Effects of ridge-furrow film mulching and nitrogen fertilization on growth, seed yield and water productivity of winter oilseed rape (Brassica napus L.) in Northwestern China

Poor soil conditions and drought stress are two main factors restricting the agriculture production in arid and semiarid areas of China. The ridge-furrow film mulching (RFFM) cultivation pattern has been shown to have the ability of improving yield and water productivity (WP) of maize, wheat and potato. However, its effect on winter oilseed rape is not clear. A two-year (2014-2016) field experiment was conducted to determine whether the RFFM cultivation pattern has the potential of improving winter oilseed rape productivity under dryland conditions. The optimal nitrogen (N) application rate for winter oilseed rape maximum yield under the RFFM cultivation pattern was also measured. Winter oilseed rape was planted in RFFM and flat cultivation patterns, both with six nitrogen (N) application rates (0, 60, 120, 180, 240 and 300 kg ha−1). The results showed that compared to the flat cultivation pattern, the RFFM cultivation pattern greatly increased leaf area index (LAI) by 18.7% on average, aboveground dry matter (ADM) by 25.6% at harvest, seed yield by 23.8% and WP by 32.7%, and decreased evapotranspiration (ET) by 7.2%. Application of N fertilizer remarkably increased LAI, ADM, ET, seed yield and WP of winter oilseed rape under both cultivation patterns. Under the RFFM cultivation pattern, average seed yield, WP, and economic benefit in 240 kg N ha−1 were 2904 kg ha−1, 8.8 kg ha−1 mm−1, and 1259.6 $ ha−1, respectively, and were significantly higher than the other five N rates. The optimal N-application amount for maximum winter oilseed rape productivity under the RFFM cultivation pattern was found to be 240 kg N ha−1. In conclusion, the RFFM cultivation pattern has the potential of improving the seed yield and WP of winter oilseed rape in northwest China.