Potential for hyperspectral technology in wild blueberry ( Vaccinium angustifolium Ait.) production

The feasibility of using the FieldSpecRTM 3 hand-held hyperspectral radiometer (Analytical Spectral Devices Inc., Boulder CO) as a sensor for precision spraying in wild blueberries (Vaccinium angustifolium Ait.) was investigated. A field experiment was conducted at two commercial fields in Nova Scotia during 2006 and 2007 to identify problematic vegetation for spectral discrimination as well as understand the impact of existing pre- and post emergence herbicides on vegetation dynamics. A randomized complete block design was used with herbicides applied at label rates. Treatments consisted of: (1) no herbicide application, (2) application of hexazinone (trade name VelparRTM),(3) application of fluazifop-p-butyl (trade name VentureRTM), and (4) application of both hexazinone and fluazifop-p-butyl. Plot uniformity was measured with a 15 cm diameter circular quadrat, 16 times within a plot, over four timings in the crop year of production. Spectral signatures were acquired for three timings. A second experiment was established to estimate leaf area index (LAI) and yield of wild blueberry stands, using four stem density treatments on two commercial fields in Nova Scotia during 2007. The most frequently occurring uncontrolled weeds were bunchberry ( Cornus canadensis L.), sheep sorrel (Rumex acetosella L.), cow-wheat (Melampyrum lineare Desr.) and hairy-cap moss (Polytrichum commune Hedw.). Sheep sorrel was chosen for spectral discrimination due to: (1) the occurance across sites and (2) the increasing concern of distribution and desired suppression by the wild blueberry industry. Discrimination accuracy of sheep sorrel infested wild blueberry canopies increased from anthesis (63%) to harvest (86%). Successfully modelled wild blueberry parameters include: (1) anthesis LAI (R2=0.90), (2) anthesis flower number (R2=0.90) and (3) harvest berry weight (R2=0.91). With the spectral discrimination of sheep sorrel and estimation of LAI and yield, the use of hyperspectral radiometry in wild blueberries is promising.