【作者】 胡浩云；

【导师】 杨金忠；

【作者基本信息】 武汉大学 ， 水利水电工程， 2012， 博士

【摘要】 本文针对我国农业地膜覆盖栽培和设施农业施肥灌溉特点,结合河北省自然科学基金项目,采用室内试验、大棚试验、计算机模拟和理论分析相结合,以计算机模拟试验为主的技术路线,研究设施膜孔灌下土壤水氮运移、分布特性及其影响因素,主要得出以下结论：1、分析了设施条件下膜孔灌平均入渗水深与膜孔直径、开孔率的关系。膜孔直径、开孔率越大,相同时间的平均入渗水深越大,并建立了湿润锋与膜孔直径、开孔率和时间的函数关系,该公式物理意义明确,计算相对误差较小。2、研究了膜孔灌湿润体形状随时间变化。在灌水初期至灌水结束,湿润体基本呈半椭球形,并随时间不断扩大,但湿润中心处于膜孔中心的地表附近；灌溉结束至湿润锋交汇前,湿润体仍呈逐渐扩大的半椭球体,但湿润中心沿膜孔中心逐渐下移；湿润锋交汇后至第3天,等值线仍有明显的趋势,湿润中心仍沿膜孔中心下移；第3天以后湿润锋基本为由上至下的水平线。3、探讨了设施条件下膜孔直径、灌水量和膜孔间距对土壤含水量分布的影响。在灌水阶段,膜孔间距对土壤含水率分布有影响,经过土壤水分再分布后,基本没有影响。灌水量对土壤含水率有直接影响,灌水量越大,湿润土体越大,湿润中心越深,湿润锋交汇时间越短；土壤水分分布的均匀系数与灌水量的关系出现峰值,以灌水16mm为最大,说明灌水定额对土壤水分分布的均匀性是有影响的。膜孔间距对土壤含水率有影响,膜孔间距越小,含水率沿水平方向的变化梯度越小,含水率分布越均匀；不同膜孔间距的含水率沿水平方向的分布出现交叉,说明膜孔间距对土壤含水率分布的均匀性有影响,但这种影响只在灌水初期比较大,经过土壤水分再分布后灌水均匀系数均能达到90%以上。因此,膜孔间距按种植要求安排即可。4、研究了设施条件下膜孔直径、灌水量对灌施硝态氮肥液下湿润锋运移影响。膜孔直径对土壤硝态氮水平湿润锋和垂直湿润锋有影响。土壤硝态氮水平运移距离随膜孔直径增大而增大,建立了水平湿润锋与膜孔直径和时间的对数函数关系式；膜孔直径对土壤硝态氮垂直湿润锋的影响却相反,且垂直湿润锋与膜孔直径之间没有明显的函数关系。灌水量对土壤硝态氮水平湿润锋和垂直湿润锋有影响。相同时间土壤硝态氮水平运移距离随着灌水定额的增大有增大的趋势,但却没有明显的函数规律；相同时间土壤硝态氮垂直运移距离随着灌水定额的增大而增大,垂直湿润锋与膜孔直径和时间之间呈幂函数关系。5、揭示了设施条件下灌施硝态氮肥液下硝态氮溶液浓度分布规律。土壤硝态氮溶液浓度沿水平和垂直方向的分布,均可以分为三段,①高浓度区,该区变化平缓,浓度梯度较小；②高梯度区,该区变化急剧,浓度梯度很大；③低浓度区,该区变化平缓,浓度梯度较小。表明土壤硝态氮的运移需要盐分积聚,形成较高的浓度梯度,才能推进,因此,上述三个分段也可称为盐分积聚区、推进区、渐受影响区。造成三段分区的原因,除了土层对溶质具有一定的过滤作用外,更主要的是由于土壤分子对盐分具有较强的吸附作用,这种作用力大于土壤分子对水分子的作用力,只有当盐分溶液的浓度梯度达到一定水平,分子扩散作用大于土壤分子对盐分的吸附作用时,盐分才能运移。施肥灌溉时,土壤硝态氮大部分集中在距膜孔中心12cm范围内,宜于作物吸收。6、揭示了设施条件下灌施硝态氮肥液水氮耦合关系。膜孔灌土壤水氮湿润锋具有明显的不同步性,土壤水湿润锋大于土壤硝态氮湿润锋,但两者呈很好的线性关系,而灌施肥液浓度对两者关系也有有规律的影响。以上研究成果为进一步开展设施条件下膜孔灌水肥高效利用研究奠定了科学基础。更多还原

