Fertilizers are responsible for over half of global food production, but there are areas in world with nutrient deficiency and other areas of nutrient excess.
Managing mineral plant nutrients requires careful application of science and skill to meet production, environmental, and social goals.
Monday, September 24, 2012
What is Going on Underground? Don't forget the Roots!
Roots: The overlooked plant part?
We spend a lot of time and money to get crops the nutrition
they need for maximizing growth and yield.
When planning for the next season, don’t forget about the part of the
plant hidden beneath the soil surface.
There are two obvious functions for roots that come to mind; anchoring
the plant to keep it upright and getting the water and nutrients needed to
support growth, but there many other things too.
Roots release a large number of organic compounds that aid
the plant in its growth. As much as
one-third of the carbon fixed through photosynthesis can be pumped out of the
roots into the soil, assisting the plant in numerous ways.
The organic compounds released from roots are grouped into
high molecular weight compounds such as carbohydrates and enzymes, and
low-molecular weight compounds such as sugars and organic acids. This zone surrounding the root is called the
rhizosphere, typically extending a few millimeters in to the soil (about the
thickness of a nickel).
A jelly-like substance is excreted at the root tip that
reduces friction and physically protects the delicate cells at the root tip,
aggregates soil particles, maintains a pathway for water and nutrient uptake,
and influences the growth and development of surrounding plants and
These root exudates play a vital role in providing a
constant nutrient supply for plants.
Some of them regulate microbial growth surrounding the roots. Specific bacteria can be triggered to form
nodules in legumes when signaled by the proper root exudates. Other compounds induce spores of mycorrhizal
fungi to germinate and assist the plant with phosphorus and micronutrient
Many exudates can directly improve nutrient
availability. For example, organic acids
released from roots can solubilize phosphorus compounds in the soil. Enzymes originating in the root can speed the
release of phosphorus from soil organic compounds to a form that can be used
for nutrition. Specialized root compounds,
called phytosiderophores, will chelate iron in the soil and enhance plant
nutrition and growth.
Roots have the ability to modify the soil pH in the rhizosphere.
Plants that receive nitrate as the primary source of nitrogen nutrition generally
have an elevated pH in the rhizosphere.
However, plants that have an abundance of ammonium often cause their
rhizosphere to become more acidic.
The physical properties of roots are also important. For example, the root length and the degree
of branching is important for exploring soil resources. A root system with a large surface area has
greater opportunity for nutrient uptake.
The presence of abundant root hairs is beneficial for water and nutrient
uptake. It is estimated that up to three
fourths of the total root surface area of many cultivated crops is provided by
Tree roots in compacted soil
Healthy root systems are often unappreciated,
but essential for vigorous plant growth and high yields. Even after the crop is harvested, the
decaying root system continues to provide benefits to the soil and to the
following crop. Providing an environment
where nutritional, chemical, physical, and biological barriers are eliminated
allows the crop to reach its full potential. Don’t overlook what you can’t see.