Assessment of irrigation and environmental quality at the hydrological basin level: I. Irrigation quality   总被引：1，自引：0，他引：1  

J. Causap  D. Quílez  R. Aragüs 《Agricultural Water Management》2004,70(3):195-209

Irrigated agriculture notably increases crop productivity, but consumes high volumes of water and may induce off-site pollution of receiving water bodies. The objectives of this paper were to diagnose the quality of irrigation and to prescribe recommendations aimed at improving irrigation management and reducing the off-site pollution from a 15,500 ha irrigation district located in the Ebro River Basin (Spain). Three hydrological basins were selected within the district where the main inputs (irrigation, precipitation, and groundwater inflows) and outputs (actual crop's evapotranspiration, surface drainage outflows, and groundwater outflows) of water were measured or estimated during a hydrological year. The highest volume of water (I = 1400 mm/year) was applied in the basin with highly permeable, low water retention, flood irrigated soils where 81% of the total surface was planted with alfalfa and corn. This basin had the lowest consumptive water use efficiency (CWUE = 45%), the highest water deficit (WD = 5%) and the highest drainage fraction (DF = 57%). In contrast, the lowest I (950 mm/year), the highest CWUE (62%), and the lowest WD (2%) and DF (37%) were obtained in the basin with 60% of the surface covered with deep, high water retention, alluvial valley soils, where 39% of the cultivated surface is sprinkler irrigated and with only 48% of the surface planted with alfalfa and corn. We concluded that the three most important variables determining the quality of irrigation and the volume of irrigation return flows in the studied basins were (i) soil characteristics, (ii) irrigation management and irrigation system, and (iii) crop water requirements. Therefore, the critical recommendations for improving the quality of irrigation are to (i) increase the efficiency of flood-irrigation, (ii) change to pressurized systems in the shallow and highly permeable soils, and (iii) reuse of drainage water for irrigation within the district. These management strategies will conserve water of high quality in the main reservoir and will decrease the crop water deficits and the volume of irrigation return flows, therefore, minimizing the off-site pollution from this irrigation district.  相似文献   

Spatial and temporal processes affecting nitrogen availability at the landscape scale   总被引：3，自引：0，他引：3  

J. M. Sogbedji  H. M. van Es  S. D. Klausner  D. R. Bouldin  W. J. Cox 《Soil & Tillage Research》2001,58(3-4):233-244

Nitrogen dynamics in soils are affected by spatial and temporal processes. Drainage class is generally regarded to be the most significant source of variability for N in temperate humid climates. A 5-year study was conducted including four rates of N fertilizer and three drainage classes within a 15 ha maize (Zea mays L.) field. Variance component analysis showed that N response was minimally affected by drainage class, but showed strong yearly variations, apparently related to early-season precipitation. Annual field-averaged economic optimum N rates had a range of 65 kg ha⁻¹ with lower rates being associated with years with low early-season precipitation. A calibrated LEACHMN model and site-specific weather data were used to evaluate the effects of early-season weather conditions on N rate and availability. During wet years, soil N availability was reduced by approximately 35–50 kg ha⁻¹ compared to dry years, largely independent of drainage class. For well-drained soils, most losses were attributed to leaching (especially in years with wet early-season), while poorly drained soils mainly experienced denitrification. It is concluded that limited benefits may be gained from spatially variable N applications within fields based on drainage class or soil type, but considerable economic and environmental gains are possible from yearly adjustment of supplemental N rates based on model simulations of N dynamics using information on early-season weather conditions.  相似文献   

排灌机械合理配套的研究          下载免费PDF全文

金树德  李龙 《农业工程学报》1997,13(2):96-99

从排灌机械配套的可靠性、经济性和合理性出发，对传统配套方法和产品特点进行了分析，提出了适应产品技术进步的新的配套方法和配套系数（１．０～１．１）。  相似文献   

Wildfire disturbance and shallow landsliding in coastal British Columbia over millennial time scales: A numerical modelling study     

Yvonne Elizabeth Martin   《CATENA》2007,69(3):206-219

An algorithm for wildfire occurrence is introduced for incorporation into a numerical model of drainage basin evolution. Within the model, fire return intervals are determined using a stochastic rule set and fire sizes are assigned according to a pareto distribution. A Weibull distribution was fit to millennial-scale lake charcoal data for calibration of fire return intervals in this study, while data for the Olympic Peninsula were used to determine the fire size distribution. Loss of tree root strength resulting from stand-replacing wildfires has been found to be comparable to loss after timber harvesting. Hence, data for increased shallow landslide activity associated with logging were used to calibrate transport equations for years following wildfire incidence. A weathering relation is incorporated in the model, which drives the supply of sediment. When sediment supply is depleted in the model, the shallow landsliding module shuts off until new material is available for transport. Time since last fire analysis indicates that the Weibull parameters defined for the Clayoquot charcoal data produce results that are weighted too heavily towards recent fires. Sensitivity analysis was undertaken, suggesting alternative values may be more reasonable for further model runs. The introduction of a weighted probability factor for aspect, whereby south-facing slopes have a higher likelihood of fire initiation, was not found to significantly affect patterns of fire age in the landscape. Patterns of net topographic change after 6000 years of model run time indicate that greatest net erosion is found on steep, upper slopes, with the highest deposition occurring in hillslope hollows and low-order channels. Depositional grid cells in interfluves show a variable response to the inclusion of wildfire in the model. Net erosion occurs over a relatively low proportion of hillslope area, with wildfire model runs showing a strong erosional signal in these locations. For stream grid cells, the additional deposition due to the inclusion of wildfire in model runs is about 9–10% for 1st to 3rd order streams. Overall, deposition rates increase with decreasing stream order, reflecting greater hillslope/channel coupling in low-order streams.  相似文献   

