ASABE Technical Library - Abstract

Wild blueberry producers apply agrochemicals uniformly without considering substantial variation in soil properties and topographic features that may affect fruit yield within a field and pollute environment. A wild blueberry field was selected in central Nova Scotia, Canada to evaluate the impact of variable rate (VR) fertilization on nutrient losses in surface runoff, from steep slope to low lying areas, and crop productivity. The field was divided into three subfields (Field 1, Field 2, and Field 3) under three management zones (Zone 1, Z1; Zone 2, Z2; and Zone 3, Z3). The runoff plots were installed to collect surface runoff samples from different zones of the field. Three fertilizer (NPK: 16.5 – 34.5 – 4.5, respectively) rates (200,150, and 100 kg ha^-1 for Z1, Z2, Z3, respectively) were applied in runoff plots of VR treatment using fertilizer spreader. Uniform fertilizer rate of 200 kg ha^-1 for comparison was applied in runoff plots of uniform application (UA) treatment. No fertilizer was applied in runoff plots of control treatment. The surface runoff samples were collected after every heavy rainfall event and analyzed for total phosphorus (TP), dissolved reactive phosphorus (DRP), particulate phosphorus (PP), and inorganic nitrogen concentrations. The VR treatment significantly (p≤0.05) decreased TP, DRP, PP, and inorganic nitrogen losses in surface runoff as compared to UA. Plant growth parameters and fruit yield were also collected from runoff plots. Plants in UA treatment were taller than VR treatment in low lying areas. Numbers of buds per stem were significantly affected by fertilizer treatments. The fruit yield in VR treatment was non-significantly different than UA treatment. The VR fertilizer application used 40% less fertilizer than standard UA of fertilizer. The VR fertilization could reduce nutrients loading in surface runoff from wild blueberry fields. The runoff plots could be used to accurately determine the surface runoff from small-scale runoff plots. However, the construction of runoff plots and data collection at field scale is laborious and time consuming.