Reasonable fertilization improves the conservation tillage benefit for soil water use and yield of rain-fed winter wheat: A case study from the Loess Plateau, China

Conservation tillage is considered an ideal management choice for improving soil water storage in dryland agriculture, but crop yield improvement also depends on soil nutrient availability. To investigate the effects of fertilization, tillage, and their interaction on crop yield, WUE, and soil water content dynamics, a split-plot experiment {with conventional fertilization (255 kg N, 180 kg P2O5 ha-1), recommended fertilization (150 kg N, 120 kg P2O5, and 90 kg K2O ha-1), and low fertilization rate (75 kg N, 60 kg P2O5, and 45 kg K2O ha-1) as main plots; and conventional tillage (CT), no till (NT), and subsoiling tillage (ST) as subplots} was conducted on a winter wheat (Triticum aestivum L.) system in the Loess Plateau from 2007 to 2017. We hypothesized that reasonable fertilization and tillage combinations can facilitate soil water storage and use, as well as crop yield improvement. Compared to conventional fertilization×CT, NT and ST improved average grain yield and water use efficiency (by 9.4% and 4.1%, and 14.4% and 9.2%, respectively) when combined with recommended fertilization, but reduced them when combined with low fertilization rate. NT and ST were more beneficial in the dry and wet seasons, respectively. The average soil water storage through fallow significantly improved by 28 mm and 15.9 mm under NT and ST, respectively, and the improvement was more significant under recommended fertilization and/or in dry fallows. From the tillering to grain filling stages, the average soil water content reduction in the 0-200 cm profile under recommended fertilization×ST was 16.4% greater than that under low fertilization×CT, and this increased water use was significantly correlated with the yield improvement. These results demonstrated that reasonable fertilization can facilitate the transformation of soil water benefit under conservation tillage to crop yield improvement.