Soil Test Levels (ppm)
Recommendations based on a soil test report (Ammonium Bicarbonate DPTA technique)
| NO3-N (nitrate nitrogen) |
Level of sufficiency |
Requirement of N/year [1] |
| < 10 ppm |
very low |
4- 5 applications (1 pound/1000 sq. ft) |
| 10- 24 |
low |
3- 4 applications (1 pound/1000 sq. ft) |
| 25-49 |
medium low |
2- 3 applications (1 pound/1000 sq. ft) |
| 50- 74 |
sufficient |
apply (1 pound/1000 sq. ft) when growth is less than desired |
| 75- 100 |
high |
0 |
| > 100 |
very high |
0 Check drainage; turf may be succulent and prone to disease and other problems |
| P (phosphorus) [8] |
Level of sufficiency |
P205/1000 sq. ft/year |
| < 5 ppm |
very low |
4- 5 app. 0.5 lb. |
| 5- 15 |
low |
2- 3 app. 0.5 lb. |
| 16- 30 |
medium low |
1- 2 app. 0.5 lb. |
| 31- 50 |
sufficient |
0 |
| 51- 75 |
high |
0 |
| > 75 |
very high |
0 |
| K (potassium) |
Level of sufficiency |
K20/1000 sq. ft/year |
| < 25 ppm |
very low |
4- 5 app. 0.5 lb. |
| 25- 75 |
low |
2- 3 app. 0.5 lb. |
| 76- 150 |
medium low |
1- 2 app. 0.5 lb. |
| 151- 300 |
sufficient |
0 |
| > 500 |
very high |
0 May indicate drainage problem |
| Fe (iron) |
Level of sufficiency [2] |
Fe recommendation/1000 sq ft area [3] |
| < 5 ppm |
very low |
2 app. 0.5 lb. [4] |
| 5- 14 |
low |
1- 2 app. 0.5 lb. [5] |
| 15- 20 |
medium low |
1 app. 0.5 lb. [6] |
| 21- 100 |
sufficient |
0 |
| >100 [7] |
high |
0 |
Cu, Zn, Mn- add organic if less than 0.5 ppm.
[1] Use split applications; follow the late-season fertilization program.
[2] Low levels of available iron may indicate over-watering, poor soil preparation, excessive phosphorus levels, or soil compaction.
[3] If liquid is used apply according to label directions.
[4] First application of ferrous sulfate or ferrous ammonium sulfate in late May or early June, second about a month later.
[5] Apply 1lb. of Fe/1000 sq. ft area. This may be sufficient for one season; if not, repeat application.
[6] Usually needed only if a very dark green lawn is desired.
[7] Often associated with acid soils that need liming; not typically a problem in Colorado.
[8]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
Placed on the Internet Tuesday, September 21, 2004 22:01
WebMaster
Dr. Curtis E. Swift, Area Extension Agent, Horticulture
Colorado State Extension
2775 US Hwy 50, Grand Junction, CO. 81503
voice: 970-244-1834
fax: 970-244-1700