Determination of the Water Potential Threshold at Which Rice Growth Is Impacted

Caio Dos Santos,José Favarin,André De Borja Reis,Paulo Mazzafera

doi:10.3390/plants7030048

Caio Dos Santos, José Favarin + Show 2 more

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https://doi.org/10.3390/plants7030048

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Abstract

Rice feeds 50% of the world’s population. Flooding is the most common irrigation system used for growing rice, a practice responsible for a large amount of water loss. Climate changes may affect water availability in irrigated agriculture, and it will be necessary to develop more sustainable irrigation practices. The aim of this work was to determine, in controlled conditions, the threshold when water potential begins to decrease plant growth. Two independent greenhouse experiments were conducted during middle summer and fall, in order to validate the results for high and low evapotranspiration conditions. Rice plants were grown in hydroponics and the water potential was adjusted with polyethylene glycol 6000, varying from −0.04 MPa (control) to −0.19 MPa. Leaf water potential, water use efficiency, leaf area, and root and shoot biomass were evaluated. All assayed parameters decreased as the water potential was decreased. The water potential threshold which starts to negatively affect rice growth was between −0.046 and −0.056 MPa, which are values close to those observed in the field in previous research. The definition of a critical value may help to improve water management in rice cultivation and to maintain productivity.

Highlights

Rice (Oryza sativa) is one of the main crops worldwide, and is grown on approximately 160 million hectares
At high evapotranspiration (HET) conditions, the total evapotranspiration (Figure 1) was 758 mm, on average, when the water potential of the solution was at the highest potential (−0.04 MPa)
The exponential regression fitted to the data indicates that the evapotranspiration started to decrease when the water potential was lower than −0.048 MPa

Summary

Introduction

Rice (Oryza sativa) is one of the main crops worldwide, and is grown on approximately 160 million hectares. Brazil is the ninth largest producer of rice in the world, and produces around 1.7% of the world’s rice: 11.7 million tons on 2.2 million hectares. In Brazil, 60% of rice production is irrigated by flooding. When the world is facing prospects of climate change and water scarcity, and given the expressivity of rice, it is important to discuss the rational use of water in agriculture. The flood irrigation system has several losses of water, such as direct evaporation on the atmosphere–water interface, lateral flow, and deep percolation [2]. These losses significantly increase the amount of water to be used in irrigation. More efficient and sustainable irrigation systems for growing rice must be found [4]

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