Document Type

Dissertation - Open Access

Award Date

2020

Degree Name

Doctor of Philosophy (PhD)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Sandeep Kumar

Abstract

Introducing cover crops (CC) and increasing crop diversity in agricultural systems are beneficial in improving the soil health and crop production. However, limited research has been conducted that focuses the influence of CC and crop rotation on soil ecosystem, root growth and development, crop production, and economic returns. The objectives of this study were to (i) assess the impacts of CC management on soil enzyme activities and soil microbial community structure changes, (ii) evaluate the crop rotation management on crop root growth and development, nutrient storage in crop grain and biomass, and crop yield, and (iii) investigate the crop rotation management effect on production input cost and economic return. The study 1 included that soils data collected at 0-5 cm depth from CC with different durations (3 to 20 years) at five locations in the Midwestern, US. Data showed that including CC into cropping system has the potential to alter soil enzyme activates and the richness of soil microbial community, and this effect varied with the duration of CC. Data from this study showed that long-term (20-year) winter rye CC increased waterextractable C and N content, B-glucosidase, urease, acid phosphatase, alkaline phosphatase, arylsulfatase, and fluorescein diacetate activities, and soil bacterial community abundance than the NCC treatment. However, no significant differences were found between short-term (3-6 years) winter rye, legume, and brassica mixture and NCC treatment regrading to the abundance of soil microbial community. There was an increment in B-glucosidase, acid phosphatase, alkaline phosphatase, arylsulfatase, FDA, and total phospholipid fatty acid concentration under short-term (3-year) legume and grass CC mixture than that under NCC treatment. The study 2 included the data on crop root distribution and nutrient storage in crop grain and biomass under a long-term no-till diverse crop rotations located at the Eastern South Dakota Soil and Water Research Farm near Brookings, SD. The results of this objective from 2017 and 2018 showed that the diverse crop rotations [corn (Zea mays L.)-soybean [Glycine max (L.) Merr.]-spring wheat (Triticum aestivum L.)-pea (Pisum sativum L.) (CSSwP), corn-pea-winter wheat-soybean (CPWwS), corn-oat (Avena sativa L.)-winter wheat-soybean (COWwS), corn-soybean-spring wheat-sunflower (Helianthus annuus L.) (CSSwSf)] had significant effects on corn root distribution and corn yield as compared with the 2-year corn-soybean (CS) rotation. Compared with other rotations, lower corn root biomass, corn root length density at the first two depths (0-15 and 15-30 cm), and total root length density at anthesis were recorded in CSSwP rotation but it led to greater corn yield. The CS rotation had lower corn and soybean yields than the other diverse crop rotations, although the differences were not always significant. There was no evidence that crop rotation influenced the crop grain nutrient storage, but a slight difference was shown in the crop biomass. The study 3 included the data on crop yield, production input cost, and economic return from the same location as the study 2. The data collected for 2013 through 2016 showed that diverse crop rotations (CSSwP, CPWwS and COWwS) provided more benefits in crop production and economic return than the CS rotation. Specifically, CS rotation required greater total input cost than the diverse crop rotations. No significant increase in corn yield was detected in diverse crop rotations compared with the CS rotation, while there was a significant reduction in soybean yield under CS rotation than the diverse crop rotations. The gross revenue and net revenue results suggested that CS rotation was less resiliency than the diverse crop rotations when the nitrogen (N) fertilizer application rate was less than that required for the maximum yield, this result was more obvious when compared with the CSSwP rotation. These findings suggested that, in general, use of long-term CC and extending the traditional CS rotation to more diversified such as CSSwP rotation could be more beneficial and sustainable systems in Northern Great Plains, USA.

Library of Congress Subject Headings

Crop rotation.
Crop rotation -- Economic aspects.
Cover crops.
Crop diversification.
Soil biochemistry.
Cropping systems.
Roots (Botany)

Format

application/pdf

Number of Pages

181

Publisher

South Dakota State University

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Rights Statement

In Copyright