【作者】 张振华；

【导师】 蔡焕杰；

【作者基本信息】 西北农林科技大学 ， 农业水土工程， 2002， 博士

【摘要】 滴灌是当今世界最先进的灌水技术之一，同传统灌水方式比较具有节水、高产、优质的优点。滴灌条件下水分运移的本质是微源入渗过程，因此，为了充分发挥滴灌优势，正确调控作物的土壤水分条件，对微源入渗特性规律的研究非常必要。膜下滴灌是地膜栽培与普通地表滴灌相结合的产物，在地膜覆盖和滴灌的综合效应下，作物的生长与在常规条件下不同，因此影响作物需水量的一些基本条件都发生了变化，对于膜下滴灌作物需水量和作物系数还需要做进一步研究。本文以粘壤土为研究对象，对微源入渗特性规律进行了系统的室内试验研究，并且对膜下滴灌大田作物棉花和玉米的需水规律进行了野外试验，得到了以下几点结论： （1）地表微源入渗土壤湿润体的形状受到土壤质地、供水强度和灌水时间的影响，一般为半个椭球体。微源入渗的水平和垂向湿润锋与入渗时间存在极显著的幂函数关系；土壤湿润体体积与入渗时间之间存在显著的线性关系，直线斜率和供水强度有关；土壤湿润体体积和灌水量之间存在显著的线性关系，在灌水量一定的条件下，滴头流量对湿润体体积影响很小，在滴头流量为2～5.3 L／h的范围内，对于同一灌水量湿润体体积的差异保持在5％以内。在粘壤土微源入渗过程中，土壤湿润体内平均体积含水率的增量和入渗时间、滴头流量无关，保持为一定值0.32cm³／cm^-3。土壤湿润体内含水率在水平方向上的分布，表现为在同一水平剖面上随着与对称轴之间距离的增加，含水率不断减小，减小的幅度在接近湿润锋处最为明显；土壤湿润体内含水率在垂直方向上的分布，亦表现为在同一竖直剖面上随着深度的增加，含水率不断减小，减小的幅度在接近湿润锋处最为明显。 （2）在灌水量一定的情况下，滴头流量对湿润体的形状有明显的影响。大流量滴头下的水平湿润锋较小流量的要大，而垂向入渗距离要小。对滴头流量在2～5.3L／h范围内的微源入渗分析表明，对应于同一灌水量，流量为5.3L／h的水平湿润锋比2L／h的大17％而垂向湿润锋则比之小20％。土壤容重对滴灌湿润体特征值有较明显的影响。在滴头流量为2L／h条件下，在相同的入渗时间内，大容重土壤的地表水平入渗距离较小容重土壤大7％，而其垂向入渗距离则较小容重土壤小20％。在滴头流量为5.3L／h条件下，在相同的入渗时间内大容重土壤的水平入渗距离较低容重的土壤大27％，而其竖直入渗距离则较小容重土壤小14％。 （3）多滴头交汇入渗条件下，湿润体交界面处水分的水平扩散和竖直入渗速率大11 微源入渗特性规律与膜下滴灌作物需水量研究于同一时间滴头正下方的入渗速率；随着入渗时间的延长，湿润体的形状也逐渐由椭球体向平行于毛管的带状分布过渡。微源交汇入渗条件下，水分在交界面处汇集有使土壤水分分布均匀的作用。表面撒施保水剂后对滴灌的入渗基本没有影响，使用前后的水平湿润锋和垂向湿润锋在入渗过程中基本重合。 O)土壤湿润体的体积在水分再分布的作用下，随看停水时间的增加而不断变大，对滴头流量为几儿供水 330min况停水后的水分再分布观测表明，到停水 4000min时，垂向湿润距离增加了25％，水平湿润距离增加了16％，湿润体的体积增加了68％，湿润体的平均体积含水率由停水时刻的 0．43cm3／cm3下降到 0二5 cm3／cm3。 m微源入渗的稳定渗透通量JO大于垂直一维入渗的稳渗率，并且JO随入渗区域的增加而减小。试验数据分析表明，微源入渗稳定渗透量和地表积水半径的倒数之间存在显著的线性关系，当积水半径无限大时，此时的稳定渗透通量即为饱和导水率，因此可用该直线的截距来表示土壤的饱和导水率。 的利用代数方法推导出等效半球模型EHM，试验证明滴灌土壤湿润体等效半径和滴灌水量的立方根之间存在线性关系，该直线斜率对于同种土壤而言是一特定值。EHM模型预测的湿润体半径同实测水平和竖直方向上的湿润锋值有一定的差异。该误差与滴头流量关系密切，表现为随着流量的降低，差异越来越小，在流量为1．ZL／h时，预测值同实测值非常接近。 门问歇供水条件下的微源入渗试验研究表明，尽管存在着供水和停水的周期性交替，间歇入渗条件下湿润锋和入渗时间之间仍然存在显著的幂函数关系。在灌水定额相同的条件下，采用间歇滴灌，能够在增加水平湿润距离的前提下可以有效地减小垂向的入渗距离。对30min、60min和120min等3种间歇周期入渗观测表明，间歇周期对滴灌湿润体的水平和垂向的湿润锋的影响没有差异，因此在应用中宜采用较长的间歇周期。 （8）用柱状流模型对微源入渗湿润锋的模拟结果表明，在较小滴头流量下 （Q＝ZL八）的模拟结果和实测值非常符合，而在大滴头流量条件下（Q＝4L／h），在入渗的开始阶段模拟值和实测值之间存在较大的差异。该模型对湿润体内含水率分布的模拟值和实测值之间非常接近。模型水量平衡误差分析表明，在入渗的开始阶段模拟值的偏差较大，其中最大流量4L儿的误差百分率最高达25％左右，流量ZL／h的误差百分率在 10％左右，最小流量 IL／h的误差百分率为 5％，随入渗时间的延长，误更多还原

