## 3 Results
### Experiment 3: Evaluation of the CAIS with Multiple Irrigation Points  
The previous experiment demonstrated that the CAIS could retain the soil moisture near the irrigation point at a constant level. This experiment used the CAIS at multiple adjacent irrigation points to maintain the soil moisture level of the whole experimental plot at a specific level. The experimental plot has night irrigation areas similar to Figure 2a. The setup of the experimental parameters was the same as Section 3.2. To guarantee that the soil moisture in the experimental plot could evaporate and diffuse completely, the CAIS performed regular irrigation every 3 h for 24 h before the experiment began. Figure 10a-c shows the moisture levels at points VPA#0, VPA#1, and VPA#4. The selectable irrigation intervals were 2, 3, and 4 h. The CAIS started the first irrigation at p.m. 04:00 on Day 1. The objective was to maintain the moisture level at 590 for all 3 cm soil depths in these three areas. Note that instead of placing the probe in the soil continuously, the soil sensor used the CAIS platform described in Section 2.3.1 to probe each VPA every 30 min. Intermittent probing can prevent rusted probes from introducing heavy metal pollution to the soil. Each probe lasted for one minute and sampled the soil moisture every second. The moisture value from the probe was averaged for all 60 data samples. The first sampled moisture levels of these three VPAs were 649, 644, and 661. These levels were higher than the required moisture level 590. The CAIS applied two 4 h irrigation intervals for all the VPAs to reduce their soil moisture levels. By Day 2 a.m. 00:00, their moisture levels were 598, 601, and 609. The CAIS adapted the irrigation interval of VPA#0 and #1 to 3 h. Their moisture levels continuously decreased until Day 2 a.m. 06:00. At Day 2 a.m. 06:00, the moisture levels of VPA#0 and VPA#1 were 584 and 589. The CAIS changed the irrigation interval to 2 h to raise their moisture levels until Day 2 p.m. 02:00. Figure 10a-c shows the results. In Figure 10a, the CAIS continuously used the 2 h irrigation interval to raise the moisture level of VPA#0 until Day 2 p.m. 04:00, when the moisture level reached 596. The CAIS then adjusted the irrigation interval to 3 h and 4 h to suppress the rising moisture level. The moisture level at Day 3 a.m. 03:00 was 589 so the CAIS changed the irrigation interval to 3 h. However, the moisture level was still close to 600 on Day 3 a.m. 06:00. The CAIS applied a 4 h irrigation interval to alleviate the moisture  
Figure 9: The constant moisture experiment with a single irrigation point. The moisture levels of VPA#4 with different depth layers of soil are sampled. The VPA#0 3 cm, which is the neighboring VPA, is also evaluated. The moisture level is ranged from 0 to 1023.  
level until Day 3 p.m. 10:00. The moisture level at Day 3 p.m. 10:00 decreased to 585, and the CAIS used the 2 h irrigation interval until Day 4 a.m. 04:00. In Figure 10b, the moisture level at Day 2 p.m. 02:00 was 590. The CAIS used the 3 h irrigation interval to moderate the increasing moisture level of VPA#1. However, the moisture level did not explicitly decrease even though the CAIS continuously applied the 3- and 4 h irrigation intervals until Day 3 a.m. 10:00. This phenomenon arose from the different density of the planting medium. However, by Day 4 a.m. 02:00, the moisture level (580) had fallen below the required level of 590. VPA#4, which was located in the center of the experimental plot, was influenced by the neighboring VPAs. Initially, its moisture level was higher than 590, and the CAIS applied the 4 h irrigation interval until Day 2 a.m. 08:00 shown as Figure 10c. By Day 2 a.m. 08:00, the moisture level had fallen to 578. The CAIS then applied 2 h irrigation to raise the level until Day 2 p.m. 08:00. The moisture level on Day 2 p.m. 08:00 was 601. The CAIS switched to the 4 h irrigation interval to lower the moisture level until Day 3 p.m. 07:00. The moisture level at this time was 588.