Response of some characteristics of two local rice cultivars to integrated management of irrigation and drainage

Alternate wetting and drying (AWD) the soil significantly increase rice production and improve water use efficiency. Other advantages of AWD over continuous flooding are a decrease in arsenic accumulation in rice grains and an increased availability and uptake of some micronutrients such as zinc in the grain Under such practice, the paddy field does not need to be continuously flooded and is allowed to dry out for a certain number of days and the soil water regime is transformed from saturated to alternately saturated and unsaturated. However, no information is available on the effect of AWD on rice quality parameters in subsurface-drained paddy fields. In this study, the effect of this type of water management was evaluated on some quality parameters of Daylamani and Hashemi rice cultivars including grain protein, milling recovery, brown rice, white rice, hard shell, fine bran, grain moisture, broken rice, seed long before backing and seed width before backing in surface- subsurface drained paddy fields.
The experiments were carried out as split plot based on randomized complete block design with three replications at the Sari Agricultural Sciences and Natural Resources University during two rice growing seasons (2014-15). Different subsurface drainage systems and a surface drainage system or control were considered as main plots and rice cultivars were considered as sub plots. Field water management was as flooding irrigation combined with three drainage periods at different times of the growing season. At harvest time, the protein content, milling recovery and other quality parameters of the rice grain were determined. Analysis of data was performed using SAS software.
Minor differences in the water management during the growing seasons resulted in various responses of the two cultivars to alternate irrigation and drainage. Subsurface drainage treatments significantly affected on fine bran, milling recovery and grain protein in the first growing season while their effecte was only significant on the soft rice bran in the second growing season. In subsurface drained area, grain protein of both cultivars was lower than that in the control. Protein content of Daylamani cultivar (8.18 %) was significantly higher than that of Hashemi cultivar (7.73 %). Also, white rice and milling recovery of both cultivars in the subsurface drainage treatments were significantly greater than those in the control. The maximum milling recovery (67.32 %) was observed in subsurface drained area.
The results showed that drying periods during a suitable period of rice growing season, can lead to improved quality of rice grain in subsurface drained paddy fields.