J.D. Hernandez, J. Bond, S. A. Ebelhar, and C.D. Hart 1
Graham and Webb (1991) describe resistance in the host-pathogen relationship as the ability of plants to limit the penetration, development and/or reproduction of invading pathogens. Although both factors “tolerance and resistance” are genetically controlled, the environment and particularly plant nutrition status of the host can certainly have an impact. We have challenging years to come with soybean production and disease management. A primary challenge will be to remain competitive when Asian rust appears in our region. Therefore, an integrated management and control program will be needed.
Research for tools in controlling soybean foliar diseases has focused on either fungicide application or genetic resistance. However, the influence of plant nutrition status on susceptibility and tolerance of crops to diseases is an important aspect to consider. Any potassium (K) plant deficiency will be associated with thin cell walls, smaller, thinner and shorter roots, lower sugar accumulation in the foliar tissue, and accumulation of unused nitrogen (N). All of which encourages disease infection, particularly soybean Asian rust (PPI, 1998). Potassium is involved in numerous functions in the plant such as in enzyme activation, cation/anion balance, stomatal movement, phloem loading; assimilate translocation and turgor regulation (Peoples and Koch, 1979). Perrenoud (1990) reviewed several thousand references and concluded that the use of K decreases the incidence of fungal diseases in 70% of cases, in the same review he reported that yield was always increased in plants infested with fungal diseases. This suggests a great potential by including appropriate K nutrition management in foliar fungus affected soybean plants, and particularly for soybean Asian rust integrated management (Piccio and Franje, 1980).
Chloride (Cl), usually in the form of potassium chloride (KCl), has been shown to reduce the severity of several fungal diseases (Fixen, 1993). Manganese (Mn) is essential in reducing the incidence of foliar disease in crops (Graham and Webb, 1991; Huber and Wilhelm, 1988). However, newer glyphosphate resistant soybean varieties have shown lower capacity for soil up-take of Mn or to translocation Mn within the plant (Huber et al., 2004). Manganese plant nutrition reduces the incidence of foliar disease in most crops. The main reason is its role in the synthesis of lignin and phenols and thus, in controlling pathogens (Graham and Webb, 1991). Research has shown that when Mn concentrations are low in soil-plant systems there is greater susceptibility for the attack of fungal pathogens (Huber and Wilhelm, 1988). Boron (B) is related to the production of small fissures and cracks that may be the initial entrance or access to fungal diseases. The new genetic information about genetic modified soybean and its relationship with uptake of nutrients combined with new arriving diseases may bring new challenges for disease control in the near future. To face this upcoming challenge in soybean production alternative ways to handle both nutrient and fungicides management is needed.
| Duration: | Three years, July 1, 2006 - June 30, 2009. |
| Locations: | Southern Illinois University Agronomy Research Center, Jackson Co. UI Dixon Springs Ag. Center farm in Johnson Co. UI Brownstown Research Center, Fayette Co. |
| Objectives: |
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Treatments identified in Table 1 were applied to soybeans grown under three soil types in Southern Illinois. The soybean treatments were established in an area where the selected disease was present, to ensure distribution of the pathogenic form all over the treatments. A split-plot field study with four replications was conducted at two locations; The University of Illinois Dixon Springs Ag. Center and the University of Illinois Brownstown Agronomy Research Center. Whole plots consisted of two soybean varieties (1 Roundup-ready and 1 conventional). Split plots consisted of a combination of +/- fungicides conventional treatment, manganese (Mn) and boron (B) plus a comparison of potassium (K) sources in the two available formulations (potassium chloride [KCl] vs. potassium sulfate [K2SO4]).
Measurements included soil samples for pH, P, K, Mn and Cl with Mn and Cl determined to a depth of 2 feet in 6" increments. Tissue samples for K, Cl, B and Mn were taken at early pod set. Evaluation of soybean eye frogeye incidence and severity was monitored throughout the growing season. An index assigned 1 to no incidence and 9 to the highest level of incidence. Plot size was 10' by 30' with the center 5' x 30' harvested for grain yield at the end of the growing season. Soils common to the region of southern Illinois represented by the Research Centers were used. Initial soil test values of pH, O.M., P, K, S and micro-nutrients were determined using standard methodologies. Plot areas were tilled in the fall. A corn soybean rotation was used with soybeans planted in 15 inch rows at optimum seeding rates. Planting date, weed and pest control was managed as a commercial crop.
Measurements
Table 1. Treatment distribution.
Table 2. Soil analysis for Brownstown and Dixon Spring Experimental locations.
Table 3. Significant contrasts obtained at Dixon Spring Ag. Research Center 2006, yield performance.
Figure 1. Nutrient vs. fungicide effects on soybeans at Dixon Spring Ag. Research Center 2006.
1J.D. Hernandez and J. Bond are Assistant and Associate Professors, respectively at Southern Illinois Univ., Carbondale. IL 62901. S. A. Ebelhar and C.D. Hart are Agronomist and Research Specialist, respectively, at Univ. of Illinois, Dixon Springs.
Fixen, P.E. 1993. Crop responses to chloride. In D. L. Sparks (ed) Advances in Agronomy, Vol. 50. Academic Press, Inc.
Graham, R.D. and M.J. Webb. 1991. Micronutrients and disease resistance and tolerance in plants. Pp. 329-370. In J.J. Mortvedt, F.R. Cox, L.M. Shuman, and R.M. Welch eds.) Micronutrients in Agriculture. 2nd edition. Soil Science Society of America.
Huber, D.M., J.D. Leuck, W.C. Smith, and E.P. Christmas. 2004. Induced manganese deficiency in GM soybeans. Proceedings of the North Central Extension-Industry Soil Fertility Conference 20:80-83. Potash & Phosphate Institute, Brookings, SD.
Huber, D.M. and N.S. Wilhelm. 1988. The role of manganese in resistance of plant diseases. In: Graham, R.D, R.J. Hannam, and N.C. Uren (eds). Manganese in Soils and Plants. Kluwer Academic Publishers, Dordrecht, The Netherlands. pp 155-173.
Koch, K. and Mengel, K. 1974. The influence of the level of potassium supply to young tobacco plants (Nicotiana tabacum L.) on short-term uptake and utilization of nitrate nitrogen. J. Sci. Food Agric. 25: 465-471.
Peoples, T.R. and Koch, D.W. 1979. Role of potassium in carbon dioxide assimilation in Medicago sativa L. Plant Physiol. 63: 878-881.
Perrenoud, S. (1990): Potassium and plant health. IPI Research Topics No. 3, 2nd rev. edition.Basel/Switzerland.
Piccio, V.L. and N.S. Franje. 1980. Rust incidence in soybean (Glycine max (L.) Merr.) as affected by varying levels of NPK applied alone and in combination. Soybean Rust Newsletter 3:18-22.
Phosphorus & Potash Institute. 1998. Effects of potassium on plant diseases. In Potassium for Agriculture, Potash & Phosphate Institute, Norcross, GA. pp 37-39.