Nitrogen Uptake and Use Efficiency in Winter Camelina with Applied N

Maize (Zea mays L.) and soybean [Glycine max (L.) Merr.] rotations in the upper Midwest are highly productive. However, these narrow rotations are followed by a long winter fallow period. Over time, this has contributed to the loss of agroecological functioning, including increased ground water pollution from nitrate-nitrogen (NO₃–N). Winter camelina [Camelina sativa (L.) Crantz] is a third crop that could grow during this fallow period, but its nitrogen (N) use and efficiency are not well known. A study was conducted at three locations in the U.S. upper Midwest to determine the N uptake and use efficiency of winter camelina in response to applied N and N application timing. Agronomic efficiency (AE), internal efficiency (IE), and nitrogen recovery efficiency (NRE) tended to decrease with increasing N rates, especially beyond 67 kg N ha⁻¹ in most instances. Total N uptake ranged from 34 to 176 kg ha⁻¹ across N rates, and was on average 1.5 fold the applied rate. Based on the observed decline in N use efficiency with increasing N rates, an application rate of 67 kg N ha⁻¹ appears to balance efficient N use, high yield, and lower environmental risk compared to higher N rates.