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Fluid Journal : Fall 2017
14 The Fluid Journal Fall 2017 Osler Ortez is a Master Student in the Agronomy Department at Kansas State University, Dr. Fernando Salvagiotti and Juan Enrico are Researchers and Extensionists in Plant Nutrition and Soil Fertility at INTA-Oliveros, Argentina, and Dr. Ignacio Ciampitti is an Associate Professor and Cropping Systems Specialist at Kansas State University. section). Yield improvement represented 33% yield gain at Rossville and 28% at Oliveros, comparing historical versus 2010 genotypes. Regarding seed N content, results ranged from 153 to 203 lbs. N ac-1 at Rossville and 153 to 200 lbs. N ac-1 at Oliveros (Figure 3, lower section). Seed N content followed a similar fashion as portrayed by yield trait, superior seed N content for modern soybean genotypes (2010s). Historical N content changes showed comparable gain, 25% and 24% increase at Rossville and Oliveros, comparing historical versus 2010’s genotypes. Nitrogen response. Yield response to fertilizer N application was recorded at both Rossville and Oliveros (P ≤0.05). The S2 (600 lbs. N ac-1) increased seed yields 20% at Rossville and 5% at Oliveros, relative to S1 treatment (Figure 4). At Rossville, S2 yielded better than S3, with the lowest yield documented for S1. At Oliveros, S2 yielded higher than S1 and S3 compared to S1 and S2 and did not statistically differ for the yield parameter. Yield response to N fertilization (600 and 50 lbs. N ac-1) was consistent across genotypes, implying an important role of N fertilization in addressing soybean nutrient demand at different yield levels. Protein levels. Historical protein concentration levels in seeds ranged from 36 to 42% at Rossville and 35 to 38% at Oliveros. Protein concentration was negatively affected as yield improved, with lower protein levels observed for the 2000 and 2010 genotypes (Figure 5). A decrease of approximately 5.8% in protein concentration was recorded at Rossville site when comparing 2010 versus the rest of the genotypes tested. At Oliveros, a similar comparison resulted only in a decrease in protein concentration of 2.4%. When looking at N effect in protein levels in seed, N application showed a statistical effect (P ≤0.05) only at Rossville (Figure 6). Regardless of genotypes and release decades, an increase of 1.3% of protein in seed was observed with the S2 (600 lbs. N ac-1) treatment at this location. Summing up Soybean yield improvement represented 33% at Rossville (US) and 28% at Oliveros (ARG) when comparing historical and modern 2010 genotypes. Seed N content followed a similar trend as yields and highest seed N content were observed for 2010 genotypes, representing a 25% gain at Rossville and Figure 4. Seed yield for soybean genotypes released from 1980’s to 2010’s evaluated under three fertilizer N strategies at Rossville (US) and Oliveros (ARG) during the 2016 growing season. Means followed by different letter are significantly different (P ≤ 0.05). Figure 5. Seed protein (%) changes for 21 soybean genotypes grouped in four release decades at Rossville (US) and Oliveros (ARG) during the 2016 growing season. Means followed by the same letter are not significantly different (P ≤ 0.05). Figure 6. Effect of fertilizer N application (zero-N versus 600 lbs N ac-1 applied) on seed protein (%) for 21 genotypes at Rossville (US) and Oliveros (ARG) during the 2016 growing season. Means followed by different letter are significantly different (P ≤ 0.05). 24% at Oliveros. Yield response to N fertilization was observed at both Rossville and Oliveros, with S2 (600 lbs. N ac=1) increasing yields 20% at Rossville and 5% at Oliveros. A tradeoff was documented for yield and protein, with protein concentration negatively impacted as yields improved. Overall decrease in protein concentrations of 5.8% at Rossville and 2.4 % at Oliveros were documented in this study. At Rossville, S2 treatment improved protein levels, with protein concentration increasing 1.3% relative to the S1 treatment (only inoculated). Nitrogen limitation impacted not only on seed yield but also protein concentration for soybean production systems.