Illinois Fertilizer
Conference Proceedings
January 28-30, 1991
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John E. Sawyer and Stephen A. Ebelhar1
Winter wheat (Triticum aestivum L.) occupies large acreages and is important in the crop rotations of southern Illinois. With current high production levels, adequate supply of nutrients must be available for optimum plant growth and production. This study was conducted to determine if sulfur nutrition (an essential element not routinely applied for wheat production) was limiting winter wheat production in southern Illinois. The effects of S rate, tillage system, and variety on wheat growth and production were investigated at two sites in southern Illinois: Brownstown -- Cisne silt loam soil (Fine, Montmorillonitic, mesic Mollic Albaqualf) and Dixon Springs -Grantsburg silt loam soil (Fine-silty, mixed, mesic Typic Fragiudalf).
In 1990, grain yield was not increased with S application. Increasing S rates from 0 to 30 lb S/acre resulted in increases in flag leaf and whole plant S concentrations, but did not increase yield. Lack of response, to S application was consistent across all varieties and tillage systems. Equal yields were produced with both conventionaltill and no-till. All plant and soil parameters measured to determine wheat response to S application indicated that sufficient levels of S were available from sources other than fertilizer S. Based on this first year of study, routine application of S for wheat production in southern Illinois is not warranted.
Winter wheat has` historically been an important crop in the rotations of southern Illinois. In recent years, the acreage of winter wheat has increased substantially. According to the January 24, 1990 Illinois Farm Report published by the Illinois Agricultural Statistics Service (USDA, 1990), total of 1.78 million acres of winter wheat were harvested for grain in 1989, an increase of 42 percent from 1988 and an increase of 87% from 1987. In addition, yield production was at record levels in 1987 and 1989.
With the current large acreage of winter wheat, especially in southern Illinois, and with the current record levels of production, increased demand on the soil to supply nutrients required for adequate growth and production of wheat may be creating deficiencies of nutrients not currently being applied for crop production, such as sulfur.
In the Past, S deficiencies have been recognized in the Midwest but have not been widespread (Alway, 1940; Hoeft and Walsh, 1970; Thorup and Leitch, 1975; Rehm, 1976; Hoeft, 1980). However, as a result of several, factors, increased likelihood of S deficiencies may occur. These factors include increased crop production level, less application of S as impurities in fertilizers (such as phosphatic fertilizers) and pesticides, less contribution of S from the atmosphere (either from precipitation, dry deposition, or direct absorption of atmospheric compounds), use of minimum tillage systems which may reduce S mineralization from crop residues and soil organic matter, and fewer crop-livestock operations and increased acreage that receives no manure applications.
As crop demands for S increase, deficiencies are more likely to occur on soils that inherently supply less available S or can retain less available S within the rooting zone; those that have low organic matter content, have a coarse texture and have low or physically unavailable sources of S in the subsoil. Many of the soils in southern Illinois could fit into this category. However, soils with acidic and high clay content (free iron and aluminum oxides) subsoils accumulate more profile sulfate-S (Kamprath 'et 'al., 1956). Most reported wheat responses to applied S have occurred on coarse-textured, low-organic-matter soils with low capacity to retain sulfate in the subsoil (Oates and Kamprath, 1985; Mahler and Maples, 1986; Wells et al, 1986; Mahler and Maples, 1987).
In a statewide survey of soils in Illinois, Hoeft et al. (1985) found little corn (Zea mays L.) response to S application in the field, a total of only 5 of 82 sites responded, but in the greenhouse 60 percent of the soils responded to S application. This was an indication that many soils in Illinois have a limited ability to supply adequate available S for crop production and that contributions from sources other than the soil were major factors in supplying S for crop uptake in the field. They did measure an average growing season rainfall deposition of 9.7 lb S/acre in 1978 at sites in southern Illinois. Also, they found no relationship between extractable soil S level, Ca(H2P04)2-HOAc extractant, and corn yield response to S application.
It has been approximately 10 years since the survey by Hoeft et al. (1985) was conducted. It may be possible- that atmospheric contributions have declined to the point that little S is applied to soils from that source. Recent measured annual average sulfate-S deposition from precipitation (1978-1987) in southern Illinois was 8.2 lb S/acre and winter plus spring deposition was 3.9 lb S/acre (NADP/NTN, 1990).
