Factors That Influence Soybean Protein and Oil Content.

Soybeans are one of the most valuable agronomic crops produced in Ohio, and Ohio is one of only two corn-belt states with more soybean acreage than corn acreage.  In 2014, the value of Ohio’s soybean crop was $2.7 billion making soybean extremely important for agriculture and the economy.  The objective of this study was to identify factors that affect soybean grain quality in Ohio soybean production.  Potential factors that were examined included soil properties, management practices, and soybean cyst nematode.  Approximately 150 soybean fields were surveyed in 2013 and 2014 throughout different geographical districts in Ohio. 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.  SCN samples were taken from each in late spring around planting time, and the samples were counted to determine the number of SCN eggs per 100cc of soil.  Grain samples were collected at the time of harvest and were analyzed for protein and oil content.  With regard to the statistical analyses, a mixed-model analysis-of-variance was used to determine if grain protein and grain oil are affected by a number of variables, including district, farm (random effect within district), field yield (low, normal), rotation, seed rate, row spacing, tillage, herbicide timing, resistant weeds, pH, organic matter, sand, silt, clay, potassium, phosphorous, modes of action, and SCN.  As noted, the farm was a random effect, and all the others were fixed effects.  Preliminary results show protein content decreased as SCN levels increased.  Oil levels decreased as SCN levels decreased.