation of atmospheric nitrogen. The economic impact of crop rotations is evident in most years just from the yield standpoint. As the cost of inputs continues to increase the more important crop rotation becomes. [ABSTRACT FROM AUTHOR]

Long-term crop rotation studies were established at the Delta Research and Extension Center near Stoneville, MS to evaluate the contributions of rotations involving cotton, corn, and soybean. The most up-to-date technology has been used that incorporates the latest advances in biotechnology, herbicides, cultural practices, irrigation, and fertility. The five cropping sequences include 1) corn-cotton, 2) corn-cotton-cotton, 3) corn-soybean, 4) soybean-corn-cotton, and 5) soybean-corn-cotton-cotton with a continuous cotton system as the basis for comparison. Each crop in a rotation system has been grown each year giving a total of 15 'treatments' in the study with each replicated four times. The cropping sequences will reach the same point after 12 years and will repeat the cycles. Crop yields, nutrient uptake, and nutrient removal are calculated annually based on harvests made with commercial harvesters adapted for plot harvest. Continuous cotton yields have been lower than any other system that included cotton and thus has the overall lowest nutrient removal. Corn yields have ranged from 185 to 223 bu/acre depending upon the year. Soybean yields have ranged from 52 to 81 bu/acre over the first five years with water tending to be the most limiting factor. Timely irrigation is needed for consistent high yields. Nutrient removal has been strongly related to the crops being grown. Soybean removed the largest percentage of nitrogen (N) and potassium (K) while corn removed more phosphorus (P) from the system. With respect to soybean production, most of the N being removed is available to the plants through symbiotic fixation of atmospheric nitrogen. The economic impact of crop rotations is evident in most years just from the yield standpoint. As the cost of inputs continues to increase the more important crop rotation becomes. [ABSTRACT FROM AUTHOR]

The article presents the result of the study which have assessed nitrogen (N) and potassium (K) applications for mono-crop cotton grown under dryland as well as determined cotton lint yield response to increase N rates and K additions. The study reveals that most significant factors influencing cotton lint yields under dryland (rain-fed) conditions are rainfall amounts and distribution along with subsoil tillage. It mentions that it has shown a little economic benefit from combining subsoil tillage and supplemental irrigation for cotton production.

A chart is presented that depicts the cotton disease loss estimate report of the U.S. National Cottonseed Treatment Committee.

The article presents a study which evaluates the cotton yield response of nitrogen (N) and potassium (K) applications in a dryland production system in the Mississippi Delta. It highlights a multi-year study on a Forestdale silty clay loam which had a 3x2 factorial arrangement of N rates and K rates. It found that rainfall amounts and distribution along subsoil tillage influenced cotton lint yields under dryland conditions. Furthermore, it cites that rainfall tends to be more limiting than N or K fertility in years.

A chart is presented which lists estimated reduction in cotton disease for 2007 in the U.S. diseases include Fusarium Wilt, Verticillium Wilt, and Bacterial Blight.

The aquaculture industry in Mississippi, primarily catfish, provides a possible source of organic nutrients that could be used in row-crop production systems in the areas where processing plants are located. The by-product fish-based fertilizer (FBF) material could provide an alternative nutrient source if the material can be used profitably in row-crop production. A series of studies were designed and established to evaluate FBF for cotton production. The material was evaluated as an in-furrow starter source, as a foliar nutrient source during the season, and in association with plant growth regulator (PGR). Organic FBF was evaluated from 2004 through 2006 at the Delta Research and Extension Center and at the Tribbett Satellite Farm under irrigated and non-irrigated culture. Climatic conditions were quite variable during the studies and yields ranged as low as 750 lb/acre to more than 1500 lb/acre depending on the year. Hurricanes in 2005 greatly reduced the harvestable yields in all studies. In general there was no significant yield response to applications of the organic FBF evaluated in these studies. The low levels of fertilizer nutrients available in the FBF material were not sufficient to alter crop yields. Since cotton is a perennial, year-to-year variations are in growth and development is common. The potential for organic fish-based fertilizer material would appear to be outside traditional row-crop production where higher levels of available nutrients are required over a short growth period. [ABSTRACT FROM AUTHOR]

The aquaculture industry in Mississippi, primarily catfish, provides a possible source of organic nutrients that could be used in row-crop production systems in the areas where processing plants are located. The by-product fish-based fertilizer (FBF) material could provide an alternative nutrient source if the material can be used profitably in row-crop production. A series of studies were designed and established to evaluate FBF for cotton production. The material was evaluated as an in-furrow starter source, as a foliar nutrient source during the season, and in association with plant growth regulator (PGR). Organic FBF was evaluated from 2004 through 2006 at the Delta Research and Extension Center and at the Tribbett Satellite Farm under irrigated and non-irrigated culture. Climatic conditions were quite variable during the studies and yields ranged as low as 750 lb/acre to more than 1500 lb/acre depending on the year. Hurricanes in 2005 greatly reduced the harvestable yields in all studies. In general there was no significant yield response to applications of the organic FBF evaluated in these studies. The low levels of fertilizer nutrients available in the FBF material were not sufficient to alter crop yields. Since cotton is a perennial, year-to-year variations are in growth and development is common. The potential for organic fish-based fertilizer material would appear to be outside traditional row-crop production where higher levels of available nutrients are required over a short growth period. [ABSTRACT FROM AUTHOR]

Host plant resistance is the most economic and effective strategy for Fusarium wilt control. To implement steps to develop resistant germplasm to this pathogen, existing commercial Acala, non-Acala Upland (Gossypium hirsutum L.) and Pima (G. barbadense) cultivars, as well as improved germplasm were subjected to FOV race 1 (R1) with root-knot nematodes and race 4 (R4) field disease pressures, and non-infested field. All cotton entries tested were infected by R1 and R4, and variability in symptoms for FOV R1 and R4 occurred in both G. hirsutum and G. barbadense cottons. Significant differences were observed for plant survival within each race and between races of FOVs. Disease severity was significantly greater for FOV R4 than for FOV R1 as expressed by foliar symptoms and vascular root staining ratings. Plants infected by FOV tended to be smaller with a larger number of nodes than those grown in non-infested soils. In host plant resistance in Pima cottons, known resistant (Phy-800) and susceptible (DP-744) commercial cultivars under R4 pressure were observed to respond significantly different under R1 pressure. DP7-44 was more resistant than Phy-800 under R1 pressure based on plant survival and vascular staining. The host plant resistance observations may suggest that two independent genes and/or an additional gene may control the R1 and/or R4 resistance. Additional research is needed to address host plant interactions between races. Certain forms of this pathogen can survive for a long time in soils even if the host plant is not present. This research is providing information about the susceptibility of commercial and improved germplasm cottons, allowing growers to make informed decisions regarding the choice of cotton cultivar to plant in fields infested with FOV R1 and/or R4. In addition, this research identified potentially improved resistant germplasm and raises the need to breed cotton in California with resistance to existing FOV races. [ABSTRACT FROM AUTHOR]

The development of specific primers for the detection of Fusarium oxysporum f. sp. vasinfectum (FOV) race 4 is described. Primers were designed from the sequence of an AFLP marker unique to race 4 and screened against a collection of California FOV isolates, virulent Australian FOV isolates, and various fungi isolated from cotton tissue. The amplification of DNA by the primers was unique to FOV race 4. Characterization of disease development caused by FOV race 4 was tested at different inoculum densities, ranging from zero to 10^6 spores per gram of soil. Results for two Upland cotton cultivars, Phytogen 72 and Ultima EF, and three Pima cotton cultivars, Delta Pine 340, Delta Pine 744, and Phytogen 800, suggest an inoculum threshold between 10^3 and 10^4 spores per gram of soil for disease development. [ABSTRACT FROM AUTHOR]

Host plant resistance is the most economic and effective strategy for Fusarium wilt control. To implement steps to develop resistant germplasm to this pathogen, existing commercial Acala, non-Acala Upland (Gossypium hirsutum L.) and Pima (G. barbadense) cultivars, as well as improved germplasm were subjected to FOV race 1 (R1) with root-knot nematodes and race 4 (R4) field disease pressures, and non-infested field. All cotton entries tested were infected by R1 and R4, and variability in symptoms for FOV R1 and R4 occurred in both G. hirsutum and G. barbadense cottons. Significant differences were observed for plant survival within each race and between races of FOVs. Disease severity was significantly greater for FOV R4 than for FOV R1 as expressed by foliar symptoms and vascular root staining ratings. Plants infected by FOV tended to be smaller with a larger number of nodes than those grown in non-infested soils. In host plant resistance in Pima cottons, known resistant (Phy-800) and susceptible (DP-744) commercial cultivars under R4 pressure were observed to respond significantly different under R1 pressure. DP7-44 was more resistant than Phy-800 under R1 pressure based on plant survival and vascular staining. The host plant resistance observations may suggest that two independent genes and/or an additional gene may control the R1 and/or R4 resistance. Additional research is needed to address host plant interactions between races. Certain forms of this pathogen can survive for a long time in soils even if the host plant is not present. This research is providing information about the susceptibility of commercial and improved germplasm cottons, allowing growers to make informed decisions regarding the choice of cotton cultivar to plant in fields infested with FOV R1 and/or R4. In addition, this research identified potentially improved resistant germplasm and raises the need to breed cotton in California with resistance to existing FOV races. [ABSTRACT FROM AUTHOR]

