Study of plant and soil factors affecting seasonal nitrogen fixation, yield formation and seed composition in soybeans

Master of ScienceDepartment of AgronomyIgnacio CiampittiSoybean [Glycine max (L.) Merr.] production currently faces several challenges linked to global food security (both quantity and quality) raised by an overgrowing human population, limited cropland, and diversified dietary in developed regions. To sustain seed yield and high protein levels, soybeans depend on large nitrogen (N) uptake, which is mostly attained by the symbiotic N fixation (SNF) process. Although SNF has been extensively investigated with single assessments during the season, just a few recent reports looked at the temporality of N sources (soil and SNF) while taking into consideration seasonal dry matter accumulation and soil nitrate (NO3) and ammonium (NH4) availability. Furthermore, it is still unclear how the overall changes in N uptake dynamics supports yield formation and seed components among canopy portions, especially considering the branches as potential contributors for high yield in modern genotypes. Following this rationale, this project presents two overall objectives: 1) to identify the impact of soil NO3 and NH4 temporal availability on seasonal SNF [N derived from the atmosphere (Ndfa)], N uptake, and dry matter accumulation (herein called study 1); and 2) to characterize seed yield, protein, oil, amino acids (AA), and fatty acids (FA) from the main stem and branches (herein called study 2) for different commercial soybean varieties. To address the first objective, four genotypes were field grown at Manhattan (Kansas, US) during 2019 and 2020 growing seasons. Dry matter, N concentration, N uptake, Ndfa, fixed N, soil NO3, and NH4 (60-cm depth) were measured at six phenological stages, along with seed yield, protein, and oil concentration at harvest time. Seasonal exposure to NH4 (area under the curve) showed a stronger suppression of Ndfa at the end of the season than NO3. However, a mid-season NO3 peak delayed uptake from soil and SNF, but only decreased maximum uptake rates from SNF. Additionally, dry matter was used as a seasonal linear predictor of fixed N to simplify the process model. However, this relationship was deeply affected by soil N availability across environments (boundary functions) and also by a potential dry matter threshold around 5 Mg ha-1 across genotypes and site-years. For the second objective, another four genotypes were field-grown during the 2018 and 2019 growing seasons at Ashland Bottoms and Rossville (Kansas, US), respectively. At harvest time, seeds from the upper, middle, lower main stem, and branch nodes were manually separated and assessed for yield, seed size, protein, and oil (seed content and concentration), abundance of limiting AA within protein, and FA ratio (oleic / linoleic + linolenic). The accumulation of protein was more responsive to node position than oil, determining high protein concentration in the upper main stem and high oil concentration in the lower main stem nodes. However, the protein quality (limiting AA) was higher in the lower main stem, while the FA ratio (oil quality) was greater in the upper section of the plant. Branches presented the less-rich seed composition relative to the main stem, but their contribution to yield was positively associated with oil and limiting AA abundance across genotypes. In summary, the main outcomes of the present thesis are related to 1) the importance of soil NO3 and NH4 to regulate Ndfa during the season, 2) the timing of Ndfa assessment or prediction for an accurate fixed N calculation throughout the season, and 3) the underlaying effect of branch yield allocation on the seed composition of the whole soybean plant, plausibly moderating changes across genotypes, environments, and management practices. A better understanding of soybean N acquisition and allocation for yield and quality formation within the plant is important to sustain the yield increase, offset protein decay, and assure cropping systems sustainability and food security in a long-term standpoint

Soybean yield, biological N2 fixation and seed composition responses to additional inoculation in the United States

