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Mark Riechers and his son Joe raise corn, soybeans and cattle on rolling slopes near Darlington in southwestern Wisconsin’s Driftless Area. Their erodible loess soils have been in continuous no-till for more than 20 years. After two decades without being disturbed, the soil is rich with what Mark calls “dirt critters,” the beneficial organisms that build soil structure and tilth. “Because we don’t disrupt the soil structure with tillage, it can take a lot of water,” he says.
As a result of their farming practices, which also include grass waterways and multiple thin applications of solid manure, just 2% of annual rainfall ran off the Riechers’ farm, according to 7 years of monitoring by the University of Wisconsin Discovery Farms. Sediment losses averaged about 300 pounds per year, or 3% of NRCA “tolerable” loss. “It’s not just no-till,” Mark says, “it’s a combination of things.”
4. Saturated soil
Risk - Up
Soil moisture influences infiltration rates. “On saturated soil, rain will run off just as it does on frozen ground,” Frame says.
Wisconsin Discovery Farms’ monitoring found that when field soil moisture was over 35%, runoff occurred with as little as one-quarter inch of rain. On dry soils under 25% moisture, it usually took 2 inches to produce a runoff event. When soil moisture was between 25% and 35%, a three-quarters-inch rain was enough to cause runoff.
If you use liquid manure, pay close attention to that intermediate range, Radatz says: 13,000 gallons of manure equals about one-half in. of rain. On soil at 25% moisture, the application could bump up the total moisture so that a rain soon after would run off, carrying your nutrients and soil with it.