Design and construction of a soil moisture tracking-based automated irrigation scheduling system

Abstract

If the traditional rain-fed cropping practices are maintained, the amount of food produced will continue shrinking thereby increasing hunger and malnutrition amongst an increasing population. Africa as of 2019, despite having about 60% of the world’s uncultivated arable land, spends about $40 billion annually on food imports yet soils in Uganda for instance are some of the most fertile for crop growing. The cultivation index (the area of land used in agriculture over the total national acreage) is shrinking year by year as more land space is being dedicated to industrialization and infrastructural development. This is due to the higher return on investment from industrialization and commercial real estate as compared to agriculture. Lower profitability in agriculture means a lower labour force in the food production industry which means lower food made available to the entire nation in general. The core contributor to low agricultural profitability is the complexity involved in delicately balancing over 30 variables. Poor seed breeds, pests, diseases, weeds, too little water, too much water, poor fertilizer quality, high labour costs, high energy costs, are some of the challenges involved in commercial agriculture. The purpose of this study was to show how my creation; the ‘automated irrigation scheduling device’ (AISD) increases water use efficiency (WUE) when integrated in pressurized irrigated agriculture. The main objective was to design, construct and test the scheduling device with inbuilt soil moisture tracking technology. Specifically, the electronic device was designed on paper, assembled and calibrated using available material (plastic, transistors, screen and many more) and programmed to track soil moisture to update irrigation interval formulas before triggering the pump. The methods used to achieve the specific objectives combine such fields as irrigation system design theory for equations, electrical engineering circuit theory for basic components like resistors and capacitors and their interactions, and arduino a c-based machine programming language and development environment for the device operating system algorithm. The system on testing responded positively to every millimetre change in available soil moisture and turns on the ‘working pump’ at the adjustable trigger point to pump for the computed time (irrigation duration) before turning it off and taking a post-irrigation reading. The probes periodically gather soil moisture data every half hour but the moisture refill cycle (irrigation interval) runs once for every twelve hours. The system nevertheless had slight variations in sensitivity when the probes are placed in different soil types, and since it was calibrated in loam soils it best operates in loamy soils.