Abstract
This study aimed to establish a comparison for theoretical water demand between rice plants grown under flooding and under different levels of water stress, imposed at distinct crop stages, in terms of plant morpho-physiology and phenology. The experiment was installed in a greenhouse, using complete randomized design and factorial scheme 3 × 4 + 1, with four replications. Factor “A” was defined as the growth stage when water stress was imposed on the treatments, these stages being (1) vegetative, (2) reproductive 1, and (3) reproductive 2; factor “B” was composed of four levels of water stress (0 to 200 kPa). The additional treatment consisted of a flooded check. Water was replenished back to saturation every time the threshold stress level was reached. There is damage to rice growth and development in water tensions greater than 30 kPa when applied between tillering start and anthesis. Main damage was observed as reduced rates of culm growth; leaf area tended to be maintained. Water luxury consumption by rice plants grown under flooding seems to be about 23% of the total demand, compared to the other irrigated treatments. The rice field should be irrigated back to saturation when soil water tension is between 10 kPa and 30 kPa. Overall, theoretical crop coefficient (Kc) for rice under sprinkler irrigation is about 20% lower than that observed for the flooded check. Key words: Water consumption, planting system, Oryza sativa.
Highlights
Rice is a staple food for nearly half the world's population, being cultivated in 112 countries, with 90% of the world’s production concentrated in Asia
The dry mass of rice plants (Figure 3A) was affected when the water stress was applied at the “V” or at the “reproductive 1 (R1)”
Plants in this group weighed more than the ones reported at “V” and “R1”; this is expected because rice plants do not stop growing at panicle differentiation but at heading
Summary
Rice is a staple food for nearly half the world's population, being cultivated in 112 countries, with 90% of the world’s production concentrated in Asia. In Brazil, about 3 million hectares are cultivated every year and rice is traditionally present in Brazilian meals, regardless of social class. The southern region of the country supplies approximately. 65% of Brazilian rice (Gomes and Magalhães Jr., 2004). The demand for water in flooded rice cultivation is considerably higher than the water requirement of crops traditionally sprinkler irrigated, such as soybeans and corn. Rice is a sub-aquatic plant adapted to a flooded environment (Correll and Correll, 1975), and may be grown without flooding if the water is managed properly.
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