It is unclear if additional inoculation with Bradyrhizobia at varying soybean [Glycine max (L.) Merr.] growth stages can impact biological nitrogen fixation (BNF), increase yield and improve seed composition [protein, oil, and amino acid (AA) concentrations]. The objectives of this study were to evaluate the effect of different soybean inoculation strategies (seed coating and additional soil inoculation at V4 or R1) on: (i) seed yield, (ii) seed composition, and (iii) BNF traits [nodule number and relative abundance of ureides (RAU)]. Soybean field trials were conducted in 11 environments (four states of the US) to evaluate four treatments: (i) control without inoculation, (ii) seed inoculation, (iii) seed inoculation + soil inoculation at V4, and (iv) seed inoculation + soil inoculation at R1. Results demonstrated no effect of seed or additional soil inoculation at V4 or R1 on either soybean seed yield or composition. Also, inoculation strategies produced similar values to the non-inoculated control in terms of nodule number and RAU, a reflection of BNF. Therefore, we conclude that in soils with previous history of soybean and under non-severe stress conditions (e.g. high early-season temperature and/or saturated soils), there is no benefit to implementing additional inoculation on soybean yield and seed composition.Fil: Carciochi, Walter Daniel. Kansas State University; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata; ArgentinaFil: Moro Rosso, Luiz H.. Kansas State University; Estados UnidosFil: Secchi, Mario Alberto. Kansas State University; Estados UnidosFil: Torres, Adalgisa R.. Kansas State University; Estados UnidosFil: Naeve, Seth. University of Minnesota; Estados UnidosFil: Casteel, Shaun N.. Purdue University; Estados UnidosFil: Kovács, Péter. University of South Dakota; Estados UnidosFil: Davidson, Dan. Illinois Soybean Association; Estados UnidosFil: Purcell, Larry C.. University of Arkansas for Medical Sciences; Estados UnidosFil: Archontoulis, Sotirios. University of Iowa; Estados UnidosFil: Ciampitti, Ignacio A.. Kansas State University; Estados Unido

Climate Change and Management Impacts on Soybean N Fixation, Soil N Mineralization, N2O Emissions, and Seed Yield

Limited knowledge about how nitrogen (N) dynamics are affected by climate change, weather variability, and crop management is a major barrier to improving the productivity and environmental performance of soybean-based cropping systems. To fill this knowledge gap, we created a systems understanding of agroecosystem N dynamics and quantified the impact of controllable (management) and uncontrollable (weather, climate) factors on N fluxes and soybean yields. We performed a simulation experiment across 10 soybean production environments in the United States using the Agricultural Production Systems sIMulator (APSIM) model and future climate projections from five global circulation models. Climate change (2020–2080) increased N mineralization (24%) and N2O emissions (19%) but decreased N fixation (32%), seed N (20%), and yields (19%). Soil and crop management practices altered N fluxes at a similar magnitude as climate change but in many different directions, revealing opportunities to improve soybean systems’ performance. Among many practices explored, we identified two solutions with great potential: improved residue management (short-term) and water management (long-term). Inter-annual weather variability and management practices affected soybean yield less than N fluxes, which creates opportunities to manage N fluxes without compromising yields, especially in regions with adequate to excess soil moisture. This work provides actionable results (tradeoffs, synergies, directions) to inform decision-making for adapting crop management in a changing climate to improve soybean production systems

Climate Change and Management Impacts on Soybean N Fixation, Soil N Mineralization, N\u3csub\u3e2\u3c/sub\u3eO Emissions, and Seed Yield

Limited knowledge about how nitrogen (N) dynamics are affected by climate change, weather variability, and crop management is a major barrier to improving the productivity and environmental performance of soybean-based cropping systems. To fill this knowledge gap, we created a systems understanding of agroecosystem N dynamics and quantified the impact of controllable (management) and uncontrollable (weather, climate) factors on N fluxes and soybean yields. We performed a simulation experiment across 10 soybean production environments in the United States using the Agricultural Production Systems sIMulator (APSIM) model and future climate projections from five global circulation models. Climate change (2020–2080) increased N mineralization (24%) and N2O emissions (19%) but decreased N fixation (32%), seed N (20%), and yields (19%). Soil and crop management practices altered N fluxes at a similar magnitude as climate change but in many different directions, revealing opportunities to improve soybean systems’ performance. Among many practices explored, we identified two solutions with great potential: improved residue management (short-term) and water management (long-term). Inter-annual weather variability and management practices affected soybean yield less than N fluxes, which creates opportunities to manage N fluxes without compromising yields, especially in regions with adequate to excess soil moisture. This work provides actionable results (tradeoffs, synergies, directions) to inform decision-making for adapting crop management in a changing climate to improve soybean production systems

