Evaluating greenhouse gas emissions from Illinois agriculture systems

Many Illinois cropping systems rely on nitrogen (N), which is an essential element and usually a limiting factor in corn (Zea mays, L.) production; yet N build-up in the soil might lead to nitrate (N-NO3) leaching, and release of nitrous oxide (N2O) by denitrification, thus contributing to both water and air pollution. Agricultural soil management accounts for much of the total N2O production in the US. Two of the most important agricultural practices aimed at improving soil properties and reducing inputs are crop rotations and no-tillage, yet relatively few studies have assessed their long-term impacts on crop yields and soil greenhouse gas (GHG) emissions. Likewise, the inclusion of cover crops (CCs) has been proposed to scavenge surplus soil N, which might lead to a decrease in the substrate needed for N2O production from the field and aqueous N losses. In chapter 2 of this dissertation, the objective was to determine the influence of tillage and crop rotation on soil GHG emissions and yields following 15 years of treatment implementation in a long-term cropping systems experiment in Illinois, USA. The experimental design was a split-plot RCBD with crop rotation as the main plot: (continuous corn [Zea mays L.] (CCC), corn-soybean [Glycine max (L.) Merr.] (CS), continuous soybean (SSS), and corn-soybean-wheat [Triticum aestivum L.] (CSW); with each phase of each crop rotation present every year) and tillage as the subplot: chisel tillage (T) and no-tillage (NT). Tillage increased the yields of corn and soybean. Tillage and crop rotation had no effect on methane (CH4) emissions (p = 0.4738 and p = 0.8494 respectively) and only rotation had an effect on cumulative carbon dioxide (CO2) (p = 0.0137). However, their interaction affected cumulative nitrous oxide (N2O) emissions significantly (p = 0.0960); N2O emissions from tilled CCC were the greatest at 6.9 kg-N ha-1-yr-1; while emissions from NT CCC (4.0 kg-N ha-1-yr-1) were not different than both T CS or NT CS (3.6 and 3.3 kg-N ha-1-yr-1, respectively). Utilizing just a CS crop rotation increased corn yields by around 20% while reducing N2O emissions by around 35%; soybean yields were 7% greater and N2O emissions were not affected. Therefore results from this long-term study indicate that a CS rotation has the ability to increase yields and reduce GHG emissions compared to either CCC or SSS alone, yet moving to a CSW rotation did not further increase yields or reduce N2O emissions. In Chapter 3, the objective was to explore the relationships between the physical and chemical properties and GHG emissions of soil, and cash crop yields over a four-year time-period and following 15 years of treatment implementation in Illinois, USA. The experimental layout was a split-plot arrangement involving rotation and tillage treatments in a randomized complete block design with four replications. The studied crop rotations were CCC, CS, SSS, and CSW, with each phase being present for every year. Again, the tillage options were T and NT. We used an array of multivariate approaches to analyze both of our datasets that included 31 soil properties, GHG emissions (N2O, CO2, and CH4) and cash crop yields. The results from our analyses indicate that N2O emissions are associated with a low soil pH, an increased Al concentration, the presence of soil nitrate throughout the growing season, an increase in plant available water (PAW) and an increased soil C concentration. Likewise, soil CO2 respiration was correlated with low pH, elevated Al concentrations, low Ca, increased PAW, higher levels of microbial biomass carbon (MBC), and lower water aggregate stability (WAS). Emissions of CH4 were associated with increased levels of MBC. Lastly, the yield index (YdI) was correlated with lower levels of soil Ca and available P and lower values of WAS. The association between high YdI and lower WAS can be attributed to tillage, as tillage lowers WAS, but increases yields in highly productive cropping systems in the Midwest. In Chapter 4, the objective was to determine the effect that corn-soybean rotations with different CCs, and tillage methods have on GHG emissions and crop yields in Illinois, USA. The experimental design was a split-block arrangement of tillage (whole plot treatment, chisel vs. no-till) and CC rotations (subplot treatment) in a RCBD with 4 replications with the corn and soybean phases present each year. GHG emissions - N2O, CO2, and CH4 – soil available N and yields were sampled from the corn phase of each rotation over a period of 4 years (2013-2017). CC rotations included five corn-soybean rotations that included different CCs and one that had fallows as control. Our results suggest that CC efficacy in IL is associated with winter temperature and precipitation. In two of the years, spring CC growth was poor due to unseasonably cold temperatures; however, in two of the other years, weather was favorable and spring CC biomass ranged from 2-3 Mg ha-1 from three of the species tested. In years where spring CC biomass was recorded, a fivefold reduction in N2O emissions occurred due to significant reductions in soil N-NO3. Corn yields were not improved with the utilization of CCs and a yield decrease of 12% occurred in the annual ryegrass (Lolium multiflorum Lam.) rotation. In Chapter 5, conclusions among the three studies are reviewed and discussed. Combining the knowledge gained from these three studies, utilization of a crop rotation system with a cover crop has the ability to substantially reduce GHG emissions. Yield benefits were observed at the crop rotation level only; however, CC’s (excluding annual ryegrass) did not reduce yields. Tillage also provided a yield increase in both studies with no increases in GHG emissions. The knowledge gained through these studies provides an insight as to how Illinois cropping systems produce GHG emissions, and more importantly, which cropping systems are able to reduce GHG emissions

