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. The objective of this study was to identify factors that contribute to yield loss in Ohio soybean production.  Potential yield-limiting factors that were examined included soil fertility (nutrients and pH), management practices (planting date, seeding rate, row spacing, and crop rotation), and soybean cyst nematode.  Approximately 150 soybean fields were surveyed in 2013 and 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.  Management practices were determined by a paper survey sent to participating growers as well as by field scouting after planting.  A multiple regression analysis was completed to determine both the effects of individual factors on yield as well as the compound effects of multiple factors.  Preliminary results show that out of 375 total samples, 25% of samples had phosphorus levels below 15 ppm and 41% above 30 ppm.  18% of potassium samples were below 125 ppm.  20% of samples had pH levels above 6.8 and 20% were below 6.0.  Only 3% of samples had SCN levels high enough to cause yield loss on resistant soybean varieties.