Water use efficiency and yield of shallot on coastal sandy soil ameliored by clay and biopolymer

Low water holding capacity and too high permeability are the main problems of coastal sandy soil. The main objective of the research was to improve water use efficiency and yield of shallot on coastal sandy soil. The experiment was arranged in a split-plot design. The main plot was three levels of watering, consisting of 9, 6, and 3 mm daily, and the sub-plot was the ameliorant types, consisting of clay soil (Vertisol or Inceptisol) combined with biopolymers (tapioca and polyvinylalcohol/PVA). The combination consisted of Vertisol + 1 tapioca, Vertisol + 0.1 PVA, Inceptisol + 1 tapioca, and Inceptisol + 0.2 PVA. Control treatment, untreated coastal sandy soil with 9 mm daily of watering, was made for comparison. The result showed that the clay soil + PVA as an ameliorant significantly increased the number of leaves and tillers compared to other ameliorants and control. The use of Vertisol + 0.1 PVA increased the fresh and dry weight of bulbs by 13.7 and 13.4 compared to the control. Its combination with the watering of 3 mm reached the water use efficiency of 7.3 kg.m^-3 and saved 51.3 compared to the control. The combination of clay and PVA is recommended for coastal sandy soil because it is able to improve the water use efficiency and yield of shallots. © 2019 IOP Publishing Ltd. All rights reserved.