An irrigation controller mechanically actuated by soil-water tension: I - Design, development and laboratory evaluations

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

doi:10.1590/1807-1929/agriambi.v21n6p369-373

Abstract

ABSTRACT The objective of this study was to develop and evaluate an irrigation controller that was mechanically actuated by soil-water tension within laboratory conditions. The controller was designed and constructed using readily available hydraulic fittings and other componentry. The main components of the controller were a tensiometer; a rubber diaphragm that moves according to the variation in tension inside of the tensiometer; an activation rod that transfers the movement from diaphragm to the switch valve; and a steel spring that regulates the activation of soil water tension. Six irrigation controller samples were tested in the laboratory to evaluate the mechanical performance and component forces required to activate the controllers. The relationship between spring adjustment and soil water tension required to open the irrigation valve was linear with a gradient ranging from 1.10 to 1.41 kPa mm-1 and a coefficient of variation of 9.2%. However, differences observed in the activation of the soil water tension could also be reduced by individual controller calibration. The calibration of the soil water tension required to initiate irrigation was easily set by adjusting the spring. The proposed controller is functional, simple to use, can be easily adjusted, and does not require electricity to operate.

Highlights

Electronic irrigation controllers are appropriate for use in most of situations and some of them are low-cost, there are certain regions where the lack of electricity limits access to those electronic devices
The controller (Figure 1) uses the energy fluctuations inside a tensiometer located in the active root zone of the crop to mechanically enable and cut-off irrigation when the soil-water tension (SWT) reaches a pre-set threshold
The relationship between the spring adjustment and the SWT required to open the irrigation valve was linear with a gradient ranging from 1.10 to 1.41 kPa mm-1 (Figure 3)

Summary

Introduction

40% of the rural population (1.3 billion people) in developing countries does not have access to electricity. In the north and northeast of Brazil, where half of the rural establishment are small-plot holders, this number is approximately 38%, and in Africa it is 58% (IEA, 2011). Electronic irrigation controllers are appropriate for use in most of situations and some of them are low-cost, there are certain regions (e.g. north and northeast of Brazil and Africa) where the lack of electricity limits access to those electronic devices. There is a need to develop alternative irrigation control technologies appropriate for use in regions where electricity precludes farmers from using electronic irrigation controllers

Objectives

Methods

Results