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1203 The widespread use of high-analysis, granular S-free NP fertilizers such as urea, MAP, DAP, and TSP, together with more intensifi ed cropping with higher yields, has resulted in increasing occurrences of soil S-defi ciency in many countries (Chien et al., 2009). Furthermore, a reduction in SO2 emissions to the atmosphere from industry, as required by environmental laws, has a signifi cant local eff ect on S deposition from the atmosphere to soils. For example, Sawyer et al. (2011a, 2011b) reported signifi cant maize (Zea mays L.) and alfalfa (Medicago sativa L.) yield increases in response to S applications at fi eld sites in northeastern Iowa. Grant (2013) reported signifi cant canola (Brassica napus L.) response to S fertilizers in Canada. Because pure ES is 100% S, incorporation of ES into highanalysis granular NP fertilizers will not signifi cantly reduce N and P contents of the NP fertilizers and minimize increase in transportation costs as compared with the inclusion of AS. However, AS is considered readily plant available, whereas ES is not, unless it is oxidized to SO4–S by soil microbes. Th e oxidation rate of soil incorporated ES particles increases with decreasing particle size of ES (Boswell and Friesen, 1993). For this reason, some fertilizer companies have been developing processes in which the very fi ne micronized ES particles (

As corn producers strive to improve the efficiency of fertilizer use in corn (Zea mays L.) production, placement of fertilizer near the seed is a management option that should be given serious consideration. The positive effect of fertilizer placed in a band close to corn seed when soil test values for P and/or K are lower than in the high range has been frequently documented in the literature. Placement of fertilizer very near the seed at planting, frequently referred to as "pop-up" is gaining in popularity. Rate of adoption of this practice by crop producers has accelerated in recent years raising several questions. To address these questions, this study was conducted for the purpose of evaluating the impact of three fluid fertilizers applied at two rates and placed near the seed at planting on corn emergence, early growth, P uptake, and yield. All combinations of three factors (fertilizer grade, rate of application, placement) were combined in a complete factorial in fields of six cooperating farmers. Three fluid fertilizers were applied at two rates either with the seed or in positions above or below the seed with a small amount of soil between seed and fertilizer. Use of 10―15―0 (10-34-0) near the seed at 93.5 L ha ― in sandy soils reduced emergence. In the same sandy soils, application of 4-4.4-8.3 (4-10-10) and 3-8-15 (3-18-18) had no impact on emergence. Placement of all grades near the seed had no effect on emergence in the fine-textured soils. The data lead to the conclusion that the rate of N, rather than the rate of N plus K, in the fertilizer to be placed near the seed should be the major consideration. Early growth and P uptake by young corn plants was improved by fertilizer placed close to the seed in fine-textured soils; but not sandy soils. Five of six sites selected had high or very high levels of soil test P. Therefore, fertilizer placed near the seed did not have a positive effect on yield. Measured reductions in yield paralleled reductions in emergence. Results of the study show that placement of fertilizer near the corn seed at planting can be an effective management practice with minimal risk if soils are not sandy.

To achieve optimum production of hard red spring wheat, growers should know if use of copper (Cu) in a fertilizer program is necessary. For this study, copper was broadcast and incorporated before planting in the sulfate or chelate form to supply both 6.7 and 13.4 kg Cu ha−1 at six sites. The soils at the majority of the sites had a loamy fine sand texture with low organic‐matter content. Application of Cu increased grain yield at one site. Grain yield response, however, could not be predicted by amount of Cu extracted from soil by the diethylenetriaminepentaacetic acid (DTPA) procedure. Concentrations of Cu in whole plant tissue did not match those reported in the literature. The results of this study do not support the addition of Cu to a fertilizer program for production of hard red spring wheat on mineral soils in the northern Great Plains.

Production of high‐quality sugar beets requires precise nitrogen (N) fertilizer management with N recommendations based on a measurement of residual nitrate‐N to 120 cm (4 ft) soil depth. The objective of this study was to determine the agronomic and economic aspects of using different grid cell sizes for sampling soil nitrate‐N. A 5‐ha field (12.4 acre) was soil sampled for nitrate‐N using 18.3×18.3 m grid cells in 1997 and 1998. Nitrogen application maps for four different grid cell sizes 18.3×18.3 m (60×60 ft), 54.9×54.9 m (180×180 ft), 91.4×91.4 m (300×300 ft), and 128×128 m (420×420 ft) were developed from these soil samples and compared with a conventional average for each field. The five nitrogen fertilizer treatments adjusted for grid cell size were applied with a fertilizer truck equipped with a variable rate applicator in two replicates of 274‐m long strips. Sugar beet quality was determined on root samples taken immediately before root harvest on a 18.3×18.3 grid. Root yield was determ...

