Abstract
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 (R2∼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.
Highlights
Soybean seed yield and quality are functions of genotype (G), M, E, and their interaction (G × E × M), but how each individual factor affects seed yield and quality, and their level of significance is not well established (Rao et al, 2002; Assefa et al, 2018)
Soybean seed oil and protein concentrations were measured using near infrared transmittance (NIT) spectroscopy (Infratec 1241 Grain Analyzer, Foss Instruments, Eden Prairie, MN or DA 7250 NIR analyzer, Perten Instruments, Inc., Springfield, IL, United States) and seed yield measurements were adjusted to 130 g kg−1 seed moisture content
Oil concentration increased slowly at rate of 1.2 g kg−1 per Mg seed yield increase but protein concentration decreased at 1.3 g kg−1 per Mg seed yield increase
Summary
Soybean seed yield and quality are functions of genotype (G), M, E, and their interaction (G × E × M), but how each individual factor affects seed yield and quality, and their level of significance is not well established (Rao et al, 2002; Assefa et al, 2018). In testing the different combinations of foliar nutrient fertilization on soybean in 112 field trials in Iowa, Haq and Mallarino (2005) concluded that total oil and protein production response to fertilizer followed a similar patter with yield response. They noted small, erratic and inconsistent changes in oil and protein concentrations. In a metaanalysis for soybean seed composition, Rotundo and Westgate (2009) documented an overall relative positive response to water stress of protein concentration, regardless of the timing of the stress and studies (field and pot trials). The same authors found an overall negative impact of water stress on both oil concentration and content
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