Abstract: An agricultural sensing system includes multiple sensor and/or actuator modules configured to communicate with a relay unit. The sensor and/or actuator modules are powered using solar energy and contain no batteries. The modules feature sleep modes in which some circuits are placed in a low energy mode to conserve energy and remove the need for batteries. Communications to or from the relay unit are optionally timed to avoid interference between transmissions from different sensor and/or actuator modules. The relay units are configured to relay sensor data and send commands to the sensor and/or actuator modules.