A new cultivation method, based on a concept of hydroponics, for vegetable crop production under wet lowland field conditions in Southeast Asia

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The tuberous roots of sweetpotato and storage roots of carrot have generally showed poor growth and development in low-lying areas due to water logging or excess moisture content of the soil In the present study, the growth and development of the tuberous roots of sweetpotato and storage roots of carrot were significantly influenced by the soil aeration nuder wet lowland conditions. The present study was then, conducted to develop new techniques to improve the rhizosphere soil aeration for increasing sweetpotato and carrot production under wet lowland areas in tropical and subtropical countries.In the result of the present study, (i) soil air composition wasimproved with providing the indigenous plant materials like rice straw, rice husk and rice husk charcoal inside the soil ridges. (ii) photosynthesis arid thus growth of sweetpotato and carrot was promoted due to lower carbon dioxide concentration in the soil and lower soil water content of the soil ridges.It is revealed that sweetpotato and carrot production under wet lowland conditions is possible if sufficient air spaces are provided inside the soil ridges using an appropriate volume of appropriate materials, e.g. a width of 150 mm and thickness of 120 mm of rice husk charcoal applied in the unmixed mass form.The cultivation method developed in the present study can be applied to other vegetable crops as well as sweetpotato and carrot which show poor growth under wet lowland conditions and can be utilized even in wet lowlands that have been left as wasteland.The indigenous plant residues used in this study to improve soil aeration are easily available with low cost in tropical and subtropical countries and easily degradable materials. Therefore, this cultivation method would contribute to establish the better agro- ecosystem for sustainable agriculture.