Abstract
Abstract Iron (Fe) chlorosis is a common symptom in many soybean (Glycine max L. Merr.) producing areas throughout the United States. On the Blackland soils found in northeast Texas, Fe chlorosis occasionally appears during vegetative growth, but often abates by the time plants flower. However, it is not clear whether preplant additions of Fe will enhance soybean growth or yield on this soil or whether different sources of Fe give different responses. In a greenhouse study, soil from a pH 8.4 Houston Black clay (fine, smectitic, thermic Udic Haplusterts), with a DTPA‐extractable concentration of 11.7 mg Fe kg−1, was treated with FeSO4 (0, 3, 10, 30, and 100 ppm Fe), sodium ferric diethylenetriamine pentaacetate (FeDTPA) (0, 0.3, 1.0, 3, and 10 ppm Fe) or sodium ferric ethylenediamine‐di (o‐hydroxyphenylacetate) (FeEDDHA) (0, 0.3, 1.0, 3, and 10 ppm Fe). Pot size was 19 L and soil dry mass was 10 kg. Soybean (cv. Hutcheson) seed were planted in November 2000 and seedlings were thinned to three per pot at the first true leaf stage. The third uppermost fully expanded leaf of each plant was harvested at growth stage R3 for nutrient analysis. Between 20 and 100 days after planting, six nondestructive leaf chlorophyll readings were obtained from the third uppermost fully expanded leaf. Entire plants were harvested at R6 (mid podfill) for nutrient and biomass yield determination. Leaf blade Fe concentration ranged from 79 to 87 mg kg−1 in the untreated check plants to a high of 109 mg kg−1 for the 10 ppm FeDTPA‐Fe treatment, all of which were greater than the acknowledged critical level of 60 mg kg−1. No visible Fe‐deficiency symptoms appeared during the study. Chlorophyll (SPAD 502) values during the R3 to R5 growth stages were greater for all of the FeSO4 treatments than for the 0 ppm treatment. The 10 ppm FeDTPA‐Fe treatment and the 3 ppm FeEDDHA‐Fe treatment exhibited higher leaf chlorophyll readings than the untreated checks during the R3 to R5 growth stage. The average seed yield from the 12 Fe fertilized treatments at growth stage R6 was only 12% greater (not significant) than the untreated check. Total biomass (root plus shoot) was not affected by the treatments. There was no evidence that the higher rates of Fe caused reduced growth. Overall, our results do not suggest that soil‐applied Fe will consistently stimulate soybean growth or yield on this soil, at least when DTPA‐extractable soil Fe is at 12 mg kg−1 or higher. However, because of the trends for increased seed yield in some of the Fe treatments, field studies using soil‐ and/or foliar‐applied Fe are warranted.
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Claims 10
Claim · model-written summary
Soybean leaf blade Fe concentration reached 109 mg kg−1 with the 10 ppm FeDTPA treatment, compared with 79 to 87 mg kg−1 in untreated checks.
- Taxon
- Soybean
Glycine maxt0 - Treatment
- 10 ppm FeDTPAe1
- Outcome
- Leaf blade Fe concentratione1
- Direction
- higherinferrede1
- Value
- 109 mg kg−1e1
- Qualifier
- 79 to 87 mg kg−1e1
- Comparator
- untreated checke1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e1“Leaf blade Fe concentration ranged from 79 to 87 mg kg−1 in the untreated check plants to a high of 109 mg kg−1 for the 10 ppm FeDTPA”
Claim · model-written summary
No visible Fe-deficiency symptoms appeared during the soybean study.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- No visible Fe‐deficiency symptomse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e2“No visible Fe‐deficiency symptoms appeared during the study”
Claim · model-written summary
Leaf chlorophyll (SPAD) values at R3 to R5 were greater for all FeSO4 treatments than for the 0 ppm treatment.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- R3 to R5 growth stagese3
- Treatment
- FeSO4e3
- Outcome
- Chlorophyll (SPAD 502) valuese3
- Direction
- greatere3
- Comparator
- 0 ppm treatmente3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e3“Chlorophyll (SPAD 502) values during the R3 to R5 growth stages were greater for all of the FeSO4 treatments than for the 0 ppm treatment”
Claim · model-written summary
The 10 ppm FeDTPA-Fe treatment gave higher leaf chlorophyll readings than untreated checks at R3 to R5.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- R3 to R5 growth stagee4
- Treatment
- 10 ppm FeDTPA‐Fe treatmente4
- Outcome
- leaf chlorophyll readingse4
- Direction
- highere4
- Comparator
- untreated checkse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e4“The 10 ppm FeDTPA‐Fe treatment and the 3 ppm FeEDDHA‐Fe treatment exhibited higher leaf chlorophyll readings than the untreated checks during the R3 to R5 growth stage”
Claim · model-written summary
The 3 ppm FeEDDHA-Fe treatment gave higher leaf chlorophyll readings than untreated checks at R3 to R5.
- Taxon
- SoybeanGlycine maxt0
- Organ / stage
- R3 to R5 growth stagee4
- Treatment
- 3 ppm FeEDDHA‐Fe treatmente4
- Outcome
- leaf chlorophyll readingse4
- Direction
- highere4
- Comparator
- untreated checkse4
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e4“The 10 ppm FeDTPA‐Fe treatment and the 3 ppm FeEDDHA‐Fe treatment exhibited higher leaf chlorophyll readings than the untreated checks during the R3 to R5 growth stage”
Claim · model-written summary
Average seed yield of the 12 Fe-fertilized treatments at R6 was only 12% greater than the untreated check, not significant.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- Fe fertilized treatmentse5
- Outcome
- average seed yielde5
- Direction
- greatere5
- Value
- 12%e5
- Comparator
- untreated checke5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e5“The average seed yield from the 12 Fe fertilized treatments at growth stage R6 was only 12% greater (not significant) than the untreated check”
Claim · model-written summary
Total soybean biomass (root plus shoot) was not affected by the Fe treatments.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- the treatmentse6
- Outcome
- Total biomasse6
- Direction
- not affectede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e6“Total biomass (root plus shoot) was not affected by the treatments”
Claim · model-written summary
There was no evidence that higher rates of Fe reduced soybean growth.
- Taxon
- SoybeanGlycine maxt0
- Treatment
- higher rates of Fee7
- Outcome
- reduced growthe7
- Direction
- no evidencee7
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e7“There was no evidence that the higher rates of Fe caused reduced growth”
Claim · model-written summary
The authors conclude their results do not suggest soil-applied Fe will consistently stimulate soybean growth or yield on this soil.
- Taxon
- soybeanGlycine maxe0
- Treatment
- soil‐applied Fee0
- Outcome
- growth or yielde0
- Direction
- consistently stimulatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e0“our results do not suggest that soil‐applied Fe will consistently stimulate soybean growth or yield on this soil”
Claim · model-written summary
The authors recommend field studies using soil- and/or foliar-applied Fe because of trends for increased seed yield in some Fe treatments.
- Taxon
- SoybeanGlycine maxt0
- Outcome
- field studies using soil‐ and/or foliar‐applied Fe are warrantede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Soybean”
e0“field studies using soil‐ and/or foliar‐applied Fe are warranted”
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