Georgia Forages Conference: We had a really wet winter. What now?
Extended periods of soggy conditions caused a myriad of problems for Georgia cattlemen and hay producers. Speakers at the 2019 Georgia Forage Conference offered tips on what may come next and what can be done about it.
The conference, held April 4 as part of the Georgia Cattlemen’s Association Convention & Trade Show, featured presentations on effects of excess water, from nutrient loss to weed pressure.
UGA Agricultural Climatologist Pam Knox suggested Georgia weather overall could be warmer and wetter than normal through most of the year and recommended that producers pay close attention to weather developments in the tropics.
“A lot of the warmer temperatures are going to be night-time temperatures,” Knox said. “That will increase evaporation rates. If night-time temperature is high and you have animals outside that don’t like the heat, they’re not going to be happy if they can’t cool off at night.
Reclaim or renovate?
UGA doctoral student Tayler Denman presented a plan for producers to follow to determine whether to perform light maintenance on their pastures or to renovate them entirely. Denman shared the pasture condition scoring system developed by the USDA’s Natural Resources Conservation Service. The system accounts for 11 indicators of pasture health and combines them into simple overall 1-5 scoring as a decision tool for producers. The factors are percentage of desirable plants, plant cover, plant diversity, plant residue, plant vigor, legume content, uniformity of use, severity of use, livestock concentration areas, soil compaction and erosion.
“All of these can be greatly affected by the past rainy conditions we’ve had,” Denman said.
The NRCS has a worksheet available at https://gfb.ag/NRCSPastureCondWksht to help producers through the scoring process.
Scores of 3 and higher indicate pasture management is appropriate, Denman said, outlining three steps: Taking soil samples, managing weeds in the pasture, and fertilizing after the weeds are under control. Scores of 1 or 2 indicate the pasture is too damaged to manage and should be renovated. She said this involves taking soil samples, planning what types of forage they want to plant, destroying the existing stand with herbicides.
Effects of excess water on soil nutrient content
UGA Extension Forage Agronomist Lisa Baxter reviewed the possible effects of excess water on nutrients in soil – runoff, leaching, volatilization, denitrification and acidic rainfall.
“The consequences of wet soil conditions really depend on where we are in the state,” Baxter said. “If we’re in the coastal plain, we have really sandy soil and low water-holding capacity and we’re going to have a lot of leaching going on. If we get up into the mountains, we have a lot of steep hill banks, that’s where we start getting into runoff,” Baxter said.
Runoff is where flowing water carries away nutrients at or near the top of the soil. Leaching is where excess water moving down through the soil carries nutrients with it. Volatilization is where nutrients are lost to the atmosphere when water triggers their conversion to vapor or gas form. Denitrification is where nitrates are lost to the atmosphere by the same process. These things happen at varying rates depending on the nutrient mobility.
Acidic rainfall isn’t as common in Georgia, though Baxter said if extreme rainfall conditions continue, it can alter the pH balance in the soil, causing it to become acidic over time.
Baxter, too, recommended soil testing, as well as splitting fertilizer application, which in continued wet conditions can help improve yield. In drought conditions, it helps prevent damaging effects like nitrogen toxicity.
For nitrogen application, splitting applications helps match plant needs, Baxter said. Ideally nitrogen should be applied after each harvest. For potassium, she suggested applying 40% to 50% of it in late spring and the rest midway or late in the season. Increasing potassium improves stand density by increasing the number of rhizomes in Bermudagrass.
Combating Weed pressure
UGA Assistant Professor of Crop & Soil Sciences Nick Basinger discussed how wet conditions contribute to weed concerns in forage land. First, he noted that at any give time in the soil there is a weed seed bank, a collection of seeds that survived from previous years and is waiting for the right conditions to germinate.
“The ones that make it through are your weed problem,” Basinger said. ‘They’re the problems you’re dealing with.”
He reviewed some key species of weeds that thrive in wet areas, particularly varieties of sedges, foxtail, Japanese stiltgrass and buttercup. Buttercup is especially troublesome in pastures because it is toxic to livestock.
Basinger said buttercup can be controlled by mowing before flowering, which reduces the number of flowers and seed production. Spraying 2-4D can be effective if used when the plants are small.
Basinger recommended maintaining strong stands of desired grasses to combat weeds and to avoid overgrazing.
“If you’re overgrazing, you’re just asking for a weed problem,” he said.