Effects of Nitrogen and Water on Nutrient Uptake, Oil Productivity, and Composition of Descurainia sophia

Descurainia sophia has potential use as an oil crop because of its high productivity, high seed oil content, and unique fatty acid composition. With regard to oil fatty acid composition, obtainable oil from this plant can be of interest to the food and non-food industries such as pharmaceuticals, cosmetics, bio-fuels, paints, and lubricants. The aim of this research was to determine the effects of various nitrogen (N) rates and different irrigation regimes on oil productivity and composition as well as on potassium (K) and phosphorus (P) parameters in D. sophia. The field experiment was arranged as split-plot in a randomized complete block design with three replications. The main plots were three irrigation regimes: 0.1 maximum allowable depletion or deficiency (MAD) of available soil water (ASW) (I1), 0.2 MAD of ASW (I2), and 0.4 MAD of ASW (I4) in 2010 and 0.2 MAD of ASW (I2), 0.4 MAD of ASW (I4), and 0.8 MAD of ASW (I8) in 2011. Sub-plots were three N rates: 0 (N0), 200 (N200), and 300 (N300) kg N ha(-1). In the first year, there was no significant difference between irrigation regimes in terms of oil yield, while oil yield decreased when plants were exposed to drought stress in comparison with the well-water condition in the second year. The application of N increased oil yield; although there were no significant differences between N200 and N300 under any irrigation regime, the highest oil yield being observed at N application rate of 200 kg ha(-1) for the I1 (561.4 kg ha(-1)) and I2 (256.1 kg ha(-1)) regimes in 2010 and 2011, respectively. Accumulation (per ha) of 21.9-29.7 kg P (50-68 kg P2O5) and 102.1-126.3 kg K (123-152 kg K2O) was required to produce 256.1-561.4 kg ha(-1) of oil yield. Overall, for most of the traits studied over the 2 years, the response of D. sophia was mainly due to N rate rather than irrigation treatment. Linolenic, linoleic, and oleic acids comprised about 70% of the fatty acid composition. The results obtained here suggest that D. sophia oil yield, P and K uptakes, and levels of saturated and polyunsaturated fatty acids are positively influenced by increasing available N under different irrigation regimes.

Automated summary

Descurainia sophia has potential as an oil crop due to its high productivity, seed oil content, and unique fatty acid composition. This study found that nitrogen application significantly influenced oil yield and composition, as well as phosphorus and potassium parameters in D. sophia under different irrigation regimes.