Reduction in soil disturbance associated with conservation tillage planting systems suggests that it is important to evaluate management practices for use of S for corn (Zea mays L.) grown in these planting situations. Evaluation of source, placement, and rate of S applied has not been the focus of past research. In this study, two S fertilizers [21-0-0-24 (ammonium sulfate), 12-0-0-26 (ammonium thiosulfate)] were applied at rates to supply 0, 6.7, 13.4, and 20.1 kg S ha -1 either in contact with the seed at planting or in a band near the seed at planting. Soil texture varied from loamy fine sand to silty day loam at the experimental sites. Corn emergence was reduced when 12-0-0-26 was placed in contact with the seed at sites with a loamy fine sand and sandy loam texture and soil was dry at time of planting. Stand reduction was most severe when 12-0-0-26 fluid material was used at rates to supply 13.4 and 20.1 kg S ha -1 . Placement maintaining soil between seed and fertilizer had no negative effect on emergence. When placed in a band near the seed, both S sources had an equal effect on yield. Reduction in emergence due to 12-0-0-26 in contact with the seed had a negative effect on grain yield. Application of fertilizer S increased yield at all sites except where the texture was a silty day loam. Optimum rate of fertilizer S was either 6.7 or 13.4 kg S ha -1 and varied with site. The response to fertilizer S on the silt loam soil suggests that inadequate S is released from soil organic matter via mineralization in conservation tillage planting systems.

Predicted physiological factors and a limited number of field studies have resulted in debate regarding the recommendation of in-season fertilizer N for soybean [Glycine max. (L.) Merrill]. The objective of our research was to evaluate several in-season N fertilization strategies on soybean seed yield response as well as to measure the effect of fertilizer N additions on late-season plant N concentrations and accumulation, seed N removal, seed protein, and seed oil composition. The research was conducted at 12 sites in the southern soybean-growing region of Minnesota in 1998 and 1999. A combination of (i) application time (July vs. August), (ii) placement method (broadcast vs. knifed), and (iii) N source (urea vs. poly-coated urea) gave five N treatments plus a control at all sites. Seed yield did not respond to the fertilizer N treatments at any of the 12 sites; however, a combined analysis indicated a significant increase (generally less than 0.06 Mg ha - 1 ) from using polymer-coated urea or applying the urea in August. Herbage dry matter (DM) and herbage N concentrations at the R6 stage were not affected by any of the N fertilizer strategies. Although soybean seed protein was statistically different among the treatments, protein was only increased 0.4 g kg -1 . Soybean oil concentration was not affected by fertilizer treatments. In general, polymer-coated urea, knifed applications, and August applications increased soil NO 3 -N in the 0- to 30-cm layer at R6 relative to standard urea, broadcast applications, and July applications. Even though in-season N fertilizer created greater levels of available soil N at all 12 sites during soybean pod filling, seed yield was not improved compared with unfertilized control plots at any site. As a result, the University of Minnesota does not recommended in-season N fertilizer applications for soybean production.

Year-to-year consistency of crop yields within a farm field is needed to use grain yield monitor data for site-specific management decisions such as yield goals for fertilizer recommendations. A 5-yr study was conducted from 1991 to 1995 to determine whether patterns of corn (Zea mays L.) grain yields are similar over a number of years and whether grain yields from one or more years can be used to predict grain yields for subsequent years. The experimental site was located at the Northern Cornbelt Sand Plain Management Systems Evaluation Area near Princeton, MN. The research area was 4.4 acres with soils mapped as three variants of the Zimmerman fine sand (mixed, frigid, argic, Udipsamment) and a Cantlin loamy fine sand (sandy, mixed, frigid, typic, Udipsamment). Continuous corn was grown from 1990 through 1995 after alfalfa (Medicago sativa L.) from 1981 through 1989. Cultural practices were applied uniformly to the 4.4 acre site each year. The 4.4 acres were divided into 60 grid cells (50 ft. by 60 ft.) and grain yields, corrected to 15.5% moisture, were determined by hand harvesting an area (two rows 20 ft. long) within each of the 60 grid cells. Differences between highest and lowest continuous corn grain yields in the research area were 72 bu/acre in 1991, 44 bulacre in 1992, 45 bu/acre in 1993, 51 bu/acre in 1994, and 57 bu/acre in 1995. Grain yields were not spatially consistent from year to year. Areas with better grain yields were not consistent from year to year, and conversely, poor production areas were not found in similar locations each year. Only 4 to 42% of the grain yield variability for a given year is accounted for by a knowledge of the grain yields from a previous year. The lack of grain yield stability as measured by ranked correlations on a sandy soil raises serious questions for the potential for use of this information. The data indicate that the use of grain yield maps for fertilizer recommendations on a site specific basis may not be possible or may require a much longer term database than the normally recommended 5 yr, unless there is a construct of inputs that explains the grain yield patterns each year.

