Effect of pine bark mulch on lowbush blueberry (vaccinium angustifolium) water demand

Abstract

Mulching has been reported to moderate soil temperatures, lessen the erosive effects of rain, suppress weeds, and reduce evapotranspiration losses from crops worldwide. Lowbush blueberry (Vaccinium angustifolium) growers seeking an alternative and/or a complement to supplemental irrigation require accurate crop-specific information on the water conserving benefits of mulch. Twenty-eight weighing lysimeters equipped with soil moisture monitors were used at five sites throughout the Downeast Region of Maine to compare water budgets of lowbush blueberry grown on un-mulched and mulched soils. Despite occurrence of the second wettest growing season in 60 years, April through September mean hourly soil water potential values at all sites indicated significantly (p < 0.001) drier conditions in un-mulched compared with mulched soils. Differences in soil water potential values between un-mulched and mulched soils were much more pronounced during three dry periods, totaling approximately 53 days, than during the 2009 growing season as a whole. Over the course of one 27 day dry-period, soil water potential values of un-mulched soils at two lysimeter stations indicated a need for irrigation more than 60% of the time, compared with 7-10% of the time for mulched soils. Mulching was found to reduce diurnal fluctuations of both soil water potential and volumetric water content. Early morning water deposition was significantly reduced by mulching at nearly all lysimeter stations; however, mulch-associated reductions in peak-hour evapotranspiration losses more than compensated for lower water inputs from dew and fog. During the three major periods of dry conditions, mulch reduced the evapotranspiration rate by an average of 0.045 ± 0.003 cm/day at three crop-rotation fields and 0.039 ± 0.027 cm/day at four prune-rotation fields. The greater variability in evapotranspiration rate reduction found among prune-rotation fields was considered due to differences in pruned shoot emergence from the mulch. These results indicate that mulching represents a viable method for alleviating drought-induced water stress for lowbush blueberry in Maine. © Taylor & Francis Group, LLC.