Michigan soybean producers evaluate foliar fertilizer effects on yields and profitability

On-farm research conducted in Michigan in 2009 and 2010 showed little yield benefit and no economic benefit to applying foliar fertilizers to soybeans.

Michigan soybean producers cooperated with the STARS project (Strip Testing at Regional Sites) to evaluate the yield and economic benefits of applying foliar fertilizer to soybeans. Two foliar fertilizers from Alpine Plant Foods were evaluated in 2009 and 2010. The 3-18-18 fertilizer treatment (NPK only) was evaluated at 27 sites and the 3-16-16 TMR fertilizer treatment (NPK + micronutrients + liquid sugar + controlled release nitrogen) was evaluated at 29 sites. The fertilizer treatments were applied at the R1 and R3 growth stages and compared to unfertilized control treatments in four replications at each site. The 2009 and 2010 data are summarized and presented in Figure 1 (3-18-18) and Figure 2 (3-16-16 TMR).

2009 & 2010 Foliar Fertilizer Trial Results (3-18-18).

There was no statistically significant difference in yields between the 3-18-18 foliar fertilizer treatment and the unfertilized control when the data from all locations conducted in 2009 and 2010 were combined and analyzed. However, there was one site in 2009 and another site in 2010 where the yields of the 3-18-18 foliar fertilizer treatment were significantly higher than the unfertilized control. A statistically significant yield increase from applying 3-18-18 in 2009 and 2010 occurred in 7% of the trials.

The 3-16-16 TMR foliar fertilizer treatment did show a 0.6 bushel per acre yield increase over the unfertilized control when the results from all locations conducted in 2009 and 2010 were combined and analyzed. However, only one trial out of the 29 trials conducted in 2009 and 2010 showed a statistically significant yield increase from the 3-16-16 TMR foliar fertilizer treatment.

Table 1 summarizes the yield and economic benefits of applying the foliar fertilizer treatments to soybeans in 2009 and 2010.

Table 1. Economic return to foliar fertilizer applications in 2009 and 2010

 
3-18-18
3-16-16 TMR
Average yield increase (bu/acre)
0.2
0.6
Additional income from foliar fertilizer ($/acre)
$2.29
$6.87
Foliar fertilizer cost ($/acre)*
$20.11
$19.46
Economic return to foliar fertilizer ($/acre)
-$17.82
-$12.5

Assumptions: Soybean market price = $11.45 per bushel
*Application costs are not included

The STARS foliar fertilizer results are consistent with those produced by hundreds of university trials conducted in the United States since the late 1970s. Soil applied fertilizers are the most economical and reliable methods for providing phosphorus and potassium to soybeans. Also well-inoculated soybeans have not shown an economic response to nitrogen fertilizer, whether applied to the soil or the foliage.

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