Irrigation controller mechanically actuated by soil-water tension: II - Field evaluations

Alexsandro C S Almeida,Conan A Salvador,Tarlei A Botrel,Antonio P De Camargo,Marinaldo F Pinto,Steven R Raine

doi:10.1590/1807-1929/agriambi.v21n5p298-303

Abstract

ABSTRACT In this study, a field evaluation of the performance of an irrigation controller mechanically actuated by soil-water tension (SWT) was performed. The controller employs a tensiometer used as a sensor of SWT to directly control a mechanically actuated hydraulic valve. Six controllers were installed in an orchard to control the irrigation for six rows of plants over 64 days. Each controller controlled the irrigation of one lateral drip line. The drip irrigation system was gravity-fed from a water source placed 7 m above the soil surface. The SWT and the pressure in each lateral line were measured to evaluate the performance of the controllers. All the controllers tested in the field autonomously initiated and terminated the irrigation during the evaluation. Irrigation events were initiated when values close to the set soil-tension values were reached and were terminated at lower soil-tension values. As the SWT in the root zone was maintained close to the setup threshold plus 20% tolerance for at least 90% of the evaluation period, the performance of the controllers was considered satisfactory. The proposed controller was shown to be functional and was operated effectively for an SWT range of up to 30 kPa, which is commonly encountered under high-frequency irrigation conditions.

Highlights

The availability of soil water for planting is one of the key factors that affect crop yield
Soil-water tension (SWT), which determines the availability of soil water to plants, is a critical factor in the regulation of plant growth
The drip irrigation system was gravity-fed from a water source placed 7 m above the soil surface

Summary

Introduction

The availability of soil water for planting is one of the key factors that affect crop yield. An effective irrigation schedule considers when to irrigate and how much water to apply for maximizing the profit and water-use efficiency (Ayars & Phene, 2007; Pardossi et al, 2009). Irrigation based on the availability of soil water has been a practical solution for simplifying irrigation scheduling on farms (Stirzaker & Hutchison, 2005; Létourneau et al, 2015; Nolz et al, 2013; Dabach et al, 2016). Automatic irrigation scheduling using soil sensors has been applied, yielding increases in the efficiency of water use (Hoppula & Salo, 2007; Dabach et al, 2013; Miller et al, 2014) and reductions in pollution by reducing the runoff or leaching of nutrients (Zotarelli et al, 2011)

Objectives

Methods

Results