Soil Microbial Indicators within Rotations and Tillage Systems

Recent advancements in agricultural metagenomics allow for characterizing microbial indicators of soil health brought on by changes in management decisions, which ultimately affect the soil environment. Field-scale studies investigating the microbial taxa from agricultural experiments are sparse, with none investigating the long-term effect of crop rotation and tillage on microbial indicator species. Therefore, our goal was to determine the effect of rotations (continuous corn, CCC; continuous soybean, SSS; and each phase of a corn-soybean rotation, Cs and Sc) and tillage (no-till, NT; and chisel tillage, T) on the soil microbial community composition following 20 years of management. We found that crop rotation and tillage influence the soil environment by altering key soil properties, such as pH and soil organic matter (SOM). Monoculture corn lowered pH compared to SSS (5.9 vs. 6.9, respectively) but increased SOM (5.4% vs. 4.6%, respectively). Bacterial indicator microbes were categorized into two groups: SOM dependent and acidophile vs. N adverse and neutrophile. Fungi preferred the CCC rotation, characterized by low pH. Archaeal indicators were mainly ammonia oxidizers with species occupying niches at contrasting pHs. Numerous indicator microbes are involved with N cycling due to the fertilizer-rich environment, prone to aquatic or gaseous losses.Fil: Behnke, Gevan D.. University of Illinois at Urbana; Estados UnidosFil: Kim, Nakian. University of Illinois at Urbana; Estados UnidosFil: Zabaloy, Maria Celina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Riggins, Chance W.. University of Illinois at Urbana; Estados UnidosFil: Rodriguez Zas, Sandra. University of Illinois at Urbana; Estados UnidosFil: Villamil, Maria Bonita. University of Illinois at Urbana; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

A Longitudinal Study of the Microbial Basis of Nitrous Oxide Emissions Within a Long-Term Agricultural Experiment

