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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.