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Reclaiming pasture and hay ground after 2019 historic flood

by Ruth Wiechmann
for Tri-State Livestock News

In 2019 record amounts of precipitation and historic flooding occurred in much of Nebraska and southeastern South Dakota. Other areas, while not experiencing quite that level of devastation, still suffered from a rare problem in the agricultural realm of the Upper Midwest: too much moisture.

Now another spring has rolled around and farmers and ranchers are hitting crucial planning points; stocking rates for pastures and what crops and forages to plant are being decided. Last year’s excess moisture is playing a critical role in those decisions.

Megan Taylor, Platte County Nebraska Extension Agent, said that a good first step is for producers to spell out their goals for a particular field or pasture.

“Are they wanting to produce a high quality forage for a cash crop? Do they plan to graze it? Is it more of a backup field for hay or fall grazing needs? Determining their goals will shape the next few months management decisions,” she said.

Some of the areas that saw the most severe impact from the 2019 flooding will never be the same. There are a lot of acres along the river bottoms that are buried under sediment and sand 6 feet deep. Areas in southeastern South Dakota are now flooding again.

Some Nebraska producers affected by the historic flooding in 2019 have chosen to remove the sediment layer and start over, but that’s not an easy or cheap task.

“Depending on the depth of the sand the cost can be quite startling,” Taylor said. “I heard estimates ranging from $500 to $3,000 per acre. These were rough numbers, because no one really knew exactly how much work it was going to take to clear the ground. The wind riffles in the sand deposits make it look like a true desert and also make it hard to determine just how deep the sediment left behind by the floodwaters really is.

“If the land was valued around $4,000 per acre it’s hard to justify that kind of expense to clear it off, so some areas the property will never be reclaimed. We’re still trying to determine what land values really look like right now.”

Some producers have hired out the job of loading the sand and hauling it off their fields. A lot of the sand has been piled in long windrows on the edges of the fields. Although some could be sold for filler, most could not be sold or even pushed back into the rivers because of the risk of contamination from the flood waters.

Taylor said that sediment layers of 4 to 6 inches covering a pasture or field was not too difficult to deal with, and that replanting into that sand layer was possible, but deeper layers posed a problem.

“Once you get past 8 to 12 inches it’s really challenging,” she said. “Most of the sediment is pure sand and there is no water holding capacity in it. There is also the challenge for the roots of any plants that start growing in the sand layer; when they hit the prior soil surface they will have difficulty penetrating. There is also the problem of trying to drive any tractor or tillage equipment through the soft depths of silt and sand.”

BEST OUTCOMES

Whether producers are trying to dig out from under 6 feet of sediment or dealing with minor flooding issues along creeks or sloughs, there are a few key points to keep in mind for the best outcome.

“The first big thing is fertility,” said Taylor. “Taking soil samples to determine where your nutrient levels are at is crucial. You need to know your nitrogen status; soils are probably low in nitrogen after that much water has moved through. Testing soil pH is also critical for determining whether lime is needed prior to planting any crops that are not yet in. Some crops are sensitive to high or low pH levels and you won’t get a good stand if it’s not balanced.”

Weed seeds have likely been brought into the area by floodwaters, so choosing to plant crops and forages that will be aggressive enough to compete with the extra weeds is also important. Consult with your local extension agent regarding what varieties of grasses, legumes and cover crops will be best suited to each field and your specific short and long-term goals.

Testing water sources and soil for any contamination caused by flooding is a wise step to take prior to turning any livestock into pastures. Make sure that wells and ground water sources do not have toxic levels of chemicals or unhealthy bacteria present. Any debris will need to be removed and fences will need to be repaired or replaced. Give grasses as much time as possible to recover and regrow prior to turning livestock in to graze.

Taylor said that there is still not a figure for the total acres affected by the flooding last spring.

“In the three counties I serve pretty much anything against a river was affected,” she said. “The Loup, the Platte, the Cedar, the Beaver: all flooded. Wetlands are filled with sand. Some pastures are completely eroded. The U.S. Geological Survey needs to completely re-evaluate the area.”

Meanwhile, farmers and ranchers are stepping up to the challenge of finding a new normal and slowly but surely restoring fields and pastures to productivity.

Sara Bauder, SDSU Extension Agronomy Field Specialist, shared some information applicable to anyone whose fields or pastures have suffered less severe flooding.

“Flooded pastures are a tough situation and are something that needs to be considered on a case by case basis depending on grazing management and the producer’s ability to let the ground rest or not,” she said. “When it comes to hay ground, areas that were flooded last spring and through the summer that have dried off enough to consider the option to plant this year will definitely need to be given special attention as well.”

Bauder said that there are several factors to consider when alfalfa ground is flooded. What season of the year did the flooding occur in? What was the age of the stand and the plant growth stage? How long was the duration of the submersion? Was the water flowing or stagnant? How fast and efficient is soil drainage on the flooded acreage? What pests are likely to put pressure on recovering plants?

If flooding occurs while temperatures are cool and plants are still dormant, alfalfa plants can survive seven to 10 days under water, but if flooding occurs in the summer months it will be less resilient. Stagnant water can be more harmful than flowing water because flowing water contains more oxygen. Well established mature stands of alfalfa are more resilient than newly planted stands.

After the water recedes, producers should check root health to determine the viability of alfalfa plants. If they seem unlikely to survive, producers may want to consider planting a warm season annual cover crop as a short term option before reseeding to alfalfa. If plants seem likely to survive, estimating a stem count per square foot can be helpful to determine whether reseeding will be necessary. Delaying the first cutting a bit longer than usual is a good idea if the stand seems dense enough. If the stand is sparse and the producer’s goal is to reestablish an alfalfa stand, it may be a good idea to plant a different crop for a year or two to give alfalfa autotoxicity time to diminish in the soil.

Perennial grasses may require overseeding, or they may be able to recover from the existing seed bank. With pasture, grass hay or alfalfa, giving as much of a recovery period as possible before grazing or cutting hay is a good idea. Check soils for chemical residue from the flooding. Keep herbicide use to a minimum. Monitor and deal proactively with pest problems such as disease, insects and weeds to reduce further stress on the plants. Discuss specific concerns and questions with your local extension specialists.

Given time and careful attention, recovery is possible. ❖


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