Today, possible S deficiencies will occur most -readily on soils that have low S supplying power. In the survey by Hoeft et al. (1985), two of the five responding sites were in southern Illinois on low organic matter soils. Also, the only crop studied was corn. Little if any S research has been conducted on winter wheat in Illinois.
The general goal of this project was to determine if sulfur nutrition is currently limiting winter wheat production in southern Illinois. Specific objectives were to: (1) measure plant nutrient composition and grain yield response of several adapted wheat varieties on two tillage systems to the spring topdress application of S fertilizer, (2) determine plant nutrient composition and wheat grain yield response to rate of spring topdress S application.
Field studies were conducted in 1990 at two sites in southern Illinois, the Brownstown Agronomy Research Center, located in south-central Illinois, and the Dixon Springs Agricultural Center, located in extreme southern Illinois. For each experiment, winter wheat was grown after a preceding soybean [Glycine max(L.) Merr.] crop.
This experiment was conducted only at Brownstown in 1990. A randomized complete block experimental design with three replicates was used with a split-split plot arrangement of treatments: main plot-- tillage system, no-till (NT) and conventional-till (CT); sub plot-- spring topdress S application, either no S or 25 lb S/acre as ammonium sulfate; and sub-sub plot-- winter wheat variety (Becker, Cardinal, Caldwell, and Pioneer® variety 2555). Plot dimensions were main plot, 48 by 165 ft; sub plot, 48 by 70 ft; and sub-sub plot, 12 by 70 ft. Chemical characteristics of the surface 6 in. of soil were pH 6.5, Pi 107 lb P/acre, and K (1M NH 40Ac, pH 7.0) 272 lb/acre.
Conventional-tillage was performed with one pass of a tandem disk and one pass with a field cultivator. Individual varieties were planted in 18-7 in. rows at a rate of 90 lb seed/acre on Oct. 12, 1989. Both the NT and CT was planted with a conventional double disk opener drill. It was not fitted with no-till coulters. Nitrogen rate was uniform on all plots (total of 110 lb N/acre) with 40 lb N/acre applied as diammonium phosphate in the fall before tillage and planting and--the remainder (70 lb N/ acre) applied either as ammonium nitrate or a combination of ammonium sulfate and ammonium nitrate as a topdress application in early spring (10 Mar. 1990).
Soil samples, 5 cores/sample from the 0-8 inch depth, were collected on March 5, 1990, May 8, 1990, and June 8, 1990 from the non-S treated sub plots. Flag leaf samples, 100/plot, were collected at Feekes' stage 10.1 (head emergence), Mal 8, 1990, and grain samples were collected at harvest. The number of wheat heads/ft was determined on June 8, 1990 by counting the number of heads in two foot sections of row at two places in each plot. Plant height to the top of the wheat head was measured on June 8, 1990 at two places in each plot. Each entire plot was harvested on June 28, 1990.
This experiment was conducted at both Brownstown and Dixon Springs in 1990. Four rates of spring topdress S (0, 5, 15, and 30 lb S/acre as ammonium sulfate applied March 2, 1990 at Brownstown and March 9, 1990 at Dixon Springs) were arranged in a randomized complete block design with four replicates. Winter wheat variety Cardinal had been conventionally planted (90 lb seed/acre) on Oct. 13, 1989 at Brownstown and Oct. 10, 1989 at Dixon Springs. The N rate was a uniform 110 lb N/acre at each location, applied as a combination of ammonium sulfate and ammonium nitrate. At Brownstown, all of the N was applied in the spring, while at Dixon Springs, 40 lb N/acre was applied as diammonium phosphate before planting. Plot size was 20 by 45 ft at Brownstown and 4.5 by 15 ft at Dixon Springs. The entire plot was harvested for grain yield at Dixon Springs and a 12.5 ft wide pass was harvested from each plot at Brownstown.
Chemical characteristics of the surface six inches of soil at Brownstown were pH 6.7, P1 72 lb P/acre, and K (1M NH4 0AC, pH 7.0) 520 lb/acre and at Dixon Springs were pH 5.5, Pi 68 lb P/acre, and K (1M NH4OAc; pH 7.0) 222 lb/acre: Potassium (muriate of potash) and phosphorus (triple superphosphate at Brownstown and diammonium phosphate at Dixon Springs) fertilizers were applied before tillage at rates of 44 lb P/acre and 100 lb K/acre. Additionally, 3 ton/acre limestone was applied at Dixon Springs.
