We use Delmhorst's GB-1 gypsum blocks to monitor soil moisture. These sensors are installed at depths of 1', 2' and 3'. We place these sensors in 2-3 sites/field, and each site is determined from Veris EC maps, aerial IR images and producer yield maps. These senors are read twice
weekly, and data entered into a database that day. Soil Moisture
Charts are updated, each day, and emailed to clients.
These blocks assume equilibrium with the soil with 48-72 hours.
The KS-D1 instrument simply sends an electrical impulse through the sensor and records These values are converted to percent of field capacity, and charts are updated with 1', 2' and 3' values and the average percent of field capacity for the top 3 feet of the soil profile is charted also. The total percent available is subtracted from the total amount the soil will hold and that value charted as the amount needed to bring back
to 90% of field capacity, if one desires.
Growth stage of each crop is recorded and appended to charts along the X axis. This allows clients to see what the moisture in the active root zone is like at critical growth stages. Our charts also allow one to much better predict (as opposed to a 'hand feel' method) what the crop needs will be in the near future. Rather than taking the time to probe, and hand feel the soil down to 3' (subjective), we are recording objective values that are used in combination with PET values to more accurately determine timing of crops needs. See chart below.
With water regulaitons about to be implementd, we will be installing a few of Spectrum Technologies Water Marks (image to the right), and their Water Scouts (below left). The Water Marks measure in bars of tension, the amount of energy the roots have to exert to pull water from the soil. The Water Scouts area a direct measure of the water in the pore space of the soil. Being a capcitance probe (Aquaspy and John Deere Probes are capacitance probes), actual water that is available to the plants roots is measured, and that value can easily be converted to percent field capacity and used to update producer charts.
One advantage of the newer sensors will be the ability to interface with remote sensing devices. By doing so, data can be remotely sent to server, converted to the appropriate format to update charts, and easily make updates daily, when needed. Not having to physically visit each site to take readings definitly has several advantages.
One positive benefit of moving to sensors that allow for being remotely sensed, is the ability to place sensors in areas of each field/zone that vary in soil type/water holding capacity, etc. And, the ability to have more sites/field monitored is definitely an advantage.
Once we begin to make the move to VRI systems (that move appears to be inevitable with impending water regulation/increased energy costs and the rapidly rising cost of nitrogen -VRN), producers should see significant savings in energy costs while maintaining yields. Several companies are now beginning to retrofit center pivots for VRI.