Abstract
Since it is the functions of soil that are of greatest concern, it is imperative to consider a unified approach with multiple indicators from all three facets (physical, chemical, and biological) and their synchronized relationships. While environmental impacts of soil management are becoming more prevalent, management for crop production remains the major fueling source for soil health research. How producers manage their land has significant impacts on soil health, and the degree to which is becoming increasingly popular in research, particularly in regions of agricultural intensity. Southern Idaho for example, is a major producer of row crops and dairy products, with vested interest in improving soil health through management practices and utilizing resources that are abundant and in proximity, such as dairy manure. In addition, research in this region focused on soil health is on the rise within the sugarbeet industry, as growers of this major state commodity strive to lower inputs, increase yield, and conserve and improve the ongoing performance of their fields. This thesis has two major objectives: to establish a comprehensive review of the impacts of dairy manure on soil physical and biological properties and develop an integrated soil-health perspective on the effects of different management practices on sugarbeet systems.
A systematic review was performed, producing a collection of existing literature detailing the impacts of dairy cattle manure on soil biophysical properties. Twenty-seven publications were selected that met qualifying factors reporting data on SOM, MBC, available C, bulk density, aggregate stability, and hydraulic conductivity. Variables considered included application method (surface applied/incorporated), manure form (solid/liquid), duration, and soil texture. Percent change was calculated for treatments with manure compared to inorganic fertilizer and/or no-amendment. In summary, dairy manure was found to increase SOM and lower bulk density with greater percent increases in SOM with longer durations of application. Differences were seen in available C based on application method and change in SOM was impacted by form of manure. Some soil health indicators, such as bulk density, were improved in every case when compared to inorganic fertilizer alone.
A survey study was carried out assessing the impacts of management practices on soil health in sugarbeet fields in the Snake River Plain. Twelve fields were selected that had been undergoing one of the following management practices for at least 5 years: no-till (NT), strip-till cover crop (STCC), organic matter amended with manure or compost (OMA), and conventionally managed (CT). Over twenty physical, chemical, and biochemical metrics were observed. No significant differences were found in sugarbeet yield and quality, POxC, or nitrogen mineralization between management types. Significant differences were seen in aggregate stability, with reduced till practices resulting in soil with the highest compared to the conventionally tilled fields. Strong correlations were seen between some properties, such as SOM and POxC, and penetration resistance and soil salts. A large range of variability was seen overall, with effects of management varying from field to field. Many expected correlations between soil properties were damped or altered by the effects of others, highlighting the intricate network of soil property interactions. Results indicate a more appropriate usage of soil health metrics may be to use indicators to track change within individual fields, rather than making assumptions of soil characteristics in different locations based on management.