Flag leaf samples were collected at Feekes' stage 10.1, 100/plot at Brownstown and 20/plot at Dixon Springs. Whole plant samples at Feekes' stage 10.1, 20 plants/plot, and grain samples at harvest were collected at Brownstown. Soil samples, 5 cores/sample from the 0-8 inc depth, were collected from the zero S rate plots at Brownstown and Dixon Springs on March 5, 1990, and at Brownstown on May 7, 1990, and June 8, 1990.
Grain weight and moisture content were determined from each plot and grain yield was adjusted to 13.5 percent moisture. Plant samples were dried at 140 F, ground in a Wiley mill to pass a 0.0394 in. screen, and analyzed for total N and S. Total N, including N03, was determined using a Leco (St..Joseph, MI) model FP-428 N analyzer. Total S was determined by digestion with nitric -perchloric acid (Blanchar et al., 1965) and analysis of the digestate by inductively coupled plasma spectrometry (ICP). Soil samples were analyzed fof S by extraction with Ca(H2P04).HOAc (Hoeft et al., 1973) and S in the extract determined by ICP. Analysis of variance for all measured parameters were carried out using the Statistical Analysis System (SAS Institute, 1988) using the General Linear Models (GLM) procedure. Orthogonal coefficients were utilized to determine significant S rate effects and to determine which regression equations to fit.
Precipitation was collected at each site and analyzed for SO4-S. Collection started on March 12, 1990 at Brownstown, with S04 determined by the turbidimetric method (Standard Methods, 1980). Dixon Springs is a collection site of the ongoing National Atmospheric Deposition Program, IR-7, National Trends Network (NADP/NTN), Fort Collins, Colo. The concentrations were used to calculate S deposited in precipitation at each site.
Plant Growth
Wheat plant heights were significantly different only for the main effects of tillage and variety in 1990 (Table 1). The overall difference in height between CT and NT was small, only 1 inch (Table 2). Height differences due to variety (Table 2) would be expected because of differing growth habits of the varieties.
Sulfur application and variety significantly influenced the number of heads/ft2 in early June. Also, the interaction between tillage and S application was significant (Table 1). The head count was consistently lower with S application, and when no S was applied, CT resulted in a higher head count than NT (Table 2). The reasons for these differences are not known. When S was deficient, Rasmussen et al. (1977) found that tillering and the number of spring wheat heads were increased with application of S, not decreased as in this study.
Overall mean head counts (Table 2) were not significantly different between tillage systems (66 heads/ft2 for NT and 70 heads/ft2 for CT). However, with NT, chickweed (Stellaria media) competition was present, especially with Pioneer$ variety 2555. Cold temperatures in early spring after wheat growth had resumed retarded that variety's growth and allowed the chickweed to become more vigorous. Reduced head count for Pioneer® variety 2555 on NT compared to CT was measured (57 versus 70 heads/ft2) but was not found to be statistically significant (Tables 1 and 2).
Flag Leaf
Flag leaves collected from the non-S treated plots (Feekes' growth stage 10.1 -initial heading) had S concentrations (Table 3) above the level (0.20 percent S) considered sufficient (Reneau et al., 1986). Flag leaf S and N concentrations were significantly different between main effects of tillage and variety (Table 1). Flag leaf S concentration was increased by S application and the interaction between S application and variety was significant (Tables 1 and 3). Even though these significant differences were found, the magnitudes were small (Table 3). For example, the significant N concentration difference due to tillage was only 0.16 percent N (Table 3). Differences in N concentration were larger between varieties, from 4.01 percent N for Becker to 3.63 percent N for Pioneer® variety 2555 (Table 3). Also, the significant S concentration difference due to tillage was only 0.02 percent S (Table 3).
Application of S consistently increased the flag leaf S concentration of each variety, but the magnitude of increase was larger for Caldwell and Cardinal than for Becker and Pioneer* variety 2555 (Table 3). The overall increase in flag leaf S concentration was small, from 0.34 percent to 0.39 percent S. Also, all measured S concentrations were above the level considered sufficient (Reneau et al., 1986).
Flag leaf N concentrations (Table 3) were within the range considered sufficient (Vaughan et al., 1990). Also, S application had no effect on flag leaf N concentration (Tables 1 and 3).