The development of specific primers for the detection of Fusarium oxysporum f. sp. vasinfectum (FOV) race 4 is described. Primers were designed from the sequence of an AFLP marker unique to race 4 and screened against a collection of California FOV isolates, virulent Australian FOV isolates, and various fungi isolated from cotton tissue. The amplification of DNA by the primers was unique to FOV race 4. Characterization of disease development caused by FOV race 4 was tested at different inoculum densities, ranging from zero to 10ˆ6 spores per gram of soil. Results for two Upland cotton cultivars, Phytogen 72 and Ultima EF, and three Pima cotton cultivars, Delta Pine 340, Delta Pine 744, and Phytogen 800, suggest an inoculum threshold between 10ˆ 3 and 10ˆ4 spores per gram of soil for disease development. [ABSTRACT FROM AUTHOR]

Increasing nutrient uptake efficiency has been a goal of researchers for years and many continue to evaluate concepts and products that may increase fertilizer efficiency. Equity™, a soil amendment from Naturize BioSciences was evaluated in a replicated field trial on a Forestdale silty clay loam soil over a 2-year period. Two Equity formulations were used in the initial trial, one with humate, one without humate, while only one was evaluated during the second year. The products were applied in-furrow (IF) at planting, as a surface band (SB) application at planting, and as a combination of in-furrow and surface band (IF+SB) applications. These treatments were then compared to untreated controls (UTC). Nitrogen rates were similar for all plots and other cultural practices maintained uniformly across all plots. Seedcotton and lint yields were determined for all treatment combinations with lint yields based on hand-grab samples taken at harvest and ginned through a 10-saw micro-gin. Plant stands were measured following harvest by counting the two harvest rows. The highest seedcotton and lint yield was obtained the first year with 2 qt/acre Equity+humate applied in-furrow. In-furrow application of 2 qt/acre increased the lint yield by 118 lb/acre (8.9%) compared to the average of the two untreated controls. In the second year, one product was eliminated and the rates increased for the remaining product. There were no significant effects measured or observed in the second year. With any in-furrow application of material, there is a risk of damage to seed and potential stand loss. There was no significant change in stand as a result of the in-furrow applications in either year even when the in-furrow rate was increased. Final stands in 2003 were 3.1 to 3.2 plants/ft of row and 2.9 to 3.0 plants/ft of row in 2004. This translated to a plant population of around 41,000 and 38,500 plants/acre for respective years. When averaged across the two sources of Equity, both the IF and SB application of 2 qt/acre significantly increased seedcotton yields compared to the UTC using a 10% level of significance in 2003. The IF+SB system was intermediate between the other systems. When seedcotton yields were adjusted for lint percent, the lint yields were not significantly different at the 10% level. The trends were similar to those observed for seedcotton with yields that were 4.1 to 4.5% higher than the UTC. In 2004, there were no significant treatment effects with respect to yield and final plant populations. Reniform nematode numbers were evaluated at the end of the growing season. While numbers were above threshold levels, there was no apparent relationship between treatments and nematode numbers. [ABSTRACT FROM AUTHOR]

Increasing nutrient uptake efficiency has been a goal of researchers for years and many continue to evaluate concepts and products that may increase fertilizer efficiency. Equity™, a soil amendment from Naturize BioSciences was evaluated in a replicated field trial on a Forestdale silty clay loam soil over a 2-year period. Two Equity formulations were used in the initial trial, one with humate, one without humate, while only one was evaluated during the second year. The products were applied in-furrow (IF) at planting, as a surface band (SB) application at planting, and as a combination of in-furrow and surface band (IF+SB) applications. These treatments were then compared to untreated controls (UTC). Nitrogen rates were similar for all plots and other cultural practices maintained uniformly across all plots. Seedcotton and lint yields were determined for all treatment combinations with lint yields based on hand-grab samples taken at harvest and ginned through a 10-saw micro-gin. Plant stands were measured following harvest by counting the two harvest rows. The highest seedcotton and lint yield was obtained the first year with 2 qt/acre Equity+humate applied in-furrow. In-furrow application of 2 qt/acre increased the lint yield by 118 lb/acre (8.9%) compared to the average of the two untreated controls. In the second year, one product was eliminated and the rates increased for the remaining product. There were no significant effects measured or observed in the second year. With any in-furrow application of material, there is a risk of damage to seed and potential stand loss. There was no significant change in stand as a result of the in-furrow applications in either year even when the in-furrow rate was increased. Final stands in 2003 were 3.1 to 3.2 plants/ft of row and 2.9 to 3.0 plants/ft of row in 2004. This translated to a plant population of around 41,000 and 38,500 plants/acre for respective years. When averaged across the two sources of Equity, both the IF and SB application of 2 qt/acre significantly increased seedcotton yields compared to the UTC using a 10% level of significance in 2003. The IF+SB system was intermediate between the other systems. When seedcotton yields were adjusted for lint percent, the lint yields were not significantly different at the 10% level. The trends were similar to those observed for seedcotton with yields that were 4.1 to 4.5% higher than the UTC. In 2004, there were no significant treatment effects with respect to yield and final plant populations. Reniform nematode numbers were evaluated at the end of the growing season. While numbers were above threshold levels, there was no apparent relationship between treatments and nematode numbers. [ABSTRACT FROM AUTHOR]

Because there is concern over the introduction of highly virulent Australian strains of Fusarium oxysporum f. sp. vasinfectum (FOV) into California, it is necessary to characterize local strains of the fungus to document the movement of genotypes in and out of important cotton-producing areas. Regulatory decisions may rely on such data regarding movement of plant material between states or countries where different strains exist. To accurately describe the strains that presently occur in California, various genetic methods were employed. Based on partial sequences of translation elongation factor and beta-tubulin genes and restriction enzyme digestion of the IGS nuclear r-DNA, Australian isolates of FOV do not exist in California. Californian isolates fell into four lineages. One group of several isolates consisted of the lineage of races 1 and 2, which are closely related to each other; a second group was represented by two isolates that may or may not belong to the race 3 lineage; a third group, race 4, was commonly collected in California; and a fourth group, race 8, was represented by two isolates. Race 4 was highly virulent on Pima in greenhouse pathogenicity tests and was considerably less virulent on Acala; isolates belonging to the lineage of races 1, 2, and 6 were relatively virulent on Acala cotton but not Pima. Race 8 and race 3(?) were weakly pathogenic on both Acala (Maxxa and Phy-72) and Pima (DP-744 and Pima S-7). [ABSTRACT FROM AUTHOR]

Acala cotton fields in several production regions of California in 2002 experienced a range of symptoms, including early cessation of main stem and sympodial branch growth, foliar red or bronze coloration followed often by leaf necrosis, and in some limited cases, observable leaf wilting. Most University of CA Advisors and private consultants we met with felt the range and severity of these occurrences were considerably worse than experienced in the same areas in any recent years in Upland / Acala cotton. Variations on these symptoms were observed in widespread locations in several San Joaquin Valley counties in 2002, and field symptoms that were similar in some respects and different in other respects were also observed in the Imperial Valley region in southern California. In most fields, the first observations of problems began about mid-bloom, with the first observable symptoms differing somewhat across locations. In many cases, more severe than normal red and purple coloration in upper canopy stem and petiole tissue, or dark red or bronze coloration in upper canopy leaf blades were among the first plant symptoms observed. In most cases analyzed, plants developed moderate to severe nutrient deficiencies after mid- to late-fruiting. Soil and plant tissue tests available from many, but not all affected fields indicate that although plant tissue levels were low in several nutrients, including nitrogen and potassium, corresponding soil nutrient levels were generally within University of CA recommended levels. The worst-affected fields in the San Joaquin Valley generally had low to moderate yields, but the fruit loads were quite high given the smaller size and reduced vigor of the plants. Observations and soil and plant tissue tests available indicate that this problem was noted in numerous varieties, but foliar symptoms developed earlier and were worse in some varieties than in others. Yield data in these fields is inadequate to determine clearly if varietal differences in timing of symptoms resulted in yield differences. Although definitive causes of observed problems have not been identified based on these field observations, some generalizations are described that may prove useful if problems recur in other years. [ABSTRACT FROM AUTHOR]

