Document Type

Thesis - Open Access

Award Date

2022

Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Sutie Xu

Abstract

Long-term tillage and crop rotation systems are important agricultural management practices as these can have direct impact on the soil’s key properties. The objectives of this study were to (ⅰ) quantify the soil pore characteristics under long-term tillage and crop rotation using X-ray computed tomography (XCT) and to assess the relationships between XCT-measured pore parameters and soil hydro-physical properties; and (ⅱ) evaluate the impacts of long-term tillage and crop rotation on select soil health indicators. The objective (ⅰ) was carried out at Haskell Agricultural Laboratory (HAL), Concord, NE; and objective (ⅰi) was carried out at South Central Agricultural Laboratory (SCAL), Clay Center, NE in addition to HAL study site. The SCAL and HAL experimental sites were initiated in 1985 and 1986, respectively. The experimental design was a randomized complete block design in split-plots with three and four replications in SCAL and HAL sites, respectively. The main plots were tillage and sub-plots were rotation treatments. The study treatments included: three tillage [no-till (NT), reduced till (RT) – disk till, and conventional till (CT) – moldboard plow] and two cropping systems [continuous corn (Zea mays L.) and corn-soybean (Glycine max [Merr.] L.)]. Results from objective (i) showed that NT with corn-soybean (CS) rotation decreased the soil bulk density (b) at 0-10 cm depth and increased the number of macropores and mesopores at 0-10 and 10-20 cm depth as compared to the CT with continuous corn (CC) systems. Similarly, NT with CS also enhanced the saturated hydraulic conductivity (Ksat) at 0-10 cm depth. Though the crop rotation did not affect the soil organic carbon (SOC) and total nitrogen (TN), the NT improved the SOC by 24 and 49% and TN concentrations by 26 and 67% at 0-10 cm depth as compared to the RT and CT, respectively. Also, the NT increased the plant available water (PAW) content by 25 and 67% at 10-20 cm depth as compared to the RT and CT, respectively. Results from objective (ii) showed that the activities of β-glucosidase and urease were higher under NT with CS rotation as compared to the other treatments at HAL study site. At SCAL study site, similar effect of NT with CS was observed with enhanced arylsulfatase activity. At the HAL study site, though there was no interaction effect, the CS rotation enhanced the microbial biomass carbon (MBC) by 9% as compared to the CC. Similarly, the NT increased the MBC by 27 and 80% as compared to the RT and CT treatments. The NT with CC system has increased the mean weight diameter and water stable aggregates as compared to the other treatments. Overall, this study showed that NT with CS rotation enhanced the soil physical and hydrological attributes along with the other soil health indicators.

Number of Pages

126

Publisher

South Dakota State University

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Rights Statement

In Copyright