Assessing Variation in US Soybean Seed Composition (Protein and Oil).

Soybean [Glycine max (L.) Merr.] seed composition and yield are a function of genetics (G), environment (E), and management (M) practices, but contribution of each factor to seed composition and yield are not well understood. The goal of this synthesis-analysis was to identify the main effects of G, E, and M factors on seed composition (protein and oil concentration) and yield. The entire dataset (13,574 data points) consisted of 21 studies conducted across the United States (US) between 2002 and 2017 with varying treatments and all reporting seed yield and composition. Environment (E), defined as site-year, was the dominant factor accounting for more than 70% of the variation for both seed composition and yield. Of the crop management factors: (i) delayed planting date decreased oil concentration by 0.007 to 0.06% per delayed week (R 2∼0.70) and a 0.01 to 0.04 Mg ha-1 decline in seed yield per week, mainly in northern latitudes (40-45 N); (ii) crop rotation (corn-soybean) resulted in an overall positive impact for both seed composition and yield (1.60 Mg ha-1 positive yield difference relative to continuous soybean); and (iii) other management practices such as no-till, seed treatment, foliar nutrient application, and fungicide showed mixed results. Fertilizer N application in lower quantities (10-50 kg N ha-1) increased both oil and protein concentration, but seed yield was improved with rates above 100 kg N ha-1. At southern latitudes (30-35 N), trends of reduction in oil and increases in protein concentrations with later maturity groups (MG, from 3 to 7) was found. Continuing coordinated research is critical to advance our understanding of G × E × M interactions.

Effect of Location, Cultivar, and Diseases on Grain Yield of Soft Red Winter Wheat in Wisconsin.

Knowledge is limited about the impact of foliar diseases on wheat yield in Wisconsin. The objective of this study was to compare yield and diseases of wheat cultivars in several locations in Wisconsin in 2009 and 2010. Thirty-six wheat cultivars were planted in a randomized complete block design at field sites near Arlington, Chilton, and Lancaster, WI. At a fourth location, Janesville, WI, the design was a split plot with foliar fungicide application at Zadoks growth stage (GS) 45 at the whole-plot level and cultivar at the subplot level. Disease assessments were made four times during the growing season for powdery mildew (PM), Septoria/Stagonospora leaf blotch (SLB), and leaf rust. Incidence and severity of Fusarium head blight were assessed on 100 heads per plot at GS 85. Linear mixed-model analyses were used to study the effects of location, cultivar, and disease on grain yield (α = 0.05). Overall, SLB and PM were the most prevalent diseases. SLB severity was uniform among locations and PM was most prevalent at Arlington and Chilton. In both years, yield was affected by location, cultivar, location-cultivar interaction, and location-SLB and location-PM interactions. Yield was also negatively affected by PM in 2010. No effect of fungicide on disease severity or yield was observed at Janesville in either year. These results suggest that cultivar selection and location strongly influence grain yield in Wisconsin and that powdery mildew is capable of reducing grain yield.