Sulfur Fertilization in Soybean: A Meta-analysis on Yield and Seed Composition

Sulfur (S) deficiency has been recently reported in soybean [Glycine max (L.) Merr.] producing regions across the United States. However, field studies have often failed to demonstrate a strong relationship between yield and S fertilization and generally attributing the lack of yield response to unfavorable weather and high soil S supply. In addition, only a few reports described seed composition changes due to S availability under contrasting field conditions. Therefore, our goals were (i) to implement a meta-analytic model to quantify the effect of S application at different growth stages on yield and seed concentration of protein, oil, essential non-S amino acids, and S amino acids (SAA, cysteine and methionine); ii) identify environmental factors underpinning the response of S to these plant traits. Field experiments were carried out from 2017 to 2019 growing seasons with a total of 44 unique site-years conditions across 18 locations in 8 states. Mineral S fertilizer (sulfate/ elemental S) was supplied depending on the study at sowing, vegetative and/or reproductive stages. A random-effects multilevel meta-analysis was conducted. The effect sizes compared yield and seed composition responses relative to the unfertilized control. A principal component analysis (PCA) separated distinctive environmental conditions and a sub-grouped meta-analysis with the main environmental factors was later executed to understand the response of the plant traits with those factors. Seed protein concentration increased by 0.3 % when S was applied at sowing. The concentration of SAA increased by ca. 1% regardless of the fertilization timing. Sites exposed to drought stress (18–29% reduction of potential transpiration) neither presented changes in yield nor seed composition due to S fertilization. Soils with organic matter between 25 and 32 g kg-1 (medium cluster) displayed significant responses to S application. This research brings extensive data and provides a comprehensive analysis of weather and soil attributes influencing soybean yield and seed composition responses to S availability

Seed Inoculation with Azospirillum Brasilense in the U.S. Soybean Systems

Symbiotic nitrogen (N) fixation (SNF) is critical to satisfying the nutritional need of soybean (Glycine max (L.) Merr.) and maintaining productivity and high seed protein concentration. Due to its low environmental impact, a key factor for increasing the sustainability of soybean systems is to enhance SNF. Seed inoculation with the free-living Azospirillum brasilense alone or with Bradyrhizobium japonicum (herein called co-inoculation) are plausible strategies that have been explored in tropical environments but lack information in temperate regions. Following this rationale, this study aimed to evaluate the impact of seed inoculation with Azospirillum brasilense (herein called Azospirillum) alone or combined with Bradyrhizobium japonicum (herein called Bradyrhizobium) in a range of environments in the United States (US) for: (i) seed yield, (ii) relative abundance of ureides (RAU) as a proxy of SNF, and (iii) seed protein concentration. Twenty-five field studies across the US states with the same experimental design were performed during the 2019 and 2020 growing seasons. The primary outcomes of this research were: (i) yield responses to co-inoculation were considered significant in only 2 out of 25 site-years, (ii) RAU was not increased by Azospirillum inoculation or co-inoculation, and lastly, (iii) seed protein concentration was marginally associated with the inoculation strategies. Although Azospirillum did not impose remarkable gain in any observed plant traits, future studies should focus on mechanistically understanding whether Azospirillum can naturalize in temperate region soils. Still, strategies for enhancing SNF are required for sustainably improving productivity and quality for US soybean systems

Historical trend on seed amino acid concentration does not follow protein changes in soybeans

Abstract Soybean [Glycine max (L.) Merr.] is the most important oilseed crop for animal industry due to its high protein concentration and high relative abundance of essential and non-essential amino acids (AAs). However, the selection for high-yielding genotypes has reduced seed protein concentration over time, and little is known about its impact on AAs. The aim of this research was to determine the genetic shifts of seed composition for 18 AAs in 13 soybean genotypes released between 1980 and 2014. Additionally, we tested the effect of nitrogen (N) fertilization on protein and AAs trends. Soybean genotypes were grown in field conditions during two seasons under a control (0 N) and a N-fertilized treatment receiving 670 kg N ha−1. Seed yield increased 50% and protein decreased 1.2% comparing the oldest and newest genotypes. The application of N fertilizer did not significantly affect protein and AAs concentrations. Leucine, proline, cysteine, and tryptophan concentrations were not influenced by genotype. The other AAs concentrations showed linear rates of decrease over time ranging from − 0.021 to − 0.001 g kg−1 year−1. The shifts of 11 AAs (some essentials such as lysine, tryptophan, and threonine) displayed a relative-to-protein increasing concentration. These results provide a quantitative assessment of the trade-off between yield improvement and seed AAs concentrations and will enable future genetic yield gain without overlooking seed nutritional value

Soybean Yield, Biological N2 Fixation and Seed Composition Responses to Additional Inoculation in the United States