All measured flag leaf N/S ratios (NTotal/STotal) were lower than the level of 18 or below considered sufficient (Reneau et al., 1986). However, the N/S ratio was significantly affected by S application' and variety (Table 1). Also, the tillage x variety and S x variety interactions were significant (Table 1). Application of S consistently lowered the flag leaf N/S ratio (Table 3), but differences between varieties were found as the N/S ratio was lowered more with Cardinal and Caldwell than for Becker and Pioneers variety 2555. Overall, S application lowered the N/S ratio from 11.3 to 9.8 (Table 3). The low N/S ratio with no S application and further decrease with S application indicates that accumulation of inorganic S above plant requirements was taking place in the leaf tissue (Stewart and Porter, 1969; Rasmussen et al., 1975).
Grain
Wheat grain yields were significantly different only for the main effect of variety in 1990 (Table 1). No interactions were significant (Table 1). Yields (Table 4) were highest for variety Cardinal and lowest for Caldwell. Some differences in variety yields were probably due to varying variety resistance to diseases present in the late spring -- Powdery mildew (Erysiphe graminis f. sp. tritici), Scab (Fusarium spp.), Glume blotch (Septoria nodorum), and Leaf blotch (Segtoria tritci). Visual observation (no data shown) indicated no difference in diseases due to tillage.
The overall effect of S application was only a 1 bu/acre increase (Table 4) and was not significant. With CT, S application increased yield for each variety, but the increases were not large enough to be deemed real (Tables 1 and 4). In contrast, with NT, yields were nearly identical with and without application of S for each variety (Table 4).
Although no interactions were significant (Table 1), grain yield of Pioneer* variety 2555 was 6 bu/acre lower on NT than CT (Table 4). This may be a reflection of the chickweed pressure found with this variety on NT. Chickweed growth and competition is a potential concern for NT wheat production.
With or without the application of S, grain S concentrations (Table 4) were above the level of 0.12 percent S considered sufficient when N supply is adequate (Rasmussen et al., 1975; Randall et al, 1981). Also, all grain N/S ratios (Table 4) were less than the level considered deficient (17 or above is considered S deficient) for wheat grain (Randall et al., 1981; Mahler and Maples, 1987).
Variety significantly influenced grain N and S concentration and N/S ratio (Table 1). The tillage x variety interaction was significant for grain S concentration and N/S ratio. Also, the S application x'variety interaction was significant for grain S concentration (Table 1).
Despite the significant effects, the magnitude of differences in A and S grain concentration and grain N/S were small (Table 4). The largest difference in grain S concentration was 0.01 percent S. The significant difference in grain N concentration due to tillage was only 0.04 percent N, 2.09 percent N for CT and 2.05 percent N for NT (Table 4). Varietal grain N concentration ranged from 2.01 percent N for Becker to 2.11 percent N for Cardinal. (Table 4). With CT, the grain N/S ratio was found to be highest for Cardinal and Caldwell, but with NT the N/S ratio was only higher for Cardinal.
Soil
Extractable S in the surface soil was quite constant throughout the growing season (17 ppm S before planting, and 15 ppm S on March 5; 16 ppm S on May 8; and 14 ppm S on June 8). Spring soil S concentrations were averages of the six samples collected from the non-S treated sub-plots. Although the S soil test has not been reliable for predicting past responses in Illinois (Hoeft et al., 1985), these test levels would indicate that no response would occur to S application -- a test level greater than 10 ppm S (Hoeft et al., 1973).
Brownstown - Grain
Sulfur application had no significant effect on wheat grain yield at Brownstown (Table 5). Yields were essentially the same for all rates of S application. Grain S concentration and N/S ratio were also not affected by S application (Table 5) and both were in the range considered sufficient -- greater than 0.12 percent S (Rasmussen et al., 1975; Randall et al., 1981) and N/S less than 17 (Randall el at., 1981; Mahler and Maples, 1977). Grain N concentration decreased slightly with the highest rate of S application (Table 5).
Brownstown - Flag Leaf
At Brownstown, flag leaf S concentration was not significantly affected by S application (Table 6) but N concentration and N/S ratio decreased with increasing rate of S application, linear response (Table 6). The range of flag leaf S concentrations (0.31 to 0.33) were above the critical level of 0.20 percent S (Reneau et al., 1986) and the range of N/S ratios (12.0 to 10.9) were within the sufficient range of less than 18 (Reneau et al., 1986).
