Understanding Soil Loss

Discovery Farms Programs in Minnesota and Wisconsin have collected edge-of-field water quality information from 25+ farms and 50+ fields starting in 2002.  More than 100 site years of surface runoff data and 30 site years of tile drainage have been collected.

 

Surface runoff is a more significant driver of soil loss than tile drainage

  • Median annual soil loss is 134 lb/ac
  • This low value equates to about 3 five gallon pails full of soil from an area the size of a football field
  • High annual soil losses suggest a need to re-evaluate tillage practices to match the landscape
  • Fields with high soil losses stand out visually with sedimentation in low areas and rills running down hillsides
  • Make sure to check fields annually for these signs and adjust practices if needed

Annual Soil Loss

 

Most soil loss occurs in May and June

  • 69% of the soil loss occurs in May and June
  • Fields are most vulnerable to soil loss from planting to crop canopy
  • Too little soil cover and too much soil disturbance for the landscape are indicated by large soil losses in May and June

Average Monthly Soil Loss

 

A small number of events cause the most soil loss

  • There have been 1074 surface runoff events monitored by Discovery Farms
  • 10% of the runoff events caused 85% of the total soil loss
  • Nearly all of those runoff events were generated by very intense storm events
  • The combination of intense storms and time periods where the landscape is most vulnerable, produces the most soil loss

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One Response

  1. don mcclure
    | Reply

    in Ohio, we have found that rain storms are getting more intense and flashy and that is a big driver for our phosphorus losses into the Lake Erie basin. We have been working to get cover crops adopted so that there are more roots to hold the soil in place and more residue (living and dead) to intercept the impact of raindrops. We have been talking more about the idea of vertical erosion happens first in a rain storm and then runoff is more of a concern. Vertical erosion is caused by raindrop impact breaking down soil aggregates into smaller pieces that plug soil pores. Once the water can’t infiltrate the soil then soil and water runoff drive the soil displacement to areas down slope and possibly offsite.

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