Soil Chemical and Biochemical Surveys of Sweet Cherry Agroecosystems In the Pacific Northwest.

We evaluated the effects of four orchard floor management (OFM) practices under nine sweet cherry orchards on soil chemical properties and biochemical functioning. Our objective was to identify soil properties most sensitive to OFM regardless of soil type, texture, climate, and aboveground management. OFM treatments were: 1) herbicide-treated bare ground (BARE), 2) landscape cloth (CLOTH), 3) organic amendments (OAm), and 4) ‘living’ organic amendments (LOAm). Soil samples (0-15 and 15-30cm depths) were collected in October 2006 and 2007 and analyzed for nutrients, pH and organic matter. Soil biochemical properties measured included five enzyme activities, N mineralization potential, and particulate organic matter (POM). Additionally in 2007, FAME profiles (for microbial community structure characterization) and leaf nutrient status were determined. Data were analyzed using non-metric multi-dimensional scaling (NMDS) and multi-response permutation procedures (MRPP) to determine group separations and analysis of variance to compare OFM. Using NMDS and MRPP analyses, biochemical variables were most sensitive to separating samples by treatment: LOAm was different from all other treatments and CLOTH was similar to OAm, which were different from BARE. LOAm generally had the highest biochemical properties, SOM, and available P. Soil samples under the LOAm treatment were separated from the other treatments according to chemical properties or FAME profiles, but more distinct separation among samples was observed according to geographic location with average annual precipitation and soil texture as important explanatory variables. Other variables that separated samples by location included OM, CEC, P, Zn, Mn, Cu, Mg, and NO3--N. Of the 44 variables investigated by ANOVA, N mineralization rate, beta-D-glucosidase and N-acetyl-beta-D-glucosaminidase activities were affected by treatment at 0-15cm with LOAm samples higher than all other treatments. This survey showed that biochemical variables are most sensitive to OFM practices and should be investigated further to determine how they affect orchard performance.