More than a decade ago, Kirk Law changed the way he grazed his cattle and now the organic matter in his Georgia pasture has rebounded, and it benefits him. Last year, for the first time, he supplemented no hay to his cattle.
Last fall, we introduced Southeast Farm Press readers to Law's rotational grazing technique. At the time, we bet the organic matter in his pasture's soil might top 3%, but he wasn't sure. He'd never pulled a test for organic matter. In December, he pulled a sample on a 40-acre pasture and gave us an update.
According to the sample run by the University of Georgia, the soil in that section of pasture contains 2.74% organic matter, and for southwest Georgia soil that is a lot, said Seth McAllister, the UGA Extension agent in Terrell County where Law's operation is located.
There's not much available information on what the typical organic matter is for pastures in the area. But a Georgia-based study titled 'Emerging land use practices rapidly increase soil organic matter' published to Nature in 2015 looked at a few Georgia dairies that converted to intense grazing strategies. The study finds, in part, that converting cropland into pasture allows the land to capture 3.6 metric tons of carbon per acre, and after six years under managed grazing, the soil retained "95 percent more nutrients and 34 percent more water."
Law's rotational grazing journey mirrors the study's findings and provides proof of the concept
About 14 years ago, Law started converting his cropland to pastureland. He farms no row crops now. The 40-acre pasture where he took the sample hasn't been in crop production for 12 years, which has helped increase the organic matter. McAllister said, Law's organic matter is almost three times that of conventional-tilled cropland in the area, where organic matter is rarely more than one percent.
Twelve years ago, Law applied commercial fertilizer to that 40-acre pasture where he took the sample. Eight years ago, he applied chicken litter at one ton per acre. The pasture has had no other added fertility since. The sample came back 'high' in phosphorus, 'very high' in potassium, calcium and magnesium and 'sufficient' in zinc and manganese. The only concern was the pH, which at six was almost too low.
Law uses a rotational grazing strategy, dividing his 240 acres of pastures into paddocks to graze his 120 Brangus mama cows. The pasture is planted mostly to Alicia bermudagrass with some Tifton 85 bermudagrass.
For winter, he drills oats into the pasture and plants clover as needed. In 2019, he didn't give his cows any stored hay because they didn't need it, reaching a goal he set when he first started the rotational system. He weens 550-pound calves for market.
Row crop farmers can also increase soil organic matter, but it takes work. Ronnie Barentine, long-time UGA Extension agent and current program development coordinator for southwest Georgia, has worked with conservation production practices in the state for decades.
Barentine said a Georgia row crop grower who implemented a decade of conservation-tillage with intense cover crop management can achieve 2.5 percent organic matter. After 30 years of conservation-tillage and cover cropping, the grower might hit three percent organic matter, but it's tough to achieve.