Effects of long-term surface mulching and N addition on winter wheat yield and soil properties

To determine reasonable cultivation mode for dry farming practice in the semi-humid prone to drought region, the effects of surface mulching and N addition on winter wheat yield and soil nutrients regimes were compared. The experiment was conducted during the seven consecutive years of 20022009 in Guanzhong Plain of Shaanxi province. The nine treatments consisted of three levels of mulching, namely, no mulching (NM), wheat straw mulching (WSM), plastic film mulching (PFM), and three nitrogen levels (N 0, 120 and 240 kg/ha). Soil samples were collected after wheat harvest in 2009 of a winter wheat-summer fallow system. In addition, wheat yields were also considered in the growing seasons of 20022009. The results showed that the yield was averagely decreased by 1.46% in the WSM treatment, and increased by 7.04% in the PFM treatment compared to the NM treatment of consecutive seven years. Moreover, the yield was averagely increased by 42.72% in the two nitrogen amended treatments compared to the no nitrogen addition treatment during 20022009, however, no significant differences between N application of 120 and 240 kg/ha treatments were found. Comparing with NM treatment, soil labile organic C content at the surface layer was significantly increased by 37.57% and 21.39% in the WSM and PFM treatments, respectively. In contrast with PFM, a significant increase of 6.84%, 4.40% and 12.68% in soil organic C, total N and available K was observed in WSM treatment, respectively. Soil labile organic C and mineral N were averagely increased by 6.03%, 40.18%, and available P and pH value were decreased by 23.55% and 0.05 pH unit in the two N amended treatments compared to the N0 treatment. In other words, these four soil parameters were significantly sensitive to different N rates. But there were no significant differences of mineral N and pH value between N120 and N240. In conclusion, there are no advantages on yield of WSM and PFM treatments in this experiment. Meanwhile, the planting mode of WSM combined with nitrogen application of 120 kg/ha can significantly increase soil organic C and available K content, and it is also a better way to improve the availability of soil nutrients in calcareous soil.