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Foliar Fertilizer Application in Soybean (07/23/20)

Some soybean growers in the area are interested in the use of foliar fertilizers, and there is currently a multitude of products available to soybean growers.

Some soybean growers in the area are interested in the use of foliar fertilizers, and there is currently a multitude of products available to soybean growers. Producers often use these products in addition to fungicide and/or insecticide applications during early soybean reproductive development. However, with low profit margins, it is important to understand the effect of foliar fertilizers on soybean yield and economic return.

Foliar fertilization has produced mixed results in hundreds of university trials conducted across the United States. Data from 117 on-farm soybean foliar fertilizer trials conducted in Michigan over 10 years showed that the foliar fertilizer application was less profitable than the unfertilized control in 109 of the 117 trials conducted in Michigan. Michigan agronomists concluded that unless visible manganese deficiency symptoms were present, applying foliar fertilizers to soybeans is not recommended. Manganese deficiency is not commonly observed in North Dakota.

Currently, extension agronomists are working together to evaluate commonly marketed foliar fertilizer products across the U.S. This will help us identify environmental and soil factors where yield response to foliar fertilizers is most likely to occur. The objectives of this project are to 1) Identify yield response in soybean to foliar nutrient applications of commonly marketed products and 2) Conduct economic analyses on the value of these products. This trial was first conducted in 2019 and is repeated in 2020. In North Dakota, we have one site with a randomized complete block design with eight replications of treatments. All agronomists are using common management practices representative in their state.

All products were applied at the R3 growth stage based on common fungicide and/or insecticide application timing where these products are often co-applied. Table 1 provides the yield for four regional sites and all the 19 US sites tested in 2019. The nutrients applied, concentration of the nutrients, and application rate are provided. There was no significant difference in yield between any product and the control. As there was no yield gain, any application of the products in 2019 resulted in a lower financial return per acre due to the cost of the foliar fertilizer.

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Previous NDSU experiments in northwestern and north-central North Dakota during three years, with six total site-years and four annual NPK foliar treatments, showed no yield increases from in-season foliar fertilizer application, and in one year, yield decreased with the application. For more information about regular fertilizing soybean, see the NDSU Extension publication “Soybean Soil Fertility.”

 

Hans Kandel

Extension Agronomist Broadleaf Crops

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