Sunday, April 28, 2013

Ten Laws of Sustainable Soil Management (Lal)

Dr. Rattan Lal developed 10 laws for sustainably meeting the demands of the growing world population.  They are worthy of some discussion and thought by soil scientists.

(1) Soil degradation and poverty: The biophysical process
of soil degradation is driven by economic, social, and political

(2) Stewardship and desperateness: The stewardship concept
is relevant only when the basic necessities are met. Desperate
people do not care about the stewardship.

(3) The soil bank: The nutrient and C pools in soil bank can
only be maintained if all outputs are balanced by the inputs.

(4) The law of marginality: Marginal soils cultivated with
marginal inputs produce marginal yields and support marginal

(5) The organic dilemma: Plants cannot differentiate the
nutrients supplied through organic or inorganic sources. It is
a question of logistics and availability.

(6) Soil as a source or sink of greenhouse gases: Agricultural
soils can be a major sink for CO2 and CH4, depending
on land use and management.

(7) Extractive farming and the environment: Extractive
farming and mining soil fertility adversely impact soil quality,
perpetuate hunger and poverty, exacerbate CO2 emissions,
and reduce ecosystem services.

(8) Synergism between soil management and improved
germplasm: The yield potential of improved germplasm can
be realized only if grown under optimal soils and agronomic

(9) Agriculture as a solution to environmental issues:
Rather than a problem, agriculture must always be integral to
any solution towards environmental development. Humans
will always depend on agriculture, and it must be the engine
of economic development.

(10) Modern innovations: Yesterday’s technology cannot
resolve today’s problems.

The entire article can be downloaded here:
Lal. 2010. Managing sols for a warming earth in a food-insecure and energy-starved world. J. Plant Nutr. Soil Sci. 173:4-15.

Thursday, April 25, 2013

Don’t Forget to Keep Your Alfalfa in Top Shape with Phosphorus!

Many factors are involved in producing a top-quality alfalfa crop. 
Healthy alfalfa growth requires adequate mineral nutrition
Although many factors (like weather) cannot be controlled, many other critical components need to be carefully managed.  As the demand for high-quality hay increases, a closer look at the role of proper nutrition is needed

There is no substitute for maintaining an adequate plant nutrient supply for production of high-yielding and high-quality alfalfa.  Alfalfa production removes large amounts of nutrients from the soil that must eventually be replaced to remain sustainable (a
bout 15 pounds of P2O5 removed in each ton of hay).  Since phosphorus (P) has many essential roles in alfalfa, both yield and quality are reduced when this nutrient is limited.
ATP uses P for energy storage
Most P in the plant is rapidly converted into organic compounds involved in a variety of essential reactions. For example, P in alfalfa is essential for formation nucleic acids, phospholipids and ATP- associated with things like photosynthesis, protein formation and nitrogen fixation.
Rhizobia nodules

Alfalfa field in Washington
In addition to direct plant growth benefits, P fertilization has also been shown to increase nitrogen fixation, nodule number and nodule size.  There are frequent reports that P or K nutrition have been found to improve disease tolerance or resistance.

Soils vary in their ability to supply P and nutrient deficiency symptoms in alfalfa are hard to detect before the deficiency becomes quite severe.  Therefore, soil testing is best way of predicting the potentially available nutrient supply.  It is generally best that P be applied prior to establishing the crop, since an adequate supply of P is critical for rapid stand development and a strong root system.  For established stands, surface applications are a good way to meet plant needs.
Harvesting alfalfa hay

Many sources of fertilizer P are successfully used for alfalfa production- including both solid and liquid forms.  A number of comparisons have demonstrated that most P fertilizer sources are equivalent, when properly used.  The selection of a specific P fertilizer is generally based on local availability, ease of application, and the cost per unit of nutrient.

Phosphorus fertilization is an essential component of alfalfa production.  High-yielding alfalfa removes large amounts of P which must be replaced when the soil P supply can not meet the plant demand.  Soil and tissue tests are useful for determining the appropriate amount of P to apply.  Failure to monitor and replace the nutrients removed in harvested hay will lead to losses of yield, plant stand, and profit. 

A productive milk cow turning a meal of alfalfa into ice cream