间接地下滴灌导水装置规格参数模型研究

根据灌水过程中质量守恒原理建立了导水装置规格(直径,高度)参数求解模型,该模型中综合考虑了滴头流量、灌水定额、土壤水力特性参数以及活动水位等因素对导水装置规格的影响。通过室内恒定水头积水入渗试验的设计和研究,定量化了土壤水力特性参数对导水装置规格参数模型的作用,并研究了导水装置内水位深度的动态变化规律。结果表明,当忽略导水装置内积水深度的动态变化对土壤水力特性参数的影响时,与一维垂直入渗规律相似,导水装置内积水入渗累计入渗量与时间的关系可用菲利普公式进行拟合,但在土壤类型一定时,间接地下滴灌的参数渗吸系数S和稳定入渗速率if还与土壤上方的积水面积有关。当滴头流量大于土壤入渗速率时,导水装置内开始产生积水,且积水深度处于不断上升的过程。该模型的建立为间接地下滴灌导水装置规格的选取提供了理论指导。     

大田土壤耕作层覆膜防渗灌溉栽培水稻研究

为了推广应用一种新的覆膜栽培水稻方法——覆膜防渗灌溉,对比分析了土壤耕作层覆膜防渗灌溉与常规灌溉条件下水稻的耗水量、水稻生长分蘖状况、水稻产量及土壤中氮磷钾营养元素的变化情况。结果表明,防渗灌溉能明显减少灌溉用水量,较常规灌溉节水9.54%。防渗灌溉可减少土壤中的肥力损失,能有效阻隔土壤中速效钾的淋溶损失。防渗灌溉与常规灌溉的耗水系数分别为711和786 kg/kg,灌耗比分别为0.5和0.6。防渗灌溉降低灌溉水在总耗水量中的比重,减少渗漏损失提高水分利用率。     

坡度和降雨强度对坡耕地入渗的影响

利用人工模拟降雨对黑龙江西部半干旱区坡耕地不同坡度和不同降雨强度下的土壤水分入渗规律进行了试验研究,采用产流历时和稳定入渗速率二项指标进行分析,发现随着地面坡度的增大,产流历时提前,稳定入渗速率逐渐减小,坡面产流历时与坡度呈对数函数关系,土壤稳渗速率与坡度呈幂函数关系;随着降雨强度的增大,产流历时提前,稳定入渗速率逐渐增大;坡面产流历时与降雨强度呈指数函数关系,土壤稳定入渗速率与降雨强度也呈指数关系。     

黑龙江省半干旱区防护林内主要气象因子观测初报

对齐齐哈尔(沙壤土区)、杜蒙(风沙土区)、青冈(黑土区)等3个代表黑龙江省半干旱区典型地点防护林区内7、8、9月主要气象因子(气温、气湿、风速、降雨量等)及土壤入渗率情况进行了定期观测,结果表明:3个月份平均气温杜蒙>齐齐哈尔>青冈,气湿为青冈>齐齐哈尔>杜蒙,风速为杜蒙>齐齐哈尔>青冈,土壤入渗率为杜蒙>齐齐哈尔>青冈,揭示了黑龙江省半干旱区防护林内不同土壤类型之间主要气象因子的变化特征及规律,为半干旱区防护林功能评价提供了重要依据。     

农牧交错带地表覆盖物对土壤入渗的影响

为了解我国北方农牧交错区不同地表覆盖物对土壤入渗的影响,以宁夏回族自治区盐池县为例,采用样线调查法进行地被状况调查,并在所设样线各样方内对应进行入渗试验。通过对外业数据的处理、分析,对各种地被状况影响入渗的情况进行了探讨。结果表明,植物的生长对水分入渗具有促进作用。植被盖度与入渗深度之间呈指数相关关系,相关系数达0.893。枯落物的覆盖对水分的入渗具有明显的阻碍作用,两者呈对数相关关系,相关系数高达0.921。生物结皮对入渗具有明显的阻碍作用,结皮盖度与入渗深度之间呈线性负相关,相关系数为-0.765,说明结皮的存在使土壤水分呈现浅层化趋势。     

