ECOWITT WH51 Wireless Soil Moisture Sensor

Before you buy: this probe cannot reach the internet by itself. It only talks by radio to an Ecowitt gateway, so buy it together with one of these:

• If your plot has only cellular coverage and sun: the ECOWITT WittField 4G & Solar Field Weather Station, whose gateway uploads over 4G, runs on solar power and holds up to sixteen of these probes.
• If a building with Wi-Fi and an outlet is within radio range: the GW1206 Soil Moisture Kit or the Wittboy weather station, each up to eight probes.

The WH51 is a soil moisture probe that you push into a bed, a row or a pot, and each probe on a gateway gets its own channel name.

Out in the field. It runs on a single AA battery, typically for about a year, and needs no cable, so it belongs out in the plot rather than in a greenhouse tray. Lithium AAs hold up best in the cold. Once paired, its readings join the rest of your data on Ecowitt.net, where a REST API serves them to your own scripts and agents.

Moisture differs across a single plot more than most growers expect. A probe in the hollow and another on the rise will tell you so, which is the same point Good Earth MCP makes when it reports the spread across a block rather than one number.