Development of efficient irrigation schedules and soil salinity monitoring system in productive green arid lands

本研究项目的目的是提出有效的灌溉制度和开发新的土壤盐分监测系统，假设有生产性的绿色旱地条件。(1)通过对模拟结果的讨论，提出了罐式灌溉系统的灌溉制度，在4~22年的灌溉周期中，取水效率为80%、日灌溉间隔期、设计灌溉间隔期、灌区面积为150~300m·d~(-1)的条件下进行了模拟计算。(2)在大麦沙丘沙中加入含&lt；@D122@&gt；D1Na的氯化钠溶液，以示踪Na在土壤和植物中的迁移。用具有数字化信息和高灵敏度的成像板(IP)代替X光胶片。结果表明，与X射线胶片相比，激电法能更好地跟踪Na在土壤中的迁移和Na在植物体内的迁移。(3)基于电磁波…的几种介质土壤水分探头的测量精度(2)共振现象，(3)复介电常数，(4)时间域反射仪和(5)幅值域反射仪。讨论了盐分浓度对土壤水分测定的影响。基于幅值域反射法的四杆平行式野外介质土壤水分测定仪的测量精度在(？)sy+-以内。[)0.01厘米；@D13@；d1/cm&lt；@D13@&gt；d1和(]sy.+-。[)0.02厘米；@D13@&gt；d1/cm&lt；@D13@&gt；d1分别在低水位和高水位范围内。与其它土壤水分测定仪相比，盐分测定仪对土壤水分测量的影响较小，测量范围为(~)~3万ppm。(4)为了监测土壤中的溶质运移，减小了四电极盐度探头的尺寸，以最大限度地减少对运移过程的干扰。用四种探头分别测定了鸟取沙(粘粒含量为2%)和不含粘粒的冲刷沙在饱和和非饱和水流中的扩散系数D。饱和渗流的弥散率几乎是恒定的(0.1厘米)，与两种砂岩的孔隙水流速v无关。非饱和渗流的弥散性大于饱和渗流的弥散性(&gt；0.3 cm)。常规沙丘沙的D大于冲刷沙，特别是在含水率较低(&gt；1 cm)的情况下。(5)根据试验和野外观测结果，建立了基于光谱反射率的植被覆盖指数(VCI)。在由沙、盐(NaC L)和植被(草皮)组成的模型表面上验证了该方法的适用性。给出了用光谱反射率估算砂土覆盖率和盐分覆盖率的方法。提出了利用光谱反射率诊断植被水盐胁迫的方法。较少

The aims of this research project are to propose the efficient irrigation schedules and to develope new soil salinity monitoring system, assuming productive green arid land conditions. The results are as follows ; (1) Irrigation scheduling for tank irrigation system was proposed by discussing simulation results estimated under conditions of water harvest efficiency of 80%, daily irrigation interval, design irrigation interval, irrigated areas of 150 - 300m<@D12@>D1 during irrigation periods of 4 - 22 years. (2) The sodium chloride solution containing <@D122@>D1Na was added to barley-grown dune sand in order to trace the movement of Na in the soil and plants. The imaging plate (IP) which has digital information and high sensitivity was used instead of X-ray film. It was found that the IP could trace the movement of Na in the soil and the translocation of Na in plants than the X-ray film. (3) The measuring precision of some dielectric soil moisture probes based on (i) electromagnetic wav … More e, (ii) resonance phenomenon, (iii) complex dielectric constant, (iv) time-domain reflectometry and (v) amplitude domain reflectometry was evaluated using salty sand. The influence of salt concentration on the measurement of soil water content was discussed. A field-type dielectric soil moisture prove with four parallel rods based on amplitude domain reflectometry had the measuring precision within (]SY.+-。[)0.01 cm<@D13@>D1/cm<@D13@>D1 and (]SY.+-。[)0.02 cm<@D13@>D1/cm<@D13@>D1 in the low and high water range, respectively. The gauge had small influence of salt concentration on moisture measurement compared with other soil moisture gauges in the range ()to 30,000 ppm of NaCl solution. (4) In order to monitor solute transport in soil, four-electrode salinity probes were downsized to minimize any disturbances of the transport processes. The dispersion coefficients, D,for a regular Tottori dune sand (2 % clay content) and a washed sand without clay were determined for saturated and unsaturated flows using the four probes. The dispersivity for saturated flow is almost constant (0.1 cm) regardless of the pore water velocity, v, for both sands. For unsaturated flow the dispersivity is greater (>0.3cm) than forsaturated flow. The regular dune sand has greater D than for the washed sand especially for lower water content (> 1cm). (5) New vegetation cover index (VCI) using spectral reflectances was derived from the results of the experiments and field observation. It's applicability was confirmed on the model surfaces which were composed of sand, salt (NaCl) and vegetation (turf). The methods to evaluate the sand cover ratio and salt cover ratio using spectral reflectances were derived in the experiment. The method to diagnose the water and salt stresses of vegetation using spectral reflectances are also proposed. Less