Repeated use of band applications, both surface and subsurface, of immobile nutrients applicable to a variety of tillage systems raises concerns about the collection of soil samples used for making fertilizer recommendations. This study was conducted to measure the effect of tillage system and fertilizer placement on soil test P in a major part of the root zone. Soil samples were collected from control treatments and from treatments where phosphate fertilizer supplying 29 kg P ha -1 yr -1 had been broadcast, applied as a surface band, or applied in a subsurface band for three consecutive years in a corn (Zea mays L.)-soybean [Glycine max (L.) Merr.] rotation. These placements were used in both a chisel and a ridge-till planting system. Soil samples were collected from depths of 0 to 7.5, 7.5 to 15.0, 15.0 to 22.5, 22.5 to 30.0, and 30.0 to 45.0 cm at distances of 0, 7.5, 15.0, 22.5, 30.0, and 37.5 cm from the row. Soil test P, to a depth of 15 cm at each position from the row, was significantly affected by fertilizer placement. Placement also had a significant effect on soil test P to a depth of 30 to 45 cm at a distance of 30 cm from the row. Tillage system had a significant effect on measured soil test P at sampling positions near the row. These results indicate that both tillage system and fertilizer placement could have a major effect on soil test values. If band locations are known, they should be avoided, if possible, during sample collection.

Potassium (K) deficiency symptoms in corn (Zea mays L.) grown in the ridge‐till planting system were a major concern for producers who used this planting system. The purpose of this study was to develop management practices for use of K fertilizer in the ridge‐till planting system. The study was conducted on a farm in southwestern Minnesota where the ridge‐till planting system had been used for several years. The first year was devoted to an evaluation of rate of K (0, 37, 74, and 148 kg K/ha) applied in a band in the center of the ridge on growth and yield of three corn hybrids. Frequency of K application was evaluated for soybean [Glycine max L. (Merril)] production in the second year and corn in the third year of the study. The response to K use and the K rate x hybrid interaction were significant. Residual effects of banded K were evident with both corn and soybeans if rates of 74 kg K/ha or higher were used. The data collected show that use of banded K is important for corn and soybean produ...

The importance of sulfur (S) for corn (Zea mays L.) production on sandy soils has been noted for a number of years. Yet, there has been no extensive evaluation of the timing of S applications on corn production in these specific situations. This study was conducted for the purpose of measuring the effect of split applications of fertilizer S on com grown on irrigated sandy soils. The study was conducted in 1985 and 1986. Fourrâtes of fertilizer S (0, 6.5, 13, and 26 kg/ha) were combined with six times of application schemes in a randomized complete block design with four replications. Granular gypsum was used as the source of S. Corn responded to the use of fertilizer S in 1986 only. Time of application had no significant effect on yield in either year. There were no advantages to the use of split applications. The S concentration in the ear leaf tissue at silking was affected by both rate and time of S application at each experimental site. The current recommendation is to apply fertilizer S, wh...

The objective of this study was to evaluate the usefulness of measures of mineralized sulfur (S), soil sulfate‐sulfur (SO4‐S), concentration of S in plant tissue, and the N: S ratio in plant tissue as predictors of the need for S in a fertilizer program for corn (Zea mays L.). Data to evaluate the use of plant analysis for S as a predictor were obtained from ten sites where various rates of N and S were applied to corn. Regression analysis was used to relate the S concentration in the ear leaf tissue as well as the N: S ratio in the same tissue to relative yield when the rate of applied N was held constant at a rate of 168 kg/ha. These measures of S in plant tissue were not significantly related to relative yield at sites where there was no response to fertilizer S as well as sites where added S increased yield. Data from the same sites were used to assess the ability of soil tests to predict the need for fertilizer S. A measurement of extractable SO4‐S in the surface soil (0–15 cm) was not relia...

A method for the determination of S in plant materials is described. The material is oxidized by nitric and perchloric acid using a heating block to reduce perchloric acid loss. The SO₄ content of the solution is determined turbidimetrically as BaSO₄. The proposed method has been found to be more accurate and rapid than the conventional dry ashing procedures for the determination of S in plant material.