Post-Drought Pasture Improvement Takes More Than Rain

Heavy rainfall throughout much of Missouri on July 2 may have lessened worries about drought damage in pastures, but one good rain won’t undo the damage to mismanaged pastures during two straight years of drought, according to two University of Missouri Extension specialists based at the MU Forage Systems Research Center in Linneus.

In fact, mismanaged pastures may continue to see a drag in production, say state forage specialist Carson Roberts and agronomist Valerie Tate.

Weakened plants and poor infiltration are two key factors that influence the continued decline in production. Weakened plants are a product of both overgrazing and drought, say Roberts and Tate. The root systems of overgrazed, drought-ridden grasses and forbs can be severely reduced. This inhibits the plants’ ability to access moisture in the soil. A few things can be done to rejuvenate root structures:

1. Allow pastures to rest. Resting pastures lets plants invest in their roots. Restocking too quickly after drought can put more pressure on the pastures before they have adequately recovered. Haying or mowing weakened swards can also keep plants from investing in their root systems.

2. Manage fertility. Weakened root systems are less capable of accessing nutrients. Good fertility can speed up recovery. Consider collecting soil samples for analysis. Priority may be given to amending pH followed by phosphorus and potassium. Good infiltration is key to highly productive pastures. The amount of precipitation is far less important than the amount of rainfall captured by the soil.

3. Reduce compaction. Compacted soils have poor infiltration and water-storing abilities. Wet or moist soils are most susceptible to compaction. Avoid driving pickup trucks, heavy equipment and tractors across pastures, especially when soils are moist.

4. Develop a litter bank on the soil surface. Litter provides a host of benefits, including reduced splash erosion, increased soil aggregation and lower soil surface temperatures.

• Splash erosion happens when raindrops impact the soil, causing movement of soil particles. These dislocated particles can clog the pores and micropores in the soil, reducing the amount of water that can infiltrate the soil. A good thatch will protect the soil from the raindrops.
• Well-developed soil aggregates can easily pull in and store water. Thatch on the soil surface increases soil aggregation through reduced erosion, improved organic matter and increased soil life.
• Soils overheated from direct sunlight can develop hydrophobic properties, decreasing water infiltration. A litter bank can protect the soil from overheating.
• A good thatch layer can be established by allowing pastures to rest and “wasting” some grass. This can be difficult, Roberts says, but remember that a deposit to the litter bank is an investment that will pay dividends in the future.

Poor infiltration and weak roots can combine to create a compounding effect on the productivity of a pasture between rains. Improving both is important to future productivity, regardless of the amount of rainfall. “Remember, it is not about how much rain you get. It’s about how much rain you can keep and access,” says Roberts.