Rate and time of nitrogen fertilizer application for winter camelina

Winter camelina [Camelina sativa (L.) Crantz] is a potential third crop to diversify maize (Zea mays L.)–soybean [Glycine max (L.) Merr.] rotations in the upper Midwest. Although generally considered a low-input crop, empirical evidence suggests that it responds to added nitrogen (N) fertilization. However, optimum agronomic N rates have not been extensively studied in the region. A study was conducted from fall 2018 to fall 2020 at three locations to assess the effects of N fertilizer application time (all N-rate applied in spring and N-rate split applied in fall and spring) and rates on biomass and seed yield, and quality of winter camelina. Nitrogen application time did not affect yields. Both biomass and seed yields were greatly affected by N rates at all locations. Nitrogen had minimal effects on the oil and protein content of seeds, although greater N rates were associated with a slight decrease in oil content and a slight increase in protein content. The number of branches and silicles per plant varied significantly with N rates in all locations. The seed-to-silicle ratio showed significant differences in two out of three locations. Residual soil N increased with increasing N rates. A fertilization rate of 67 kg ha⁻¹ provided the highest camelina seed yield. While this study has determined the agronomic maximum rate for applied N, further economic analysis could provide comprehensive decision-making for farmers.