Iron Chlorosis

Soil Solutions, LLC has cooperated on several research projects using PRO CAL 40 to offset the soil conditions that cause iron chlorosis in soybeans. We have seen visual differences where we have applied PRO CAL 40 usually using rates of one or two tons per acre. Below are some pictures of plots where we successfully reduced the amount of yellowing of the soybeans.

In this picture the yellow soybeans were untreated. The green plants in front of the yellow strip had 1 ton/acre PRO CAL 40 applied. Yield responses in this field averaged 3 to 4 bushels better with the PRO CAL 40. Yields were in the 65-70 bushel range this year.

Below are pictures from another plot we had with Monsanto to compare the effects of PRO CAL 40 on iron chlorosis. These are small plots.

In this picture, to the right of the stake is the untreated plot.

In this picture is the plot that received .75 ton/acre.

And in this picture, the plot that received 1.5 tons of PRO CAL 40. You can see that both treatments have soybean plants that are darker green and the leaves were larger also.

We have also worked with Monsanto one year to determine the differences in response among soybean varieties. One year’s results do indicate that there is differences among varieties. Yields are shown below of several varieties. It is obvious from the pictures and from the yields that the iron chlorosis in these plots were not too severe.

Variety	Treated	Check
AG2403	68.6	61.02
DKB25-51	70.78	63.63
AG2703	69.08	67.48
AG2801	59.63	47.56
DKB29-51	58.48	56.00
AG3005	53.90	54.34
AG3305	58.18	60.37
AG3401	63.69	62.94

The benefits of PRO CAL 40 in decreasing Platte Valley Yellows or iron chlorosis appear to last only one year. Although we saw yield benefits the second year in the corn (6-15 bushels better) we did not see visual differences when we rotated back to soybeans in the third year.

The data below is from research that was done by Dr. Wiese, etal. while he was at the University of Nebraska. He used granulized gypsum at lower rates in the row and saw similar responses as we experienced.

1982 Soybeans

*Band was 3 inches deep and 1 1/2 inches to side of row.
Treatment	Rate, Method	Yield, BU/A
Check	0, In Band to Side of Row	25
Gypsum	450#, In Band to Side of Row	44

1983 Soybeans

Treatment	Rate, Method	Yield, BU/A
Check	0, In Row at Planting	19
Gypsum	75, In Row at Planting	30

More recent research has revealed that bicarbonate has a direct role in inducing iron deficiency. Bicarbonates are produced in high pH soils especially under more moist conditions. Gypsum (CaSO4 2H2O) has shown to react with bicarbonate (HCO3) to form CaCO3 or lime decreasing the amount of bicarbonate that affects iron uptake and iron availability.

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