关于砀山县水果业发展的思考     

孟晓芹  张莉莉 《安徽农业科学》2005,33(7):1340-1340,1358

分析了砀山县水果业的发展现状及存在的问题,并提出了相应的对策。  相似文献   

Spatial Influence of Topographical Factors on Yield of Potato (<Emphasis Type="Italic">Solanum tuberosum</Emphasis> L.) in Central Sweden     

Andreas?PerssonEmail author  Petter?Pilesj?  Lars?Eklundh 《Precision Agriculture》2005,6(4):341-357

This study has evaluated the sampling density for creation of high-resolution digital elevation models (DEMs) for precision agriculture purposes. The relationships between yield and topographical factors were investigated in a study area located in the central Sweden province of Dalarna. The DEM data sampling was carried out with a RTK-GPS system. A dense sampling scheme was employed and data was divided into two for both interpolation and validation. Kriging interpolation was used for DEM generation. From the DEM, topographical parameters were extracted and topographical indices were estimated. The indices were calculated with slope length and its vertical and horizontal components. The drainage area for a point of interest and the relationship of this area to the total drainage area were also estimated. The relationship of yield and the topographical parameters and indices was investigated using both circular and spatial statistics. A spatial regression was used to calculate a model for the relationship. Up to 20% of the yield could be explained in the final model for one of the fields.  相似文献   

Rangeland hillslope lengths: A case study at the Walnut Gulch Experimental Watershed,southeastern Arizona     

《国际水土保持研究(英文)》2022,10(4):597-609

Rangeland hillslopes provide much of the sediment supplied to channel systems and their lengths exert a fundamental constraint on hillslope diffusive processes. However, information regarding lengths of rangeland hillslopes, and how best to estimate them, is limited. In this study, three groups of watersheds (10 in total) were selected from the Walnut Gulch Experimental Watershed according to their geology, soil and vegetation characteristics. Group 1 watersheds were at lower elevations dominated by shrubs, Group 3 were at high elevations dominated by grass, and Group 2 were mixed shrub and grass. Their hillslope lengths were calculated from 1 m-resolution DEMs using three methods: a flow routing algorithm, slope-area relationships, and inverted relationship with drainage density. Parameters that characterize the current watersheds, including Hack's exponent and coefficient, watershed shape coefficient, channel concavity and steepness, and surface roughness, were quantified and related to hillslope lengths. Results shows: (1) estimated hillslope lengths were different for the three methods and between the three groups of watersheds; (2) hillslope lengths that measured from the flow routing algorithm for the ten selected watersheds primarily ranged from 30 to 100 m, with a median value of 63.0 m, which was 20%–50% greater than those derived from slope-area plots or drainage densities; (3) hillslope lengths estimated from the flow routing method were greater in Group 3 watersheds than in Group 2 and then in Group 1 watersheds. We attributed these differences in hillslope lengths to the historic epeirogenic pulses, watershed and drainage network morphology, and differences in vegetation characteristics; (4) measured hillslope lengths from the flow routing algorithm were best correlated with hillslope relief, then surface roughness, channel steepness and concavity. These results would benefit the applications of hydrological and erosion models in rangelands.  相似文献   

不同渍涝灾害应对措施对夏玉米长势与产量的影响          下载免费PDF全文

闫振华  吴浩  翟雪洋  柯鑫  明博  王克如  李少昆  谢瑞芝 《玉米科学》2023,31(3):83-87

2021年7月18-21日河南省漯河地区连续4 d强降雨共计185.60 mm，正值当地夏玉米孕穗期。在渍涝发生后，在河南省漯河市的中国农业科学院作物科学研究所试验田，通过设置雨停后立即排水(T1)、雨停后立即排水+滴灌追氮肥(T2)、雨停后3 d排水(T3)、雨停后3 d排水+滴灌追氮肥(T4)共4个应对措施和不处理(CK)共5个处理，测定不同处理下关键生育期的地上与地下部生物量、叶面积指数及产量相关性状。结果表明，CK处理(5 d后田间无地表积水)绝产，其他4个处理获得平均产量6.98 t/hm²，其中，及时排水处理产量平均较3 d后排水处理提高21.28%，及时排水后施肥处理较不施肥处理产量提高8.07%，3 d后排水并施肥处理较仅排水不施肥处理产量提高15.33%，较及时排水处理低5.04%。及时排水、补充氮肥缓解了涝渍对根系生长、叶面积及地上部干物质积累的负面影响，从而降低产量损失，是应对玉米孕穗期渍涝的有效手段。  相似文献