Effect of Diverse Compost Products on Soil Quality and Potato Productivity.

Potato (Solanum tuberosum L.) is an important arable crop in the province of New Brunswick, Canada. However, the productivity and quality of potato fields has been declining for decades due to soil erosion and declining soil organic matter (SOM). Addition of compost may be an effective means to rapidly increase SOM and soil quality, and thereby increase productivity. This study compares five composts from a diversity of sources with a no compost control for their effects on soil quality and productivity. The compost products primarily contained wood wastes, poultry manure, or marine feedstocks, and the C:N ratio ranged from 10 to 63. High rates of compost (45 Mg ha^-1, dry weight) were fall-applied to field plots in a randomized complete block design with four replicates. Soil quality was evaluated by measuring physical, biological and chemical soil properties including water holding capacity, saturated hydraulic conductivity (k_sat), aggregate stability, bulk density (BD), resistance to penetration, particulate organic matter (POM), soil organic carbon (SOC), microbial biomass carbon (MBC), soil respiration, tuber disease, populations of Collembola, soil nutrient availability and cation exchange capacity (CEC). Soil quality was significantly affected by compost treatments in the growing season following application as indicated by a decrease in BD and an increase in k_sat and SOC. Compost products with lower ash (higher organic matter) tended to result in greater improvements in soil quality. However, changes in soil quality did not translate into an effect on tuber yield.  The lack of a measurable yield response to compost treatments was attributed to a combination of generally good initial soil quality and favourable growing season soil moisture conditions. This study will help identify the properties of compost which will be most suitable for use in potato production systems to enhance crop productivity and sustain soil quality.