Soil moisture measurement for better irrigation management

Dear friends, I want to know some user-friendly and cheap solutions for measuring soil moisture at farm level. I am trying to optimise the water use in agriculture for irrigation. If you have used any moisture sensor which provides correct results, please share information with me. Let me tell you that the Tensiometers are not suitable for us as the soil characteristics are different across the field at our project area. Please share your suggestions for measuring soil moisture at farm level.