Attributes of irrigated rice and soil solution as affected by salinity levels of the water layer

Thiago Isquierdo Fraga,Felipe De Campos Carmona,Elio Marcolin,Ibanor Anghinoni

doi:10.1590/s0100-06832010000400005

Thiago Isquierdo Fraga, Felipe De Campos Carmona + Show 2 more

Open Access

https://doi.org/10.1590/s0100-06832010000400005

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Abstract

In the State of Rio Grande do Sul, Brazil, flooded rice fields using Patos Lagoon as the source of water for irrigation are subject to be damaged by salinity, since this source is bound to the sea on its southern end. The sensitivity of rice is variable during plant development, being higher in the seedling and reproductive periods. However, there is not enough information about the behavior of plants under salt stress during the course of its development, especially in the vegetative stage. This study evaluated the effect of different levels of salinity of irrigation water on the salinity of soil solution over time and on some plant attributes, during the vegetative stage of rice. The study was conducted in a greenhouse, where seeds of the variety IRGA 424 were sown in pots and irrigated with water with electrical conductivity (ECi) levels of: 0.3, 0.75, 1.5, 3.0 and 4.5 dS m-1; from the tillering initiation (V4) until the panicle initiation (PI). The evaluations made were the electrical conductiviy of soil solution (ECe), the dry biomass of plants and stems, tillering, height and the transpiration of plants. The ECe increased with the ECi over time, and was determined by water transpiration flux in pots. The ECe values at the end of the experiment were high and, in most cases, higher than the critical values for flooded rice. The growth attributes of rice were negatively affected from ECi of 2.0 dS m-1 and ECe of 4.0 dS m-1.

Highlights

The salinity is one of the main factors of land degradation in the world, acting negatively on crop growth
The relationship between electrical conductivity of the water layer (ECi) and Effective electrical conductivity (ECe) depends on the leaching fraction (LF), i.e., the amount of irrigation water that moves below the root zone, which in turn varies with soil texture
A higher ECe in this treatment may be related to the salt effect of fertilizers applied in the early stage of rice development, as well as to the electrochemical reactions that occur in waterlogged soil, which increases the concentration of ions in the soil solution (Ponnamperuma, 1972)

Summary

Introduction

The salinity is one of the main factors of land degradation in the world, acting negatively on crop growth. In the case of rice (Oryza sativa L.), especially in the coastal areas and floodplains of the State of Rio Grande do Sul, Brazil, the irrigation water salinity can affect large areas of three producing regions: Southern, Internal Coastal Plain and External Coastal Plain, since the main source used in these regions is the Laguna dos Patos lagoon, which is connected to the Atlantic Ocean on its southern edge. This effect occurs both in the winter months because of the prevalence of south winds, as well as in the summer months, when low rainfall, associated with the increased demand for water from the surrounding crops, reduce the level in the lagoon, allowing the entry of saline water from the sea (Marcolin et al, 2005). Zeng & Shannon (2000) found that the salinity of the soil solution (ECe) from 1.9 dS m-1 was enough to affect rice (cultivar M-202), suggesting the need for studies for the varieties and climatic conditions in southern Brazil

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