Abstract
A challenge for the design of drip irrigation systems with non-pressure compensated emitters is to increase the maximum length of the lateral lines without significantly reducing water application uniformity. This work evaluated the effect of the flow-rate variation and the local head loss in the maximum length of drip tape with a non-pressure compensated flat emitter. The tests were carried out in a laboratory, using a collapsible drip tape non-pressure compensated in three 50-meter segments. The production line was configured to generate drip tapes without insertion of emitters and with closed emitters (0.30 m spacing). The experimental local head loss was compared with the Darcy-Weisbach equation's estimates using the Blasius friction factor. In the sequence, simulations were generated for the flow-rate variations of 10 and 20% for the emitter spacings of 0.30, 0.40, and 0.50m. The results showed that the local head loss had little influence on the lateral line's maximum length, generating variations of 2.5% on average. However, increasing the allowable flow rate variation from 10 to 20% resulted in a 34% increase in the lateral line maximum length. Also, the reduction in uniformity coefficients was less than 5%, enabling the indexes to remain above 90%. The adoption of higher flow rate variation values allowed gains in the lateral line length with a small decrease in uniformity, making it an alternative to reduce design and operational costs.
Highlights
Micro irrigation systems apply dripping water slowly to the root systems of plants, either directly near the root zone or onto the soil surface (Baiamonte, 2018)
This work evaluated the effect of the flow-rate variation and the local head loss in the maximum length of drip tape with a non-pressure compensated flat emitter
A collapsible drip tape (CDT) consisting of polyethylene resins with the manufacturer's technical specifications shown in Table 1 was used to carry out the study
Summary
Micro irrigation systems apply dripping water slowly to the root systems of plants, either directly near the root zone or onto the soil surface (Baiamonte, 2018). The drip tape emitters can be pressure-compensated or non-pressure-compensated. The compensated drippers provide a constant flow rate under pressure variations along the lateral line, allowing longer lengths, but they are more expensive. Using non-pressure compensating emitters, the flow rate decreases as the pressure is reduced, resulting in shorter lateral lines to obtain the desired uniformity (Ludwig and Saad, 2013). Lay-flat drip tapes with non-pressure compensated emitters are widely used to irrigate field crops and seasonal horticultural crops due to their high application efficiency and uniformity, ease of installation, and low investment cost (Provenzano et al, 2014; Wang et al, 2020). The limitation is that, due to head loss, the lateral line length must be short to maintain uniformity, even when installed in level ground conditions
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