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Zhang J.,CAS Institute of Soil and Water Conservation | Zhang J.,Shaanxi Land Construction Group | Niu W.,CAS Institute of Soil and Water Conservation | Zhang L.,CAS Institute of Soil and Water Conservation | And 2 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2014

In order to identify effects of soil initial water content on line-source infiltration characteristics in moistube irrigation, the wetting front advance distance and soil moisture variation feature were investigated through indoor simulation experiments for isotropic soil under four initial water contents: 2.1%, 5.6%, 8.0% and 10.1%. The experimental results revealed that soil initial water content had a great effect on line-source infiltration, the advance speed of wetting front and surface wetting time were raised and extended with increasing initial water content, and could be presented by a power function of irrigation time. Meanwhile, the shape of wetting soil was slightly affected by initial water content and its cross-section shape was kept to be nearly circular. During an irrigation event, the cumulative infiltration and average infiltration rate were positively correlated with initial water content, but the time for a stable infiltration rate was negatively related to the content. The water content inside a wetting soil body was distributed concentrically, and the moisture gradient was decreased with increasing initial water content, however, the uniformity coefficient of moistube-irrigation was increased with the content. Those results may be useful for application of moistube-irrigation. Source


Niu W.,CAS Institute of Soil and Water Conservation | Zhang J.,Shaanxi Land Construction Group | Zhang L.,CAS Institute of Soil and Water Conservation | Xue W.,CAS Institute of Soil and Water Conservation
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | Year: 2013

In order to research the characteristics of wetted soil under miostube-irrigation, five different buried depths and six different pressure heads were designed to investigate soil water movement through indoor soil box experiments. The results revealed that the pressure was the key factor to decide the miostube-irrigation flow, and the buried depths of miostube-belt had significant effect on the shape of wetted soil. The horizontal migration distance and ratio of width to depth of γ decreased with the increase of buried depths and vertical migration distance slightly increased with the increase of buried depths. There was a negative correlation between cumulative infiltration and buried depths and changing process of infiltration with irrigation time was accorded with Kostiakov infiltration model. The simulation model of cumulative infiltration under different buried depths was established and tested with measured values. The results showed that the experimental equation of infiltration had a high correlation coefficient between the measured value and the calculated value. There was a positive correlation between soil moisture uniformity and buried depth, and the suitable buried depths of clay loam of miostube-irrigation were between 15 and 20 cm. Source


Shi Z.,Northwest University, China | Li X.,Northwest University, China | Zhang L.,Northwest University, China | Zhang L.,Shaanxi Land Construction Group | Wang Y.,Northwest University, China
Journal of Plant Nutrition and Soil Science | Year: 2015

Land-use change often affects the sizes of soil organic carbon (SOC) stocks and the activities of soil enzymes. Responses of relevant soil quality indices caused by farmland conversion to orchard are largely unknown in the semiarid loess regions. This study was conducted at orchard sites, which have been under very intensive cultivation, to evaluate the impacts of farmland conversion to apple (Malus domestica) orchard on SOC stocks and soil enzyme activities in the semiarid loess region of Weibei, Shaanxi province, China. The spatial and temporal changes in a variety of soil quality indices were measured for the 0-100 cm soil profile in apple orchards of three age groups (< 10 y, juvenile; 10-15 y, mature; > 15 y, over-mature) and adjacent farmlands (control). After farmland conversion, total SOC (TOC) content and density and soil alkaline phosphatase activity significantly decreased, while soil catalase activity increased for the 0-100 cm soil profile. The labile SOC (LOC) content, its proportion to TOC content, and carbon management index (CMI, changes in the total content and lability of SOC) significantly increased in the 0-40 cm soil layer, whereas soil urease and invertase activities only increased in the 0-20 cm layer (P < 0.05). With increasing age of apple orchards, SOC stocks significantly increased after 10 y, being more than 10% larger in mature and over mature orchards than in adjacent farmlands. The LOC content and CMI value also had an increasing trend, while soil enzyme activities showed different response patterns. There were significant correlations between soil enzyme activities, SOC fractions, and CMI value (P < 0.05). We concluded that farmland conversion to apple orchard affected soil quality by reducing SOC stocks in the soil profile and changing SOC content as well as soil enzyme activities at various depth intervals. Long-term apple cultivation was effective to restore SOC stocks, although it took over a decade to rebuild a new increasing trend after farmland conversion. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Liang T.,Northwest University, China | Tong Y.,Northwest University, China | Xu W.,China Agricultural University | Wei Y.,Shaanxi Land Construction Group | And 4 more authors.
Atmospheric Pollution Research | Year: 2016

