As someone who has done a lot of gardening, and automated that gardening, I personally find soil moisture to be a complete boondoggle of something to measure.

As someone who has done a lot of gardening, and automated that gardening, I personally find soil moisture to be a complete boondoggle of something to measure. It doesn't tell you if the plant is taking up the moisture, or if the pH is correct (or you have some kind of nutrient salt lockout). The author says they are having trouble because the water isn't evenly distributed. While it sounds scary, hydroponics is much easier to automate. Use a substrate like grodan blocks that can't be overwatered, and have it drain back into the reservoir you are pumping from. Then it's just a matter of setting your cycle time appropriately, and watering for x seconds every y hours, and changing the water after a set number of days, and adding new nutrients. By using more water than you need without risk, you can ensure an even level of watering over the entire medium. It's also much easier if you have a nutrient problem as you can easily flush with a large amount of properly pH'd water to 'reset' your substrate, which is very hard to do with soil. This doesn't even get into things like potting mix typically has eggs for all sorts of pests, if not pests themselves. If you are lucky and get a clean batch, you are still providing a great environment for pests to live. While it does cost a bit more to do hydro, it's honestly not that much. If you want to be super cheap you can use pH papers or by a $20 pH pen. A starter nutrient kit from general hydroponics should be under $30. PS - here's a link to my raspberry pi automated hydro system on hackaday (https://hackaday.io/project/12418-garden-squid https://hackaday.io/project/12418-garden-squid)