Which soybean inputs actually increase yields?

Thumb Ag Research and Education finds that a fungicide sprayed prior to August rains increase yields, while foliar and pop-up fertilizers do not.

Michigan State University Extension educators in Michigan’s greater Thumb area studied various soybean inputs individually and together for the second year in 2012. Soybeans were planted at two sites in the greater Thumb area – Sandusky and Avoca, Mich. The variety Pioneer 92Y51 was planted at each site at a target population of 160,000 seeds per acre. The final stand count was 136,000 plants per acre.

2011 treatments included an untreated check, a pop-up fertilizer treatment of Alpine 2-20-18 applied at 2 gallons per acre on the seed, a foliar fertilizer treatment of Wilbur Ellis NDemand –HIGHEND at 1 gallon per acre at the R3 growth stage, a foliar fungicide treatment of Headline applied at 10 ounces per acre at the R3 growth stage, and a final treatment that received the same pop-up fertilizer, foliar fertilizer at R3, and fungicide at R3 treatments.

Soybean yields with “all treatments” and the fungicide treatment yielded significantly higher than the untreated check in 2011. There was no significant difference between the fungicide-treated soybeans and the foliar fertilizer-treated soybeans. There was no significant difference between the foliar fertilizer and the untreated check, and there was no significant difference between the pop-up fertilizer and the untreated check.

In 2012, treatments were expanded and modified. Stratego was used as the foliar fungicide and Nachurs 6-24-6 was used as the pop-up fertilizer at 2 gallons per acre. The foliar fertilizer treatment remained the same.

Three treatment variations were added in 2012 to help answer the question whether the 2011 significant difference in the “all treatments” treatment was due to fungicide alone, or a synergism of the treatments working together. Treatments were paired, including a foliar fungicide + foliar fertilizer treatment, a foliar fungicide + pop-up treatment and a foliar fertilizer + pop-up treatment.

In 2012, the “foliar fungicide”, “foliar fungicide + foliar fertilizer,” and “all treatments” yielded significantly higher than the untreated check. The “pop-up + foliar fungicide” treatment yielded similarly to the other treatments that included fungicide, and also similarly to the untreated check. The “all treatments,” “pop-up + foliar fungicide,” “foliar fertilizer,” and “pop-up + foliar fertilizer” yielded similarly to one another, and similarly to the untreated check. The “pop-up” treatment yielded similarly only to the untreated check.

It would appear from 2012 data (Table 1) that the yield response was from the foliar fungicide rather than a synergism of the inputs working together. Note that it is not unusual to see a response to fungicides in soybeans in years with significant August rain. June and July were very dry, but a significant rain event occurred during August 9 and 10. Keep in mind that when fungicides are used on soybeans for plant health reasons rather than combating a specific disease, users are likely narrowing the window for resistance development for not only soybeans, but other crops as well.

Table 1. Soybean yield response to fungicides and fertilizer treatments in 2011 and 2012

Treatment

2011 yield (bu./a.)

2011 Sig

2012 yield (bu/a.)

2012 Sig

All Treatments

56.2

a

59.5

ab

Foliar Fungicide

54.6

ab

60.4

a

Foliar Fertilizer

52.7

bc

57.9

bcd

Pop Up Fertilizer

51.3

c

56.8

d

Untreated Check

51.8

c

57.1

cd

Foliar Fungicide + Foliar Fertilizer

-

-

60.2

a

Foliar Fungicide + Pop Up

-

-

59.2

abc

Foliar Fertilizer + Pop Up

-

-

57.6

bcd

LSD @ 0.05

1.9

 

2.1

 

C.V. %

4.3

 

3.6

 

Yields followed by the same letter were statistically similar.

The educators gratefully acknowledge the support of Gerstenberger Farms, Peters Brothers Farms and the Michigan Soybean Promotion Committee.

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