Soil Aggregation and Soil Carbon Measurements to Assess Cover Crop Improvements to Soil Health in Indiana
Abstract
Cover crop use, especially in no-till systems, is an evolving practice to maintain or improve soil health. There are many possible indicators of soil health, but this study focuses on the analysis of soil aggregate stability, soil active carbon, and soil organic matter. Soil aggregate stability is related to water infiltration and potential for soil erosion, while active carbon serves as an indicator of a readily-available food source for microbial activity, and soil organic matter serves as a mediator for the soil physical, chemical, and biological processes. The sites involved in this study were: three Purdue Agricultural Centers, two soil and water conservation district sites, 12 farmer sites with conservation cropping systems, and seven conventional comparison sites. The treatments consisted of cover crop versus no cover crop use, or cover crop use with different tillage systems or nitrogen rates. In 2016 and 2017, mostly in the summer, soil samples were collected at a depth of 0-5 cm, air-dried, and separated into two soil size fractions: 0-2 mm and 2-8 mm. The wet sieve method was used to measure the mean weight diameter of the water stable soil aggregates from the 2-8 mm soil size fraction in both years. The potassium permanganate method was used to measure the soil active carbon from the 0-2 mm and 2-8 mm soil size fractions in both years. The dry combustion method was used to measure the soil organic matter from the 0-2 mm and 2-8 mm soil size fractions for the samples taken in 2017 only. Results showed relatively small improvements in soil active carbon and aggregate stability with the addition of three to four years of cover crops to the long-term no-till systems. However, these improvements were greater when comparing the cover crops plus no-till treatments to the conventional-till without cover crop systems. More work is needed to understand the dynamics of soil aggregate stability, soil active carbon, and soil organic matter in relation to soil health and cover crop use. Cover crops will likely have more impact on soil aggregate stability, soil active carbon, and soil organic matter with a longer duration of use.
Degree
M.Sc.
Advisors
Kladivko, Purdue University.
Subject Area
Education|Agricultural chemistry|Agriculture|Agronomy|Chemistry|Design|Organic chemistry|Soil sciences|Water Resources Management
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.