Improvement of the chemical properties and buffering capacity of coastal sandy soil as affected by clay and organic by-product application

The main problem with coastal sandy soil is its low water and nutrient retention due to its low clay and organic matter content. This study was aimed at improving the chemical properties and buffering capacity of these soils by using ameliorants of clay and organic polymers. The leaching experiment was conducted with two factors and three replications. The first factor was a clay ameliorant (5% clay, whether from the soil type Inceptisol (I) and the soil type Vertisol (V)). The second factor was a natural or synthetic organic polymer (tapioca 1% and 2% (T1 and T2), tapioca dregs 1% and 2% (TD1 and TD2), polyvinyl alcohol 0.1% and 0.2% (P1 and P2)). The leaching was carried out at 1-month intervals and the leachate was collected for the analysis of the soluble Ca, Mg, K and Na. The leaching was stopped after all the treatments reached the electrical conductivity values < 100 μS/cm. The ameliorants of clay (I or V) and natural polymer (T or TD) significantly increased the cation exchange capacity, the available cations, and the buffering capacity of the coastal sandy soil. The single treatment of I was better than V in increasing the available Mg, while the combination with organic natural polymers could increase the available Ca and K. The treatment of ITD2 was able to increase the soil buffering and maintain the soluble Ca, Mg and K in the coastal sandy soil. Therefore, TD which is a by-product of the tapioca flour industry when combined with I has the potential to be a prospective ameliorant for coastal sandy soils.