Garden with Insight v1.0 Help: loosely/tightly bound/held
We use these terms both for nutrients in organic matter and for nutrients in mineral deposits.
In organic matter
Nutrients tightly held to organic matter are incorporated in complex molecules such as proteins and
are only released when these molecules are absorbed by soil microbes and digested. Nutrients loosely held in organic matter are in
smaller molecules with oxygen, hydrogen and carbon or are adsorbed
to clay or organic matter particles at cation exchange sites. Plants
depend on release of tightly held and loosely held nutrients so that they can absorb them. A healthy soil
microbial community is essential for release of nutrients from organic matter.
In this simulation nitrogen moves between loosely held (active) and tightly held (stable) forms in organic
matter by an equilibrium equation based on the long-term cultivation of
the soil. The simulation makes no such distinction between loosely and tightly held phosphorus in the
organic matter, because phosphorus tends to be held much more tightly in organic compounds than is
nitrogen (therefore it is never "loosely held").
In mineral deposits
Nutrients tightly held in mineral deposits are found in large mineral particles (rocks) that break down
over very long periods of time. Nutrients loosely held in mineral deposits are in smaller particles (in sand
grains, for example) or rocks that break down more quickly. Different types of mineral deposits break
apart at different rates; this produces some of the variation in different
Nitrogen in mineral deposits is not simulated here because very few mineral deposits contain significant
amounts of nitrogen, and thus over 99% of nitrogen in the soil is usually contained in organic matter.
However, in mineral deposits the distinction is made between loosely and tightly held phosphorus. This is
because phosphorus appears in many mineral deposits of varying types.
How it works: