Database Research Summaries
2018 Row Spacing & Fungicide Timing on Disease Control & Profitability in Double Crop Soybeans

calendar_today Year of Research: 2018
update Posted On: 12/05/2019
group Andrew Kness (Principal Investigator, University of Maryland)
bookmark Maryland Soybean Board

Research Focus

The focus of this project is to assess the impact of row width and fungicide utility on double crop soybeans.


  • Evaluate the effects of row spacing on disease development in double crop soybean systems.
  • Evaluate the efficacy and utility of foliar fungicides for disease control and/or profitability.


Research on the Impacts of Row Spacing and Fungicide Timing on Disease Control and Profitability in Double Crop Soybeans found that average crop yield was significantly affected by fungicide/row width treatments and location, but not relative yield (calculated as a percent compared to the mean yield for untreated control for the trial location) or test weight. Although there were no significant differences in relative yield between treatments, wide row treatments did yield significantly higher at one location where all three wide row (15” rows) soybean treatments yielded significantly more than narrow row treatments (7.5” rows). Excessive rainfall may have contributed to increased variability in the yield at a different location. Although foliar fungicides can occasionally kept plants greener for longer, no green stem treatment effects, nor any significant differences in NDVI (plant greenness) were measured after fungicide application in this study. The most prevalent disease present in this trial was frogeye leafspot, but it was not prevalent enough at any of the locations to warrant a disease rating.

Heavy and frequent rainfall throughout 2018 may have contributed to a significant amount of the variability observed in the data. Foliar fungicides applied at R1 or R3, on narrow or wide row soybeans, did not provide any agronomic or plant health benefits. There was no significant treatment effect on relative yield, test weight, plant greenness, or green stem. Trials performed by other researchers in 2017 had opposite results and this between-year variability in results as well as weather challenges in the 2018 trial indicate that more data needs to be collected over multiple years and sites to improve the robustness of the dataset and to make sound production recommendations for growers in the Maryland region.


Double cropping is valuable to Maryland producers as it increases total production without requiring additional acreage, helping growers meet the demands of increasing food production on reduced land resources, while providing significant environmental benefits.

A brief survey of consultants, agricultural agents, and growers indicated that approximately 20-30% of double cropped soybeans receive a fungicide application. Because double crop soybeans have a shorter growing season and are typically exposed to drier weather than full crop soybeans, there is less time for yield-limiting diseases to develop and impact plant development and growth, potential negating the need for fungicide applications. However, when spacing between rows is reduced, plant canopy closure occurs sooner, but rapid canopy closure may result in increased canopy humidity, and potentially increased foliar disease and associated yield impacts.

Farmers will benefit from knowing the trade offs between row spacing and fungicide application in double cropped soybeans potentially saving time and money and increasing crop yields.

For more information about this research project, please visit the National Soybean Checkoff Research Database.

Funded in part by the soybean checkoff.