It is unclear if additional inoculation with Bradyrhizobia at varying soybean [Glycine max (L.) Merr.] growth stages can impact biological nitrogen fixation (BNF), increase yield and improve seed composition [protein, oil, and amino acid (AA) concentrations]. The objectives of this study were to evaluate the effect of different soybean inoculation strategies (seed coating and additional soil inoculation at V4 or R1) on: (i) seed yield, (ii) seed composition, and (iii) BNF traits [nodule number and relative abundance of ureides (RAU)]. Soybean field trials were conducted in 11 environments (four states of the US) to evaluate four treatments: (i) control without inoculation, (ii) seed inoculation, (iii) seed inoculation + soil inoculation at V4, and (iv) seed inoculation + soil inoculation at R1. Results demonstrated no effect of seed or additional soil inoculation at V4 or R1 on either soybean seed yield or composition. Also, inoculation strategies produced similar values to the non-inoculated control in terms of nodule number and RAU, a reflection of BNF. Therefore, we conclude that in soils with previous history of soybean and under non-severe stress conditions (e.g. high early-season temperature and/or saturated soils), there is no benefit to implementing additional inoculation on soybean yield and seed composition

Sulfur fertilization in soybean: A meta-analysis on yield and seed composition

Sulfur (S) deficiency has been recently reported in soybean [Glycine max (L.) Merr.] producing regions across the United States. However, field studies have often failed to demonstrate a strong relationship between yield and S fertilization and generally attributing the lack of yield response to unfavorable weather and high soil S supply. In addition, only a few reports described seed composition changes due to S availability under contrasting field conditions. Therefore, our goals were (i) to implement a meta-analytic model to quantify the effect of S application at different growth stages on yield and seed concentration of protein, oil, essential non-S amino acids, and S amino acids (SAA, cysteine and methionine); ii) identify environmental factors underpinning the response of S to these plant traits. Field experiments were carried out from 2017 to 2019 growing seasons with a total of 44 unique site-years conditions across 18 locations in 8 states. Mineral S fertilizer (sulfate/ elemental S) was supplied depending on the study at sowing, vegetative and/or reproductive stages. A random-effects multilevel meta-analysis was conducted. The effect sizes compared yield and seed composition responses relative to the unfertilized control. A principal component analysis (PCA) separated distinctive environmental conditions and a sub-grouped meta-analysis with the main environmental factors was later executed to understand the response of the plant traits with those factors. Seed protein concentration increased by 0.3 % when S was applied at sowing. The concentration of SAA increased by ca. 1% regardless of the fertilization timing. Sites exposed to drought stress (18–29% reduction of potential transpiration) neither presented changes in yield nor seed composition due to S fertilization. Soils with organic matter between 25 and 32 g kg-1 (medium cluster) displayed significant responses to S application. This research brings extensive data and provides a comprehensive analysis of weather and soil attributes influencing soybean yield and seed composition responses to S availability.Fil: Fróes de Borja Reis, André. Kansas State University; Estados UnidosFil: Moro Rosso, Luiz H.. Kansas State University; Estados UnidosFil: Davidson, Dan. No especifíca;Fil: Kovács, Péter. University of South Dakota; Estados UnidosFil: Purcell, Larry C.. University of Arkansas for Medical Sciences; Estados UnidosFil: Below, Frederick E.. University of Illinois. Urbana - Champaign; Estados UnidosFil: Casteel, Shaun N.. Purdue University; Estados UnidosFil: Knott, Carrie. University of Kentucky; Estados UnidosFil: Kandel, Hans. North Dakota State University; Estados UnidosFil: Naeve, Seth L.. University of Minnesota; Estados UnidosFil: Carciochi, Walter Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible - Instituto Nacional de Tecnología Agropecuaria. Centro Regional Buenos Aires Sur. Estación Experimental Agropecuaria Balcarce. Instituto de Innovación para la Producción Agropecuaria y el Desarrollo Sostenible; ArgentinaFil: Ross, Willian J.. University of Arkansas for Medical Sciences; Estados UnidosFil: Rampazzo Favoretto, Vitor. University of Illinois. Urbana - Champaign; Estados UnidosFil: Archontoulis, Sotirios. ;Fil: Ciampitti, Ignacio Antonio. Kansas State University; Estados Unido