Document Type

Dissertation - Open Access

Award Date

2023

Degree Name

Doctor of Philosophy (PhD)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Peter Kovacs

Abstract

The application of manure and inorganic fertilizer in row crops may significantly influence soil and greenhouse gas (GHG) emissions. Understanding the long-term influence of these management practices on soil pore characteristics, hydro-physical properties and greenhouse gas emission is essential in developing proper conservation practices. However, there is limited information on the impact of cattle manure and inorganic fertilizer application on soil hydro-physical properties, soil pore characteristics at lower depths and surface GHGs emissions. Therefore, the objectives of this study were to; (i) utilize X-ray computed tomography (XCT) technique to quantify the impact of manure and fertilizer amendments under a corn (Zea mays L.)-soybean (Glycine max L.)- spring wheat (Triticum aestivum) rotation system on soil pore characteristics to the depth of 40 cm; (ii) assess the impact of different manure and inorganic fertilizer application rates on soil profile organic carbon and hydro-physical properties under corn-soybeanspring wheat rotation; (iii) to investigate the impacts of cattle manure and inorganic fertilizer on soil surface greenhouse gases (GHG) [carbon dioxide (CO2), nitrous oxide (N2O), and methane (CH4)] fluxes from soils managed under corn-soybean- spring wheat rotation. The study was conducted at Brookings (initiated in 2008) and Beresford (2003) in South Dakota. Treatments included: low manure (LM), medium manure (MM), high manure (HM), medium fertilizer (MF), high fertilizer (HF), and control (CK). Four replicated intact cores were collected from all the treatments at 0-10, 10-20, 20-30, and 30-40 cm depths. Data showed that treatments by depth interactions were mainly significant for soil organic carbon (SOC) content at 0-20 cm. The HM treatment increased the SOC by 8 to 68% compared to the CK and MF at 0-20 cm for either site. However, treatments did not always impact these parameters beyond 20 cm depth. The HM increased the SOC and TN stocks by 16-62% as compared to the CK, MF, and HF at 0-10 cm for either site. However, treatments did not always impact these parameters beyond 20 cm depth. Considering treatment as the main effect, the MM, HM, and HF increased the total number of pores (TP) compared to the CK at Beresford site. Soil depth impacted the TP and the total number of macropores (Tmacro), where more Tmacro was observed at 0-10 cm compared to the 30-40 cm depth at Beresford site. The MM and HM increased the SWR at 0, -5 kPa compared to MF, HF, and CK in Brookings, and the MM increased the SWR at -30 kPa as compared to the MF in Beresford at 0-40 cm depths. The cumulative soil surface N2O, and CH4 fluxes were increased by the MF treatment compared to the MM and CK in 2020. In general, the MF treatment on average resulted in higher cumulative GHG emissions compared to the MM and CK in both years. Also the global warming potential rate increased in 2020 by inorganic fertilizer rate as compared to the MM and CK. This study illustrates the improvement in the XCT-derived pore characteristic with the long-term application of manure to a greater depth in the soil and highlighted the importance of the XCT technique in quantifying soil pore characteristics. For the soil hydro-physical study, it was observed that the continuous manure application may enhance organic carbon and hydro-physical properties at deeper depths. The study also concluded that long-term manure application is more beneficial when you consider the application rate and its timing. It can improve hydro-physical properties, thereby stabilizing the soil structure and improving water retention at deeper depths. For the greenhouse gas study, data showed that inorganic fertilizer application in crops can be harmful to the environment by emitting higher GHG emissions, therefore, sustainable management practices needs to be explored to mitigate GHG emissions and reduce or eliminate the negative environmental impacts.

Library of Congress Subject Headings

Crops and soils -- South Dakota.
Fertilizers -- South Dakota.
Cattle -- Manure -- Environmental aspects.
Nitrogen fertilizers -- Environmental aspects.
Soil profiles.
Greenhouse gases.
Crop rotation.

Publisher

South Dakota State University

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Rights Statement

In Copyright