Nitrogen Source and Timing for Optimal Yield of Irrigated Processing Potato in Manitoba.

For irrigated potato production systems delaying nitrogen (N) applications to coincide with crop N uptake serves as a strategy to reduce the total amount of N applied and can simultaneously limit the potential for nitrate leaching to groundwater. The current study sought to compare alternative 4R nitrogen management practices (timing, source) and different methods of applying synthetic N fertilizers on the yield and quality of Russet Burbank potatoes.  Based on spring soil test N levels urea, Environmentally Smart Nitrogen (ESN)®, SuperU™, along with urea-ammonium nitrate (UAN) applied as fertigation treatments, were applied at 80% of the optimal N rate at two locations (Carman, Carberry) in Manitoba in 2013 and 2014.  Soil and petiole samples were collected prior to fertilizer application and following fertigation to measure soil and plant N status throughout the growing season.  With respect to yield, no significant relationship could be determined between petiole and soil nitrate levels and marketable tuber yields.  At the Carman location tuber yields were comparable across both growing seasons.  However, at the Carberry location, tuber yields in 2014 were lower due to seed rot.  Across all site years examined nitrogen fertility treatments led to significant increases in tuber yield relative to untreated checks.  When averaged across locations marketable tuber yields were highest for ESN (449 cwt) and fertigation A (446 cwt) treatments in the 2013 growing season, and banded urea (434 cwt) in the 2014 growing season.