Increased dryland wheat economic returns, and decreased greenhouse gas emissions by year-round straw mulching in dryland areas of China

Dryland wheat (Triticum aestivum L.) usually suffers from amplified drought because of the decline in precipitation, and thus conserving soil moisture through mulching with plastic film or straw is inevitable. We carried out a 3-year field experiment to determine the most suitable mulching period and method for dryland wheat production based on grain yield, soil water storage, nitrate-nitrogen (NO3−-N) leaching, greenhouse gas emission intensity (GHGI) and economic profits. The experiment included two main treatments [summer fallow mulching (SFM) and year-round mulching (YRM)], and three sub-treatments [ridge plastic mulching plus furrow seeding (MP + F), whole-field plastic mulching plus bunch seeding (MP), and crop straw mulching (MS)]. The average grain yields for SFM and YRM were statistically similar. The average grain yields for MP + F, MP and MS were 5501, 5733 and 5690 kg ha−1 under SFM, and 5609, 6488 and 6462 kg ha−1 under YRM, respectively. The MS under YRM achieved the highest economic profit of 1587 US $ ha−1 per season. Both the average and yearly soil water contents before wheat sowing for SFM and YRM were statistically similar. However, MS showed greater potential for soil water storage before sowing, followed by MP and MP + F, under both YRM and SFM. For both SFM and YRM, the NO3− –N accumulation in the 0–200 cm soil profile at sowing time was significantly higher than at harvest, thus suggesting that no NO3− –N leaching occurred during the present study. The MS under YRM had the lowest GHGI of 314 kg CO2 eq Mg−1. Therefore, MS under YRM should be recommended to local farmers in dryland areas of China and other similar areas around the world.