Skagit Soil Quality Study: Raw Data

High soil quality is tantamount to agricultural sustainability. Soil quality refers to the soil’s ability to function as a living system in sustaining biological productivity and promoting soil organismal health. The ­­­­­­­­­­­­­­­­­­­objective of this research was to investigate whether differences in soil quality between organically and conventionally farmed fields could be determined in matched pair comparisons. The soil parameters studied were soil moisture, soil compaction, pH, electrical conductivity, soil organic matter, and annelids. Research sites were vegetable fields in Skagit County, Washington, a county characterized by climate, soil, and water resources highly favorable for vegetable and bulb production. Farm fields were matched on farming and crop history, soil type, aspect, hydrology, climate, parent material, and relief. All soil sampling and associated field and laboratory work was conducted in the spring of 2013. Statistical analyses, including Cohen’s d to indicate small and medium effects, were conducted. Data averaged for all matched pairs showed statistically significant differences for pH (conventional fields), soil organic matter (organic fields), and annelids (organic fields). The Cohen’s d figures indicated a small-to-medium effect in increased soil moisture, a medium effect in decreased compaction, and a small effect in decreased electrical conductivity in organic compared to conventional fields. One reason for low pH in organic fields was the use of shallow tillage resulting in stratification with a more acidic pH in the top 30 cm of topsoil. Higher values in organic fields for soil organic matter are indicative of several factors, including the systematic use of organic matter (green manures, some compost) as part of a soil fertility management regimen. The statistically significant higher levels of SOM and annelids, although qualified, suggest a greater biological soil quality in organic farms in relation to their conventional counterparts. Confirmation of this effect is not surprising as the majority of the available research suggests similar results. At the very least, the results indicate a role that organic farm systems may play in improving biological properties of soil quality.