Date of Award


Degree Name

MS in Environmental Sciences and Management


Natural Resources Management


College of Agriculture, Food, and Environmental Sciences


Charlotte Decock

Advisor Department

Earth and Soil Sciences

Advisor College

College of Agriculture, Food, and Environmental Sciences


Compost application has become a common practice in vineyard management to increase soil and crop health, however, the environmental externalities such as greenhouse gas emissions (GHG) from cropping systems that utilize organic fertilizers, such as compost, is uncertain. Vermicompost, which is compost created through the digestion of organic matter by earthworms, and its related ‘extract’ are commonly thought to provide more benefits for soil and crop health compared to standard compost. However, organic fertilizers such as vermicompost, vermicompost extract, and compost have not been compared in their effects on soil health in Mediterranean vineyards. In this two-year study, I assessed the effect of vermicompost, vermicompost extract, and standard compost compared to a non-amended control treatment in their ability to affect soil health and GHG emissions on a vineyard under organic management in San Miguel, California. Soil from the under-vine location and mid-row location was collected and analyzed for soil organic matter (SOM), nutrient concentrations, and phospholipid fatty acids (PLFAs) as an indicator of microbial community structure. Additionally, GHG emissions were measured using static flux chambers in the under-vine location and mid-row location. The objective of this project is to inform the California Department of Food and Agriculture (CDFA) “Healthy Soils Program” on the soil amendment that will best increase soil health and decrease GHGs. Vermicompost increased the soil organic matter (SOM) and soil nitrate (NO3--N) concentrations, while standard compost increased soil potassium (K) and phosphorus (P) concentrations compared to the unamended control. There was no major impact of vermicompost extract on soil organic matter or soil nutrient contents. Microbial community structure did not experience any consistent shifts with the application of amendments. In addition, potential negative externalities of organic amendments in the form of GHGs were found to be negligible. My results demonstrate that different organic fertilizers lead to different soil health outcomes. Thus, organic fertilizer recommendations should be guided by a growers’ soil health goals, especially in the context of plant nutrition.