Precision agriculture practices are finally starting to show a clear payout for growers in the Cotton Belt, thanks to the hard work of many growers, consultants, institutions, and manufacturers in strong collaboration. One of these individuals, Tim Sharp, was the subject of an in-depth profile in The Power and the Promise.
Sharp created and shaped a cotton precision program from scratch at Tennessee’s Jackson State Community College, driven by his sheer determination and salesmanship derived from more than a decade of work for manufacturer DuPont.
He and 15 students at the college started the efforts in 1998 with an eye toward bringing greater profitability to growers. Recording the relationship between field variability and plant growth and determining how to best use inputs to increase yield based on this relationship was the goal for Sharp and his students. But the early years were all about getting started.
“Precision agriculture programs are brutally expensive to operate, and really cash hungry when you are ramping up,” said Sharp in an interview last year. “So, you need to fund it like a startup company — beg, borrow, find grant money — it took better than $1 million for us to really get started.”
He was able to garner a wide range of support for the program, including distributor/retailers Helena Chemical and MFA Inc., seed company Delta & Pine Land, and software maker SST Development Group. The Cotton Foundation, Cotton Incorporated, the National Science Foundation, and USDA also lent support.
Field Of Vision
Sharp’s research into cotton production revolved around the theory that every field can be broken down into three basic zone types — high, medium, and low. In high zones, cotton will not only grow faster, but also produce an excess of vegetation to the detriment of actual bolls. On the other hand, cotton in low zones tends to grow more slowly and mature earlier.
Sharp and his team used satellite and aerial imagery early on to determine the growth rate of cotton in experimental fields using an imagery variable known as NDVI. This factor is a reflection of the amount of vegetation across a given field, allowing an agronomist to make distinctions between high, medium, and low zones.
Through extensive imagery analysis and painstaking ground truthing, the imagery proved successful in predicting plant vigor. The next step was to determine whether the zones would remain stable from year to year.
This past year was the fourth for the project, and Sharp is completely confident in the stability of the zone. “Clearly, the imagery works, and zones are consistent year to year,” says Sharp.
With zones of vigor identified, Sharp looked at ways to influence the plants in the zones by varying the planting rates, as well as insecticides and plant growth regulators through good, basic cotton growing practices.
In Sharp’s experiments, seeding rates are increased in high zones vs. low zones to take advantage of the favorable growing conditions. It’s an important factor with today’s expensive biotech hybrids that often also feature seed treatment.
Insecticide applications are focused in high zones where pest insects tend to colonize first, and low zones may get no application, both saving money and providing a refuge for beneficials to develop.
Plant growth regulators (PGRs) also are reserved for the high zones to reduce vigor and encourage boll development, and low areas may receive no PGR at all, again reducing input cost.
The vigor zone profile is the engine that drives this precision machine, and after four years of consistency — 96% of zones do not vary — mission plans can be developed for the field to match the zones.
The “mission plan” is a piece of software programming that is used to guide the variable-rate seeder or applicator throughout the season on where applications should be made. Since the zones are stable, the same mission plan can be used essentially for as long as the farmer is planting cotton in that field.
Sharp recently announced that he’s leaving Jackson State and taking his precision program to another southern university, but he pledges that the work will go on.
And there is much still to learn. One of the biggest challenges has been imagery consistency, a problem that he is trying to alleviate by using the Green-Seeker on-the-go imagery system.
“With satellite and aerial imagery, the NDVI from shot-to-shot can vary in resolution,” says Sharp. “With the ground-based sensor, you get output that is georeferenced right off the machine that’s ready to use, and the system works well off our mission plans.”
Sharp also wants to examine the effect of nitrogen rates and hybrid selection on the total mission as part of future research.
Another challenge is in trying to make the system as accessible and easy to use as possible, but Sharp says nearly all growers will need help implementing the system regardless.
“The grower does not have the time to learn this system — there really needs to be a technical expert in the loop to use the GIS system and build the mission plans,” says Sharp.
Even the consultant that implements Sharp’s program needs some special skills. “There are really three skills that a person needs to run this program — agronomy, computer skills, and some background in electronic engineering,” he said. “Even with my students, they are challenged in the electronic components area — you have to know exactly what to do when any of these components fail on you.”
Editor’s note: This article first appeared in the Winter 2004 issue of PrecisionAg Special Reports.