SPATIAL AND TEMPORAL VARIABILITY OF CRANBERRY SOIL PH

Abstract

Soil pH is an important factor impacting plant nutrient availability and soil microorganism activity. Therefore, the careful monitoring of soil pH characteristics may predict plant productivity. This is especially significant for the perennial crop cranberry (Vaccinium macrocarpon Ait.) that is periodically flooded and, as a typical Ericaceous plant, requires an acidic soil. Temporal and spatial variability in pH can impact plant vigor during much of its active growth. Typically in cranberry production systems soil samples are collected from multiple locations in a field, composited, and analyzed for soil pH. The sampling is generally conducted in the spring or fall to a depth of 15 cm, the normal maximum depth of cranberry root growth. We hypothesized that cranberry soil pH varies not only from region to region and field to field but within field (spatially) and throughout the growing season (temporally). To test this, a minimum of 4 fields were identified in the five principal US cranberry growing regions - Massachusetts, New Jersey, Oregon, Washington, and Wisconsin. Samples were collected from 0 - 15 cm depth in a 1 m sampling radius of twelve georeferenced sample points within each field. Samples were collected at monthly intervals throughout the growing season to evaluate temporal variability. In several of the growing regions samples were also collected at 2 depths - 0 to 7.5 cm and 0 to 15 cm - to determine if a shallow soil sample might be a better indicator of soil pH in the concentrated root zone. The data indicate that the greatest variability in soil pH is from field to field although both spatial and temporal variability occurs within a field and that differences related to sampling depth were not great enough to justify modifying current practices.