【Abstract】 Aimed to the characteristic of film covering cultivation and irrigation and fertilization under facilities and combined with the National Natural Science Foundation of Hebei, this paper uses the technical route including indoor and shed experiment, computer simulation and theoretical analysis, and studies the characteristics of soil water and nitrogen transport and distribution and the factors to the characteristics. The main research results are as follows:1. Analysis the relationship between mean water infiltration depth and film hole diameter and percentage of open area. The mean water infiltration depth increases with film hole diameter and percentage of open area. The function relationship between wetting front and film hole diameter, percentage of open area and time is set up, which has an clear physical meaning and a little relative error.2. Studies the change of wetting front with time. From the early irrigation time to irrigation end, the wetting body looks like a semi-ellipsoid and increases with time, the wetting center of which is near top soil of film hole center; form irrigation end to wetting front intersect, the wetting body is still semi-ellipsoid, but the wetting center of which moves down along the film hole center; from wetting front intersect to the third day, the wetting front still looks like a semi-ellipsoid; after the third day, the wetting front assumes horizontal lines from top to bottom.3. Discusses the effect of film hole diameter, irrigation amount and film hole spacing on soil water content.In the stage of irrigation, the film hole spacing has effect on soil water content and has no effect during soil water redistribution.Irrigation amount has a direct effect on soil water content. With the increase of irrigation amount, the wetting body is bigger, the wetting center is deeper and the time of wetting front interact is shorter; among the relationship between irrigation quota and even coefficient, the most value appears when irrigation quota is16mm, so irrigation quota has an effect on water even coefficient.Film hole spacing has an effect on soil water content. With the decrease of film hole spacing, the gradient of soil water in horizontal direction is little and soil water content changes more evenly; soil water happens to intersect in the horizontal direction under different film hole spacing, so film hole spacing has an effect on water even coefficient. The effect is obvious in the early irrigation time and up to90%after soil water redistribution. The film hole space can be determined according to planting requirements.4. Studies the effect of film hole diameter and irrigation amount on wetting front transport under applying nitric nitrogen solution.Film hole diameter has an effect on soil nitric nitrogen front in the horizontal and vertical direction. The horizontal front transport distance of soil nitric nitrogen increases with film hole diameter and the function relationship between horizontal wetting front and film hole diameter is set up; the effect of film hole diameter on soil nitric nitrogen front in the vertical direction is reverse and there is no obvious function relationship between them.Irrigation amount has a direct effect on soil nitric nitrogen front in the horizontal and vertical direction. The horizontal front transport distance of soil nitric nitrogen increases with irrigation quota, but there is no obvious function relationship between them; the vertical front transport distance of soil nitric nitrogen increases with irrigation quota, there is power function between them.Most of soil nitric nitrogen is in the range of12cm away from film hole center and can be easily absorbed by plant.5. Reveal the distribution rule of soil nitric nitrogen concentration under applying nitric nitrogen solution.The distribution of soil nitric nitrogen concentration can be divided into three parts:①the part can be named high concentration area which change gently with little concentration gradient;②the part can be named high gradient which change sharply with big concentration gradient;③the part can be named low concentration area which change gently with little concentration gradient. So the soil nitric nitrogen transports by high concentration gradient. The three parts above can also be named salt accumulation area, pushing area and gradually effected area.6. Reveal the relationship between soil water and soil nitric nitrogen under applying nitric nitrogen solution. The soil water wetting front does not synchronize with soil nitric nitrogen front, but there is a good line relationship between them and the effect of solution concentration on them is also obvious.These results provide theoretic proof for developing water and fertilizer application with film hole irrigation under facilities.更多还原