Core Ideas Brassica carinata is a new crop in the Northern Great Plains. Best management practices including N fertilizer recommendations should be developed. Seed yield and oil yield were optimized at 84 kg ha–1 of applied N fertilizer. Seed oil concentration decreased linearly at a rate of 0.26 g kg–1 for every 1 kg ha–1 increase in N rate. Economic optimum N rate varied from 60 to 81 kg N ha–1. ABSTRACT Ethiopian mustard (Brassica carinata A. Braun) is a non‐food oilseed crop that has received attention for its potential as a low‐input biofuel feedstock suitable for production in the semiarid regions of the Northern Great Plains (NGP). Because B. carinata is a new crop to the NGP, the best management practices have yet to be developed. The objective of the study was to evaluate the effects of N fertilizer rate on seed yield, seed oil concentration, and oil yield of B. carinata and to determine the economic optimum N fertilizer rates. Field studies were conducted at two locations in South Dakota to evaluate the response of two B. carinata varieties to five N fertilizer rates (0, 28, 56, 84, and 140 kg N ha−1) during the 2015 and 2016 growing seasons. Increasing N fertilizer rate increased seed yield and oil yield, each reaching a peak at 84 kg ha−1 N and then slowly decreasing following a quadratic model. On the other hand, increasing N rate linearly decreased seed oil concentration. The economic optimum N rate ranged from 60 to 81 kg N ha−1 depending on cost of N fertilizer and the price of carinata seed. These results show that the N requirement for B. carinata is lower than that for many crops grown in the NGP, including corn and small grains. These findings confirm that B. carinata requires low N fertility and has the potential for incorporation into cropping systems in the semiarid regions of the NGP.

Camelina (Camelina sativa L. Crantz,) a new oilseed crop in the Brassicaceae family has favorable agronomic traits and multiple food and industrial uses. Appropriate production practices for optimal camelina yield in temperate climates of North America are lacking. This study investigated the response of camelina seed yield and quality, and agronomic traits to applied N (5 levels, 0, 28, 56, 84, 140 kg ha−1) and four seeding rates (4.5, 9, 13, 17.5 kg ha−1). Separate experiments were conducted at four environments (site-years) for N and three environments for seeding rate in South Dakota. In three of the four environments, the highest N rate increased seed yield by 30 to 60% compared to the control. The increase in seed yield with increasing N rate was linear in a high yielding environment and quadratic in a low yielding environment. Increasing seeding rate increased plant stands but had inconsistent impacts on seed yield depending on location and year. Seed oil concentration ranged from 149 to 350 g kg−1, was inversely related to N rate but was not influenced by seeding rate.