Manipulating organic amendments to improve potato productivity and soil quality

Organic amendments are well-known for increasing crop production and improving soil quality. This study was designed to examine organic amendment effects on potato systems in Montcalm County, Michigan. In the first chapter, I investigated the effects of poultry compost application and cover crops in different potato rotations on yield and soil quality by establishing a laboratory experiment on soils collected in 2006. In the second chapter, I organized a field experiment at the Montcalm Research Farm to examine the effects of poultry compost application rates and timing on potato yields and soil quality in 2009 and 2010. The result from the first study showed that compost applications at a low rate (5.6 Mg ha-1) significantly increased potato yield in a potato-snap bean system both with and without rye cover and promoted soil microbial activity and soil characteristics. Additionally, clover cover crop significantly increased N in the light fraction as well as soil microbial activity in a potato-wheat system. In the second experiment, the compost applications were consistent across 2 years in increasing potato yield and also increasing soil pH, inorganic N, microbial biomass and enzyme activities. Scab incidence was negatively correlated to soil aggregate size > 1000 mum, net N mineralization, soil C&N, and cellobiohydrolase, glucosidase, and acid phosphatase activities. However, scab reduction was followed with high rates of compost application in the first year but not in second year. These results suggest that the combination of a low rate of compost with rye cover in potato-snap bean system will improve potato yields and soil quality.