For Gunnison, Miss., cotton producer Kenneth Hood, variable-rate application of inputs is a matter of survival. “There are two factors that influence how we do things,” Hood said during a panel on variable-rate technology at the 2006 Beltwide Cotton Conferences in San Antonio. “One is legislation and regulation. The other is economics. The latter is the driving point. Since 1995, we had one little blip (where cotton prices rose in 2004) but since then, prices have been down.”
Hood farms cotton on Perthshire Farms, about 100 miles south of Memphis. His cotton land is highly variable, which Hood traces back to 1897, the year a levee broke west of the farm. “Today, our soil type changes at least five times from one end of the field to the other. It's a challenge to farm that kind of land.”
In addition, cotton producers face increasing costs, decreasing returns, a hostile legislative environment and increasing global competition.
Variable-rate application of inputs can help Hood do a better job with the economic side of the issue by finding the least cost of production for each input. Varied inputs on Hood's operation include seed, fertilizer, insecticides, herbicides, plant growth regulator and defoliants. Here's a closer look at the savings:
Cotton seed — “We took our soil sampling data, overlaid our yield maps and bare soil aerial imagery on top of the data and wrote a prescription for variable-rate seeding.”
The result was a 10 percent increase in yields. “We also reduced our seed costs tremendously and increased our profits by 7 percent to 13 percent. When you can do that with precision ag technology, it makes you take notice. Today, our cost of planting the seed is approaching $100 an acre. You can't just put out X-number of plants per acre. You need to know where to put the plants.”
Nitrogen — Hood overlaid soil sampling data, yield maps and Veris rig maps. The Veris machine measures the soil's electrical conductivity and clay content. The maps showed five classes of soil. Armed with this information, Hood's scouts can go to each of the five areas to soil sample and not have to spend valuable time grid sampling.
Imagery also indicated where there was carryover nitrogen in a portion of a field that had been in corn. Hood was able to reduce his nitrogen application in those zones.
“On one 2,810-acre block, we applied 182.6 tons of ammonium nitrate using variable-rate technology. The previous year, we used 330 tons. That's 147 tons that we actually saved. When you multiply that by $230 it is quite a bit a savings ($33,810) using variable-rate technology.”
Insect control — Hood has found that certain types of insects like certain types of cotton better than others (some insects may prefer stressed cotton, for example). “You can go to those spots in the fields and find where your thresholds are.”
On a neighboring farm, a variable-rate plant bug application saved 53 percent in chemical applications, according to Hood. “That has got to get your attention. And remember, the applicator is either on or off during the insecticide application. So where the chemical was not applied, beneficial insects were not eliminated. You're leaving them there to help control your damaging insects.”
Plant growth regulator — Aerial images indicate seven different management zones with various levels of plant vigor. “It makes sense that we don't over-apply or under-apply plant growth regulators. The plants will respond positively.
“How many times have you planted two fields, just a jump in the turnrow from each other, and one field picks 800 pounds and the other picks 1,100 pounds? Something went right in the 1,100-pound field.”
Defoliation — Another neighbor using variable-rate applications reported 16 percent chemical savings because he was able to go with a once-over defoliation due to a more uniform crop. “Another farm in Arkansas did its variable-rate defoliation by air. It cost him $15.94 to put it out and it was a one-time defoliation.”
On another field, imagery indicated a potassium deficiency. “The prescription was applied using an airplane. The chemical cost of the variable-rate application was $5.85. Had he made a blanket application, the cost would have been $9.39.
Variable-rate technology will also allow the farmer to estimate the cost of the application versus a blanket spray.
Hood noted that users of the imagery can often get multiple uses from an image.