Have you ever heard of or seen the Rainfall Simulator? No, I’m not talking about the extended forecast or cloud seeding. The NRCS has a machine that does what the name indicates. It can simulate whatever rainfall amount you would like. The purpose of it is to take different landscapes and measure runoff and soil water infiltration rates. Basically, how much water will come off and how much will soak in on the different land types.
The simulator is hauled to many events to illustrate the results to many different audiences from kids to seasoned producers. How it works is that sections of soil are taken from the land types we want to compare like conventional tillage vs no-till and introduced grass pasture vs native grass pasture. It can be lined up however we want, compare what different land types we want but the comparisons I just mentioned are most common.
When talking water runoff and infiltration I wonder how many of you would think there could be differences between grasslands? Yeah, tillage vs notill isn’t a surprise but is there really a difference between a Kentucky Bluegrass – Smooth Brome pasture and a diverse native pasture on runoff and water infiltration? If you put all four of those scenarios into the rainfall simulator you will be surprised at some of the results. If I give you the four conditions of a conventional tilled crop field, a no-till crop field, a Kentucky Bluegrass-Brome pasture, and a native grass pasture, which would you say would have the most runoff? If you said the tilled crop field you would actually be wrong. When we put these scenarios into the rainfall simulator we see that the introduced cool season pasture actually has the most runoff. What would you think would have the best water infiltration? The notilled field? Nope the native grassland. The no-till field has considerably better water infiltration than the tilled field for sure but still can’t compare to that of our native rangeland. If we wanted to add another scenario to it a no-till field with consistent cover crops will have better water infiltration rate than the no-till without cover crops.
The whole point of the demonstration is to show that with some different practices we can increase our soil’s ability to hold water whether that is in a cropland setting or in a pasture setting. I don’t need to tell all of you how important water is to production for our crops and our livestock, but by using season long grazing and conventional tillage we have less water available when we need it the most. I don’t think many of you would be surprised that the water infiltration rate of a tilled field would be less than that of a no-till field, but are you surprised that your tame grass pasture would be actually worse than that of the tilled field?
Just as your lawn turns brown when the water shuts off, so does that tame pasture as there is very little root activity in that soil. Kentucky Bluegrass has roots only a few inches under the surface and this almost impenetrable mat that acts more like a water repellant than a sponge. Compare this to your native grasses that have roots 10 to 15 feet deep that create space in the soil for water to enter and get stored rather than runoff. Forget the fact that the introduced species are cool season and aren’t as productive during the summer, just the lost production from the lack of water should be a reason to sit up and take notice.
Imagine for a second the water holding capacity between a tilled field and a notilled field, or the water holding capacity between a tame pasture and a native pasture is 8 inches. Now take some of the big rain events we have had this summer and imagine that the land had this ability. How much less water would have run off and wouldn’t be standing right now? Beyond that, how much more water would our soil have when it’s not raining?
When you think of the substantial economic return tied to moisture that all ag producers have whether it’s crop or livestock would it not be in our best interest to keep it rather than let it run away?
P.S. If you have an event that you might like the Rainfall Simulator to be at; I can get you in touch with the folks that will come out and run the demonstration i.e. 4 H events, schools, FFA, Co-op meetings, customer appreciation, etc.