We present the quantification information on atmospheric nitrogen (N) deposition in the Loess area in Yangling District of Shaanxi Province, China using combined methods of a long-term field measurement (2006-2012), a potted experiment (2009-2011) and a long-term site-specific experiment (1991-2008). Our results showed that the annual deposition fluxes of dissolved inorganic N (NH4 +-N and NO3 --N) via both precipitation (wet-deposition) and dustfall (dry-deposition) ranged from 12.73 to 37.87 kg N ha-1 yr-1 and averaged 21.76 kg N ha-1 yr-1, with large contributions from wet deposition. The annual mean ratios of deposition amounts of ammonium N (NH4 +-N) to nitrate N (NO3 --N) were less than 1 in all the study years with an exception of the year 2007. Based on crop N uptake (approximately 52 kg N ha-1 yr-1) in the pot experiment, it was estimated that the dry N deposition fluxes (including gas and particles) was about 23.81 kg N ha-1 yr-1, accounting for 45.8% of the total N deposition. According the long-term site-specific experiment, the contribution of N input to farmland from the atmosphere was estimated to account for 52.8% of the environmental N input. Our results suggested that atmospheric N deposition was an important N input that must be taken into consideration when calculating nutrient budgets in agricultural ecosystems. © 2015 Turkish National Committee for Air Pollution Research and Control. Source


Wang J.,Xian Shiyou University | Wang J.,Shaanxi Land Construction Group | Sha J.,Shaanxi Yanchang Petroleum Group Co. | Guo D.,Shaanxi Yanchang Petroleum Group Co. | And 3 more authors.
Jilin Daxue Xuebao (Diqiu Kexue Ban)/Journal of Jilin University (Earth Science Edition) | Year: 2014

Combineing closely the practical exploration and guided by multidisciplinary geological theory and technology, a comprehensive geological model has been set up to explain and restore paleogeomorphology unit attributes of the Ordovician weathering crust of eastern Ordos basin. Meanwhile, according to drilling and logging geologic data, authors also combine basin tectonic evolution with results of "impression method" organic integration and results of "residual thick method", discuss the methods and thinking of Ordovician weathering crust paleogeomorphology restoration, and its ancient landscape development characteristics through in-depth analysis of the stratigraphic combination under and above Ordovician unconformity erosion surface, and explore a new method of palaeogeomorphologic reconstruction-"synthetic method". The research results show that the stratigraphic combination, under and above Ordovician unconformity erosion surface in the eastern of Ordos basin, can be divide into four basic types including "up thin down thin", "up thick down thick", "up thick down thin", "up thin down thick", and eight sub models which were "up relative thickening down relative thinning", "up relative thinning down relative thinning", "up relative thinning down relative thickening", "up relative thickening down relative thickening", etc. The corresponding paleogeomorphology explanation includes three two-level paleogeomorphology units as karst highland, karst slope, karst basin, and eleven three-level paleogeomorphology units including monadnock, tableland, residual tableland, level terrace, cheuch, shallow depression, deep depression etc. The Karst highlands occurs restrictively in the southwestern research area. The Karst slope occupies most of the study area where the main paleogeomorphology units were slope tableland and slope level terrace. The Karst basin is located in the eastern study area and the main paleogeomorphology units include basin shallow depression. Source

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