Highly accurate automatic guidance systems can steer a tractor and cultivator through tomato plants at speeds up to 7 mph without damaging plants.
Just how accurate are the ultraprecise RTK GPS guidance systems? University of California-Davis researchers determined they can steer a tractor and cultivator at speeds of 7 mph without damaging the plants.
A team of engineers set the test up using tomatoes irrigated with drip tape buried beneath the plants. The plots were cultivated with an implement that had knives spaced to operate 2 to 3 inches from the plant. The cultivator ran at speeds of 31/2 and 7 mph.
Before cultivating, the researchers centered the implement directly behind the tractor's PTO. This helped eliminate any error from the cultivator not trailing directly behind the tractor.
The researchers placed sway blocks on the three-point hitch, which provided a clearance of about 1/16 inch at the hitch points. This was done to ensure that the cultivator would follow the tractor without influencing the tractor's steerability. If the hitch was entirely blocked, the implement tended to steer the tractor and resulted in loss of auto guidance accuracy, the researchers noted.
After several cultivation trails, the researchers discovered there was no significant difference between the high and low operating speeds in regard to plant damage. In fact, they observed total plant damage at the 7 mph speed was less than 2%.
In a second test, the researchers ripped the field the following spring using a fertilizer shank that ran 2 to 3 inches to the side of the irrigation drip tape. The shank was set to operate 6 to 8 inches deep while being pulled at speeds of 31/2 and 7 mph. No damage to the drip tape occurred at either speed, supporting the high accuracy of RTK GPS guidance systems.
For more on the research, see http:// CaliforniaAgriculture.ucop.edu/ 0401JFM/abstracts.html#7.