Long-term rotation studies with cotton following corn were initiated in 2000 at the Delta Research and Extension Center (DREC) on a Bosket very fine sandy loam (Mollic Hapludalfs) and at the Tribbett Satellite Farm (TSF) on a Forestdale/Dundee silty clay loam (Typic Endoaqualfs). The studies were designed to examine the rotational benefits and problems associated with crop rotations in the Mississippi Delta on both 'poorly' drained to 'somewhat-poorly' drained soils (Forestdale /Dundee) as well as better drained soils (Bosket). The selected sites are characteristic of soils suited for corn and cotton production. Producers now have the opportunity to shift plantings and crop mix within their farm enterprise and evaluate alternative crops or cropping sequences to replace some of their mono-crop cotton acreage. The objectives of the studies included, a) determining the effects of N and K nutrition on cotton lint yields and corn grain yields for different soil types; b) determining rotational effects of corn on cotton production and the implications of these rotations on whole farm economics; and c) evaluating the effects of nitrogen (N) and potassium (K) rates and rotational effects on nematode dynamics. The third objective was added in 2007 and will continue as an area of interest in the future. Areas were defined at both locations that could be rotated over a 3-year period with corn followed by one or two years of cotton. Within each location (soil type), each section had a factorial arrangement of N and K treatments. The sections consisted of 4-row (40-in spacing) plots, 90 to 100 feet in length, with either four (TSF) or five (DREC) replications. Annual N rates were 60, 90, 120, 150, and 180 lb N/acre for cotton and 120, 160, 200, 240, and 280 lb N/acre for corn with the fertilizer N applied as urea-ammonium nitrate solution (32% N). Potassium rates for all rotations were 0, 40, 80, and 120 lb K/acre. Nitrogen was applied at a uniform rate (60 lb N/acre for cotton, 120 lb N/acre for corn) prior to or near planting with the different N rates established as a sidedress application at early square formation for cotton and at the 5- to 6-leaf stage of corn. Potassium applications were made after planting utilizing a 0-0-16 solution (1.3 lb K/gal) applied with the same equipment used for N applications. The K solution (muriate of potash, KCl) was chosen for ease of application with available equipment and does not imply that granular muriate of potash could not be used with incorporation. High-yield potential corn and cotton cultivars were planted at each location and maintained throughout the growing season and have been adjusted as new cultivars become available or as the cultivar of choice has been removed or replaced. Soil moisture sensors were installed to measure soil water relations and used to initiate, schedule, and terminate irrigations for both corn and cotton. The crops were harvested with commercial harvesters modified for plot harvest with cotton grab-samples taken for ginning and corn samples taken at harvest for determination of harvest moisture, bushel test weight, and seed weight. Seedcotton samples taken at harvest were ginned through a 10-saw micro-gin for calculation of the lint percentage. Data were summarized and statistically analyzed using SAS (Statistical Analysis Systems) with mean separations by Waller Duncan K-ratio t-tests and Fisher's Protected Least Significant Difference (LSD). On the sandy loam soil at DREC, corn yields have ranged from 167 to 244 bu/acre (excludes 2000 data due to herbicide injury in corn following many years of continuous cotton) when averaged across all N and K levels. Between 2001 and 2009, yields have been optimized with 200 to 240 lb N/acre in most years. The average corn yields at DREC are 204 bu/acre/yr. On the more poorly drained soils at TSF, a minimum of 240 lb N/acre has been required to optimize corn yields for most years. Corn yields have ranged from 141 to 221 bu/acre with an overall average of 182 bu/acre/yr (excludes 2000 data for comparison). There has been no significant response to increasing K rates even though the lower K rate areas have had no fertilizer K applied in ten years and there has been no interaction between K rates or N rates. The highest corn yields have occurred with early planting at this location. Corn yields have topped 200 bu/acre in three of the ten years of the study. Cotton lint yields have been affected by rainfall patterns throughout the duration of the study and have been quite variable with respect to rainfall during the growing season and annual totals even though some irrigation has been available. In 2000, August became the driest month on record when no rainfall occurred while August 2001 became the wettest on record with nearly 9 inches of rainfall occurring during the month. At DREC, cotton yields have been as low as 510 lb lint/acre in 2009 where cotton followed cotton to a high of 1416 in 2003 with cotton following corn. When averaged across years, N rates, and K rates, cotton yields have averaged 949 lb lint/acre for cotton following corn compared to 807 lb lint/acre for cotton following corn. The range in response at DREC was -147 to +334 lb lint/acre with an average response of 142 lb lint/acre (17.7% increase) for cotton following corn as compared to cotton following cotton. The largest reductions in yield (2004 and 2007) occurred where excess rainfall and cloudy weather impacted disease and insect problems. Recent research has shown a marked effect of the rotation on reniform nematode numbers with little indication that the N and K treatments make a significant difference. Yield reductions have also been related to excess vegetative growth and the associated problems with getting insecticides into the dense canopy and subsequent insect damage in cotton following corn. Cotton lint yields following corn at the TSF location ranged from 748 to 1394 lb lint/acre with an overall average of 1044 lb lint/acre/yr when averaged across all N rates and K rates (2000 to 2009). When cotton followed cotton, the lint yield range was 650 to 1276 lb/acre with an average yield of 950 lb/acre/yr. The response to rotation has ranged from a 5.1% (44 lb lint/acre) decrease to a 50.1% (341 lb lint/acre) increase with an average response of 9.9% (94 lb/acre/yr, increase). Irrigation has been more consistent at the TSF location as the irrigation water comes from an underground well. At DREC, surface water is used for irrigation and the availability of pumps is limited. In only one year, the cotton following corn rotation system resulted in a significant yield reduction (5.1% in 2001) where record rainfall was recorded in August. In the other years where no response to rotation was observed, the weed pressure in cotton following corn resulted in competition for nutrients and water. Shifting cultivars has helped to overcome this problem. Response to N fertilization has been evident in most years while the response to K fertilization has been limited even though no fertilizer K has been supplied to some plots for the duration of the study. In most years, 90 to 120 lb N/acre has been sufficient for optimum cotton yields on the sandy loam soil. At TSF, on the silty clay loam soil, cotton yields have been optimized with 120 to 150 lb N/acre. In some years optimum yields for cotton following cotton have required higher N rates to optimize yields even though that yield does not equal the yield obtained behind a corn crop. The different N rate requirements have not been evident at the DREC location. In summary, the study has shown a range in response to rotations but an overall average increase in lint yields from 10-17% depending on the location and soil type. As grain acreage increases and with the higher prices for fertilizer, the benefits from rotation become more and more important. Also, as the populations of nematodes increase, control through rotation offers an alternative to pesticide applications. [ABSTRACT FROM AUTHOR]

Long-term cotton/corn rotation studies were begun in 2000 at the Delta Research and Extension Center (DREC), Stoneville, MS on a Bosket very fine sandy loam (Mollic Hapludalfs) and at the Tribbett Satellite Farm (TSF), Tribbett, MS on a Forestdale/Dundee silty clay loam (Typic Endoaqualfs). The studies were intended to evaluate benefits and problems associated with crop rotations in the Mississippi Delta. The two sites had different soil types and included 'poorly' drained to 'somewhat-poorly' drained soils (Forestdale/Dundee) at Tribbett along with a well drained soil (Bosket) at Stoneville. The selected sites are characteristic of soils suited for good corn and cotton production, especially with irrigation. The objectives of the studies included, a) determining the effects of N and K nutrition on cotton lint yields and corn grain yields for different soil types; b) determining rotational effects of corn on cotton production and the implications of these rotations on whole farm economics; and c) evaluating the effects of nitrogen (N) and potassium (K) rates and rotational effects on nematode dynamics. Soil samples have been taken following harvest each year in order to monitor changes in soil test parameters across years. The changes that have occurred are of particular interest. Areas were defined at both locations that could be rotated over a 3-year period with corn followed by one or two years of cotton. Within each location (soil type), each section had a factorial arrangement of N and K treatments. The sections consisted of 4-row (40-in spacing) plots, 90 to 100 feet in length, with either four (TSF) or five (DREC) replications. Annual N rates were 60, 90, 120, 150, and 180 lb N/acre for cotton and 120, 160, 200, 240, and 280 lb N/acre for corn with the fertilizer N applied as urea-ammonium nitrate solution (32% N). Potassium rates for all rotations were 0, 40, 80, and 120 lb K/acre. Nitrogen was applied at a uniform rate (60 lb N/acre for cotton, 120 lb N/acre for corn) prior to or near planting with the different N rates established as a sidedress application at early square formation for cotton and at the 5- to 6-leaf stage of corn. Potassium applications were made after planting utilizing a 0-0-16 solution (1.3 lb K/gal) applied with the same equipment used for N applications. The K solution (muriate of potash, KCl) was chosen for ease of application with available equipment and does not imply that granular muriate of potash could not be used with incorporation. The crops were harvested with commercial harvesters modified for plot harvest with cotton grab-samples taken for ginning and corn samples taken at harvest for determination of harvest moisture, bushel test weight, and seed weight. Seedcotton samples taken at harvest were ginned through a 10-saw micro-gin for calculation of the lint percentage. End-of-season soil samples consisted of composited cores from 10-12 locations within each plot. The samples were placed in refrigerated storage until nematode analyses can be completed. The remaining sample was dried, ground, sieved, and mixed prior to analysis in the Soil Testing and Plant Analysis Laboratory at Mississippi State University. Nutrient uptake and removal has also been estimated based on published nutrient concentration information and summarized by location and rotation section. After ten years, N applications total 840, 1180, 1520, 1860, and 2200 lb N/acre where corn has been grown four of six years. The applications total 780,1110,1440,1770, and 2100 lb N/acre when corn is growing in three of the ten years. Since K rates have been the same for both corn and cotton, total K applications were 0, 400, 800, and 1200 lk K/acre. On the sandy loam soil at DREC, corn yields have ranged from 167 to 244 bu/acre (excludes 2000 data due to herbicide injury in corn following many years of continuous cotton) when averaged across all N and K levels. The average corn yield at DREC was 204 bu/acre/yr. On the more poorly drained soils at TSF, corn yields have ranged from 141 to 221 bu/acre with an overall average of 182 bu/acre/yr (excludes 2000 data for comparison purposes). In evaluating K applications at DREC, no significant response to increasing K rates has been observed at either location in most years. Total K removal from the study areas range from 323 to 361 lb K/acre based on yields with no real difference in K removal as related to K application rates. Total K removal at TSF ranged from 342 to 373 lb K/acre over the 10-year duration of the study. With these levels of removal, in theory, one should expect to see lowering of soil test K levels where no K has been supplied and a build-up where application exceeds removal. This should be evident if plots continue in the same area and tillage does not shift plot locations or move the applied fertilizer material. For comparison purposes, soil results from 2008 were compared to the initial set of samples taken following the first growing season (2000). At present, soil samples following the 2009 growing season have not been analyzed. No samples were available prior to the initiation of the studies at either location. At the DREC location, initial soil test K averaged less than 300 lb K/acre within the three sections. After the 2008 growing season, soil test K levels showed increases in soil test K at every K application rate including the 0 K/acre rate. Where no K had been applied, soil test K in 2008 was 50 to 100% higher than in the initial set of samples even though more than 300 lb K/acre had been removed. This provides strong indication that the plots have shifted or tillage has moved the applied fertilizer material and the O K plots have not remained in their original location. The data also suggests the possibility of some K release from clay minerals in the soil (release of fixed K). At the TSF location, the 0 lb K/acre plots have also increased in soil test K. Overall soil test K has not increased as much as that observed at the DREC location. These results again suggest movement across plots with tillage but also suggest some K supplying power in the soil. No K response has been observed in most years. High N rates have been responsible for decreases in soil pH, however, irrigation has been thought to increase soil pH due to liming materials dissolved in the irrigation water. As indicated earlier, up to 2200 lb N/acre has been applied to the high N plots at each location. Crops removal estimates range from 890 to 1000 lb N/acre at DREC and 820 to 1050 lb N/acre at TSF with the highest removal at the higher N rates. In most cases, where N applications exceed N removal by the crop, much of the excess N is lost through biological processes such as denitrification and is removed from the soil N pool. Soil pH has decreased some with increasing N rates at both locations when averaged across K rates. At both locations, there has been little change in soil pH at the lower N rates. Soil organic matter is the other factor that receives attention with respect to crop rotation. Adding corn to the crop mix is thought to increase soil organic matter or soil organic carbon. Increasing K rates and increasing N rates has not increased organic matter at either location. To date some slight changes have been observed when comparing the areas but no large changes have been observed. These research areas remain in conventional tillage systems that involve both subsoil and surface tillage. Further evaluations will continue for this area as rotations continue. Further analysis of the data is needed to really understand the year-to-year variation that occurs in the soil. Since the system is dynamic, changes are not always as expected. [ABSTRACT FROM AUTHOR]

