Document Type

Dissertation - Open Access

Award Date

2017

Degree Name

Doctor of Philosophy (PhD)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Sandeep Kumar

Keywords

hydrology, soil bio-physics, soil health, soil quality

Abstract

Diverse cropping systems and no-till (NT) are beneficial in improving soil organic carbon (SOC) and other soils properties. The present study was conducted to evaluate the interactions and impacts of long-term tillage and diverse crop rotation systems on soil quality indicators that include a range of soil chemical, physical, hydrological, and microbial properties. The study was established in 1991 at Beresford, South Dakota and included three crop rotation systems [2-yr; maize (Zea mays L.)-soybean (Glycine max L.), 3-yr; maize-soybean-oat (Avena sativa L.), and 4-yr; maize-soybean-oat-wheat (Triticum aestivum L.)] managed under two tillage systems (NT and CT; conventional- tillage). Soil sampling was conducted only after maize harvest (maize phase) and soybean (soybean phase) harvest of each rotation. Soil samples were collected in fall 2014 at four depths (0- to 7.5-, 7.5- to 15-, 15- to 30-, and 30- to 60-cm) for soil chemical properties, intact core samples were collected from 0- to 7.5-, 7.5- to 15-cm for hydrological properties in fall 2015, and two sets of samples were collected in summer-fall 2016 at surface depth (0- to 7.5-cm) for microbial analysis. The selected soil quality parameters include soil organic carbon (SOC), total nitrogen (TN), bulk density (ρb), water aggregate stability (1-2 mm), and light fractions of carbon (LFOC) and nitrogen (LFON). The physical-hydrological parameters include soil water infiltration (qs), water retention (SWR), pore-size distribution (PSD), bulk density, and penetration resistance (SPR). The microbial parameters include microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil carbon fractions [labile; HWC, stable; CWC, and inert; 1M and 6M], soil urease enzyme, and soil β-glucosidase. Data of soil quality showed that after 23 years, the 4-yr rotation significantly increased SOC concentrations up to 30-cm in both tillage systems. Averaged across all the tillage systems, the 4-yr rotation increased SOC by 10.6 and 12.4%, respectively, compared to 2-and 3-yr rotations in the 0- to 7.5-cm, 14.2 and 4.95% in the 7.5- to 15-cm, and 12.1 and 15.3% in the 15- to 30-cm depth compared to that under 3-yr and 2-yr rotations respectively. Increase in SOC subsequently decreased the ρb by 3.8 and 3% in soybean phase and by 3 and 2.3% in the 4-yr rotation for these depths compare to 2-yr and 3-yr rotation systems. Physical-hydrological properties data showed that NT with 4-yr rotation had the lowest soil ρb under both the phases compared to same rotation system under CT soil management. Similarly, NT 4-yr rotation decreased SPR by 20% as compared to that under CT 4-yr rotation under soybean phase. In 0- to 7.5-cm depth, SWR under NT with 4-yr rotation was higher by 27% at 0 kPa, 27% at - 0.4 kPa, 28% at -1.0 kPa, 32% at -2.5 kPa, 33% at - 5.0 kPa, 30% at -100 kPa, and 26% at -300 kPa compared to same rotation system under CT. A similar trend was observed for qs under same treatments where it was higher under NT 4-yr by 31% rotation compared to CT 4-yr rotation. Microbial properties results showed an increase in MBC, MBN, HWC, and urease, β-glucosidase enzyme activity under NT with 4-yr treatments under both phases. At planting, under soybean phase, NT with 4-yr rotation increased MBC by 29% compared to same cropping system under CT. Similarly; 4-yr rotation with NT was significantly higher in MBN by 23% compared to the same cropping system (4-yr) under CT system. Labile carbon fraction under 4-yr rotation system with NT (92.1 μg C g −1 soil) was significantly higher than that under 4- yr rotation with CT system (60.2 μg C g −1 soil) by 52%. The 4-yr rotation with NT significantly increased urease enzyme activity compared to all other treatments by 52%, 72%, 169%, 159%, and 168% under the 2-yr and 3-yr rotations with NT and the 2-yr, 3- yr, and 4-yr rotations with CT, respectively. β-glucosidase enzyme activity was increased only under 2-yr cropping system with NT system. Results showed that for important in soil quality, physical-hydrological, and microbial properties diverse cropping system need to be paired with NT practices. Conversely gains from NT were most realized when paired with a diverse 4-yr rotation in Northern Great Plain (NGP) region and particularly in southeast portion of South Dakota, USA

Library of Congress Subject Headings

Soils -- Quality -- South Dakota.
Tillage -- South Dakota.
Crop rotation -- South Dakota.

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

240

Publisher

South Dakota State University

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Rights Statement

In Copyright