Water is one of the most essential inputs for production
of crops, and rice among all the cereals consumes the
most water for irrigation. In many systems, production of
1-kg rice takes 5000 L of water although this can be
reduced to about 2000 L (Lal 2007). The water status of
the soil has a dramatic effect on yield, and it also affects
grain quality (Dingkuhn and Le Gal 1996). Traditionally,
rice is planted under submerged condition; however, nonflooded
plastic film mulching (PM) and nonflooded
wheat straw mulching (SM) are being considered new
water-saving techniques in rice production. Different
water management treatments, namely PM, water-saving
irrigation, and conventional irrigation, significantly
affected brown rice rate, head rice rate, chalky grain rate,
amylose content, and protein content in a cultivar and
grain position dependent manner. Of all variables, water
treatment had the strongest effect on protein content
(Cheng et al. 2003b). SM was found to significantly
increase milling quality and reduced the percentage of
chalky grain, chalky size, and chalkiness, while PM
showed opposite effects. Gel consistency was found
decreased under PM (Zhang et al. 2008b). Rice is the
only crop which can survive periods of submergence.
However, flooding just before harvest brought visible
changes to the physical appearance of grains. The kernels
in flood-affected samples became soft and developed fissures
which contributed to low head rice recoveries, and
the milled rice had lower kernel weight and protein content,
but showed higher amylose and ash content (Singh
et al. 1990).
Growing rice in an upland nonflooded environment
also affects grain quality. A recent study involved several
cooking and nutrient quality traits, including amylose
content, gel consistency, gelatinization temperature, and
protein content, in the same populations grown under
upland and lowland conditions. The phenotypic values of
all four traits were significantly higher under upland environment
than lowland environment (Guo et al. 2007).