A study in the southeastern United States showed that conversion of cropland to management-intensive grazing of perennial grassland increased organic matter content, cation exchange capacity and water holding capacity. The study, titled 'Emerging Land Use Practices Rapidly Increase Soil Organic Matter', was authored by University of Georgia scientists and was published in the May issue of 'Nature Communications'.
Three Georgia farms that had been converted 2-7 years earlier from conventionally tilled cotton and peanut production were studied. The farmers grew hybrids of Bermuda- and stargrass (warm-season perennials) overseeded with annual ryegrass every fall.
The fields were grazed by dairy cows at a density of 30-60 animal units per acre (30000-60000 lbs liveweight/A) for 12-hr periods. Dairy cattle was rotated over the paddocks every 15-45 days, depending on forage production. They were moved 2 times a day.
The soils were sandy coastal plain soils with initially very low organic matter content (about 1%). The organic matter content increased very rapidly in the 2nd-6th years after conversion to grazing to 2% in the top foot, and appeared to plateau out after that. The increase in organic matter led to a drastic increase in cation exchange capacity and water holding capacity of the soil.
I oversee a project that will document how no-till, cover cropping and grazing can be integrated for improved soil health and profitability in our state. Based on information from Brazil and the Plains regions there is potential for increased profitably by bringing grazing animals back on the croplands. The collaborative project includes a dairy farm in Lancaster County and two grain/beef producers (in Juniata and Forest Counties) and also two cover crop seed companies (King's Agriseed and Cover Crop Solutions).
One field day took place on a dairy farm in Leola, Lancaster County, on July 7th with King's Agriseed, and two more field days will be upcoming in September, one in Forest County and one in Juniata County.
At the field day in Leola we observed cover crop mixtures of tillering corn, sudangrass and sorghum-sudangrass hybrids and forage soybeans, cowpeas, brassicas and sunnhemp planted after harvest of triticale or triticale/annual ryegrass mixes. The summer and winter annuals can be rotated with the perennial pastures for added benefits.
The farmer and crop and livestock experts discussed how combining nighttime-grazing and daytime stall feeding permit high milk production (75 lbs/day). The perennials are tremendous soil builders and the annuals add benefits such as meeting forage needs during the summer slump when the weather is hot and dry as well as in late fall, and are a break crop between an old and new perennial pasture stands. More information will be shared in upcoming Field Crop News articles.