Organic Pasture–Crop Rotations: Pasture Duration and Input Level Impacts On Soil Physical Properties.

Understanding the soil characteristics and their changes under organic farming systems is crucial to explain their benefits, support their existence and ongoing success. However, the claim of “soil health sustainability” is still a debatable issue; more research needs to be done in this area.  This study was performed in an ongoing crop rotation at the West Virginia University Certified Organic Farm, specifically in plots currently in the rest (grassland) from tillage period.  A 3x2 factorial experiment with three blocks was analyzed using SAS (Proc GLM).  The first factor was years under grassland (orchardgrass/red clover 1, 2 or 3 years), and the second manure input level (with and without).  Dry aggregate stability, bulk density, penetration resistance, soil organic matter, and texture were our selected indicator soil variables.       
Using correlation analysis, we observed that moisture content was negatively related to clay content regardless of manure treatment, and for the without-manure treatment there was a positive relationship between soil moisture and sand content; the with-manure treatment showed lower soil bulk density.  We were able to determine correlations between variables, but we do not have enough experimental information to explain all our results.  ANOVA indicated that not all soil properties selected for this study were significantly affected by years under pasture and manure treatment.  However, there were significant effects on variables such as organic matter and aggregate size.  Soil penetration resistance was able to detect in some plots the presence of a plow pan caused by previous tillage in the rotation.  Ongoing studies will help to understand the effects of the crop rotation on soil dynamic properties (aggregate size, bulk density, penetration resistance and organic matter).