Much of the global nitrous oxide emissions are derived from agricultural management driving microbial N transformations. Crop rotation, no-till, and cover cropping are feasible conservation agronomic strategies used to prevent N losses to the environment, though their effect on soil microbial N cycling at the field scale remains relatively unknown. Our goal was to determine the effect of crop rotation (continuous corn [Zea mays L.], CCC; and continuous soybean [Glycine max (L.) Merr.], SSS), tillage (no-till, NT; and chisel tillage, T), and cover crops (cover crop mixture, CC; and no cover crop, NCC) on the quantification of functional genes related to the N cycle from different times throughout the growing season. The study was conducted during the growing season of the cash crops following the first season of cover crops introduced after 23 years of management. Using quantitative polymerase chain reaction (qPCR) techniques, we quantified nifH (N2 fixation), amoA (nitrification) and nirK, nirS, and nosZ (denitrification). Our results show that CCC increased nitrous oxide emissions by 44% compared to SSS and reduced soil pH by nearly 1 unit. The reduction in soil pH, coupled with an increase in fertilizer-derived ammonium, caused ammonia-oxidizing bacteria (AOB) and nirK copy numbers to increase. The SSS rotation showed opposite results. Bacterial denitrification via the nirK pathway was likely the N cycle mechanism behind nitrous oxide emissions in CCC. The cover crop mixture of cereal rye [Secale cereale L.] and hairy vetch [Vicia villosa Roth] reduced soil nitrate levels, though they did increase nitrous oxide emissions, likely due to priming and the inclusion of a legume in the cover crop mixture. Nitrous oxide emissions were affected by sampling date, crop rotation, and cover crop use, suggesting management factors that add abundantly available N alter the microbial N cycle directly or indirectly. Chisel tillage increased the abundance of all N cycle genes compared to no-till. Together, our work adds further insight into the microbial N cycle, especially nitrous oxide evolution, from three common conservation agricultural management practices, contributing to our understanding of key soil biogeochemical processes.Fil: Behnke, Gevan D.. University of Illinois at Urbana; Estados UnidosFil: Kim, Nakian. University of Illinois at Urbana; Estados UnidosFil: Riggins, Chance W.. University of Illinois at Urbana; Estados UnidosFil: Zabaloy, Maria Celina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Bahía Blanca. Centro de Recursos Naturales Renovables de la Zona Semiárida. Universidad Nacional del Sur. Centro de Recursos Naturales Renovables de la Zona Semiárida; Argentina. Universidad Nacional del Sur. Departamento de Agronomía; ArgentinaFil: Rodriguez Zas, Sandra L.. University of Illinois at Urbana; Estados UnidosFil: Villamil, Maria Bonita. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. University of Illinois at Urbana; Estados Unido

Greenhouse gas emissions from production of Miscanthus x giganteus on a Mollisol

Biofuels have a great potential to alleviate our dependence on non-renewable fossil fuel products; however the beneficial effects of substituting biomass for fossil fuel is reduced if the biofuel crops also emit large amounts of greenhouse gases (GHGs), such as carbon dioxide (CO2) and nitrous oxide (N2O) during their production. Most crops require nitrogen (N) fertilization to maximize productivity, but the amount of N fertilizer Miscanthus x giganteus might need is currently not known. Because M. x giganteus is highly efficient in its N use, it is a great potential energy crop because it has had large yields even at low N inputs from fertilizers (including no additions of N fertilizer). Therefore, it is critical to determine the response of M. x giganteus to N fertilizer rates and determine the effect of fertilization on GHG emissions. The main objective of this study was to examine the effect of N fertilization rates (0, 60 and 120 kg N ha-1 of urea) on GHG emissions from production of M. x giganteus on a central Illinois Mollisol. The study had twelve, 10x10 m plots organized in four replicate rows with each of the three N fertilizer treatments placed randomly in each row. Gas samples to determine N2O and CO2 fluxes were taken near noon throughout the year (March-November) when soil temperatures were warm enough to support microbial activity. In addition, soil moisture and soil temperature were continuously measured, and soils were regularly sampled for inorganic N to make specific inferences about abiotic factors affecting the GHG emissions. Furthermore, inorganic N leaching was assessed using resin lysimeters buried at 50 cm in each plot; the lysimeters placed in the soil in April of each year and excavated the following April. M. x giganteus biomass was measured on each plot, along with N and C concentrations in the harvested material. At the end of 2009 cumulative N2O and CO2 emissions did not have a significant response due to fertilization. However, at the end of 2010, cumulative N2O emissions significantly increased with fertilizer additions (0.35, 0.77, and 2.91 kg N ha-1 for the 0, 60, and 120 kg N ha-1 fertilizer treatments, respectively). Carbon dioxide emissions did not respond to fertilization in 2010. Larger NO3- concentrations were significantly related with larger N2O emissions. Greater temperature and greater soil moisture at 10 cm were significantly related to larger N2O emissions. Higher temperature at 10 cm was significantly related to larger CO2 emissions; conversely, soil moisture was not related to CO2. In 2010, several large precipitation events occurred following fertilization, leading to greater N2O emissions due to greater soil moisture. This study shows the potential for large N2O releases in fertilized M. x giganteus when rates were greater than 60 kg N ha-1, but this response is dependent on precipitation and resulting soil moisture status following fertilizer application. Soil CO2 emissions were unaffected by N fertilization. During the first year of the study, NO3- leaching was not significantly affected by fertilization, but by the second year, the treatment plots had significantly different NO3- leaching at 50 cm soil depth (8.9, 15.3, and 28.9 kg N ha-1 yr-1, for the 0, 60, and 120 kg N ha-1 fertilizer treatments, respectively). Yield data the first year of the study showed no significant difference among treatments and were quite small, likely due small to the previous crop failure during the establishment year and replanting (1.1, 4.1, and 4.0 Mg ha-1, for the 0, 60, and 120 kg N ha-1 treatments, respectively). After the second year, biomass was much larger for all the treatments, but was still not significantly different due to fertilization with N (14.9, 15.8, and 17.0 Mg ha-1, for the 0, 60, and 120 kg N ha-1 treatments, respectively). The amount of N removed from harvesting the biomass was significantly larger with additional fertilizer in year 2; therefore, fertilization removed more N while yielding relatively the same biomass. Overall, fertilization of M. x giganteus can lead to important N2O releases, which reduces the overall favorable GHG balance; increased fluxes of inorganic N (primarily NO3-) through the soil profile; and increases in harvested N without a significant increase in biomass

