The photo above is from an excellent soil health demonstration I witnessed yesterday that was put on by a soil health guy from the Oklahoma office of the USDA Natural Resource Conservation Service (NRSC). Basically what he did was go out to five different places and accumulate strips of sod/soil from them, which he then set up in trays with a runoff catchment system and an infiltration catchment system. While he talked to us, he ran about 1.5 inches of rain through a sprinkler in about 20 minutes, simulating a heavy but by no means unusual rain.
I wish I'd taken some sort of notes about his description of the five different plots where he got his samples. As I remember them, they are (from left to right in the photo):
1) What he called "natural range" from protected public land not subject to agriculture or ranching. Dense vegetation, little bare soil.
2) What he called a "managed grazing operation" where the grass is under cattle for limited periods only. I think said 18 days at a time in this case, no info on herd density. Vegetation was short-cropped but soil tilth was visibly excellent.
3) What he called "our standard Bermuda grass pasture with cows on it 365 days a year." Grass looks OK but has many bare spots between the tufts.
4) A plot he characterized as "no-till cover cropped". He mentioned sorghum grass and a couple of other covers that I forget. Dense matted vegetation. I had the impression that this plot, too, was from a pasture, but if he mentioned the grazing system or pressure it didn't stick.
5) A plot of "traditional farm land" that has been plowed and disked.
The picture above is from
my shorter facebook post but you can study
a hi-resolution version here. The photo was taken about halfway through the "rain" event, but you can already see the dramatic difference in the amount and quality of the runoff from the different plots. The results will not surprise anybody here at permies; the blasted-out pasture and the bare farm dirt are terrible at soaking in the rain and they are worse at holding onto their soil particles. The no-till cover-crop piece was a tiny bit better than the natural range, but the difference was real minimal. The managed-grazing parcel was way better than I expected from looking at it; soil structure must be excellent because the runoff, though substantial, was surprisingly clear.
I found that seeing this demo in action was surprisingly powerful. It's all very well to have intellectual knowledge, but sometimes just
seeing is hard to beat!