Millet irrigation with treated wastewater: Gas exchange response and nutrient accumulation

Matheus Mendes Reis,Luan Mateus Silva Donato,Érika Manuela Gonçalves Lopes,Rodrigo Eduardo Barros,Leonardo David Tuffi Santos,Ariovaldo José Da Silva

doi:10.1590/1413-7054201943023519

Matheus Mendes Reis, Luan Mateus Silva Donato + Show 4 more

Open Access

https://doi.org/10.1590/1413-7054201943023519

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Abstract

ABSTRACT Wastewater can be considered an excellent nutritional and water source for cultivated plants. However, the presence of high concentrations of salts and toxic compounds can negatively affect crops. The effect of irrigation with different concentrations of treated wastewater on the accumulation of nutrients and gas exchange aspects of millet (Pennisetum glaucum (L.) R. Br.) grown in clay soil and sandy loam soil was analyzed. This study was conducted in a greenhouse (16°40’57,50” S; 43°50’26,07” O; 650 m) in a 5 x 2 factorial design, consisting of five levels of concentration of treated wastewater (0, 25, 50, 75, and 100%), combined with two types of soil (clay and sandy loam). The experiment was designed in randomized blocks with four replicates. The increase in treated wastewater concentration in irrigation water applied to clay soil and sandy loam soil favored the increase of net photosynthesis, transpiration rate, stomatal conductance, leaf chlorophyll content and accumulation of macro- and micronutrients in millet plants. Millet plants grown in clay soil showed an average increase of 23% in gas exchange capacity and 71% in accumulation of macro- and micronutrients, when compared with treatments in sandy loam soil. Therefore, treated wastewater contributes to the increase in gas exchange capacity and greater accumulation of nutrients in millet plants, which represents an alternative for reduced demand for fresh water and use of chemical fertilizers.

Highlights

Lower demand for fresh water, nutrient recycling and reduced in the discharge of pollutants in water bodies are potential benefits of the use of treated wastewater (TW) in the irrigation of agricultural crops (Hanjra et al, 2012)
This study aimed to evaluate the effect of the irrigation of clay and sandy loam soil with different TW concentrations on the accumulation of nutrients, leaf chlorophyll content and photosynthetic capacity of millet plants (Pennisetum glaucum)
The treatments corresponded to five levels of concentration of treated wastewater (TW) (0, 25, 50, 75, and 100%) applied through irrigation combined with two soil types (clay soil (CS) and sandy loam soil (SLS))

Summary

Introduction

Lower demand for fresh water, nutrient recycling and reduced in the discharge of pollutants in water bodies are potential benefits of the use of treated wastewater (TW) in the irrigation of agricultural crops (Hanjra et al, 2012). The use of wastewater in irrigation may present risks that need to be observed, such as soil salinization and sodification (Bedbabis et al, 2015), nutrient excess (Kalavrouziotis et al, 2008), and contamination by microorganisms (Bernstein, 2011; Obayomi et al, 2019), heavy metals (Meng et al, 2016; Farahat; Linderholm, 2015) and pharmaceuticals and personal care products (PPCPs) (Thelusmond; Strathmann; Cupples, 2019). These risks may negatively affect human health, the environment and agricultural production. An option to mitigate such impacts is to use wastewater with fresh water, if available, to reduce the application rate of chemical and biological constituents in irrigated crops (Ayers; Westcot, 1999; Malash; Flowers; Ragab, 2005; Yu et al, 2012)

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