Carbon and Nitrogen Content of Soil Organic Matter and Microbial Biomass under Long-Term Crop Rotation and Tillage in Illinois, USA

Crop rotation and tillage alter soil organic matter (SOM) dynamics by influencing the soil environment and microbes carrying out C and N cycling. Our goal was to evaluate the effect of long-term crop rotation and tillage on the quantity of C and N stored in SOM and microbial biomass. Two experimental sites were used to evaluate four rotations—continuous corn (Zea mays L.) (CCC), corn-soybean (Glycine max [L.] Merr.) (CS), corn-soybean-wheat (Triticum aestivum L.) (CSW), and continuous soybean (SSS), each split into chisel tillage (CT) and no-till (NT) subplots. The CSW rotation increased soil organic carbon (SOC) content compared to SSS; SSS also reduced total nitrogen (TN) compared to other rotations. Levels of SOC and TN were 7% and 9% greater under NT than CT, respectively. Rotation did not affect microbial biomass C and N (MBC, MBN) while tillage reduced only MBN at 10–20 cm compared to NT, likely related to dispersion of N fertilizers throughout the soil. Despite the apparent lack of sensitivity of microbial biomass, changes in SOC and TN illustrate the effects of rotation and tillage on SOM dynamics. The inclusion of crops with high C: N residues and no-till use both support higher C and N content in the top 20 cm of the soil

Exploring the Relationships between Greenhouse Gas Emissions, Yields, and Soil Properties in Cropping Systems

