Soil Moisture Management and Variability in Cranberry Beds

Abstract. Summer irrigation is a major management input in cranberry production, and traditionally, cranberry beds have received 25 mm of water per week from either rain, capillary action from groundwater, irrigation , or some combination of these from late spring through the summer. However, environmental conditions and drainage characteristics can vary from bog to bog, meaning that the 25-mm rule does not always result in ideal soil moisture conditions. Measurement of cranberry soil water status has been based on two technologies; (i) measuring the amount of water in the soil using volumetric water sensors or measuring the depth of the water table in the soil by means of water level floats, and (ii) measuring the energy status of the water (water potential) using a tensiometer. Ideally, irrigation scheduling should consider plant processes in conjunction with the status of the soil water matrix to quantify water stress under different soil conditions. This project assessed various tools of measuring soil water moisture in cranberry beds including a FieldScout TDR 300 Soil Moisture Meter and wireless tensiometers. Six cranberry beds primarily growing cultivar ‘Stevens’ were monitored throughout the growing season for tension readings; wireless tensiometers reported data to a web portal at 15-min intervals, making it easy to download data. The FieldScout TDR 300 Soil Moisture Meter was used to develop soil moisture maps of monitored beds on a weekly basis during the season. The Moisture Meter was connected to a GPS unit so that generated maps could be overlaid on a satellite image of the bed providing precise locations of soil moisture content at the time of measurement. The FieldScout TDR 300 Soil Moisture Meter maps indicated a great variability in soil moisture throughout monitored cranberry beds. Soil moisture variability demonstrated a 10-20% range of differences. This lack of uniformity in soil moisture content makes it difficult to choose an ideal location for installing a soil moisture monitoring device such as a tensiometer. The relationship between soil moisture content and tension was developed in a previous project and has been reported in MA (Jeranyama et al., 2014) and in Canada (Pelletier et al., 2013)