Irrigation should be implemented when soil moisture measurements and crop growth stage indicate that it would be helpful to maximize yield and profitability.
What to Watch For
Soil moisture sensors can be used to complement evapotranspiration (ET) soil water estimates. Comparing actual soil moisture measurements to predicted ET levels every couple of weeks is a good strategy for irrigation management.
Soil water sensors need to be in direct contact with undisturbed soil in order to provide accurate readings. During installation, minimize damage to roots and soil structure and avoid air voids, large roots, rocks, and other obstructions. Also, avoid placing sensors in field high spots, depressions where water may collect, and slope changes. In essence, place sensors in areas where soil and plant properties are most representative of the entire field. Sensors should be placed at different depths in the crop root zone as typical installations include one or more sensors for each foot of rooting depth. It is important to calibrate all soil moisture sensors in the field for the specific soil type. Examples of some common soil moisture determination methods and their advantages/disadvantages are included in Table 1.
1 Crookston, M.A. 2011. Utilizing soil moisture readings in irrigation scheduling. Proceedings of the 2011 Central Plains Irrigation Conference
2 Irrigation Handbook for the Great Plains. Water Utilization Center. Monsanto. http://www.monsanto.com. Web sources verified 03/20/18