Flooded rice yield as affected by levels of water salinity in different stages of its cycle

Abstract

SUMMARYLosses of productivity of flooded rice in the State of Rio Grande do Sul, Brazil, may occur in the Coastal Plains and in the Southern region due to the use of saline water from coastal rivers, ponds and the Laguna dos Patos lagoon, and the sensibility of the plants are variable according to its stage of development. The purpose of this research was to evaluate the production of rice grains and its components, spikelet sterility and the phenological development of rice at different levels of salinity in different periods of its cycle. The experiment was conducted in a greenhouse, in pots filled with 11 dm 3 of an Albaqualf. The levels of salinity were 0.3 (control), 0.75, 1.5, 3.0 and 4.5 dS m -1 kept in the water layer by adding a salt solution of sodium chloride, except for the control, in different periods of rice development: tillering initiation to panicle initiation; tillering initiation to full flowering; tillering initiation to physiological maturity; panicle initiation to full flowering; panicle initiation to physiological maturity and full flowering to physiological maturity. The number of panicles per pot, the number of spikelets per panicle, the 1,000-kernel weight, the spikelet sterility, the grain yield and phenology were evaluated. All characteristics were negatively affected, in a quadratic manner, with increased salinity in all periods of rice development. Among the yield components evaluated, the one most closely related to grain yields of rice was the spikelet sterility.Index terms: yield components, spikelet sterility, Oryza sativa.(

Mitigation of methane and nitrous oxide emissions from flood-irrigated rice by no incorporation of winter crop residues into the soil

“…When the rice plants had three to four leaves, 1,200 mg N and 720 mg K 2 O were applied per plot, as urea and potassium chloride, respectively. The fertilizer quantities in this study were calculated for an optimum rice development, estimated based on a previous study using the same soil (Fraga et al, 2010).…”

Laboratory Salinization of Brazilian Alluvial Soils and the Spectral Effects of Gypsum

“…Alluvial soils occur over these rock substrata along the rivers [19]. This area was selected, because it presents many problems of salinization that affect the productivity of irrigated rice [20]. According to the Köppen classification, the climate in the region corresponds to very hot and semi-arid (BSW'h') with average annual rainfall of 600 mm, a mean annual temperature of 27.5 °C and a potential evapotranspiration greater than 2000 mm [21].…”

Attributes of irrigated rice as affected by soil sodicity and potassic fertilizer application

“…Of all biomass assessments, however, the shoot dry matter at full flowering correlated best with yield ( Figure 3e). The literature reports that different rice cultivars are inhibited in biomass production with increasing salinity of the medium, as presented by Zeng et al (2001), Grattan et al (2002) and Fraga et al (2010). The decrease in osmotic potential of soil solution induces the accumulation of abscisic acid in plants (Chazen et al, 1995), decreasing stomatal conductance and intercellular CO 2 concentration.…”

“…For sodicity, Fairhurst et al (2007) determined the critical level according to the exchangeable Na percentage (ESP); soils with ESP > 20 % are considered harmful to the crop. According to Pearson & Bernstein (1959), salinity is critical to rice in the seedling and flowering stage, resulting, respectively, in plant density reduction (Oster et al, 1984;Shannon et al, 1998) and spikelet sterility (Ehler, 1960;Fraga et al, 2010), a property highly correlated to grain yield (Grattan et al, 2002).…”

“…Most studies on the effects of salinity and sodicity on rice in Rio Grande do Sul have been performed in controlled environments, such as pots or tanks (Machado et al, 1991;Marcolin & Macedo, 2001;Schoenfeld et al, 2007, Fraga et al, 2010, where the response of different plant properties, e.g., biomass and grain yield of genotypes under sodicity levels in irrigation water are evaluated. In these studies, however, Na is accumulated in the root zone, since water with excessive levels of this ion is continually added while on the other hand, leaching and deep water percolation do not occur, which are real field conditions, especially in sandy soils.…”