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

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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