Effect of Split Variable Rate Fertilizationon Ammonia Volatilization in Wild Blueberry Cropping System

Abstract

<abstract><title><italic>Abstract. </italic></title> Currently, fertilizer is applied uniformly in wild blueberry (Vaccinium angustifolium. Ait) fields, once in a two year production cycle, without considering substantial variation in soil/plant characteristics, topographic features, and fruit yield. The heavy rainfall, gentle to severe topography with high proportion of bare spots, and weed patches in wild blueberry fields emphasizes the need for variable rate split (VRS) fertilization to avoid environmental contamination. Two commercial wild blueberry fields were selected in central Nova Scotia to examine the impact of VRS fertilization on ammonia volatilization losses. Management zones (MZs) were delineated based on slope variation within the selected fields (steep slope (Zone-1), moderate slope (Zone-2), and low slope areas (Zone-3)). The fields were divided into two sections (VRS section and uniform rate (UR) section). Global positioning system (GPS) guided prescription maps based on slope variation were generated in ArcGIS 10 software to apply fertilizer in both fields. In VRS section, fertilizer was applied three times with commercial variable rate (VR) fertilizer spreader in Zone-1, Zone-2, and Zone-3 with fertilization rates of 66, 50, 33, and kg ha^-1, respectively. Single uniform grower’s fertilizer rate (200 kg ha^-1) was applied in UR sections of the selected fields for comparison. The ammonia volatilization trials were established under VRS and UR fertilized sections of the selected fields immediately following the fertilization. The ammonia volatilization samples were collected after each fertilization in VRS sections and once in UR sections. The samples were analyzed for ammonium nitrogen (NH₄⁺-N) concentrations. Leaf samples were collected in third week of July at tip-dieback stage and analyzed for leaf nutrient concentrations. The results of repeated measure analysis of variance showed ammonia volatilization losses were significantly (p < 0.05) lower in VRS sections as compared to uniformly fertilized sections of the selected fields. Secondly, the study found that the leaf nutrient concentrations were not reduced using VRS fertilization. Results of this study also indicated that the VRS fertilization improved the nitrogen use efficiency and reduced the ammonia volatilization in wild blueberry fields.