Nitrogen and Sulfur Fertilization Effects on Carbon Sequestration and Greenhouse Gas Emissions in S-deficient Soils

• Author / Creator

  Giweta,Mekonnen H.

• Depending on management practices, agricultural soils have the potential to be both a source and a sink of greenhouse gases (GHGs). Long-term fertilization and crop rotation management practices are considered to have an impact on carbon (C) sequestration and nitrous oxide (N2O) emissions. Sulfur (S) deficient soils occupy a large area in agricultural production regions in Western Canada; however, much past research has focused mainly on the effect of long-term N fertilization on N2O emissions, and there are only a few examples of the effects of long-term N and S fertilization on C sequestration. The research in this thesis, mainly aimed to investigate the effects of long-term combined N and S fertilization and crop rotation practices on soil C sequestration and N2O emissions in S-deficient soils at the Breton Classical Plots, AB, Canada. This thesis reports the results of three studies. First, the influence of long-term N and S fertilization on the change in total soil organic C (SOC) over 28 years (1980-2008) was quantified. The results revealed that long-term S fertilization in combination with other macro nutrients (NPK) resulted in an increasing trend in SOC concentration over the years and increased accumulation of SOC at a rate of 0.11 Mg C ha-1 yr-1 over N fertilizer alone. In the second study, a 3-year growing season field study was carried out in order to quantify the growing season N2O emissions from S-deficient soils from five soil fertility treatments with different fertilization history (Control (unfertilized), Manure, NPKS, NPK and PKS) under a 2-yr wheat-fallow (WF) and a 5- yr wheat-oat-barley-hay-hay (WOBHH) crop rotation. The results indicate that the 3-yr cumulative growing season N2O-N emissions were higher in the WOBHH rotation than the WF rotation. On the other hand, WOBHH had a higher yield and reduced N2O emission intensity (kg of N2O-N per kg of grain, or kg of N2O-N per kg crop N uptake) compared to the WF crop rotation system. In both crop rotation systems, N2O emissions from the manure treatment were the highest of all soil fertility treatments. Soils with long-term combined N and S fertilization history had a highest yield and lowest N2O emission intensity compared to the other soil fertility treatments, particularly in the WOBHH rotation. This implies that long-term balanced fertilization of S with other macro nutrients reduced the N2O emission intensities without compromising the benefit of higher yield. Finally, a laboratory incubation experiment was conducted in order to examine whether different N and S fertilizer sources significantly interact with fertilization history with respect to N2O emission potential, and whether N2O emissions are influenced by the interaction of elemental S oxidation and nitrification. Results revealed that N2O-N emissions from the contemporary applied N and S fertilizers were significantly influenced by fertilization history. Furthermore, since elemental S (S0) oxidation did not affect the nitrification process in soil, N2O emissions from fertilizer treatments with S0 or without S0 were not significantly different. Investigating the interactions between S and N transformations in agricultural soils is vital in order to better understand the effects of long-term fertilizer management practices on N2O emissions and C sequestration. The results presented in this thesis may have significant implication for sustainable agriculture, and can be considered in nutrient management strategies that can mitigate N2O emissions, while also optimizing crop yield and increasing organic C storage in S-deficient soils.

• Subjects / Keywords

  • Nitrous oxide
  • Emission intensity,
  • Fertility treatment
  • Sulfur deficient
  • Crop rotation

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R32F7K014

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.