Various nitrogen management systems have been evaluated with plant growth regulation (mepiquat pentaborate) for the past six years at the Delta Research and Extension Center (DREC) near Stoneville, Mississippi on very productive cotton soils. Each cotton crop followed corn in a 1:1 cotton/corn rotation with both crops receiving supplemental irrigation. Pentia™ plant growth regulator (PGR) was applied during each growing season based on experimental design with half of the plots receiving the PGR and the other half serving as the control. The higher N rates required for optimum corn production as compared to cotton production could lead to a buildup of residual N in the soil profile if biological processes do not decrease the pool. The potential residual N pool along with N fertilizer at recommended levels could lead to excessive growth in subsequent cotton crops following corn in rotation. Excessive growth can be controlled with PGR applications, reduced fertilizer N rates, or combinations of both. The objectives of this study were to determine the interaction effects of N management and PGR application in cotton following corn and to evaluate the main effects of N management and PGR where interactions were not significant. A 4x2x2 factorial combination of N rates (60, 90, 120, and 150 lb/A), N application systems (preplant [PP] and preplant + sidedress [PP+SD]), and a new chemistry plant growth regulator (Pentia) was evaluated from 2003 through 2008. Product literature indicated that the PGR resulted in improved boll retention, faster uptake, earlier maturing cotton, and superior height control. In 2003 and 2004, a total of 28 oz/acre Pentia was applied as a split application with the first application made during early bloom and the remainder applied about two weeks later during peak bloom. In both 2003 and 2004, optimum lint yields were achieved with 120 lb N/acre when yields were averaged across the PGR levels. In 2003, application of PGR had no significant effect on lint yield when N rates were at least 90 lb N/acre. At the lowest N rate (60 lb N/acre); PGR application resulted in an 8.1% reduction in lint yield. In 2004, with PGR applications initiated at first bloom (FB), lint yields were reduced at all N levels by 6.7 to 10.0% with the greatest reduction occurring at the lowest N level (60 lb N/acre). Other studies at DREC in 2004 showed similar reduction in lint yields with applications initiated at FB, especially at higher PGR rates. Treatments from these same studies, initiated at pin-head square (PHS) at lower application rates, showed positive responses compared to the untreated controls. With these results in mind, the PGR applications were modified in 2005 and 2006. The initial application (6 to 8 oz/acre) was applied at PHS and a second application (8 oz/acre) applied two to three weeks later, near first bloom. In these cases most of the PGR applications occurred before the initial applications were made in the two previous years. The 2005 harvest was delayed until after the adverse effects of both hurricanes Katrina and Rita and lint yields were reduced compared to 2003. Lint yields ranged from 1082 to 1228 lb /acre with the highest yields achieved at the 150 lb N/acre level. This was the only year of the study where 150 lb N/acre produced significantly higher yields than 120 lb N/acre. With the delays and damage to the crop from the adverse weather conditions, later maturity associated with the higher N level was actually an advantage. Lint yields increased significantly with respect to PGR applications. The increase ranged from 6.1 to 9.2% and was positive at each N level. The greatest responses were observed at the 90 and 120 lb N/acre rates. The 2006 lint yields were similar to those measured in 2005; however, there was no difference between N rates. When averaged across N management systems, there was a significant increase in lint yields with the application of PGR begun at PHS. The increases ranged from 5.2% to 8.5% with the largest increase at the 120 lb/acre N rate. The cotton crop was defoliated in 2006 prior to reaching full maturity. This tended to mask the yield potential of later maturing bolls since these bolls were not allowed to mature on their own. In the first four years of the study there was no significant difference between N application systems. Yields from the 100% PP N treatments were just as effective as sidedress N applications for producing optimum yields. In the case preplant N, N application was made shortly before planting rather than two to six weeks prior to planting as had been the practice in earlier years. In an effort to reduce the potential for N loss, N applications are made closer to the time that the plant can utilize the nutrient. With this in mind the application systems were modified in 2007 and 2008 to include a uniform preplant N rate (60 lb N/acre) with the various N rates determined as sidedress applications of 0, 30, 60, and 90 lb N/acre. In both 2007 and 2008 there was still no significant difference between this system and the 100% PP system. Cotton yields in 2007 ranged from 1128 to 1416 lb lint/acre with no significant increase above 120 lb N/acre. In 2008, yields ranged from 1214 to 1371 lb lint/acre with the highest significant yield at 120 lb N/acre. These yields represent averages across N application systems and PGR levels with no significant interaction. The 2007 lint response to PGR application ranged from -1.0% to +9.1% with the greatest response at the highest N rates. The same effect was observed in 2008 with the lint response to PGR ranging from -0.1% to +7.2%. In both 2007 and 2008 the response to PGR was greater at the higher N levels (120 and 150 lb N/acre) Plant height and nodes increased with increasing N rates in each of the four years. The PGR applications reduced plant height, total nodes, and height:node ratio. Plant heights were reduced more with the higher PGR rates in 2003 (14.4 to 22.5%) and 2004 (7.3 to 15.4%) as would be expected with higher application rates. In 2005, plant height was also lower with a range from 1.9 to 14.0%. The 2006 plant heights were 9.0 to 14.0% lower. At the lower PGR rates initiated at PHS, there was more variability in plant characteristics than observed in the previous years. End-of-season plant characteristics were not determined in the latter two years of the study. Under the conditions of this research, it was concluded after the first two years, that application of mepiquat pentaborate was not successful in increasing lint yields when the initial application was delayed until first bloom or early bloom. However, in 2005 and 2006, where PGR applications were initiated at PHS, the use of mepiquat pentaborate at lower application rates did show significant lint yield increases (88 lb lint/acre, 7.9% in 2005; 74 lb lint/acre, 6.6% in 2006; 64 lb lint/acre, 5.0% in 2007; and 41 lb lint/acre, 3.2% in 2008) compared to the untreated control. Nitrogen recommendations would include the application of 120 lb N/acre applied either 100% PP or as a split application with at least 50% of the N applied prior to planting. This practice insures having N available early in the growing season for early plant growth and development. While data has shown significant responses to Pentia (mepiquat pentaborate) applications, economic considerations should be included in the decision making process. Application and material costs may not be covered by the additional yield. Fruit load continues to be the best plant growth regulator for cotton production. [ABSTRACT FROM AUTHOR]