Brownstown - Whole Plant
Whole plant S concentration increased with increasing S rate, quadratic response, but whole plant N concentration and N/S ratio decreased with increasing S rate, linear response (Table 6). Whole plant S concentration with the zero S rate (0.14 percent S) was just below the 0.15 percent S sufficient level of Ward et al. (1973). The first increment of applied S, 5 lb S/acre, brought the S concentration into the sufficient range. Whole plant N/S ratios were below the critical range of 15 to 16 (Stewart and Porter, 1969; Rasmussen et al., 1975, 1977; Spencer and Freney, 1980; Mahler and Maples, 1986). The decrease in N/S ratio with increasing S rate indicates accumulation of inorganic S above plant requirements (Roberts and Koehler, 1965; Stewart and Porter, 1969; Rasmussen et al., 1975): Whole plant N concentrations were above the critical level of Ward et al., 1973 (1.25 percent N), but low with the 30 1b S/acre rate.
Dixon Springs - Flag Leaf and Grain
At Dixon Springs, grain yield, flag leaf S concentration, and flag leaf N/S ratio were all significantly influenced by S application (Table 7). Only flag leaf N concentration was not significantly different (Table 7). Grain yield decreased as S rate increased, but the magnitude of decrease was small. Fluctuating yields with increasing S rate resulted in the residual or cubic response to be significant. Because of the low yields (due to severe disease pressure at this location) the results probably have little meaning. Increasing rate of S application increased flag leaf 'S concentration and lowered the N/S ratio, quadratic responses (Table 7). Both S concentrations and the N/S ratios were in the sufficient ranges (Reneau et al., 1986).
Soil
Soil S test level varied slightly throughout the growing season at Brownstown -- 15 ppm S before planting, 15 ppm S on March 5; 19 ppm S on May 7; and 15 ppm S on June 8). Spring soil S levels were averages of the four samples collected from the zero S rate plots. According to the soil S test (Hoeft et al., 1973), this soil would not be predicted to respond to the application of S.
One soil sample set was taken from the study at Dixon Springs, March 5, 1990. The average of the four zero S rate plots was 16 ppm S. Again, this soil would, not be expected to respond to the application of S.
S Deposition
At Brownstown, rainfall was collected to determine S deposition from March through May 1990 and June. through August 1990. Total S deposition for the March through May period was 6.4 lb S/acre and for the June through August period was 4.3 lb S/acre. At Dixon Springs, a NADP/NTN collection site, the October 1989 through June 1990 precipitation S deposition was 5.2 lb S/acre (NADP/NTN, 1990). The;,1987 through 1989 annual average S deposition in precipitation was 7.5 lb S/acre:At4yDixon Springs (NADP/NTN, 1990).
In 1990, southern Illinois winter wheat grain yield was not increased by a spring topdress application of S. The lack of yield response was consistent across all varieties tested and on both tillage systems, no-till and conventional-till. Application of S rates from 0 to 30 lb S/acre resulted in increases in plant S, but not grain yield. All parameters used to determine possible wheat response to application of S, including plant S concentration and N/S ratio, flag leaf S concentration and N/S ratio, grain S concentration and N/S ratio, and soil S test, indicated that sufficient levels of S were available without application of supplemental fertilizer S.
Most likely, combined input of available S from sources other than fertilizer S -- such as precipitation, dry deposition, atmospheric S02 absorption by plants, mineralization of organic matter, or subsoil sulfate -- supply more than an adequate amount of available S for wheat production, for example, the total amount taken up by an 80 bu/acre wheat crop, approximately 20 lb S/acre (Beaton and Wagner, 1985).
If is important to remember that most reported wheat responses to application of S have occurred where the soil supply of available S was low -- coarse textured sands with low organic matter and low capacity to retain sulfate in the subsoil. The silt loam soils of southern Illinois have low organic matter, but clay subsoils limit the leaching or movement of sulfate out of the profile. Also, it is important to note that most of southern Illinois is in the highest SO4-S precipitation deposition area of the continental United States -- 1989 annual average deposition pattern of 6 to 9 lb S/acre (NADP/NTN, 1990).
Important: This is the first year of results from this research work. Better interpretation will be possible at the end of the three years of study.
Table 5. Effect of S application on wheat grain yield and S and N concentration, Brownstown - 1990.
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1John E. Sawyer is associate agronomist, University of Illinois, Brownstown Agronomy Research Center. Stephen A. Ebelhar is agronomist, University of Illinois, Dixon Springs Agricultural Center.
