a sensor that is economical and cost efficient even if it is not as accurate as the other SMS. Another example is a farmer whose priority is to deal with saline and/or heavy soils, leading to paying more to have reliable and functional SMS.
Table 1. FC, PWP, and PAW based on soil texture (adapted from Easton and Bock, 2016)
| Soil texture | FC (inch of water/inch of soil) | PWP (inch of water/inch of soil) | PAW capacity (inch of water/inch of soil) |
|---|---|---|---|
| Sand | 0.05 | 0.12 | 0.07 |
| Sandy loam | 0.09 | 0.21 | 0.12 |
| Loam | 0.16 | 0.36 | 0.20 |
| Silt loam | 0.18 | 0.39 | 0.21 |
| Clay loam | 0.24 | 0.39 | 0.15 |
| Silty clay | 0.26 | 0.39 | 0.13 |
| Clay | 0.27 | 0.39 | 0.12 |
Table 2. A short description and photos of highly used SMS for irrigation (adapted from Kelleners et al., 2004; Ling, 2004; Sample et al., 2016; Labodia Prima, 2019; SwitchDoc, 2019; Edaphic, 2021; Robinson, 2021; Trellise, 2021)
| SMS | Short description | Photo |
|---|---|---|
| Tensiometer | Soil particles hold water through either tension or adhesion. Tensiometers are SMS that measure the tension between soil particles and water molecules. In order for plants to access this water, they must overcome the tension to draw water molecules away from the soil particles and into their roots. The soil matric potential or soil moisture tension reading tells how hard the plant must work to extract water. A tensiometer is a vertical, water-filled tube with a porous tip that is inserted into the soil at recommended depths; the soil draws water out of the porous tip of the sealed tube, creating a vacuum. Drier soils create a stronger vacuum since water molecules are harder to pull off soil particles. |  |