Moisture Sensor’s Role in Irrigation Initiation.

Last week Dr. Eric Larson wrote an excellent article dealing with corn irrigation initiation.  At that time, a few growers had already begun to irrigate.  Dr. Larson stressed the importance of accurately assessing soil moisture verses leaf wilting when determining irrigation initiation.  The role of soil moisture sensors in determining when to initiate irrigation is proving more beneficial.

Over the last three years the moisture sensors in our test plots have allowed us to delay irrigation initiation just long enough to capture the next rainfall event.  This past week was no exception!  Here is an example.  One of our growers had already initiated irrigation.  We had Watermark sensor data of 93, 73, 36 at the 6″, 12″, 24″ zones respectively.  Based on the movement of the 24″ sensor from the prior weeks reading of 22 to 36, we knew the root system had begun to utilize water at the 24″ level.  If you recall how to calculate the initiation value, we assign a factor of 25% to the 6″ and 12″ sensor and 50% to the 24″ sensor. The average soil moisture values look like this.

With an average available soil moisture value of 59.5cb, we knew we had a few more days before reaching the trigger values of 80cb to 100cb at this growth stage.  Knowing how much available moisture we had allowed us to delay irrigation initiation just long enough to capture this weekend’s two inch rainfall event.

A review of available moisture calculations can be found here;

https://www.mississippi-crops.com/2014/06/21/how-to-use-watermark-sensors-to-assess-soil-moisture-and-schedule-irrigation/