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A Look at In-Furrow Fungicides and Starter Fertilizers for Soybeans

With increasing attention being paid to producing high yields to increase profit potential from soybean production, scientists and extension specialists are continually looking at possible contributors to this goal.

Such is the case in a study that was conducted in Arkansas, Indiana, Iowa, and Mississippi in the US and in Ontario, Canada during 2014-2015. Results from this multi-site study are reported in an article titled “Soybean Yield Response to In-Furrow Fungicides, Fertilizers, and Their Combinations” by Pierson et al. (CFTM, July, 2018). A summary of the research and its results follows, along with a commentary on what they mean for producers.

•    Basis for research: 1) planting soybean seed into cool, wet soils slows emergence and thus lengthens the time of exposure of planted seed to soil-borne pathogens, and 2) starter fertilizers with vital nutrients placed near or in-furrow at planting can enhance early-season root development and nutrient uptake.

•    Study objective: evaluate the effect of a fungicide, starter fertilizer, and their combination on soybean yield across multiple locations.

•    Studies were conducted in Arkansas, Indiana, Iowa, and Mississippi in the US and in Ontario, Canada during the 2014 and 2015 cropping seasons (14 site-years).

•    The Arkansas and Mississippi studies were planted in late June in 2014, and in early May (Arkansas) and late June (Mississippi) in 2015.

•    Planted seed were treated with Acceleron seed treatment (pyraclostrobin + fluxapyroxad + metalaxyl) at the Arkansas locations. Seed planted in Mississippi were untreated both years.

•    N, P, and K starter fertilizer was applied in-furrow at planting at all sites both years. Sulfur and Zinc were part of the starter fertilizer mix applied at the Mississippi location both years.

•    Priaxor (fluxapyroxad + pyraclostrobin) or Headline (pyraclostrobin) fungicides were applied in-furrow at planting at all sites both years. 13 of the 14 site-years had both fungicides applied.

•    Treatments were 1) non-treated control (NTC), 2) an in-furrow application of a fungicide, 3) an in-furrow application of starter fertilizer, and 4) a combination of fungicide and starter fertilizer applied in-furrow.

•    Treatment effect on plant population was inconsistent across the trials, and fungicide application alone did not affect plant population in any trial. Starter fertilizer alone reduced plant population in the 2014 and 2015 Arkansas trials.

•    Neither fungicide nor starter fertilizer alone significantly affected grain yield in any of the studies. The combination of the two resulted in a significant yield increase in only one site-year.

•    Overall, the lack of a yield response to treatments and their combinations in almost all of the site-years shows that the cost of applying in-furrow fungicides and fertilizers at planting will not be recouped. Thus, they are not economical to use.

These results support results from previous studies that have shown it is not economical to apply starter fertilizers or any other fertilizers to soybeans if soil nutrient levels are in the range recommended for optimum soybean productiion.

It is also apparent from these and other results that the cheapness and effectiveness of efficacious seed-treatment fungicides is still the best management option to use for protecting planted soybean seed from soil-borne pathogens that are generally always present and can cause stand loss if environmental conditions are favorable for their activity. Thus, until there is definitive research that pinpoints when and where in-furrow application of fungicides are needed to protect planted soybean seed, this practice should not be considered in lieu of the proven protection provided by seed treatment fungicides.

Composed by Larry G. Heatherly, Feb. 2019, larryheatherly@bellsouth.net