Spatial and Temporal Variability of Potato Petiole Nitrogen in Response to Nitrogen Fertilizer, Implications for Variable Management.

Recent increases in the cost of fertilizer nitrogen have prompted producers to assess the potential to vary inputs in space and time to produce the highest marketable yield of potatoes.  A study was conducted from 2005 to 2007 near Brandon, Manitoba Canada, to assess the spatial variability of potato yield in upper, middle and lower landforms on a sandy loam soil in response to a range of nitrogen fertilizer rates and split application.  Petiole nitrogen, determined late in the growing season, was correlated with potato yield and was used to assess nitrogen sufficiency through the growing season.  Petiole nitrogen varied with time during the growing season, from uniform levels in June across all fertilizer treatments, to those which varied with fertilizer treatment in July and August.  Furthermore potato petiole nitrogen was higher in lower landforms during July and August, where higher total and marketable yields were recorded.  The potential for split application of nitrogen in potatoes based on management zones or sensor readings will have to be carefully assessed to account for temporal and spatial variability.