Management Effects on Soil Quality in Organic Vegetable Systems in Western Washington

K. Pritchett¹, A. C. Kennedy² and C. G. Cogger²

Abstract
Management practices in organic vegetable cropping systems can differ widely depending on soil, location, landscape, region, and climate. Soil quality indicators may help organic farmers choose the best management practices.

The objectives of this study were to: (i) assess the sensitivity of soil properties to detect differences in organic management systems; (ii) identify a minimum soil quality set for future analyses; and (iii) provide baseline data for future system comparisons of soil quality.

Data were collected from the first 3 yr of a field experiment comparing cropping systems (pasture every other year, relay cover crop, and post-harvest cover crop), tillage strategies (conventional tillage and modified tillage with a rotary spader), and amendments (broiler litter and on-farm compost) arranged in a split-split-plot design. Soil analyses included dehydrogenase and β-glucosidase activities, phospholipid fatty acid methyl esters (PLFA), substrate utilization using ECO plates (Biolog, Hayward, CA), total C, particulate organic matter C, bulk density, and aggregate stability.

Enzyme activities were more sensitive than PLFA and substrate utilization to changes in management. The β-glucosidase activity was greater in relay and pasture treatments than the post-harvest treatment and the modified (spader) tillage had greater β-glucosidase activity than the conventional tillage. There were no differences in β-glucosidase activity between amendments. Dehydrogenase activity showed transient responses to tillage and amendment. Soil C and bulk density were affected by amendment and showed more consistent differences among treatments than did other properties.

The changes occurring in soil properties may lead to early identification of differences among organic management practices.


Source
Soil Science Society of America Journal (2011) 75: 605-615
DOI: 10.2136/sssaj2009.0294


Author Locations and Affiliations
(1) USDA-ARS, 215 Johnson Hall, Washington State Univ., Pullman, WA 99164-6421
(2) Washington State Univ., 2606 West Pioneer, Puyallup, WA, 98371-4998


Posted April 2011