NUTRIENT ENRICHMENT

Sediment in runoff has greater nutrient concentrations than the soil from which it was eroded. The enrichment is known for soil organic matter, total N, total P and total K (Table 5).  This occurs because the sediment in runoff contains a greater percentage of finer particles than the initial bulk soil and the finer particles have greater nutrient concentrations.

The enrichment also shows in soil test P concentrations, even on predominantly sprinkler irrigated tracts (Table 6).
 
 
 
 
 
 
 

Table 5.  Enrichment Ratio (E.R.)-Summary

 Soil Variable
Runoff E.R.
Organic Matter
4 - 6
Total Nitrogen
2 - 8
Total Phosphorus
2 - 5
Total Potassium
  2 - 10

 

Table 6.  Phosphorus Enrichment

 
Field Soil
Eroded Sediment
Tract
NaHCO3-P 
mg/kg
Total P 
mg/kg
NaHCO3-P
mg/kg
Total P
mg/kg
A
24
722
138
1163
B
22
839
44
932

A - Northside Canal Company (75% Sprinkler)
B - Twin Falls Canal company (90% Surface)

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