Effects of ridge-furrow with plastic film mulching combining with various urea types on water productivity and yield of potato in a dryland farming system

Ridge-furrow with plastic film mulching (RM) has the potential to enhance crop yields and water productivity, particularly in semi-arid regions. However, the combined effects of RM and various urea types on rainfed potato (Solanum tuberosum L.) production remain unclear. A three-year field experiment (2018–2020) was conducted to elucidate the effects of the RM combined with various urea types on water productivity, tuber yield, and economic benefits in a dryland farming system. Treatments consisted of two mulching patterns [RM and no plastic film mulching (NM)], combined with the application of three urea types [common urea (U), controlled-release urea (C), and mixed C and U at a ratio of 1:1 (CU)]. Our results indicated that compared to NM, the RM system reduced soil evaporative losses, which ultimately increased average soil water storage for the 0–60 cm soil layer by 6.7% (P < 0.05). In addition, RM increased the mean soil temperature for the 0–10 cm soil layer by 1.4 °C compared with NM. These changes in soil under RM helped increase plant height, leaf chlorophyll, and nitrogen balance index, but reduced leaf flavonoid, thereby improving tuber yield. The application of CU further improved plant height, leaf chlorophyll, and nitrogen balance index, which allowed the exploitation of more soil water to increase tuber yield and water productivity (P < 0.05). The interactions of mulching and urea type had significant influence on the tuber yield, water productivity, and partial factor productivity of nitrogen, especially with the RMCU. RMCU significantly (P < 0.05) increased potato yield (up to 23.5%), water productivity (23.7%), partial factor productivity of nitrogen (23.5%), and economic benefit (38.4%), compared to the NMU during both drought and non-drought growing seasons. We conclude that compared with other treatments, RMCU resulted in the highest tuber yield, water productivity, and economic benefit across three growing seasons and should be considered an effective strategy to foster sustainable potato production in dryland farming systems.