Corn acreage has increased from 140,000 acres for grain in 1990 to a high of 940,000 in 2007 with yields reaching 150 bu/acre across the state. In the Mississippi Delta, yields have been reported in excess of 250 bu/acre. In just the last three years cotton production has decreased from 1.62 million acres in 2001 to 360,000 acres harvested in 2008. The 2004 crop produced an all-time record yield of 1,024 lb lint/acre on 1.1 million acres. The 2005 and 2006 yields averaged around 850 lb/acre and were down due to hurricane damage and drought in the respective years. In 2007, cotton acreage dropped dramatically as grain crop acreage increased due to excellent prices for those crops while cotton prices declined along with world demand. As the corn acreage increases, the opportunity for rotations rises significantly. Cotton yield increases due to rotation have averaged 10 to 15% with higher benefits observed in drier years. The cotton yield advantage in multi-crop systems has been attributed to several factors including better soil tilth, improved water infiltration, increased organic matter content, depressed nematode populations following corn, as well as benefits due to rotation of herbicides. Some yield decreases following corn in rotation have been documented and have generally been weather related where excess growth has been detrimental and affected both yields and quality. In most cases, cotton yields have been maintained following corn with less total fertilizer N required. However, little information is available on how much N rates could be reduced for cotton following corn, how much residual N is available to the subsequent cotton crop, and what effect rainfall totals and distribution have on residual N. Excess N has led to increased vegetative growth and reduced both lint yield and lint quality. Efficient utilization of available N can reduce the overall cost of production while reducing the potential release of nutrients from the field into waterways and streams. In order to address these issues, a multi-year study was established in 2004 at the Delta Research and Extension Center with one-half of the research area planted to corn each year and the remaining half planted to cotton. Fertilizer N rates for corn ranged from 120 to 300 lb N/acre in 30-lb increments and were applied as urea-ammonium nitrate (32% N) with 120 lb N/acre applied prior to planting (PP) and the remainder applied as a sidedress (SD) application. Potassium was applied at rates of 0, 30, 60, and 90 lb K/acre with liquid muriate of potash as the K source. The N and K rates were only applied to the area when it was planted to corn. The following year, a uniform N rate, 90 lb N/acre, was applied to the cotton with no additional K. The 7x4 factorial arrangement of treatments was laid up in randomized complete block design with eight replications. All cultural practices and pesticide applications were maintained uniformly across the corn or cotton study. Plots were harvested with commercial harvesters adapted for plot harvest and samples collected for determination of harvest moisture, bushel test weight, and seed weight for corn and lint percentage on cotton. There was no significant interaction between N rates and K rates, so only the main effects were examined for both crops. In the initial year of the study (2004) corn yields ranged from 154 to 165 bu/acre with no significant yield increase achieved with N rates above 180 to 210 lb N/acre. These yields are lower than expected for the soil types included in the study. Yields in subsequent years were significantly higher and more in line with yields potentials for the area. Since 2004 was the establishment year, no cotton following corn was evaluated. In 2005, cotton yields following the previous corn crop ranged in yield from 864 to 903 lb lint/acre with no significant difference in yields as they related to the previous year=s N rates. Corn yields of 165 bu/acre removed about 150 lb N/acre from the field as harvested grain. Thus at the 300 lb N/acre application rate, 150 lb N/acre was not removed in the grain and should be left in the field as residue, organic matter, or as inorganic N remaining in the soil. Some of the cotton yield effects could have been masked due to losses from the hurricane-related wind and rain in 2005. However, visual observations did not lead to that conclusion. Corn yields in 2005, harvested before the hurricanes, ranged from 197 to 207 bu/acre. While yields were significantly higher than the previous year, there was still no large range in yields associated with N rates. Grain yields were not significantly increased with N rates above 180 lb N/acre. As with the previous year, grain yields were probably limited due to the limited availability of supplemental irrigation. The 2006 cotton yields following corn in 2005 ranged from 1,316 to 1,373 lb lint/acre. There was no significant difference in yield as related to residual N levels but there was a slight trend. Lint yields were excellent in 2006 compared to the previous year and were more indicative of yield potential in the area. Corn yields in 2006 ranged from 206 to 227 bu/acre with no significant response above 210 lb N/acre. In both 2005 and 2006 there was no apparent cotton yield response to residual N from the previous corn crop. Rainfall totals and distribution can be used to shed some light of the potential for N loss from the systems. After the 2004 growing season, rainfall totals for October to the next April were 39.92 inches. Actual rainfall in 2004 was 68.00 inches (14.71 inches above normal) nearly 20 inches falling in May and June after the initial N application. High rainfall and prolonged saturated conditions can lead to nitrification and denitrification and loss of available N. October through December rainfall in 2005 was just over 5 inches, however August and September rainfall was over 12 inches. January through April rainfall totaled more than 26 inches again leading to the potential for decreases in the available N pool. September 2006 to April 2007 rainfall was lower than in previous seasons at 33.05 inches with little rainfall occurring after January. Cotton yields in 2007 were significantly influenced by residual N from the 2006 corn crop. Lint yields with 120 lb N/acre applied to corn were 1164 lb/acre compared to a high of 1258 lb lint/acre where 270 lb N/acre had been applied to the corn. While the differences are not great they are significant and 2007 was the only year where differences occurred. In 2008, there was no response to residual N with lint yields ranging from 1351 to 1383 lb/acre. Rainfall totals for the September to April period were 34.43 inches 23.65 inches falling in February through May 2008. The excess rainfall in the spring along with warmer temperatures should be indicators of the potential for N loss from the residual pool. After four years, cotton response to residual N was only evident in one of the four years. In that year rainfall was lower compared to other years. From this study, 90 lb N/acre was sufficient to optimize yields in three of four years. The normal recommendations would call for 110 to 120 lb N/acre for optimum production. Based on cotton yields, there appeared to be little buildup on residual N from higher N applications on corn. Corn yields improved after the first season with yields limited by the supply of water from either rainfall or irrigation. [ABSTRACT FROM AUTHOR]

An abstract on the article "Update on Cotton/Corn Rotations in Mississippi," by M. Wayne Ebelhar, Davis R. Clark, and H.C. Pringle is presented.

An abstract of the article "Factors Influencing Rotational Effects in Cottons/Corn Systems in the Mississippi Delta," by M. Wayne Ebelhar, Davis R. Clark, and H. C. Pringle

In recent years, differences have been noted in field situations with the fungal pathogen Fusarium oxysporum f. sp. vas infectum in Acala and Pima cotton in the San Joaquin Valley of California. Typically, earlier-recognized races of this organism found in California cotton only caused significant crop foliar damage and yield impacts under conditions where it was found in combination with susceptible varieties of cotton and at least moderate populations of root knot nematode. A race 4 isolate of Fusarium oxysporum f. sp. vasinfectum (FOV) has been identified in Pima and Acala cotton fields in the San Joaquin Valley in recent years, and research to date has shown that this race can infect susceptible varieties, cause damage, and may reproduce inoculum under soil conditions that do not support significant root knot nematode populations. Research efforts to date have focused on (1) development of genetic tools to more clearly identify current Fusarium races found in California cotton samples; (2) evaluation of plant samples under field conditions to verify presence or absence of the pathogen, and (3) initiation of variety screening programs under both greenhouse conditions with inoculated soil, and in field sites where this FOV race 4 pathogen has been confirmed. Field screening trials to evaluate relative FOV resistance in commercial and experimental cotton lines have shown that susceptible Pima varieties are more severely affected in terms of foliar damage, stem vascular staining and plant stunting or mortality than tested Acala and non-Acala Upland varieties. The most tolerant (lowest seedling mortality, least stunted) varieties in field screenings have also been Pima cottons. Field and greenhouse trials have both repeatedly confirmed that tested Acala and non-Acala Upland varieties can also be infected, although generally with reduced plant mortality and stunting. Significant varietal differences in susceptibility to the race 4 FOV pathogen have been seen in both Pima and Acala cotton entries. [ABSTRACT FROM AUTHOR]

In recent years, differences have been noted in field situations with the fungal pathogen Fusarium oxysporum f. sp. vas infectum in Acala and Pima cotton in the San Joaquin Valley of California. Typically, earlier-recognized races of this organism found in California cotton only caused significant crop foliar damage and yield impacts under conditions where it was found in combination with susceptible varieties of cotton and at least moderate populations of root knot nematode. A race 4 isolate of Fusarium oxysporum f. sp. vasinfectum (FOV) has been identified in Pima and Acala cotton fields in the San Joaquin Valley in recent years, and research to date has shown that this race can infect susceptible varieties, cause damage, and may reproduce inoculum under soil conditions that do not support significant root knot nematode populations. Research efforts to date have focused on (1) development of genetic tools to more clearly identify current Fusarium races found in California cotton samples; (2) evaluation of plant samples under field conditions to verify presence or absence of the pathogen, and (3) initiation of variety screening programs under both greenhouse conditions with inoculated soil, and in field sites where this FOV race 4 pathogen has been confirmed. Field screening trials to evaluate relative FOV resistance in commercial and experimental cotton lines have shown that susceptible Pima varieties are more severely affected in terms of foliar damage, stem vascular staining and plant stunting or mortality than tested Acala and non-Acala Upland varieties. The most tolerant (lowest seedling mortality, least stunted) varieties in field screenings have also been Pima cottons. Field and greenhouse trials have both repeatedly confirmed that tested Acala and non-Acala Upland varieties can also be infected, although generally with reduced plant mortality and stunting. Significant varietal differences in susceptibility to the race 4 FOV pathogen have been seen in both Pima and Acala cotton entries. [ABSTRACT FROM AUTHOR]

An abstract of the article "Interaction of Nitrogen and Mepiquat Pentaborate for Cotton Production in the Mississippi Delta" is presented.

