Topographic and Soil Apparent Electrical Conductivity-Driven Management Zones for Nitrogen Fertilization Under Wild Lowbush Blueberry Production

Wild lowbush blueberry (Vaccinium angustifolium Ait.) production is conducted in fields with heterogeneous growing conditions due to topography, soil properties, and crop density. This crop generally grows on sandy, acidic, and nutrient-poor soils. Precision agriculture technologies provide means to manage different cropping areas according to their site-specific needs. The objective was to determine wild blueberry crop response to nitrogen (N) fertilization according to four management zones in one undulated field (FieldUnd) and one flat field (FieldFlat). Four management zones were established on each field: Low Elevation: High ECa; Low Elevation: Low ECa; High Elevation: High ECa; and High Elevation: Low ECa. The N treatments consisted of four rates of ammonium sulfate (0 to 90 kg N ha−1) applied in the sprout year. Fruit yield was measured in the production year. Soil pH and ammonium (NH4-N) were determined. Fruit yields increased by 72% in the FieldUnd and 54% in the FieldFlat with N rates. For the FieldUnd, the response to N fertilization was greater when the soil ECa was Low with High Elevation (increase of 2242 kg ha−1), and for the FieldFlat, the response was greater when the soil elevation was High but with High ECa (increase of 2335 kg ha−1). Nitrogen fertilization had a rapid effect on soil pH but management zones had limited effect. Soil NH4-N increased rapidly after N application. The residual N remained under 3 kg NH4-N ha−1. The greatest response to N fertilizer was obtained in management zones with High Elevation, regardless of the field, but under Low ECa in the FieldUnd and High ECa in the FieldFlat.