Tree and Shrub Fertility
Curtis E. Swift, Ph.D., Colorado State University, Area Extension Agent, Horticulture
Soil Test Levels (ppm)
Recommendations based on a soil test report (Ammonium Bicarbonate DPTA technique)
|
NO3- N (nitrate nitrogen) |
Level of sufficiency |
Requirement [1] |
||
|
0- 13 ppm |
low to moderately low |
Apply from 1 to 6 lbs N/1000 sq ft area |
||
|
14 |
sufficient |
0 |
||
|
> 50 |
excessive |
0 Likely a drainage problem. |
||
|
|
Level of sufficiency |
Requirement: P2O5/1000 sq ft area |
||
|
0- 6 ppm |
very low |
No more than 1 lb |
||
|
7 |
sufficient [3] |
0 |
||
|
K (potassium) [2] |
Level of sufficiency |
Requirement: K20/1000 sq ft |
||
|
0- 60 ppm |
very low |
up to 8.5 lbs |
||
|
61- 120 |
low |
up to 5 lbs |
||
|
120- 150 |
medium low |
up to 1.75 lb |
||
|
> 151 |
sufficient |
0 |
||
|
Fe (iron) [2] |
Level of sufficiency |
Fe recommendation/1000 sq ft area |
||
|
< 5 ppm |
very low |
1 lb/1000 sq ft |
||
|
5- 10 |
low |
0.5 lb/1000 sq ft |
||
|
> 10 |
sufficient |
0 |
||
[1] Do not apply Nitrogen to newly planted trees and shrubs; apply to established trees and shrubs only.
[4]The extraction method used to determine the P in the sample needs to considered with using this fertility chart. Conversion information based on the extraction method used is provided at Phosphorus_analysis_techniques.html
[2] Must be applied and worked into the soil prior to planting.
[3] Excess levels of P can increase iron chlorosis problems. Levels above 50 ppm may kill mycorrhiza.
Placed on the Internet Tuesday, September 21, 2004
Updated on June 16, 2009