Capturing and keeping pasture rainfall

Farm Forum

A month ago I discussed the drought in the northeast part of South Dakota. What a difference a month and a bit of rain can make. Over the last several weeks, we’ve seen some significant rains in much of the region which has relieved the most severe drought conditions. In fact, the latest U.S. Drought Monitor report has most of the northeast in a “No Drought” status. Central Roberts County is still categorized as abnormally dry, but much improved over its previous extreme drought designation.

While always a blessing, my observations have been that the rains came a bit late to have a great impact on our native warm season grass production. Through the dry conditions of July and early August much of the regions pastures stayed surprisingly green as a result of decent early spring moisture, but overall production of warm season grasses has been ‘light’ this summer based on pastures I’ve visited. Even with recent rains, we’re not seeing a great response in warm season grass production, and now with the cooler fall weather we will likely not see much additional warm season grass growth. I encourage you to visit your pastures and take stock of your grass and water resources. September and October are typically when the majority of growth shuts down for the season, so keep a close eye on pastures as the volume of forage can disappear quickly and be willing to make necessary adjustments to your grazing operation.

Last week SDSU Extension hosted a large tent at Dakotafest in Mitchell. As part of our daily presentation we ran the NRCS Rainfall Simulator. If you’ve never seen this presentation, it is well worth the effort to attend a tour or event where it is displayed. While the rainfall simulator is somewhat famous for showing the inability of conventionally tilled cropland to capture precipitation, the same holds true for poorly managed pastures.

It is often assumed that because we are managing grasslands our soils and vegetation communities must be in good condition, nothing could be further from the truth. In fact, as the rainfall simulator so clearly demonstrates, overgrazed poorly managed pastures suffer from poor water infiltration, high volume of runoff, and erosion similar to poorly managed crop land. Key management elements such as keeping the soil covered and maintaining a diverse and healthy plant and soil community are just as important for healthy pasture management as they are for healthy cropland management.

A simple indicator to pasture health can be stock dams and dugouts. In dry times producers often feel relieved if dugouts and dams fill quickly with rainfall. Full dams and dugouts are always desirable, but how fast they fill is an important measure of good pasture health. If a dam or dugout fills quickly after a rain event it is likely that it filled with runoff water from the surrounding pasture, indicating that very little of the rainfall soaked into the ground. This runoff water is often heavy with sediments eroded from the soil surface of the surrounding watershed. Overall, this rainfall event did little to help overall pasture production. Eventually, this dam or dugout will have to be cleaned out, an expense that could have been avoided. Generally, for every inch of rainfall that runs off and does not infiltrate into the soil we lose about 200 lbs. of pasture production potential.

Conversely, if dugouts and dams fill one or two days after a rain event we can be reasonably assured that the surrounding pasture has infiltrated most of the precipitation, making it available to the plants. The water moved through the soil and filled the dam or dugout with very little sediments from soil erosion. This type of management, along with keeping cattle out of the dams and dugouts, greatly extends the life of these water sources and improves pasture production.

For more information on water management in pastures, including designing water systems that keep cattle out of dams and dugouts, feel free to call or email me at the Watertown Regional Extension Center: 605-882-5140 or

Upcoming events

• Aug. 29 and Sept. 1 — Greg Judy Pasture Management Workshop. Sponsored by South Dakota Grassland Coalition and partners. Aug 29 workshop to be held near Faith, S.D., and Sept. 1 workshop to be held near Gary, S.D. Single day events with presentations in morning and field demonstrations in afternoon. Workshop and noon meal free to South Dakota Grassland Coalition members, $30 for non-members (includes noon meal and membership). For information or to register for Faith call 605-244-5222 ext. 3 or for Gary call 605-882-5140 or email

• Sept 12-16: South Dakota Grazing School. FULL. To get on waiting list for 2017 contact Pete Bauman at 605-882-5140 or

• Sept 21-23: South Dakota Soil Health School. Sponsored by South Dakota Soil Health Coalition and partners. Aberdeen, S.D. $150/student ($75 for additional person). For information or to register call 605-770-2989 or email

• Oct. 6-7: Cedar Tree Control Workshop. Gregory County Area. Details to be announced soon. Call 605-882-5140 or email if interested in attending or if you’d like to demonstrate equipment at this event.