Cranberry (Vaccinium macrocarpon Ait.) evapotranspiration (ET) has not been documented. Micrometeorological techniques based on canopy temperature minus air temperature were used to estimate ET on `Stevens' and `Crowley' cranberry at Long Beach (lat. ≈46°20′N, long. 124°W) and Grayland (lat. ≈46°47′N, long. 124°W), Wash., in 1991 and 1992, respectively. Cranberry ET was 55% of Priestley–Taylor reference ET and ranged from <0.5 to >4 mm·d–1. The Priestley–Taylor reference ET was a very good predictor of cranberry ET (r 2 = 0.795). Running 7-day cumulative ET ranged from 7 to 17 mm·week–1.
M.J. Hattendorf and J.R. Davenport
J.R. Davenport, C.A. Redulla, M.J. Hattendorf, R.G. Evans, and R.A. Boydston
An accurate yield map is imperative for successful precision farming. For 3 years (1998 to 2000) two to four potato (Solanum tuberosum) fields on a commercial farm in southeastern Washington were yield-monitored using commercial yield monitoring equipment without operator interaction. Multiple potato diggers were used to harvest the fields and diggers used were not necessarily the same at each harvest. In all years, yield monitoring data were missing due to equipment failure or lack of yield monitoring equipment on all diggers. Banding, due to dissimilar calibrations, different equipment used, or differential digger performance was observed in 1998 and 2000. Based on experience described here, some yield monitor data need minimal postprocessing or correction, other data need substantial postprocessing to make them usable, and other data may not be reliable due to equipment failure, improper calibration, or other causes. Even with preharvest calibration, it is still likely that the potato yield monitor data will need differential postprocessing, indicating that yield maps lack accuracy. In addition, comparison to yield data collected at multiple points within the field, this study found that the yield monitor over estimated potato yield. Thus, with some postprocessing, a useful yield map showing within field differences is possible. However, without significant postprocessing, the practice of using multiple diggers and yield monitors for potato harvest, both within and between fields, severely limits the ability to make consistent yield maps in commercial potato operations.