MSU Extension Soil Web pages for Consumers

Example of the recommendations section of a soil test report:

Target pH indicates the desired acidity for this crop.  The lime recommendation is calculated to adjust the soil to this level. For info on applying lime, see raising pH.

Tillage depth in this case indicates sample depth.

What fertilizer should I use?  Nitrogen is the nutrient generally needed in greatest quantity by plants, but it is not stable in soils.  That is why the standard soil test does not include a Nitrogen measurement, and the recommendations are based on the amount plants are expected to use during the season. You must adjust the amount of nitrogen if your trees are newly planted, actively growing, or mature, see below. Trees in situations where 3 or more applications of lawn fertilizer are made per year in the root zone seldom need additional nitrogen.

Use a fertilizer calculator, enter your recommendation and the fertilizer you want to use, and the calculator will tell you how much to buy and apply,

or Learn to calculate  the amount of fertilizer that will meet the recommendations.

How should I apply to established trees?   Small amounts of fertilizer can be scattered evenly by hand around a small tree or shrub or dissolved in water and poured slowly around it. Although Nitrogen fertilizer will dissolve in rain and move through the soil, phosphate and potash fertilizers do not, so although lawn-type spreaders can be used for surface applications, large trees are often fertilized through root feeders or in holes.  Fertilizer stakes are easy to use, but they are costly. Root feeders and application into holes can put the nutrients where they are needed.

Timing of applications: Mid to late fall, and early spring when the ground has thawed are the best times to fertilize trees and shrubs.  Tree roots continue to grow and absorb nutrients long after the leaves turn and fall. They begin growing again before leaves come out in spring, so they will take up nutrients in time to supply top growth.

Surface applications  produce less unwanted turf growth in late fall, but the nitrogen is subject to leaching and in sandy soils some may wash out of the root zone. The greatest use of nitrogen is in the spring as the leaves are expanding.  So, in sandy soils or for young trees, early spring may be a better time than fall, or applications could be split between those times.

The worst time to fertilize trees is June through September, because then the nutrients may stimulate late growth which will not have time to mature and harden off before winter.  Also, especially with small trees and shallow-rooted shrubs, fertilizer may aggravate drought injury.

 Fertilizer recommendations are calculated for the following types of trees and shrubs:

One of the main differences among these categories is that evergreen trees and shrubs generally require more acid soil, especially broadleaf evergreens such as Rhododendron, Azalea, Boxwood, and Holly.  Less lime would be required for the same pH, or in many Michigan soils, no lime would be needed.  More about "acid-loving" trees and shrubs.

Use a fertilizer calculator, enter your recommendation and the fertilizer you want to use, and the calculator will tell you how much to buy and apply,

or Learn to calculate  the amount of fertilizer that will meet the recommendations.

This site was last updated 11/16/09