Illinois
Fertilizer Conference Proceedings
January 24-26, 2000
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K.A. Ames, S.A. Ebelhar, K.L. Barber, and W.L. Pedersen1
Soil-borne diseases are responsible for significant yield losses each year. Plant pathogens can reduce stand, reduce root development, and ultimately reduce yield. These pathogens can be controlled with the use of fungicide seed protectants; however, most fungicides are effective for only a few weeks. Furthermore, most soybeans grown in Illinois are not treated with seed protectants.
Previous research has proven that the severity of several soil-borne diseases is reduced by the application of chloride fertilizers. Take-all of wheat was suppressed by a spring application of Cl in Oregon. Potassium chloride (KCl) reduced common root rot of barley at eight of 14 sites studied in North Dakota. Previous research has shown that control of chloride uptake in soybeans is divided into two categories, inclusion and exclusion. Uptake also is subject to the influence of environmental conditions. Varieties classified as includers may have symptoms of Cl toxicity (for example, symptoms of leaf scorch and reduced yield). Data from one study reported that five out of 15 cultivars absorbed a high amount of Cl and showed symptoms of Cl toxicity. From this study, the authors suggested the planting of tolerant cultivars in areas of concern to avoid Cl toxicity and reduction of yield.
Environmental conditions have an effect on chloride accumulation by soybeans due to chloride accumulation in the soil. Parker et al. found that soil conditions that restricted leaching had an effect on Cl accumulation in soybeans. Conditions such as potash fertilization, poorly drained soils, and limited precipitation are all factors that can make chloride accumulation more severe.
Chloride has also been shown to reduce seed germination and induce mortality in young plants. This decrease in germination percentage is related to a decrease in rate of germination as well as a decrease in percent emergence. Abel and MacKenzie reported that increasing the salinity levels at seedling emergence decreased percentage of germinating seeds. Salinity levels as low as .10% were shown to affect germination.
The objectives of this study were to determine the effects of chloride on soybean and wheat production and on the severity and incidence of Rhizoctonia solani and Fusarium solani on soybeans.
Soybean—Rate of Potassium Chloride: Field studies were conducted at University of Illinois research stations located in Urbana, IL and Dixon Springs, IL, in 1999. This study consisted of four varieties (Pioneer 9363, Pioneer 9395, Pioneer 9451, and Essex), three Cl rates (0, 15, and 30 lb Cl/acre as KCl), two application methods (preemergence and V2 post applied), and four replications. A split plot randomization was used, with the main plot treatments being the Cl level by method of application combinations and subplot treatments being cultivars.
Soybean—Chloride Source Fertilizer Study: Field studies were conducted at University of Illinois research stations located in Urbana, IL and Dixon Springs, IL in 1999. This study consisted of four varieties (Pioneer 9363, Pioneer 9395, Pioneer 9451, and Essex), three sources of salts (KCl, K2SO4, and CaCl2), two methods of application (preemergence and V2 post applied), and four replications. Plots receiving K-containing material were applied at 64 lbs of K per acre, whereas S-containing materials were applied at 26 lbs S/acre. A split plot randomization was used, with the main plots being the type of salt by method of application combinations and the subplot treatments being soybean varieties.
Wheat—Rate of Potassium Chloride: Studies were conducted at Urbana, Brownstown, and Dixon Springs in 1999. The three varieties included Ernie, Pioneer 2540, and Patterson. Treatments included 0, 15, 30, and 60 lbs Cl/acre. These treatments were applied both as a preplant in the fall or in the spring. Plots were 4 feet by 15 feet in size and treatments had a split plot arrangement of a randomized complete block design.
Wheat—Chloride Source Comparison Study: Field studies were done at Urbana, Brownstown, and Dixon Springs to evaluate different sources of K. The sources included CaCl2, KCl, and KNO3. Plots were arranged as described for the level of K study with one rate of each fertilizer applied at either planting or spring top-dressing. Roots were examined and rated for disease severity and yields were determined.
The initial objective of this project was to determine if the application of chloride fertilizer affected yield and/or disease levels for both wheat and soybean. Throughout the study, there were examples of significant increases in yield for both soybeans and wheat. For example, the mean yield of all soybean varieties was increased five to eight bu/acre at both Urbana (Table 1) and Dixon Springs (Table 2) with the high rate (30 lbs Cl/acre) when applied at planting. The application at growth stage V2 had no significant effect on yield at either location. In contrast, when the source of chloride was evaluated (Figures 3 and 4), there was a great deal of variation, and it was difficult to identify any specific trends.
It has been previously shown that there is a specific genetic background that conditions the ability of the plant to take up the chloride and translocate it into the tissue. We evaluated a number of commercial varieties for grams dry weight (plant size), germination, and chloride uptake (ppm) (Table 5). There was distinct grouping of varieties based on the source (seed company). For example, most of the varieties from Growmark accumulated significantly higher levels of chloride than varieties from other companies. Varieties from Kruger were intermediate, while the rest of the companies' varieties were much lower. We are in the process of completing this study and will include the results in the final report.
Our initial intent was to study the interaction between SDS and chloride application. However, in 1997, 1998, and 1999, we had no SDS in the fields we selected, despite a history of SDS in several of the fields. Therefore, we evaluated the effect of chloride on SDS in a greenhouse experiment (Table 6). The mean disease severity values were significantly reduced with the application of KCl, especially with several varieties including P9451 and Spencer. Varieties also differed in their ability to take up chloride (Table 7). It appears that Jack and Savoy are includers, while Pioneer Brand 9362 has a relatively high chloride content without additional KCl. These are the first results of our variety screen, with the remainder to be completed by March.
Wheat
There was little effect of chloride on wheat in 1999. The timing and rates had no significant effect at either location (Figures 1 - 4). There was an increase in chloride concentration from the flag leaves, especially for the preemergence treatment. However, the source of the fertilizer (Figures 7 - 8) showed an increase in yield at Dixon Springs, but not Urbana. There was no visible root or foliar diseases present in 1999.
Results from 1997-99 and greenhouse results indicate that there may be a correlation between chloride fertilizer and increased yield. This research was done on small plots, which was necessary for the large number of variables but which may not reflect real-world production. We are planning on scaling the study to a larger size in the year 2000, using drill strips at least 200 feet long. The second variable involves the potential relationship with SDS. We have identified a method of inoculating fields with SDS that will ensure consistent infection. It is now possible to evaluate this interaction in a field experiment.
The results from 1997-99 indicate that there is little benefit to applying chloride fertilizer to wheat in Illinois. The chloride was taken up by the plant and present in the flag leaves, but it did not give a consistent response. This may have been due to low inoculum pressure on wheat seedlings, especially in 1999. The plots were planted after soybean, which is a nonhost for many plant pathogens. If the study had been done in fields following corn, there may have been higher disease pressure, especially by Gibberella zeae, causal organism of both Gibberella stalk rot and Fusarium root rot of wheat.
Figures 5 - 6. Chloride concentrations (ppm) from wheat flag leaves from Urbana in 1999.
Figures 7 - 8. Yields of wheat plots from Dixon Springs and Urbana for the source study in 1999.
1 K.A. Ames is Graduate Research Assistant, Dept. of Crop Sciences, Univ. of Illinois; S.A. Ebelhar is Agronomist, Dept. of Crop Sciences, Univ. of Illinois; K.L. Barber is Agronomist, Golden Harvest; and W.L. Pederson is Associate Professor, Dept. of Crop Sciences, Univ. of Illinois, Urbana, IL.