An abstract of the article "Cotton Response to Residual Nitrogen and Potassium Following Corn Production," by M. Wayne Ebelhar and Davis R. Clark is presented.

An abstract of the article "Factors Affecting Rotational Benefits From Cotton/Corn Rotations in the Mississippi Delta," by M. Wayne Ebelhar, Davis R. Clark, and H. C. Pringle is presented.

Research studies were setup at the Delta Research and Extension Center (DREC, Bosket very fine sandy loam [Mollic Hapludalfs]) and at the Tribbett Satellite Farm (TSF, Forestdale/Dundee silty clay loam [Typic Ochraqualfs/Aeric Ochraqualfs]) beginning in 2000 to investigate the interaction of nitrogen (N) rates and potassium (K) rates in cotton/corn rotation systems. The studies were designed to evaluate rotation effects on both poorly drained to somewhat-poorly drained silty clay loam soils (Forestdale/Dundee) as well as better drained sandy loam soils (Bosket) typically used for optimum cotton and corn production. The studies were established to examine both the benefits and problems associated with corn/cotton rotations in the Mississippi Delta. In the last decade changes in farm legislation has allowed mid-south producers the flexibility to shift from continuous mono-crop cotton to alternative crops and cropping sequences. Replacement of traditional cotton acres, in certain years, while using rotation to improve soil productivity, offers potential for profitability not available with mono-crop systems. This series of studies were intended to examine the impact of cotton/corn rotations on the whole farm enterprise. The objectives included a) determining the effects of N and K nutrition on cotton lint yields and corn grain yields for different soil types, and b) determining rotational effects of corn on cotton production and the implications of these rotations on whole farm economics. Factors that influence the degree of increase or decrease in lint yield associated with rotation have also been examined. Areas were setup on each research farm that could be rotated over a 3-year period with one year planted to corn and the two subsequent years planted to cotton. Each of the three sections at each location had a factorial arrangement of nitrogen (N) and potassium (K) rates. The corn and cotton sections consisted of 4-row (40-in spacing) plots, 90 to 100 feet in length, with either four (TSF) or five (DREC) replications. Nitrogen rates were 60, 90, 120, 150, and 180 lb N/acre for cotton and 120, 160, 200, 240, and 280 lb N/acre for corn with the fertilizer N applied as urea-ammonium nitrate solution (32% N). Potassium rates for all rotations were 0, 40, 80, and 120 lb K/acre. Nitrogen was applied at a uniform rate (60 lb N/acre for cotton, 120 lb N/acre for corn) prior to or near planting with the various N rates established as a sidedress application. Potassium applications were made after planting utilizing a 0-0-16 solution (1.3 lb K/gal) applied with the same equipment used for N applications. Corn and cotton cultivars having high yield potential were planted at each location and maintained throughout the growing season. Soil moisture sensors were installed to measure soil water tension and the data used to initiate, schedule, and terminate irrigations for both corn and cotton whenever possible. Crops were harvested by use of commercial harvesters modified for plot harvest with grab-samples taken for laboratory analyses and ginning. Stand counts were taken in the corn studies by counting the stalks in one of the two remaining border rows. The seedcotton grab-samples taken at harvest were later ginned through a 10-saw micro-gin for calculation of lint percent. Data were summarized and statistically analyzed using SAS (Statistical Analysis Systems) with mean separations by Waller Duncan K-ratio t-tests and Fisher=s Protected Least Significant Difference (LSD). Means across both N rates and Krates were used to measure the benefits from corn in the production systems. Comparisons were made of cotton following cotton and cotton following corn with the latter used to measure the actual benefits from corn in the system. There was no significant interaction between N rates and K rates at either location over the years.… [ABSTRACT FROM AUTHOR]

The article keys out the symptoms and disease development of fusarium in cotton varieties Acala and Pima in California. It states that fusarium wilt damage in cotton is caused by the fungus known as Fusarium oxysporum f.sp. vasinfectum (FOV) that has been observed in both varieties in loam and clay loam soils. Fusarium is identified to induce plant even in the absence of root-knot nematode. When such disease hits at the seedling stage, leaves can turn brown and dry right on the plant that will eventually result to bare stems. Containment options for use in fields with FOV infestations are being suggested.

Long-term rotation studies were established in 2000 at the Delta Research and Extension Center (DREC) and at the Tribbett Satellite Farm (TSF) to examine the rotational benefits and problems associated with corn/cotton rotations in the Mississippi Delta. The studies were designed to evaluate rotation effects on both poorly drained to somewhat-poorly drained silty clay loam soils (Forestdale/Dundee) as well as the better drained sandy loam soils (Bosket) that are more suited to optimum corn and cotton production. The most recent farm legislation has allowed producers the opportunity to look into alternative crops and cropping sequences to replace some of their cotton acres in certain years. These studies are intended to examine the impact of cotton/corn rotations on the whole farm enterprise. The objectives included: a) determining the effects of N and K nutrition on cotton lint yields and corn grain yields for different soil types; b) determining rotational effects of corn on cotton production and the implications of these rotations on whole farm economics; and c) supplementing the growing knowledge base for site-specific management utilizing GPS/GIS technology. Areas were defined at both locations that could be rotated over a 3-year period with two years planted to cotton and one year planted to corn. Within each area, each of the three sections would have a factorial arrangement of nitrogen (N) and potassium (K) treatments. The corn and cotton sections consisted of four-row (40-in spacing) plots, 90 to 100 feet in length, with either four (TSF) or five (DREC) replications. Nitrogen rates were 60, 90, 120, 150, and 180 lb N/acre for cotton and 120, 160, 200, 240, and 280 lb N/acre for corn with the fertilizer N applied as urea-ammonium nitrate solution (32% N). Potassium rates for all rotations were 0, 40, 80, and 120 lb K/acre. Nitrogen was applied at a uniform rate (60 lb N/acre for cotton, 120 lb N/acre for corn) prior to or near planting with the different N rates established as a sidedress application at early square formation. Potassium applications were made after planting utilizing a 0-0-16 solution (1.3 lb K/gal) applied with the same equipment used for N applications. The K solution (muriate of potash, KCl) was chosen for ease of application with available equipment and does not imply that granular muriate of potash could not be used with incorporation. High-yield potential corn and cotton cultivars were planted at each location and maintained throughout the growing season. Soil moisture sensors were installed to measure soil water tension and used to initiate and schedule irrigations for both corn and cotton. Both crops were harvested with commercial harvesters modified for plot harvest with grad samples taken for laboratory analyses and ginning. Stand counts were taken in the corn studies by counting the stalks in one of the two remaining border rows. The seedcotton grab samples taken at harvest were later ginned through a 10-saw micro-gin for calculation of lint percent. Data were summarized and statistically analyzed using SAS (Statistical Analysis Systems) with mean separations by Waller Duncan K-ratio t-tests and Fisher=s Protected Least Significant Difference (LSD). [ABSTRACT FROM AUTHOR]

Interest in higher nitrogen (N) rates in combination with plant growth regulators continues with a renewed interest also in crop rotations involving corn or grain sorghum and cotton. High N rates required for corn production, relative to cotton production, could lead to a buildup of residual N in the soil profile. This residual N carryover could be exhibited as excess growth in subsequent cotton crops. In order to assess the interaction of N management with plant growth regulation of cotton following corn, a 4×2×2 factorial combination of N rates (60, 90, 120, and 150 lb/A), N application systems (preplant [PP] and preplant+sidedress [PP+SD]), and a new chemistry plant growth regulator (Pentia™, mepiquat pentaborate) was evaluated in 2003 and 2004 at the Delta Research and Extension Center near Stoneville, MS. Pentia™ product literature indicated that the product resulted in improved boll retention, faster uptake, earlier maturing cotton, superior height control, and superior rain-fastness. The objectives of this study were to determine the interaction effects of N management and mepiquat pentaborate (PGR) on cotton yields in a cotton/corn rotation and evaluate end-of-season plant characteristics with respect to N management and PGR use. A total of 28 oz/acre Pentia was applied as a split application with the first application during early bloom and the remainder about two weeks later during peak bloom. [ABSTRACT FROM AUTHOR]

