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.
【 预 览 】
附件列表
Files
Size
Format
View
Evaluating greenhouse gas emissions from Illinois agriculture systems
PDF
download
878987797
028-85220240