一维土壤入渗特性数值模拟

以非饱和土壤水分运动理论基础,利用Richards模型模拟不同实验处理下的一维垂直入渗过程,采用SWMS-1D软件对模型求解,用试验资料对模拟的累积入渗量与湿润锋运移距离结果进行了对比验证,二者基本吻合。对模拟结果分析得出,土壤质地和容重对一维垂直入渗累积入渗量、入渗速率和湿润锋运移距离影响较大,土壤初始含水率和入渗水头对其影响较小;并分别建立了不同土壤质地下的累积入渗量、入渗速率和湿润锋运移距离与入渗历时单参数幂函数计算式。     

区域尺度土壤入渗特征参数的变异性研究

以杨凌地区为例,进行野外双环入渗试验研究,运用2种常用模型(Kostiakov模型和Philip模型)对土壤入渗参数进行模拟。在分析土壤特征参数,寻求适合区域尺度的最优入渗模型同时,对土壤的状态变量进行标定并研究标定系数的空间变异性,研究结果表明:Philip模型可作为区域最优入渗模型,土壤入渗特征参数存在明显的空间变异性,标定系数aA比as对模型参数的标定效果好,且在较大范围内存在一定的趋势性,有较好的预测效果。因此,可根据标定系数随机模拟得到某一具体时刻的土壤入渗量的空间分布,为定量分析土壤水分运动、研究土壤水分入渗的空间分布提供理论基础。     

不同硝酸钾溶液浓度对垂直一维入渗特性影响研究

通过室内不同浓度溶液的垂直一维入渗试验,分析了不同浓度碳酸钾溶液影响下的湿润锋和累积入渗量的变化规律以及土壤含水量和硝态氮浓度的分布规律,由不同浓度溶液累积入渗量,依据GREEN-AMPT入渗模型,反推出湿润锋面平均吸力和饱和导水率,结果表明增大溶液浓度提高了垂直一维入渗的饱和导水率,但减小了湿润锋面的平均吸力,溶液浓度通过影响湿润体的饱和导水率和湿润锋面的平均吸力来影响入渗量,二者的综合作用是增大了入渗量。     

Effects of different land use types on infiltration capacity in a catchment in the highlands of Ethiopia

Infiltration capacity is an important variable for understanding and predicting a range of soil processes. This study investigated for different slope positions the effects of forest conversion to cultivation and grazing on soil infiltration capacity. Infiltration capacity was measured in the field in each land use type using a double‐ring infiltrometer. A total of 108 soil samples (3 slope positions × 3 land use types × 4 soil profiles × 3 soil depths) were collected to determine the variables that affect infiltration capacity viz. particle size distribution, organic carbon content, dry bulk density and soil moisture content. The results showed that in the cultivated and grazed land compared with forest, infiltration capacity and soil moisture content were 70 and 45% smaller respectively, and dry bulk density was 13–20% larger. Changes in soil structure caused by surface soil compaction because of tillage and animal trampling coupled with a smaller soil organic carbon content, are likely to be the principal factors causing the decline in infiltration capacity and soil moisture content after conversion of forest to cultivation and grazing.     

Effect of Gypsum Application on Long Term Changes in Soil Properties and Crop Growth in Sodic Soils under Field Conditions

In a field study, conducted on farmer's waste sodic soils, Aquic Natrustalf, 12.5 t/ha gypsum was surface mixed. Effect of gypsum application on soil properties and crop yields of rice and wheat grown in succession was evaluated after one to five years of gypsum application. The results showed that soil pH, electrical conductivity, calcium carbonate and soil dispersion decreased, whereas organic carbon, hydraulic conductivity, water infiltration and storage increased considerably after five years of gypsum application. In the initial years the improvement in soil properties was more in the surface layers and extended to lower layers slowly in the following years. Average grain yields of rice and wheat in the first year were 4.2 and 1.8 t/ha, respectively. The yields further increased to 6.1 and 2.5 t/ha in the 5th year, but the yields were lower than the yields obtained in research experiment. Relationships between wheat grain yield and pH of 0–15 and 15–30 cm layers were established. Wheat yield reduced by 45 percent when pH of 0–15 cm layer increased from 9.0 to 9.5. The sodicity of sub soil was still too high to permit the cultivation of deep rooted crops even after five years of gypsum application. Normal crop production is possible in these sodic soils, given sufficient time to reduce the sub soil sodicity.