Performance of rice (Oryza sativa) planted on raised-bed under different soil-moisture tensions

An experiment was conducted at New Delhi during rainy season of 2001 and 2002 on aerobic rice (Oryza sativa L.) cultivated on raised-beds under different soil-moisture regimes (field capacity, 20 and 40 kPa tensions). The yield was considerably less on raised-beds, varying from 12–24% at field capacity to 40–46% in beds irrigated at 40 kPa soil-water tension compared with the direct-seeded flat land at 20 cm row spacing. Nitrogen in the form of nitrate was dominant in raised-beds (>23%) compared with ammonical form in flat land, and the proportion of nitrate also increased in beds (3–10%) with the increase in soil-moisture stress. Cultivar ‘Pusa 44’ on raised-beds did not withstand soil-moisture stress, which was reflected in further rapid reduction in its yield by 23–40% when moisture-stress was built-up at 40 kPa tension compared with that at field capacity. The nitrogen content in grain and its uptake also decreased significantly by more than 21 and 42% with the imposition of moisture stress from field capacity to 40 kPa tension. It is necessary to develop special aerobic lowland rice cultivar which can compensate the space left for furrows by producing more number of productive tillers, and can withstand soil-moisture stresses at varying degrees by profuse root growth and proliferation.