With built-in long life internal batteries and underground telemetry, the Terrasonde can operate without wires or solar panels – those nuisance additions that ultimately get damaged during farming operations such as harvesting, sowing or spraying. In the dryland model, the primary lithium batteries has a lifetime of >10 years and the probe samples once per day. However, for application in horticulture, especially in drip irrigated crops, more data is required and hourly readings are typical. Such a high energy use would drain the internal battery in 2 years, but there is a solution – replaceable primary batteries.
The horticultural model of the Terrasonde is 120cm long and has eight sensors spaced apart at 10cm intervals. The top sensor is 20cm under the cap so that it can make the first measurement at 10cm depth. This probe model is ideal for row crops, cotton, nuts, grapes, citrus, veges. It is installed with a hand auger and sealed into the soil with a slurry compound. The IP68 battery housing holds two primary lithium C-cells and the dust cap keeps dirt and water away from the housing o-rings, so the probe can last for many, many years.
In late 2017 we installed the new horticultural probe in the sultana farm. The chart below shows the stored water in Block 8.
You can view the soil moisture data on our farm in real-time by clicking on the Demonstration sites.
The first soil moisture probe that Hussat built was installed in 2016 in our family vineyard at Farm 1396 in Hanwood, near Griffith, NSW, Australia. It was the 160 cm long dryland model (Model No. S08L16) with sensors every 20 cm and an internal primary lithium battery. It was installed with the top sensor at 10 cm below the ground, directly beneath a dripper and flush with the ground surface.
It remains there today, although an auxiliary battery pack (6 x AA) was added to prolong the life of the lithium battery as the probe was set to make hourly measurements which would have otherwise depleted the internal battery in 2 years.
The moisture data has been very important to the smooth running of our irrigation schedule. Early in the season we irrigate every third night, then later every 2nd, then in peak season we irrigate every night for 9 hours plus all weekend. The sultanas are a thirsty crop with a large canopy and Griffith is renown for hot clear summer days. We used the soil moisture data as a signal to increase (or decrease) the interval between irrigation events. The data also showed us that there is little root activity in the sultanas below 90 cm depth, as shown by the smooth change in water content of the deeper sensors (see below). On occasions the deeper sensors changed value due to winter rainfall or early season irrigation. We thus irrigate frequently, but not for so long that drainage occurs beyond 90 cm.
The sensor was placed half way down the row and the base-station near the headland. At harvest it is a simple matter of taking the base-station off the mounting pole; the sensor is unaffected by the passage of the harvester.
You can follow the moisture on our farm by opening the link to the Demonstration sites.
In the winter of 2015 Vince Conlan of Farm 274 in Yenda grew a dryland crop of barley, but the season ended with not enough soil moisture and the grain pinched, so he had to bail the crop. Had the soil probe been installed in that season, then he most certainly would have predicted that the crop could not finish so would have bailed earlier than he did. Thus, 2016 started with a dry soil profile. The probe was installed in April ’16. It then rained and later, flooded. Vince sowed 3rd week of May ’16 with 65kg/Ha Yarran oats and 70 kg/Ha DAP. From late August to early October over 200 mm rain fell and by the 1st week of Oct ’16 the paddocks were flooded and probe showed that the Plant Available Water reached 160 mm. However, the crop did not suffer too bad so during the drier period from Oct-Nov ’16 the oats took off although there was some lodging. In Jan ’17 there was another large rain event and some of the fallen oats germinated and subsequently the oats used up the entire available water.
Vince’s soil is a deep Mirrol Clay with a Plant Available Water Capacity of 160 mm. He agreed to test the new Terrasonde probe in 2016 and has gained useful insight into his farming. In particular, he did not crop his farm in ’17 due to the deep drying recorded, but is planning to sow based upon the 135 mm of Plant Available Water available at sowing in 2018.