idea behind balanced plant nutrition is to apply the nutrients that
cannot be adequately supplied by the soil. We therefore need to
use soil analysis to determine how much of each nutrient the soil
will provide to our crop.
often contain high amounts of nutrients, but the majority are in
solid forms. Plants take up nutrients in solution, therefore most of
the solid nutrients may be unavailable. For example, a soil may
contain 5,000 lbs of potassium per acre, but only 50 lbs may be
available to a crop.
trick to soil analysis is to determine both the amount of each
nutrient that is immediately available and the amount that can
become available during the life of the crop. Various methods have
been developed and the key to success is that the methods must be
must be done to show that the results of the analysis consistently
indicate the amount of nutrient that a crop will actually get from
the soil. Once the method and its interpretation are shown to be
reliable, they can then be used to predict whether or not a crop
will need additional nutrients and how much needs to be added.
numbers on a soil report do not indicate the exact amount of
nutrients available to a crop, but when interpreted correctly, they
give a description of the soil fertility.
potassium analytical result may be 0.25 meq/100 cm3, but
this number does not mean anything by itself. What really matters is
that for our method, this value indicates that the potassium level
laboratory may use a different method and get a different potassium
value on the same sample. The results from the two laboratories
cannot be directly compared. However, if they are both properly
calibrated, the two methods should give the same fertility
description; they should both indicate that the soil is deficient in
analytical result is used to suggest how much nutrient should be
applied. The exact amount needed will depend on the crop to be grown
and must be modified to suit the conditions under which it is