Uniformity of Sand Deposition on Cranberry Farms and Implications for Swamp Dodder Control

Abstract

Uniformity of sand deposition on cranberry (Vaccinium macrocarpon) farms was examined to evaluate the potential use of two sanding methods to suppress swamp dodder (Cuscuta gronovii) seedling emergence by seed burial. During a 2-year study, 24 farms were evaluated with sand applied by either water barge or directly on ice. To measure the depth of sand deposited on the surface, soil cores were taken every 5 m in a grid pattern on a randomly selected portion of a commercial Massachusetts cranberry farm. Both application methods delivered nonuniform depositions of sand with the majority of the samples measuring less than the target depth. Surface diagrams depicting sand depths indicated no particular patterns of error or deposition that could be advantageously adjusted by the grower at the time of application. Mean actual: target depth ratios were 63% and 66% for barge and ice sanding, respectively (100% indicating actual equaled target). In the best scenario (two farms), 47% of the sanded area received less than the target amount; 11 farms had at least 90% of actual sand depths below the target depth. For farmers targeting 25-mm sand depths (depth expected to suppress dodder germination), the mean actual: target depth ratio was 58%, indicating half of the actual sand depths measured less than 15 mm. Compaction of the sand layer due to the elapsed time period (6 weeks or more) between sand application and measurement may have contributed to the large number of samples that were lower than the target depth. Even so, the irregularity of deposition patterns and the large proportion of sand depths that were less than 25 mm indicated adequate suppression of dodder seedling emergence would be unlikely with either sanding method.