Abstract
Concern for S deficiencies of corn ( Zea mays L.) is common among producers and fertilizer dealers in the Midwest. This concern results from emphasis on high yields with subsequent large S needs, accompanied by a decreasing S supply from incidental sources. A survey was made of corn response to fertilizer S in Missouri. Sites were selected on the basis of high yield potential and on soils that the farmers and fertilizer dealers suspected needed S, but that had not previously been considered S deficient. During 1991 and 1992, fertilizer S rate studies were conducted at 53 sites throughout Missouri. Sulfur rates of 0, 15, 30, and 60 lb S/acre were used. Ammonium sulfate and ammonium thiosulfate were the S sources that were applied at planting or within 4 wk following planting. Grain yields exceeded 175 bu/acre at 29 of 47 site‐years. Grain yield increases from fertilizer S were observed at three of 47 harvested sites, and yield decreases at five sites. However, leaf S concentrations were above previously established critical levels. Leaf S concentrations were increased by fertilizer S at 36% of the sites at the six leaf stage and at 38% of the sites at anthesis. Grain S concentrations were increased by fertilizer S at 15% of the sites. Leaf and grain S concentrations and N:S tissue ratios correlated very poorly with relative yield. Fertilizer S recommendations (none recommended for all but one site) based on soil sulfate measured at planting were incorrect for only three sites. Consequently, this research indicates no change is needed from present S fertilizer recommendations for corn groan in Missouri. Research Question Corn grown in Missouri on medium to fine textured soils has not historically required S fertilizer. In addition to S supplied by the soil, S has been incidentally supplied with field applied‐manures, low analysis S containing fertilizers, pesticides, and from deposition in rainfall and dust. Since the S supply from these sources has been reduced from previous years, and increased grain yields have greater crop S requirements, this study sought to survey corn response to fertilizer S on soils that were not previously considered S deficient for corn. Literature Survey Most documented corn grain yield responses to fertilizer S in the Midwest have been on coarse textured, low organic matter soils. Greenhouse evaluations have shown many midwestern soils supply inadequate S to a growing crop. An Illinois study conducted in the late 1970s measured grain yield increases from fertilizer S at five of 82 sites. In the past, S deposited in rain probably has been a significant portion of the S used by a crop. However, the amount of S deposited in rainfall in mid‐Missouri has decreased by 50% in the last 10 yr, and present yield levels require more S. In recent years, first time responses to fertilizer have been observed on fine textured soils. Study Description Fifty‐three S rate experiments were established on 25 different soil types across Missouri during 1991 and 1992. Sulfur fertilizer was applied at or near planting at rates of 0, 15, 30, and 60 lb S/acre. The S sources were ammonium sulfate (21‐0‐0‐24 N‐P‐K‐S) or ammonium thiosulfate (32‐0‐0‐5). Applied Question Does high yielding corn in Missouri require fertilizer S for maximum grain yield and quality? These data do not support a need for fertilizer S. Several geographic areas of Missouri, soil types, and management systems were represented by the sites. Yet none of these were identified as specific factors that relate to yield loss in the absence of fertilizer S. Grain quality (crude protein) was unaffected by fertilizer S (data not presented). When the yields of all sites were averaged, yields were similar for the zero S treatment and the S fertilized plots (Table ). Can S fertilizer effects be predicted for corn grown on Missouri soils? Soil samples were taken at 0‐ to 6‐ and 6‐ to 12‐in. depths at planting. Soil sulfate values varied from 0.8 to 11.7 ppm in the surface 6 in. and were often higher in the subsoil. Using present recommendation criteria, soil sulfate values accurately predicted the lack of response to fertilizer S at all but three sites. Fertilizer S increased leaf S concentrations at vegetative and silking growth stages at many sites. Leaf S concentrations were above previously established critical levels associated with S deficiencies. But under these circumstances, leaf S concentrations at these stages were not good indicators of grain yield response to fertilizer S. Results of this study suggest that corn grown on fine textured soils in Missouri obtains adequate S without S fertilization. Recommendation Missouri farmers on medium to fine textured soils do not need S in their corn fertilizer program. The frequency of crop response to fertilizer S is so low that even the cost of “insurance” S applications must be weighed against the alternative use of capital associated with such applications. Grain yields averaged across sites for 1991 and 1992. S rate, lb/acre Year 0 15 30 60 ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ bu/acre ‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐ 1991 159 160 160 158 1992 184 184 181 184 1991–1992 174 174 172 174
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Claims 15
Claim · model-written summary
Corn grain yields exceeded 175 bu/acre at 29 of 47 site-years.
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yields exceeded 175 bu/acre at 29 of 47 site‐years.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Sulfur fertilizer increased grain yield at three of 47 harvested sites.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain yield increases from fertilizer S were observed at three of 47 harvested sites”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Sulfur fertilizer decreased grain yield at five sites.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yield decreases at five sites”
e1“Grain yield increases from fertilizer S”
e2“corn ( Zea mays L.)”
Claim · model-written summary
Leaf sulfur concentrations were above prior critical levels.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“leaf S concentrations were above previously established critical levels”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Fertilizer sulfur increased leaf sulfur concentrations at 36% of sites at six-leaf stage.
- Organ / stage
- six leaf stagee0
- Treatment
- fertilizer Se0
- Outcome
- Leaf S concentrationse0
- Direction
- increasede0
- Value
- 36%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf S concentrations were increased by fertilizer S at 36% of the sites at the six leaf stage”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Fertilizer sulfur increased leaf sulfur concentrations at 38% of sites at anthesis.
- Organ / stage
- anthesise0
- Treatment
- fertilizer Se1
- Outcome
- Leaf S concentrationse1
- Direction
- increasede1
- Value
- 38%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“at 38% of the sites at anthesis”
e1“Leaf S concentrations were increased by fertilizer S”
e2“corn ( Zea mays L.)”
Claim · model-written summary
Fertilizer sulfur increased grain sulfur concentrations at 15% of sites.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain S concentrations were increased by fertilizer S at 15% of the sites.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Leaf sulfur concentration correlated poorly with relative yield.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf and grain S concentrations and N:S tissue ratios correlated very poorly with relative yield.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Grain sulfur concentration correlated poorly with relative yield.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Leaf and grain S concentrations and N:S tissue ratios correlated very poorly with relative yield.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Tissue nitrogen-to-sulfur ratios correlated poorly with relative yield.
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“N:S tissue ratios correlated very poorly with relative yield.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Soil sulfate recommendations were wrong at only three sites.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Fertilizer S recommendations (none recommended for all but one site) based on soil sulfate measured at planting were incorrect for only three sites.”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Fertilizer sulfur did not affect grain crude protein.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Grain quality (crude protein) was unaffected by fertilizer S”
e1“corn ( Zea mays L.)”
Claim · model-written summary
Across sites, fertilized and zero-sulfur plots had similar yields.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“yields were similar for the zero S treatment and the S fertilized plots”
e1“corn ( Zea mays L.)”
Claim · model-written summary
No tested site factor was linked to yield loss without sulfur fertilizer.
Not reportedSettingDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“none of these were identified as specific factors that relate to yield loss in the absence of fertilizer S”
e1“corn ( Zea mays L.)”
Claim · model-written summary
The authors recommend against routine sulfur fertilizer for Missouri corn on medium to fine soils.
- Taxon
- corn
Zea mays subsp. mayse0 - Outcome
- do not need S in their corn fertilizer programe0
- Setting
- Missourie0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Missouri farmers on medium to fine textured soils do not need S in their corn fertilizer program.”
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