Soil improvement at sand dune by using tropical peat.

为了评价热带沿海地区沙丘土壤改良后作物生长的可能性，研究了热带泥炭和（或）山地土壤混合成沙的效果。以下结果表明，改良土壤后作物种植的可能性。泥炭与山地土的混合降低了砂土的水力导水性，增加了砂土的持水量；过多的混合可能会导致排水不良，通风不良，有效含水量降低。在干重基础上，砂泥炭山地土的最佳混合比为84:6:10；混合比使有效含水量提高3倍。采用SPAC模型模拟对混合效果进行了评价。在泰国最南部的那拉提瓦省的沙丘区收集气象资料和作物资料。结果表明，优化后的混合条件使土壤蒸腾量增加1.5倍，入渗降水的排水量从43%下降到27%。利用突破曲线和模拟排水估算了土层营养的淋失量。砂土层中所有肥料仅占年总排水量的30%；据估计，在年总排水通过后，20%的肥料仍会残留。

In order to evaluate the possibility of crop growth after improvement of the soil layer at sand dune in tropical coastal area, the effect of mixing of tropical peat and/or mountain soil into sand was examined. The following results showed the possibility of crop cultivation after improvement of the soil.1. Mixing of the peat and the mountain soil decreased hydraulic conductivity and increased water holding capacity of the sand ; too much mixing may cause poor drainage, aeration, and available water content. The optimum mixing ratio in dry weight basis was estimated to be 84 : 6 : 10 for sand peat mountain soil ; the mixing ratio increased the available water content 3 times.2. SPAC model simulation was applied to evaluate the effect of the mixing. Meteorological data and crop data were collected at sand dune area in Narathiwat province, the southmost of Thailand. The results showed that the optimum mixture condition increased transpiration 1.5 times more than original sand and drainage of infiltrated rainfall decreased from 43% to 27%.3. Eluviat ion of nutrition from soil layer was estimated by using the break-through curve and simulated drainage. All fertilizer in sand soil layer was estimated to eluviate by only 30% of yearly total drainage water ; 20% of fertilizer was estimated to remain after yearly total drainage water had passed.