Soil infertility is the main barrier to dryland agricultural production in China. To provide a basis for the establishment of a soil amelioration technical system for rainfed fields in the semiarid area of northwest China, we conducted a four—year (2007–2011) field experiment to determine the effects of wheat straw incorporation on the arid soil nutrient levels of cropland cultivated with winter wheat after different straw incorporation levels. Three wheat straw incorporation levels were tested (H: 9000 kg hm-2, M: 6000 kg hm-2, and L: 3000 kg hm-2) and no straw incorporation was used as the control (CK). The levels of soil nutrients, soil organic carbon (SOC), soil labile organic carbon (LOC), and enzyme activities were analyzed each year after the wheat harvest. After straw incorporation for four years, the results showed that variable straw amounts had different effects on the soil fertility indices, where treatment H had the greatest effect. Compared with CK, the average soil available N, available P, available K, SOC, and LOC levels were higher in the 0–40 cm soil layers after straw incorporation treatments, i.e., 9.1–30.5%, 9.8–69.5%, 10.3–27.3%, 0.7–23.4%, and 44.4–49.4% higher, respectively. On average, the urease, phosphatase, and invertase levels in the 0–40 cm soil layers were 24.4–31.3%, 9.9–36.4%, and 42.9–65.3% higher, respectively. Higher yields coupled with higher nutrient contents were achieved with H, M and L compared with CK, where these treatments increased the crop yields by 26.75%, 21.51%, and 7.15%, respectively.

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Flood, drought, hail, low temperature and frost disasters from low temperature and frost (DLTF), and snowstorm are the five main meteorological disasters (MDs) in China. Based on the collection of historical documents during 1950-2013 and official records between 2012 and 2013, this paper analyzed the temporal trends of affected area induced by MDs during 1950-2013 and the spatiotemporal characteristics of disaster frequency in recent 2 years in China. Besides, the direct economic losses and deaths caused by MDs were further discussed at a provincial level. Results showed that the affected area of MDs, especially flood, drought and DLTF significantly increased during the past 60 years. Flood was the most frequent disaster in China during 2012 and 2013, followed by hail. Spatial patterns of disaster frequency showed that there were more frequent floods in the middle and lower reaches of the Yellow River and the Yangtze River basin, droughts in central and southwest China, hails in north, northwest and southwest China, DLTFs and snowstorms in north, northwest China and individual areas in south China. However, the economic losses caused by MDs were higher in economically developed provinces, and the deaths were higher in mountain regions. Additionally, flood was the major disasters type that contributing to the most losses in most regions of China. These results play an important theoretical guiding role in meteorological disaster prediction, disaster prevention and reduction in the future.

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