Variable Rate Irrigation Cody Daft April 13 th, 2007

Precision Agriculture Where Have We Been –Soil Sampling –Yield Monitors –GPS Where Are We At Today –Greenseeker –Variable Rate Technology –Auto Steer

Why Use Precision Agriculture? Why Adopt New Methods/Technology? –95% of all cropland in South America is no-till Bottom line= $$$$ Money –Reduce Labor –Intensive Management Strategies Environmental Control

Law of The Minimum Yields are directly proportional to the most limiting growth factor –Nutrients – Heat – Light – Water

Limiting Growth Factor Water is most limiting growth factor in many regions of the world

Limiting Growth Factor When a limiting growth factor, such as water, is removed by installing an irrigation system it will generally improve plant response to fertilizer used to correct nutrient deficiencies that are also limiting growth

Irrigation For a large portion of the US, the single most important production factor is irrigation management Challenges –Optimization of water use –Environment CP systems are relatively efficient –Uniformity

Uniform Application Over A Non-Uniform Landscape Non-Uniformity may be a result of –Irregularly shaped fields resulting in off-site application of water –Overlapping of CP systems –Multiple crops under the same system –Variability in soil type –Variability in topography

Non-Uniformity

Variable Rate Irrigation Site Specific Irrigation Delivery of irrigation water in optimum amounts over an entire field Challenges –Variability in soil texture –Variability in water holding capacity –Variability in water infiltration/drainage rates –Non-Uniform cropping patterns due to terraces

Variable Rate Irrigation Match the non-uniformity of the field with an appropriate non-uniform CP application “CP systems are particularly well suited to variable rate irrigation because of their current level of automation and large coverage with a single pipe.” (Evans et al.,2000)

VRI: How Does It Work A GPS is mounted on the end span of a pivot.

VRI: How Does It Work A controller, much like a spray controller, is mounted near the pivot point. It contains a "water map" on a data card programmed from a desktop computer.

VRI: How Does It Work Uses information from GPS to control banks of sprinklers which are then cycled on/off according to a pre-determined prescription map Prescription maps are created using PC desktop software The application map divides the circular area covered by the pivot into 1-10° pie slices and every slice is divided into segments

VRI: How Does It Work Application Maps The water map and controller manage the water rates.

VRI: How Does It Work Hydraulic valves are mounted at each nozzle that is to be controlled, that is turned off or left on when moving across areas of the field to have a rate or irrigation greater than or less than the base rate. An air compressor provides the air to close the hydraulic valves as directed by the controller.

VRI: How Does It Work The controller communicates with electronic "node boxes" mounted down the system. Each node box can control up to EIGHT "banks" of nozzles. The controller tells which solenoids to open, allowing air from the air compressor to pass through the solenoid, closing the bank of nozzles associated with that solenoid

Variable Rate Irrigation VRI Clip

Variable Rate Irrigation Pivots can be programmed to automatically shut off, to avoid overlap and non-crop inclusions in the field Application rates can be pre-determined for automatic rate control on different soil types Accounts for spatial variability in the field

Variable Rate Irrigation Improve uniformity Save water Optimize pumping costs Help to keep water out of non-farmed areas Prevent "double watering" where pivots overlap. Improve irrigation management decisions Increase flexibility in fields with multiple crops or planting dates Improve the benefits of other precision agriculture practices

Variable Rate Irrigation Base Cost of System: $ Cost per Node:$ (1 to 4 nodes per system, depending on size) Cost per Variable Rate Valve:$32.00 (1 valve per sprinkler) Labor:$ (includes 1 year of technical support) Distance Surcharge:$2.00 per mile, miles greater than 100 from Ashburn, Georgia (Example: location 500 miles away has a single charge of $800, $2 X 400 miles) Hobbs & Holder, LLC / NESPAL / Farmscan (Australia),