Evaluation of Variable Rate Nitrogen and Reduced Irrigation Management for Potato Production.

Availability of soil moisture and N are primary limiting factors for potato growth on sandy soils in humid climates. This study was conducted to determine whether tuber yield or net economic return were affected by variable rate (VR) N or reduced irrigation management, and to evaluate methods to detect crop N status including remote sensing, chlorophyll meter, and petiole sampling. The effects of six N rate, source, and timing treatments and two irrigation rate treatments on tuber yield, quality, and net profitability for potato [Solanum tuberosum (L.) 'Russet Burbank'] were investigated in 2016 and 2017 at Becker, MN, on a Hubbard loamy sand. A VR N treatment based on the N sufficiency index (NSI) approach using remote sensing was also tested. Irrigation treatments included a conventional rate (100%) and a reduced rate (85%). The VR treatment reduced N applied relative to the recommended rate by 22 and 44 kg N ha^-1 in 2016 and 2017, respectively. Irrigation rate was reduced by 29 and 33 mm in 2016 and 2017, respectively. Neither VR N nor reduced irrigation produced significant differences in tuber yield or net return compared to full rate treatments. Using NSI, remote sensing was able to predict crop N status with comparable accuracy to petiole sampling while chlorophyll meter measurements were less sensitive to detecting crop N stress. Managing N using remote sensing and reducing irrigation rate are strategies that could be used on sandy soils in humid climates without having agronomic or economic impacts on potato production. [ABSTRACT FROM AUTHOR]