Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department

Agronomy, Horticulture, and Plant Science

First Advisor

Sandeep Kumar

Abstract

Crop diversification can be beneficial in improving soil quality parameters. Diverse crop rotations and integrated crop-livestock systems (ICLS), are two examples of crop diversification used in this study to assess soil quality. The objectives of this study were to: (i) assess the impacts of diverse rotations on soil quality parameters, and (ii) assess the impacts of low and high stocking density on soil quality parameters. Both of the studies were conducted separately and are presented as two different chapters. To accomplish objective (i), a long-term experiment was selected which was established near Brookings, South Dakota, USA at USDA-ARS lab in 2000 on a Barnes (Fine-loamy, mixed, superactive, frigid Calcic Hapludoll) soil. Treatments selected for this study included five crop rotations: (i) 2-yr, corn (Zea mays)-soybean (Glycine max) (CS), (ii) 4-yr, corn-pea (P. sativum)-winter wheat (T. aestivum)-soybean (CPWwS), (iii) 4-yr, corn-soybeanspring wheat-pea (CSSwP), (iv) 4-yr, corn-soybean-spring wheat-sunflower (Helianthys) (CSSwSu), (v) 4-yr, corn-oats-winter wheat-soybean (COWwS) with four replications. Soil samples were collected in the spring after 12 and 16 years of cropping (2013-2017) at two sampling depths (0-5 cm and 5-15 cm). Results indicated that a previous crop, winter wheat under COWwS rotation had the highest soil organic carbon (SOC) content with 22.7 g kg-1 compared to other previous crops at the 0-5 cm depth. Also, previous crop of oat under COWwS rotation had significantly lower bulk density (BD) content than other crops. Additional soil quality parameters were analysis utilizing the Soil Management Assessment Framework (SMAF) tool. The COWwS and CSSwP rotations increased the soil quality compared to the CS, CPWwS and CSSwSu rotations. This study showed the benefits of using the long-term impacts of diverse crop rotations on soil quality parameters. To accomplish objective (ii), an on-farm assessment of soil quality was assessed at four producers’ farms where the specific objective to assess the impact of low and high stocking rates under ICLS on soil quality parameters such as bulk density, pH, soil nutrient parameters (N, P, K, Na, Ca, and Mg), soil organic carbon and nitrogen, and microbial biomass carbon. The four farms were located at: (i) Roscoe, (ii) Gettysburg, (iii) Raymond, and (iv) Selby in South Dakota. Each farm location included two different treatments; grazing cover crops under ICLS and control treatment without grazing. Soil samples were collected from 0-5, 5-15, and 15-30 cm depths in June 2017 and 2018. Study results showed that low stocking rate under ICLS at Roscoe increased soil organic carbon (SOC) from 20.7 to 28.2 g kg-1, total nitrogen (TN) from 2.06 to 2.60 g kg-1, and microbial biomass carbon (MBC) from 72.7 to 241.8 μg g-1 at the surface 0-5 cm depth. However, high stocking rates under ICLS at Gettysburg and Selby sites decreased the SOC. Additional analysis of the parameters was conducted to assess the soil quality index (SQI). Data showed that the low stocking rate under ICLS improved the soil quality index (SQI) while the high stocking rate under ICLS decreased the SQI. This study showed that ICLS with low stocking density can be beneficial in enhancing soil quality at the farm scale. In conclusion, the present study showed that crop diversification can be beneficial in enhancing soil quality, however, long-term assessments are needed that include different diverse crop rotations with cover crops, and different stocking rates and cover crops under ICLS, and monitoring different soil quality parameters, crop yield, and economics.

Description

Includes bibliographical references

Format

application/pdf

Number of Pages

164

Publisher

South Dakota State University

Rights

In Copyright - Non-Commercial Use Permitted
http://rightsstatements.org/vocab/InC-NC/1.0/

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