A new paper published in Agricultural and Forest Meteorology details the University of Nebraska–Lincoln’s efforts to identify causes for yield gaps in soybean production systems in the north central region of the United States.

Average soybean yield in the north central region from 2010-2014 was 43 bushels per acre, yet some producers reached soybean yields over 80 bushels per acre.

The three-year study, led by Patricio Grassini, assistant professor in the Department of Agronomy and Horticulture, and Shawn Conley, associate professor in the Department of Agronomy at the University of Wisconsin, sought to identify causes of yield gaps over large agricultural areas and diverse climates and soils. Faculty from 10 land-grant universities looked at rainfed and irrigated soybean in the north central U.S., which accounts for roughly one-third of worldwide soybean production.

Grassini and his colleagues explored the use of producer survey data as an alternative approach to traditional field research to identify management practices that explain highest soybean yields for different combinations of climates and soils. In Nebraska the team relied on Nebraska’s Natural Resources Districts and 20 Nebraska Extension educators to obtain real-world producer data. In total, 3,568 soybean fields across 10 states were surveyed for this study, covering approximately 300,000 acres.  

 “Regional soybean yield was on average 22% and 13% below the yield potential estimated for rainfed and irrigated soybean,” said Grassini. “Sowing date, tillage and in-season foiliar fungicide and/or insecticide were identified as explanatory causes for yield variation.”

To reach these conclusions, researchers combined producer survey data with a spatial framework to measure yield gaps, identify management factors explaining the gaps and understand the biophysical drivers influencing yield responses to field management. According to Grassini, earlier sowing dates was the most consistent management factor leading to yield increases.

Juan Ignacio Rattalino, research assistant professor at Nebraska who authored the paper, sees this study as a proof of concept about the power of using producer data to identify opportunities for improving farm management and profit.

“There are a lot of studies about yield response to planting date but this is the first one to explain why such response varies across years and regions. We found that the yield benefit derived from earlier planting depends on the degree of water limitation during the period of pod setting in soybean,” Rattalino said.

The study was supported by $1.4 million from the North Central Soybean Research Program, with complementary funding from the Nebraska Soybean Board and Wisconsin Soybean Marketing Board. Other institutions involved include Iowa State University, Kansas State University, Michigan State University, North Dakota State University, Ohio State University, Purdue University, University of Illinois-Champaign, University of Minnesota and University of Wisconsin.

For more, read the full paper, Assessing causes of yield gaps in agricultural areas with diversity in climate and soils.