Nitrogen and sulfur fertilizers effects on growth and yield of Brassica carinata in South Dakota

Carinata ( Brassica carinata A. Braun), a non‐food oilseed and an alternative biofuel feedstock, has received attention for its potential as a low‐input option for production in the semi‐arid regions of the Northern Great Plains (NGP). This study was conducted to (a) determine the economic optimum N and S fertilization rates and (b) determine the interactive effects of N and S fertilization on seed yield and agronomic traits in carinata. The field experiment conducted in 2017 and 2018 at Brookings, SD, had four N rates (56, 84, 112, and 140 kg N ha −1 ) and three S rates (0, 22, and 45 kg S ha −1 ). Increasing N rate increased seed and oil yield each peaking at 112 kg N ha −1 in both years. Applying S fertilizer increased seed and oil yield and oil concentration over the control but with the two S rates performing similar in both years. In the absence of S application, seed yield was reduced irrespective of N rate indicating that S is critical to obtain a positive response to N fertilizer. Economically optimal N rate ranged from 47 to 93 kg N ha −1 whereas economic optimum S rate ranged from 20 to 26 kg S ha −1 . The economic optimum yield ranged from 1.0 Mg ha −1 to 1.5 Mg ha −1 . These findings suggest that carinata seed yield and agronomic trait response to N fertilization can vary depending on S availability in the soil.