Design of a sequential irrigation system for on farm water management
Loading...
Date
2007-02-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
To obtain maximum crop yield out of the inputs like water, fertilizer, food, seed etc., invested in crop production, the most important single factor is the field water management. Crops should be irrigated at the proper soil wetness with just enough water to replenish the soil moisture deficit created in the root zone. Therefore a well-controlled irrigation system is one, which optimizes the spatial and temporal distribution of water, not necessarily to obtain the highest yield or to use the least amount of water possible, but to maximize the benefit-to-cost ratio. Tensiometer and gypsum block are the two basic devices that can be used as soil moisture sensors to schedule irrigation. Use of infiltrating agents and observation of moisture deficiency symptom are other methods for irrigation management. In order to control irrigation automatically by continuously monitoring soil water requirement, an electronic tensiometer and an electrical resistance sensor were developed at Central Plantation Crops Research Institute, Kasargod and are being used. But sensitivity of a tensiometer is upto a maximum of 0.85 atmospheres beyond which it seize to function. Many times the soil moisture tension is to be measured even up to 15 atmospheres. However electrical resistance sensors are used for measurement of soil moisture up to this range. Another method of scheduling irrigation is by sequential irrigation system. This paper gives the sequential irrigation system developed at Central Plantation Crops Research Institute. It consists of a time switch and a switching circuit. According to a set time in the time switch, a control circuit operates a solenoid valve connected on the irrigation pipeline to switch on the irrigation and keep it on for a predetermined period of time and then switch it off. The heart of the time switch is a quartz oscillator vibrating at a particular frequency. This frequency is converted to a 1 Hz. pulse in an integrated circuit. This pulse drives a stepper motor, which in turn drives a gear train that is connected to a switching dial. According to a set time in the time switch, a control circuit operates the solenoid valve or the starter of the electric pump either to switch on or switch off the irrigation. This system was installed in a coconut garden and was tested for one season. It is reported that the irrigation requirement for coconut palm is 32 liters/palm/day. Accordingly the number of hours the irrigation is to be done can be calculated by knowing the operating pressure in the irrigation pipeline and discharge rate of the emitter used.Depending on the availability of electric supply the starting time, the period, and the end point of irrigation can be set in the time switch. The practical utility of this circuit is that, this can be used along with any high frequency irrigation system such as sprinkler, perfo etc. and this works automatically and so no man power is required to do the irrigation.
Description
Keywords
Citation
Fourteenth national convention of agricultural engineers national seminar on role of agricultural engineers in hi-tech agriculture in the next millenium p 96-102