The best single overall strategy for nutrient management
the Abcs of nutrIent MAnAGeMent
is to enhance the levels of organic matter in soils (figure
a. Build up and maintain high soil organic matter levels.
18.1). This is especially true of N and P. Soil organic
b. Test manures and credit their nutrient content
matter, together with any freshly applied residues, are
before applying fertilizers or other amendments.
well-known sources of N for plants. Mineralization of
c. Incorporate manures into the soil quickly, if
P and sulfur from organic matter is also an important
possible, to reduce N volatilization and potential
source of these nutrients. As discussed earlier, organic
loss of nutrients in runoff.
matter helps hold on to positively charged potassium
d. Test soils regularly to determine the nutrient
(K+), calcium (Ca++), and magnesium (Mg++) ions. It
status and whether or not manures, fertilizers,
also provides natural chelates that maintain micronu-
or lime is needed.
trients such as zinc, copper, and manganese in forms
e. Balance nutrient inflows and removals to maintain
that plants can use. In addition, the improved soil tilth
optimal levels and al ow a little “drawdown” if
and the growth-promoting substances produced during
nutrient levels get too high.
organic matter decomposition help the plant develop a
f. Enhance soil structure and reduce field runoff
more extensive root system, allowing it to obtain nutri-
by minimizing soil compaction damage.
ents from a larger volume of soil.
g. Use forage legumes or legume cover crops to
provide N to following crops and develop good
IMPROVINg NUTRIENT cYclINg ON THE FARM
soil tilth.
For economic and environmental reasons, it makes
h. Use cover crops to tie up nutrients in the off
sense for plants to more efficiently utilize nutrient
season, enhance soil structure, reduce runoff
cycling on the farm. Goals should include a reduction in
and erosion, and provide microbes with fresh
long-distance nutrient flows, as well as promoting “true”
organic matter.
on-farm cycling, in which nutrients return in the form
i. Maintain soil pH in the optimal range for the
of crop residue or manure to the fields from which they
most sensitive crops in your rotation.
came. There are a number of strategies to help farmers
j. When P and K are very deficient, broadcast some
reach the goal of better nutrient cycling:
of the fertilizer to increase the general soil fertility
• Reduce unintended losses by promoting water
level, and band apply some as well.
infiltration and better root health through enhanced
k. To get the most efficient use of a fertilizer when P
management of soil organic matter and physical
and K levels are in the medium range, consider band
properties. Ways organic matter can be built up and
application at planting, especial y in cool climates.
maintained include increased additions of a variety of
sources of organic matter, plus methods for reducing
salts from the irrigation below the root zone.)
losses via tillage and conservation practices. In addi-
• Enhance nutrient uptake efficiency by care-
tion, apply only the amount of irrigation water needed
fully using fertilizers and amendments, as well as
to refill the root zone. Applying more irrigation water
irrigation practices. Better placement and synchro-
than needed can cause both runoff and leaching losses
nizing application with plant growth both improve
of nutrients. (In arid climates occasional extra water
efficiency of fertilizer nutrients. Sometimes changing
applications will be needed to leach accumulating
planting dates or switching to a new crop creates a
205
Building SoilS for Better CropS: SuStainaBle Soil ManageMent