Date of Award


Document Type


Degree Name

Master of Science (MS)

Legacy Department

Plant and Environmental Science

Committee Chair/Advisor

Zehnder, Geoffrey

Committee Member

Jiang , Xiuping

Committee Member

Knap , Halina

Committee Member

Wells , Christina


Organic vegetable production is a rapidly growing sector of agriculture. Due to limitations on synthetic inputs imposed by the USDA National Organic Program (NOP), research is necessary to determine which soil amendments are viable options for organic farmers. Field trials were conducted at the Clemson University Calhoun Fields Laboratory Student Organic Farm. A variety of vegetable crops were grown, including Jericho lettuce in the springs of 2005 and 2006, yellow crookneck squash in the summers of 2005 and 2006, and Early Jersey Wakefield cabbage in the fall of 2005. Soil amendment treatments consisted of combinations of the following: poultry compost, poultry litter, dairy compost, dairy manure, blood meal, feather meal, and Fertrell 5-5-3. Poultry litter and dairy manure were applied 120 days prior to harvest, in accordance with NOP standards. Yield and weekly plant growth were measured. The Clemson University Agricultural Service Laboratory performed compost, manure, plant tissue and post-harvest soil analyses. Poultry compost resulted in the greatest yield and plant growth in all trials, though differences were not significant in the spring 2006 lettuce and summer 2006 squash trials. Poultry litter and dairy manure resulted in depressed yields and plant growth as compared to the compost treatments. Trends showed soil and tissue phosphorus to be greatest in poultry compost and poultry litter treatments. Application of poultry compost should be alternated with other soil amendments or applied according to phosphorus requirement of a crop to avoid phosphorus buildup in the soil.



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