“What happens in these fields in Arkansas is the soil varies a lot,” says Cartwright. “You may have four different soil types in one field. Each soil type then has different characteristics, and it’s pretty important to know that if you’re going to maximize the yield on that field. You may have to put more fertilizer on one soil type than another.”
For example, Cartwright says you may have to apply zinc fertilizer in areas where the pH is high versus where it’s low.
“It’s important to know some of these characteristics of the soil,” Cartwright says. “Precision ag allows you to divide up the field into zones so you can better manage it.”
According to Scott Taylor, agronomic program coordinator, Agro Tech, Hoxie, Ark., grid sampling on precision-graded soil is very important because it helps growers identify where they need to pay special attention. The practice of precision leveling can take its toll, stripping topsoil and making management critical.
“You’re dealing with the subsoil on a lot of these precision-graded fields,” says Taylor. “If you’re trying to grow your crop on this leveled subsoil, your rice will be stressed. We’re nearly 98 percent precision-graded around northeast Arkansas, so grid sampling is very important.”
Using GPS monitoring, growers can pull soil samples every 2.5 acres. The technology allows growers to sample for nutrients, lime, phosphorus, zinc and potassium. Variable rate technology helps growers apply fertilizer where it needs to be to get the field back into optimum production faster.
Grid mapping can even help growers determine what kind of rice herbicide to use to maximize yields. For instance, rice that is stressed may require a herbicide that is gentler, such as Ricestar, says Ed Barnhill, rice consultant, Jonesboro, Ark.
“If the rice crop is stressed because it’s planted in a newly leveled field, Ricestar is a safer herbicide,” says Barnhill. “Grid mapping can caution you on what you shouldn’t do depending on the shape of your field.”
According to Barnhill and Taylor, Ricestar is especially effective on stressed rice where other hebicides could harm the crop. Ricestar controls barnyardgrass, sprangletop, fall panicum, seedling johnsongrass and broadleaf signalgrass post-emerge prior to permanent flood.
“The flexibility of Ricestar without concern for crop injury is a key benefit,” Taylor says. “It has a good safety margin. Using precision mapping helps growers identify the importance of their herbicide choice and other management options for fields.”