Determining Yield Limiting Factors in Ohio Soybean Production.

Ohio is one of the leading soybean producing states in the U.S., and with an increasing demand for agricultural commodities, it is important to continue to increase soybean production. In 2013, the state average soybean yield for Ohio was 49 bu/ac. From 1924 to 2013 yield has increased by an average of 0.37 bu/year; however, maximum yield is not being achieved due to yield-limiting factors. The objective of this study was to determine the various factors that contribute to yield loss in soybean production in Ohio. Potential yield-limiting factors that were examined included soil quality (nutrients, pH, texture, organic matter, water holding capacity, and water aggregate stability), pests (diseases, insects, weeds, and soybean cyst nematode), and management practices (planting date, seeding rate, row spacing, and crop rotation). A survey of 65 growers’ soybean fields was completed in 2013 and 82 fields are currently being surveyed in 2014. In order to better identify factors influencing yield, in each field, three areas are selected based on historical yields: two normal-yielding areas and one low-yielding area. Soil samples were collected in the spring prior to planting to examine soil quality. Trifoliate samples were collected at R1 (initial flowering) and were analyzed for macro- and micro-nutrient concentration. Disease, insect and weed ratings of the fields were also completed during this time. Management practices were determined by a paper survey sent to participating growers as well as by field scouting after planting. Multivariate statistics were completed to determine both the effects of individual factors on yield and quality as well as the compound effects of multiple factors. Preliminary results from 2013 showed that 39% of fields’ soil test values were below the P critical level, 5% were below the K critical level, and 29% of fields were below the recommended minimum pH of 6.0. SCN was present in 79% of the areas sampled in 2013, but only 4% of areas had 2000 or greater eggs/100cc soil, which is the level where yield loss may occur in resistant varieties. These factors could cause significant yield reduction, and further analysis of other factors will show which cause the greatest yield loss potential.