I forwarded the ECOLOG-L discussion about fertilizing tropical soils to
William Woods, Director of the Environmental Studies Program at the
University of Kansas <[EMAIL PROTECTED]>, who studies soils in the Amazon
valley. Here is his response:
Without major amendments tropical soils are generally considered to offer
poor prospects for agricultural development. Amazonian soils represent a
textbook case. Soil quality equals destiny in many readings of Amazonia's
past, present, and future. Yet in the past few decades archaeologists have
uncovered evidence of large and complex prehistoric societies in Amazonian
environments despite earlier consensus that such development was
untenable. More recently, geographers have discovered that these sites
coincide with fertile, dark soils termed "terra preta" that occur in a
variety of landscape contexts and extents, from patches of less than a
hectare to many square kilometers. It is now clear that these soils are
anthropic in origin and represent fonts of local environmental knowledge
and know-how with ancient roots and contemporary pan-tropical
applications. An intriguing property is their apparent persistence, even
after cultivation cessation ranging from decades to centuries and possibly
millennia. Local people continue to generate these soils with skilled
practices, including carbon amendments and microbial management. Both the
soils and these practices are important agricultural resources within
contemporary Amazonia. They provide a global model for developing long-
term future sustainability of food production in lowland tropical
environments. They also constitute a significant reservoir for the short-
and long-term sequestration of carbon.
----- Original Message -----
From: <[EMAIL PROTECTED]>
Sent: Tuesday, February 06, 2007 2:29 PM
Subject: Re: What would adding fertilizer do to a tropical forest?
In most tropical soils adding mineral fertilizers to soil is not likely to
have much impact. Since these soils have very low cation exchange
capacity, cations, such as potassium, added to soils will be leached away
very quickly. Phosporus is most likely to be fixed as iron and alluminium
phosphates and will not be available to plants.
Bob Mowbray
Tropical Forest Ecologist
----- Original Message -----
From: "Jonathan Adams" <[EMAIL PROTECTED]>
Sent: Thursday, February 01, 2007 5:36 PM
Subject: What would adding fertilizer do to a tropical forest?
For a long time I've heard people talk about the effects of adding mineral
fertilizers to grasslands - how it causes a crash in species richness.
Has anyone ever tried adding mineral fertilizer to tropical forest and
studying (say) the species diversity of seedlings, or long term effects on
regeneration?
It may be interesting from the point of view of understanding maintainance
of species richness.
Examining effects on growth rate of tropical trees might also be relevant
to the idea of setting up artificial forests for carbon sequestration.
Jonathan Adams
