There are several factors to consider when choosing a hose reel irrigation machine. These include a plan of the plot showing contour lines, detailing the point where the water intake is located and any obstacles that might prevent the normal movement of the machine.
The crop rotation, taking into account the water needs and the average depth of roots. The type of soil, its water retention capabilities, and the infiltration rate. The prevailing winds in the irrigated areas. The available flow, pressure (where applicable) and water quality.
Calculating the irrigation parameters and volume to be pumped
By taking into account the land’s water storage capacity, the crop’s root depth, and the permissible water deficit, you can determine the millimeters of water or liters per square meter to be applied (rounded up after applying an application efficiency of 75%). Once you know the expected watering hours per day (coinciding with off-peak energy hours), you can determine the greatest number of placements per day, estimating one hour for changing the position of the hose reel irrigation system.
The cubic meters per hour that the pump needs to supply is found by dividing the volume of water to be applied by the number of hours to apply it. We recommend increasing the flow between 15-20% to account for unforeseen issues, including breakdowns or, for example, when winds reach above 4 meters per second, as this makes it difficult to irrigate.
Pressure needed at the hose reel input
This can be found by adding to the pressure that the sprinkler requires for normal operation, its height above the ground, the slope of the land at its most unfavorable point, and the losses of pressure in the polyethylene pipe and in the propulsion and regulation mechanisms.
Selecting the sprinkler and separation between irrigation positions
Once you know the flow and the recommended pressure, you can select the sprinkler using the manufacturer’s charts. The chart of the selected model indicates the reach and the flow needed for said pressure, which varies depending on the selected nozzle. We recommend using a sprinkler that covers an area of between 200 and 220 degrees. It is important to periodically check for wear on the nozzle and replace it if necessary so as not to vary the discharge rate.
Taking, for example, an average wind speed of 2.5 meters per second, the most advisable spacing between irrigation positions is 75% of the wetted diameter.
Forward speed of the hose reel machine and irrigation time
The forward speed (between 5-50 meters/hour) is calculated by dividing the flow (liters/hour) by the product of the gross irrigation dosage (liters/m2) and the meters of spacing. The time it takes to complete an irrigation position will depend on the distance to cover and the forward speed. You also have to take into account the operating time when not moving forward, which comes into play at the beginning and end of each positioning.