Relationships between greenhouse gas emissions, yields, and soil properties are not well known. Utilizing two datasets from long-term cropping systems in Illinois, USA, our we aim to address these knowledge gaps. The objective of this study was to explore the relationships between the physical and chemical properties and greenhouse gas (GHG) emissions of soil, and cash crop yields over a four-year time-period and following 15 years of treatment implementation in Illinois, USA. The experimental layout was a split-plot arrangement involving rotation and tillage treatments in a randomized complete block design with four replications. The studied crop rotations were continuous corn [Zea mays L.] (CCC), corn-soybean [Glycine max (L.) Merr.] (CS), continuous soybean (SSS), and corn-soybean-wheat [Triticum aestivum L.] (CSW), with each phase being present for every year. The tillage options were chisel tillage (T) and no-tillage (NT). We used an array of multivariate approaches to analyze both of our datasets that included 31 soil properties, GHG emissions (N2O, CO2, and CH4) and cash crop yields. The results from our analyses indicate that N2O emissions are associated with a low soil pH, an increased Al concentration, the presence of soil nitrate throughout the growing season, an increase in plant available water (PAW) and an increased soil C concentration. Likewise, soil CO2 respiration was correlated with low pH, elevated Al concentrations, low Ca, increased PAW, higher levels of microbial biomass carbon (MBC), and lower water aggregate stability (WAS). Emissions of CH4 were associated with increased levels of MBC. Lastly, the yield index (YdI) was correlated with lower levels of soil Ca and available P and lower values of WAS. The association between high YdI and lower WAS can be attributed to tillage, as tillage lowers WAS, but increases yields in highly productive cropping systems in the Midwest

Long-term crop rotation and tillage effects on soil greenhouse gas emissions and crop production in Illinois, USA

Two of the most important agricultural practices aimed at improving soil properties are crop rotations and no-tillage, yet relatively few studies have assessed their long-term impacts on crop yields and soil greenhouse gas (GHG) emissions. The objective of this study was to determine the influence of tillage and crop rotation on soil GHG emissions and yields following 15 years of treatment implementation in a long-term cropping systems experiment in Illinois, USA. The experimental design was a split-plot RCBD with crop rotation as the main plot: (continuous corn [Zea mays L.] (CCC), corn-soybean [Glycine max (L.) Merr.] (CS), continuous soybean (SSS), and corn-soybean-wheat [Triticum aestivum L.] (CSW); with each phase of each crop rotation present every year) and tillage as the subplot: chisel tillage (T) and no-tillage (NT). Tillage increased the yields of corn and soybean. Tillage and crop rotation had no effect on methane (CH4) emissions (p = 0.4738 and p = 0.8494 respectively) and only rotation had an effect on cumulative carbon dioxide (CO2) (p = 0.0137). However, their interaction affected cumulative nitrous oxide (N2O) emissions significantly (p = 0.0960); N2O emissions from tilled CCC were the greatest at 6.9 kg-N ha−1-yr−1; while emissions from NT CCC (4.0 kg-N ha−1-yr−1) were not different than both T CS or NT CS (3.6 and 3.3 kg-N ha−1−yr−1, respectively). Utilizing just a CS crop rotation increased corn yields by around 20% while reducing N2O emissions by around 35%; soybean yields were 7% greater and N2O emissions were not affected. Therefore results from this long-term study indicate that a CS rotation has the ability to increase yields and reduce GHG emissions compared to either CCC or SSS alone, yet moving to a CSW rotation did not further increase yields or reduce N2O emissions

Soil Microbial Indicators within Rotations and Tillage Systems.

Recent advancements in agricultural metagenomics allow for characterizing microbial indicators of soil health brought on by changes in management decisions, which ultimately affect the soil environment. Field-scale studies investigating the microbial taxa from agricultural experiments are sparse, with none investigating the long-term effect of crop rotation and tillage on microbial indicator species. Therefore, our goal was to determine the effect of rotations (continuous corn, CCC; continuous soybean, SSS; and each phase of a corn-soybean rotation, Cs and Sc) and tillage (no-till, NT; and chisel tillage, T) on the soil microbial community composition following 20 years of management. We found that crop rotation and tillage influence the soil environment by altering key soil properties, such as pH and soil organic matter (SOM). Monoculture corn lowered pH compared to SSS (5.9 vs. 6.9, respectively) but increased SOM (5.4% vs. 4.6%, respectively). Bacterial indicator microbes were categorized into two groups: SOM dependent and acidophile vs. N adverse and neutrophile. Fungi preferred the CCC rotation, characterized by low pH. Archaeal indicators were mainly ammonia oxidizers with species occupying niches at contrasting pHs. Numerous indicator microbes are involved with N cycling due to the fertilizer-rich environment, prone to aquatic or gaseous losses