Ridge–furrow with plastic film mulching in combination with reduced nitrogen application rate improves water productivity and yield of sunflower in dry semi–humid regions

Ridge–furrow with plastic film mulching (RFPFM) is quite successful under dryland agriculture. However, its suitability for sunflower (Helianthus annuus L.) production with different plastic film mulching techniques such as ridge–furrow fully covered with plastic film mulching (FM) and half mulching (HM), in combination with appropriate nitrogen (N) fertilizer management remains uncertain. The current research investigated the performance of sunflower crop under three planting patterns (HM, FM and CP, i.e., conventional planting on flat land without plastic film mulching) and two N doses (120 and 240 kg N ha–1) in northwest China. The objectives were to evaluate the soil hydrothermal conditions, crop performance, water productivity (WP), N harvest index (NHI) and seed yield, under different combinations of these treatments. The results showed that both HM and FM had 1.8 °C higher topsoil temperature during seedling stage and soil moisture (+21 % and +30 %) during the whole growth stage, respectively, when compared to CP. The favorable hydrothermal conditions under HM and FM accelerated the seedling emergence and shortened the crop growth duration by nearly 5 days, and further improved seed yield (+23 and +33 %), WP (+26 and +36 %), and N uptake (+20 and +24 %), compared to CP. A comparison between FM and HM treatments did not show a significant increase in WP or yield for the former, despite improved soil hydrothermal conditions. In addition, increasing N application rate from 120 to 240 kg N ha–1 did not lead to a consistent and significant effect on total N uptake, WP and seed yield. Overall, the present study suggests that HM, when coupled with a reduced N dose, can replace FM in sunflower production. This approach reduces the use of plastic film and N fertilizer, while efficiently conserving water, enhancing WP and improving seed yield of sunflower under dry and semi–humid conditions.