Groundcover Management System and Nutrient Source Impact Physical Soil Quality Indicators in an Organically Managed Apple Orchard.

摘要

In March 2006, four groundcover management systems (GMS) and two nutrient sources (NS) were implemented for their ability to alter the soil physical condition of a newly established, organically managed apple (Malus x domestica Borkh.) orchard. Annual applications of municipal green compost (GC), shredded office paper (SP), wood chips (WC), and mow-blow (MB) grass mulch were utilized as GMS, and NS supplied to trees were from composted poultry litter (PL), a commercial organic fertilizer (CF), or an untreated control (NF) in a 4x3 factorial study. An established, conventionally-managed orchard was located adjacent to the organic research orchard on the same silt loam soil. Physical soil characteristics were measured from the conventional orchard providing a qualitative comparison of orchard management systems. Soil organic matter (SOM) concentration averaged 1.5% from 0 - 10 cm depth across all treatments at orchard establishment (2006). By 2012, SOM increased to 5.6% in GC, and SOM in MB, SP, and WC increased to 2.6%, 3.0%, and 3.2%, respectively. Commercial organic fertilizer and NF treatments with GC resulted in greatest SOM increases. The change in SOM impacted physical soil characteristics. Mow-blow treatments provided the least measured change in soil quality and served as a comparator to other GMS not measured in 2006. Significant increases in estimated plant available water, water stable aggregate formation, water infiltration rate, and saturated hydraulic conductivity were observed in GC. No differences were found in bulk density (BD) in 2006 from 0 - 6 cm, but BD decreased in following years for all GMS. All GMS treatments increased TC and TN concentrations from 2006 to 2011 in the top 7.5 cm soil layer, most significantly in GC. The greatest increases in TC and TN contents from 2006 were also observed in the GC treatments. Compared to the conventional orchard, GC most improved soil quality. Collectively, the soil quality indicators measured in this study show the addition of GMS and organic NS has improved soil quality since organic orchard establishment, and are a tangible means of meeting NOP requirements for improving soil quality in Ozark Highlands apple orchards concurrent with production of certified organic crops.