Abstract
The industrial quality of grain is an important parameter to determine the commercial value of rice and can be influenced by water availability and type of cultivar. The present study aimed to evaluate the milling yield as well as the protein and nutrient contents of polished grains originated from two upland rice cultivars grown under rainfed and sprinkler-irrigated conditions. A randomized block design was used in a split-plot arrangement with eight replicates. Plots consisted of two cropping systems (rainfed and sprinkler-irrigated) with subplots consisting of two cultivars recommended for upland ecosystems (IAC 201 and Carajás). The sprinkler irrigation system increased upland rice milling (8.0%) and head rice yield (23.7%), for years with hot and dry weather spells occurring during the reproductive and maturation stages. Under conditions of lower water availability, the Carajás cultivar showed a milled yield value 5.1% higher than that of cultivar IAC 201. Lower water availability provided increases in protein, N, P, Ca, Mg, Fe, and Zn contents but reductions in S and Cu in the polished grains. Cultivars IAC 201 and Carajás had similar nutrient contents in the polished grains.
Highlights
In addition to low yield, upland rice grown under the dryland system in general presents lower grain quality when compared to grains originating from lowland systems
The lower tolerance to water deficit shown by the IAC 201 cultivar can be explained by the fact that this cultivar originated from a cross between cultivar IAC 165 and cultivar Labelle (Arf et al, 2002)
Sprinkler irrigation provided higher milling yields in both cultivars, both during the 1994/95 cropping season and the following year, indicating that water supplied through sprinkler irrigation may have promoted root growth, allowing better plant nutrition and grain filling, increasing milling yield, and allowing a continuous supply of water during periods when no precipitation was available
Summary
In addition to low yield, upland rice grown under the dryland system in general presents lower grain quality when compared to grains originating from lowland systems. The presence of broken grains in a rice lot is an undesirable characteristic, since it decreases quality and economic value, and leads to a reduction of the milling yield since small grains may be thrown away along with the hulls (Crusciol et al, 1999a). Grain breakage, verified during the milling process, is caused by cracks or weaker regions in the grains, and occurs especially during the hulling process and when the grains are polished (Crusciol et al, 1999b). Inadequate crop management as well as weather conditions (temperature, humidity, and precipitation) may influence milling yield and broken-grain ratio, decreasing the product’s physical quality (Chen & Kunze, 1983; Srinivas & Bhashyam, 1985)
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