The fate of fertilizer nitrogen in raspberry production as affected by nitrogen inputs and irrigation regime : an experiment in the Fraser Valley, British Columbia

The lower Fraser Valley is an important agricultural region in British Columbia, Canada whose central portion is underlain by the Abbotsford-Sumas Aquifer. The aquifer has been identified as vulnerable and high concentrations of nitrate that have been linked to application of nitrogen (N) fertilizers to crops, particularly red raspberry. The region has the most concentrated raspberry production in Canada and therefore raspberry management has the potential to influence N losses to the aquifer. The goal of this study was to determine how variations in irrigation and N fertilization affect the fate of N from fertilizer (NFF) from one year’s application in order to identify practices that maximize crop acquisition of N and minimize the risks of nitrate leaching. Specific practices that were compared include rate of N inputs (50 vs. 100 kg N ha-¹), mode of N application (fertigation vs. broadcast), and irrigation method (fixed schedule vs. plant need based). To determine the influences of different management practices, the fate of NFF was traced by applying ¹⁵N labeled fertilizer in April and May 2011, as a split application, and then analyzing movement of the ¹⁵N into plant tissues, leachate, and soil at four critical times during the subsequent year. This study found that irrigation regime had a strong influence on N losses by leaching. Reduced water inputs reduced nitrate -N leaching and did not negatively affect productivity. Fertigation, which employed a combination of reduced N and water inputs, improved plant acquisition of NFF, resulting in reduced leaching of nitrate-N. The 50 kg N ha-¹ treatments produced berry yields comparable to the 100 kg N ha-¹ treatments while the higher N inputs resulted in greater NFF being removed from the system by berry harvest and pruning. Peak plant uptake of NFF was found to be in July 2011 with the maximum held in the floricane component. By August, NFF content in both the floricane and primocane components had decreased and the primocane component had relocated NFF from the leaves to the cane. After the drop between July and August, NFF in the system remained relatively stable into the following growing season.Arts and Sciences, Irving K. Barber School of (Okanagan)Earth, Environmental and Geographic Sciences, Department of (Okanagan)Graduat