【Abstract】 Drip irrigation is one of the most advanced irrigation technique. The main reasons for the growth in drip irrigation are the advantages, which it offers over sprinkler and certain conventional forms of surface irrigation. Drip irrigation lends itself to easy adaptation for chemigation and automation, conserves water, and has lower energy and maintenance costs than sprinkler systems. In addition to this, drip irrigation maintains higher soil-water potentials in the root zone, which increases the availability of water to the plant thus enhancing plant growth and yield. Drip irrigation is quite different from other forms of irrigation. Water moves across the soil surface away from the drip emitter until the infiltration rate of the ponded area matches the emitter discharge rate. Beyond this free-water pond water moves into the soil by unsaturated flow. It is very important to research the characteristic and pattern of trickle source infiltration. Drip irrigation under mul:h is a new irrigation method, as utilize the advance of drip irrigation and plastic film cultivation technique. The conditions influenced crop water requirement are changed in drip irrigation under mulch, thus crop water requirement pattern is different from conventional irrigation forms. It is very useful to research field mulched crops water requirement pattern watering with drip irrigation. This research was conducted to: (1) understand the characteristic and pattern of trickle source infiltration, (2) Study mulched crop evapotraspiration for cotton and corn in a arid climate sandy loam soils. According to the researches of the dissertation, the main results are as follows:(1) The shape of wetted soil volume is influenced by soil texture, discharge rate and the total volume of applied water in case of trickle source infiltration. In general, the wetted soil volume is a semi-elliptic cone. The relationship between horizontal and vertical wetting front and infiltration time is remarkable power function. The relationship between wetted soil volume and infiltration time is remarkable stright line, and in case of certain volume of applied water, the wetted soil volume is not influenced by discharge rate. In the process of trick source infiltration, the increased soil water content is a constant value 0.34 for clay loam soil. The distribution pattern of water content in horizontal is similarly with vertical level. The more of the distance away axis, the less of the soil water content, and the decrease is most notable near the wetting front.(2) In case of specified volume of applied water, the shape of wetted soil volume is influenced by discharge rate. The horizontal wetting front in big discharge rate is wider than that of small discharge rate, and the vertical wetting front in big discharge rate is shallower than that of small discharge rate. The horizontal wetting front of 5.3L/h is wider17 percent than 2 L/h, and the vertical wetting front of 5.3 L/h is shallower 20 percent than 2 L/h. The influence of soil bulk density on wetting front is related to discharge rate. In case of big discharge rate, the influence in horizontal is notable. However, in case of small discharge rate, the influence in vertical wetting front is notable,(3) In case of trickle source wetting front overlapping, the infiltration pattern is different from that of single trickle source infiltration. The infiltration rate in wetting front interface is speeder than that under single trickle source. The wetted soil volume shape becomes a strip which parallel lateral. The soil water content distribution under trickle source wetting front overlapping is more than that of single source. The scatter super absorbent polymer in soil surface don’t influenced the infiltration process of trickle source, the wetting front is almost coincide with checking treatment.(4) Because of the influence of soil water redistribution, the volume of wetted soil increase and the average soil water content decrease. In case of applied water 330min with a discharge rate 1 L/h, the hori更多还原