Fusarium wilt of cotton in California has been considered a potentially serious fungal disease caused by the organism Fusarium oxysporum vas infectum (also called "FOV") for many decades in areas of the San Joaquin Valley (SJV). This fungus is a soil-inhabiting organism. Certain forms of this pathogen can survive for long periods in soils, even if the host plant is not present, making it nearly impossible to eradicate from soil once the inoculum is widely distributed. In the past, FOV in the SJV and in western U.S. states was primarily FOV races, Nos. 1 or 2, and typically was found in coarse-textured soils in association with root-knot nematode (Meloidogyne incognita). Recently, a strain of Fusarium (race 4) was identified in the SJV that damages most cultivars of Pima cotton and many Upland cultivars. For the last seven years, we have conducted many field and greenhouse evaluations. These efforts have had two primary purposes: (1) support field efforts to collect plant tissue samples for identification and characterization of FOV race (focusing on race 4); and (2) to conduct germplasm evaluation-trials to identify useful genetic differences in susceptibility/resistance to race 4 FOV. Germplasm evaluations to date can be summarized as follows: (1) most Pima varieties show more severe symptoms and suffer higher levels of stunting and plant mortality than Acala/Uplands; (2) several highly-resistant commercial Pima varieties and USDA-ARS experimental germplasm have been identified at evaluations done at multiple sites; and (3) most Acala / Upland germplasm tested, while less severely impacted than most Pima varieties, were infected by the race 4 FOV when present in soil at field sites or when inoculated in greenhouse trials. Results from our studies can be utilized in further genetic evaluations and to identify sources of host plant resistance useful to growers and breeders. Development of host-plant resistance is currently considered the most economic and effective strategy for managing FOV in California cotton production regions. [ABSTRACT FROM AUTHOR]

An understanding of the pathogenic diversity present in a population of a given disease organism is necessary for the effective development and deployment of host-plant resistance. The need for rapid and accurate diagnostic tools for identifying races or genotypes of the Fusarium wilt pathogen, Fusarium oxysporum f. sp. vasinfectum, has increased since it was shown that populations in the United States are no longer limited to races 1 and 2. Multi-gene phylogenies have revealed the presence of races 3, 4, and 8, as well as four novel genotypes in the U.S. A DNA-based macroarray using the translation elongation factor gene was developed to rapidly and accurately identify races 1, 3, 4, 8, and Australian biotypes. A broad understanding of the genetic diversity of this fungus is a first step toward characterizing its pathogenic diversity. [ABSTRACT FROM AUTHOR]

Meloidogyne incognita, the southern root-knot nematode, causes greater yield losses in cotton than any other single pathogen in the US. Although highly-resistant germplasm has been available for years, it is now generally considered to be obsolete when compared to the yield and fiber quality of newer genotypes. In 2001, we began incorporating resistance to M. incognita from M-120 RNR into the susceptible PD94042, which has better yield and fiber quality than the available highly-resistant germplasm lines. A single seed descent method was used and plants in each generation were selected individually for resistance. Individual plants with the highest level of resistance were back crossed into PD94042 for three generations followed by eight generations of self-pollination with selection of only the most resistant plants carried to the next generation. After eight generations, individual plant selection ceased, and a line designated GA120R1B3 was selected for field evaluation. In 2007, yield and nematode resistance were evaluated at one location infested with M. incognita. In 2008, yield, resistance, and fiber quality were evaluated in two nematode-infested fields (data pooled for analysis) and two non-infested fields (data pooled for analysis). All reported differences are at P ≤ 0.05. In 2007, root galling (0 to 10 scale) on GA120R1B3 (0.8) was equal to the resistant parent M-120 RNR (galling = 0.6) and less than on the susceptible standards DP147RF (7.4) and FM966 (8.0). Similarly in 2008, root galling on GA120R1B3 (1.0) was equal to M-120 RNR (0.4) and less than on DP147RF (6.1) and FM966 (7.3). In a root-knot nematode infested field in 2007, yield of GA120R1B3 (954 kg/ha) was greater than FM966 (537 kg/ha) and equal to DP147RF (800 kg/ha) and M-120 RNR (782 kg/ha), and the lint fraction for GA120R1B3 (0.416) was equal to DP147RF (0.407) and PD94042 (0.405) but greater than FM966 (0.397) or M-120 RNR (0.383). In the infested fields in 2008, yield of GA120R1B3 (1291 kg/ha) was equal to FM966 (1114 kg /ha) and M-120 RNR (1131 kg/ha) and greater than DP147RF (953 kg/ha), and the lint fraction was greater for GA120R1B3 (0.444) than for DP147RF (0.427), FM966 (0.419), or M-120-RNR (0.397). In the non-infested fields, yield of GA120R1B3 (859 kg/ha) was equal to DP147RF (865 kg/ha) and FM966 (974 kg/ha), but GA120R1B3 had a greater lint fraction (0.455) than DP147RF (0.429) or FM966 (0.417). In infested fields in 2008, fiber length of GA120R1B3 (1.25) was equal to DP147RF (1.23) and greater than FM966 (1.16) and M-120 RNR (1.15), and micronaire of GA120R1B3 (4.63) was equal to DP147RF (4.58) and FM966 (4.78) but less than M-120 RNR (5.13). In non-infested fields in 2008, neither fiber length nor micronaire differed among GA120R1B3, DP147RF, and FM966. The germplasm line GA120R1B3 suppresses M. incognita as well as existing resistant germplasm, and GA120R1B3 has longer fiber length, lower micronaire, and greater lint fraction than existing resistant germplasm. A germplasm release is in preparation. [ABSTRACT FROM AUTHOR]

The last survey of Fusarium oxysporum f. sp. vasinfectum in the U.S. was conducted in 1985. Since that time, race 4, previously thought to occur only in Asia, appeared in California in 2001, causing significant problems for the San Joaquin Valley cotton industry. Also, the presence of race 8 has been confirmed in California, Arkansas, Louisiana, Georgia, and Missouri, and race 3 was found in California and Louisiana. In addition to new distributions of known races, four novel genotypes of the pathogen were recently reported from a small sample of isolates collected from Arkansas and Georgia. These developments point to the need for a current and comprehensive survey of the Fusarium wilt pathogen. We initiated a multi-state collaboration to characterize the F. oxysporum f. sp. vasinfectum population in the United States, and present a progress report on preliminary samples from Alabama, Arkansas, Mississippi, and Texas that have been screened with sequences of the translation elongation factor gene. [ABSTRACT FROM AUTHOR]

An abstract of the article "Fusarium Race 4: Commercial Cultivar Screening for Resistance," by Robert B. Hutmacher, Mauricio Ulloa, Steve Wright, R. Michael Davis, Rebecca Bennett, Brian H. Marsh, Mark P. Keeley, Peter B. Goodell and Gerardo Banuelos is presented.

Fusarium wilt (FOV) of cotton in California has been considered a potentially serious fungal disease for many decades in areas of the San Joaquin Valley (SJV). In the past, damage from Fusarium has been notable only in areas with the combination of: (a) moderate to high populations of one or more specific races of FOV (usually race 1); (b) soils with a coarse texture; and (c) where root knot nematodes existed in populations adequate to cause significant root damage. While most cotton crop loss in the SJV from Fusarium wilt likely remains associated with nematode damage and race 1 FOV, field investigations recently have found Fusarium symptoms across a range of soil textures in which root knot nematode populations were very low. This more-recently identified FOV identified in these studies has been identified as race 4. Field and greenhouse studies were initiated to conduct germplasm screening trials to identify useful genetic differences in susceptibility / resistance to race 4 FOV that can be utilized in further genetic evaluations and to identify sources of host plant resistance useful to growers and breeders. Screening efforts have included Gossypium hirsutum (Upland) and Gossypium barbadense (Pima) plantings as well as other, more exotic Gossypium species to gain a broader perspective of susceptibility and host plant resistance. Screening efforts can be summarized as follows: (1) most Pima varieties show more severe symptoms and suffer higher levels of stunting and plant mortality than Acala/Uplands; (2) one highly-resistant commercial Pima variety and several USDA experimentals have been identified; (3) most Acala / Upland germplasm tested, while less severely impacted than most Pima varieties, were still infected by the race 4 FOV when tested at infested field sites or when inoculated in greenhouse trials. [ABSTRACT FROM AUTHOR]

An abstract of the article "A 3-ear Summary of the Interaction of Nitrogen Management With Mepiquat Pentaborate Plant Growth Regulator," by M. Wayne Ebelhar, Steve P. Nichols, and Cavis R. Clark is presented.

