Evaluation of dynamic uniformity and application efficiency of mobile drip irrigation

Abstract

Irrigation uniformity, application efficiency and seasonal irrigation uniformity of mobile drip irrigation (MDI) were compared to those of low elevation spray application (LESA) and low energy precision application (LEPA). A center pivot fitted with two sets of MDI (with dripper flow rates of 3.8 L/h and 7.6 L/h), LESA and LEPA was used in this study. Irrigation uniformity tests were conducted in accordance with the American Society of Agricultural Engineers’ standards. Application efficiency was computed as the ratio of depth of water retained in the root zone to that applied. Potential differences in season-long irrigation uniformity were evaluated by analysis of periodically acquired aerial vegetative index data. The coefficient of uniformity of the 3.8 L/h and 7.6 L/h MDI was 93.8% and 93.7%, respectively, and 95.1% for LEPA, and 83.8% for LESA. Application efficiencies for the 3.8 L/h and 7.6 L/h MDI, LEPA and LESA were 76.1, 96.8, 98.4 and 51.2%, respectively. There were no significant differences (p value = 0.5749) in the amount of water stored in the soil profile between MDI, LESA and LEPA, 72 h after irrigation. For three irrigation capacities of 6.2, 3.1 and 1.6 mm/day, there were no significant differences in mean seasonal Advanced Difference Vegetative Index (ADVI) between MDI, LESA and LEPA, with p value = 0.987, 0.999 and 0.999, respectively. A similar observation was made for Normalized Difference Vegetative Index, with p value = 0.998, 0.999 and 0.999, for MDI, LESA and LEPA, respectively. Higher coefficient of uniformity and higher application efficiency for MDI and LEPA indicate that they were more efficient than LESA. These results show that MDI can adapt the high efficiency of traditional drip irrigation to center pivot systems.