The interaction of nitrogen (N) management with the utilization of Pentia™ (mepiquat pentaborate) plant growth regulator (PGR) has been evaluated for three years at the Delta Research and Extension Center near Stoneville, Mississippi with each cotton crop following corn in rotation. The use of higher N rates required for optimum corn production, relative to cotton production, could lead to a buildup of residual N in the soil profile. The potential residual N carryover could be exhibited as excess growth in subsequent cotton crops. To assess the interaction of N management with plant growth regulation, a 4x2x2 factorial combination of N rates (60, 90, 120, and 150 lb/A), N application systems (preplant [PP] and preplant+sidedress [PP+SD]), and a new chemistry plant growth regulator (Pentia) was evaluated from 2003 through 2005. Product literature indicated that the PGR resulted in improved boll retention, faster uptake, earlier maturing cotton, superior height control, and superior rain-fastness. The objectives of this study were to determine the interaction effects of N management and PGR on cotton yields and evaluate end-of-season plant characteristics with respect to N management and PGR use. In 2003 and 2004, a total of 28 oz/acre Pentia was applied as a split application with the first application made during early bloom with the remainder applied about two weeks later during peak bloom. In both 2003 and 2004, optimum lint yields were achieved with 120 lb N/acre. In 2003, application of PGR had no significant effect on lint yield as long as N rates were at least 90 lb N/acre. At the 60 lb N/acre rate, PGR application resulted in an 8.1% reduction in lint yield. In 2004, total lint yields were lower than those observed in 2003 with no significant difference between N application systems. The PGR application was initiated at first bloom (16 oz/acre) followed by an additional 12 oz/acre. These applications resulted in significant yield reductions of 6.7 to 10.0% with the greatest reduction at the lowest N level (60 lb N/acre). This reduction in lint yield with PGR application was evident in other studies conducted at the Delta Research and Extension Center where higher PGR rates were applied at first bloom to early bloom. Treatments from the same studies, initiated at pin-head square (PHS) at lower application rates, showed positive responses compared to the untreated controls. With these results in mind, the PGR applications were modified in 2005 with the initial application (6 oz/acre) made at PHS and a second sequential application (8 oz/acre) made two weeks later during peak bloom. Harvest in 2005 was delayed until after the adverse effects of both hurricanes Katrina and Rita.. Lint yields were 1082, 1152, 1162, and 1228 lb lint/acre fro the 60, 90, 120, and 150 lb N/acre rates, respectively. Unlike the two previous years, there was a significant N response up to 150 lb N/acre. There was no difference between the two application systems evaluated and no interaction between N management and PGR system. There was a significant increase in lint yields in 2005 from the application of PGR. The increase ranged from 6.1 to 9.2% and was positive at each N level. The greatest response was observed at the 90 and 120 lb N/acre rates. There did not appear to be any visual difference between treatments with respect to yield reductions following the storms. Plant heights were significantly lower where PGR application were made in 2003 (14.4 to 22.5%) and 2004 (7.3 to 15.4%) as would be expected with higher application rates. In 2005, plant height was also lower with a range from .9 to 14.0%. With lower PGR rates initiated at PHS, there was more variability than observed with the in the previous years. When averaged across N management, PGR applications reduced plant height by 18.0, 12.4 and 8.2% for the three respective years.… [ABSTRACT FROM AUTHOR]

The article examine the impact of cotton or corn rotations on the whole farm enterprise in Mississippi Delta. The studies were designed to evaluate rotation effects on both poorly drained silty clay loam soils, as well as the better drained sandy loam soils that are more suited to optimum corn and cotton production. Meanwhile, the objectives of the studies are threefold including the determination of the effects of Nitrogen (N) and potassium (K) nutrition on cotton lint yields and corn grain yields for different soil types, to determine the rotational effects of corn on cotton production and the implications of these rotations on whole farm economics and to supplement the growing knowledge base for site-specific management using global positioning system (GPS) technology.

The article focuses on the study that evaluates the nitrogen management with pentia growth regulator for crop rotation including cotton and corn. The aim of the study is to determine the interaction effects of nitrogen (N) management and mepiquat pentaborate (PGR) on cotton yields in a cotton or corn rotation, as well as the end-off-season plant characteristics with respect to N management and PGR use. The study concluded that applications of mepiquat pentaborate were not successful in increasing lint yields. However, the additional studies where PGR applications were conducted earlier than early bloom, did not show any yield loss using mepiquat pentaborate.

An abstract of the article "Breeding for Fusarium Wilt (FOV) Race 4 Resistance in Cotton," by Mauricio Ulloa and Michael R. McGuire is presented.

Fusarium oxysporum f.sp. vasinfectum (FOV) Atk. Sny & Hans continues to threaten cotton production in the U.S. Several troubling developments with this pathogen (e.g., newly-recognized Australian FOV races) highlight the need for additional comprehensive research to protect our cotton industry against this pathogen, either from introduced virulent populations or virulent strains arising from within our borders. Recently, a FOV race 4 isolate has been identified in California soils. Disease expression of this race has been most severe in Pima cotton fields, but also has the capability to infect many Acala and Upland cotton varieties to a high degree depending upon inoculum levels. In order to assess the U.S. cotton gene pool and study the resistance inheritance of FOV race 4, in 2003 and 2004 more than 150 Pima and Acala/Upland commercial and experimental varieties, and improved germplasm were evaluated in known infested fields and in inoculated greenhouse assays. For the heritability study, 32 Pima (Gossypium barbadense L.) populations were used. Each population was derived from a single F2 plant. Preliminary results showed that most commercial Pima varieties grown in California were observed to be more susceptible to FOV race 4 (stand loss, stunting, etc) than any Upland cottons (G. hirsutum L.). However, tested Acala and non-Acala Upland cotton varieties were still infected by FOV race 4 at levels where plants would be expected to reproduce the fungus and expand inoculum. Highly resistant germplasm to FOV race 4 were identified on Pima for inoculum levels tested (field and greenhouse). In Pima for this study, preliminary results showed that resistance for FOV race 4 may be inherited quantitatively and controlled by several genes. Heritability estimates indicated that selection for FOV race 4 may be accomplished in early as well as advanced generations. Development of highly resistant germplasm and genetic mapping populations are ongoing in order to further study FOV resistance and its heritability. [ABSTRACT FROM AUTHOR]

The article reports on the symptoms and disease development of Fusarium wilt in Acala and Pima Cotton. It has been found that Fusarium wilt of cotton is a vascular wilt disease which are commonly caused by Fusarium oxysporum. During such stage, the fusarium wilt can affect the growth stage of cotton, thus causing many changes of the young plants' cotyledons and leaves. Other symptoms carried by Fusarium wilt to cotton plants have been demonstrated. Information regarding various ways to control as well as contain such diseases is discussed.

Damage to cotton from nematodes and diseases results in significant economic loss each year throughout the cotton belt. The average crop loss caused by nematodes has been reported to be as high as 10% in some states, though losses in individual fields can be more than 50%. Such losses occur despite the widespread use of nematicides. Losses caused by seedling diseases are highly variable and hard to predict, but losses can be devastating when conditions are favorable for disease: for example, Tennessee reported a statewide average loss to seedling diseases of 20% in 2002. Crop rotation can help minimize damage from nematodes and diseases, but potential rotation crops are often less profitable than cotton. A rotation crop that is profitable in one area may be economically unsuitable in another, so rotation recommendations must be evaluated with due consideration of local experience. Crop rotations may have beneficial effects regardless of nematode and disease problems if they improve soil fertility, soil tilth, cation exchange capacity, soil organic matter, or other factors that are likely to increase the yield of a subsequent cotton crop. Various legumes, sod-forming grasses, and crops that leave a lot of organic matter in the field are the most likely rotations to improve soil quality. The greatest cotton losses often occur in varieties and fields with the highest yield potential. If the percent loss is the same for two varieties, the variety with the greatest yield potential will lose more actual pounds of lint: a 25% loss is greater if the yield potential is 1,000 pounds per acre than if the potential is only 600 pounds. There is some evidence that varieties with the highest yield potential may suffer greater percent losses, but that has not yet been documented conclusively. However, it is clear that nematode and disease management become more important as yield potential increases. Rotation crops will reduce the damage caused by nematodes in a subsequent cotton crop if nematode reproduction is sufficiently limited on the rotation crop, so the best rotation crops must be very poor hosts for the nematode you wish to suppress. To illustrate why a rotation crop must be matched to the specific problem in a field, consider an example: corn is a very poor host for the reniform nematode and a good host for the southern root-knot nematode, so corn could reduce reniform damage but increase root-knot damage in a subsequent cotton crop. A few examples of crops that have been shown to be useful rotations for reniform nematode suppression in cotton include corn, peanut, bahiagrass, and coastal bermudagrass; crops useful for southern root-knot nematode suppression include peanut, sorghum, and coastal bermudagrass. Some crops that are generally susceptible to a specific nematode may have certain cultivars that are highly resistant, and the resistant varieties may be suitable for rotation with cotton: for example, most soybean varieties are very susceptible to the reniform nematode, but a few varieties have a high level of resistance and are effective at suppressing reniform nematode population levels. In most instances, one year of a nematode-resistant rotation crop will have a significant effect, and two years will be sufficient to achieve the maximum benefit. Unfortunately, nematodes typically rebound to pre-rotation levels after only one year of cotton. Cotton seedling diseases may be suppressed slightly by a rotation crop that is a poor or non-host for the fungal pathogen, but the fungus Rhizoctonia can grow on dead plant residue in a field and on some weeds, so even several years of a poor host may have limited effect. Rhizoctonia may possibly be suppressed by growing several years of corn, bahiagrass, or bermudagrass, but problems will be increased by growing peanut or soybean, which are good hosts for Rhizoctonia. Direct effects of rotations on the fungus that causes Fusarium wilt are not known, but suppression of the southern root-knot nematode will reduce the amount of Fusarium wilt in a field because the nematode and the fungus have a synergistic interaction. Winter cover crops that are good nematode hosts can increase nematode population levels in a field if soil temperatures are sufficient, and this can reduce the beneficial effect that a summer rotation crop might otherwise have had. Nematode resistant cover crops will not reduce nematode levels compared to winter fallow, but they should be used when nematodes are present in a field because they will not increase nematode levels as a susceptible cover crop might. As with all plants, a cover crop may be resistant to one nematode species and susceptible to others, so the resistance must be matched to the nematodes present in a field. Weeds that are good hosts for nematodes also can reduce the nematode-suppressive effect of a rotation crop. For example, Florida beggarweed is a good host for the reniform nematode and it is one of the most common weeds in Southeastern peanut fields, so it has the potential to allow significant reniform nematode reproduction when peanut is grown, even though peanut is virtually a non-host. [ABSTRACT FROM AUTHOR]