permaculture

["Lawrence F. London, Jr." <venaurafarm@bellsouth.net>]

-------- Original Message --------
Subject: [SANET-MG] soil organic matter in tropical vs. temperate soils
Date: Fri, 31 Dec 2010 12:26:22 -0500
From: Joel Gruver <jgruv@HOTMAIL.COM>
To: SANET-MG@LISTS.IFAS.UFL.EDU

Hello Jim,

I haven't personally conducted research on soil organic matter farther 
south than North Carolina but there is lots of evidence in the 
scientific literature that SOM levels can be enhanced in sub-tropical 
and tropical soils through the implementation of cropping systems that 
grow more SOM (especially roots) and reduce losses:

here are a few references you may want to look at:

http://ipmsouth.com/2010/04/20/alabama%E2%80%99s-old-rotation-proves-crop-rotation-improves-yields/

“Cover crops grown on cropland in the southeastern United States build
SOC, improve soil physical and chemical characteristics, supply
additional N, and reduce erosion of topsoil during the high rainfall
winter months,” say the authors. “After 99 years, the Old Rotation
indicates that winter legumes increase amounts of both carbon and
nitrogen in soil, which ultimately contribute to higher cotton yields.”

http://xbiblio.ecologia.edu.mx/biblioteca/Cursos/Manejo/Craswell_Lefroy.pdf

"Although the myths of lower quantity and quality SOM in tropical soils 
compared to temperate soils have been countered (Sanchez 1976; Greenland 
et al. 1992), there are some broad differences in the soil C dynamics 
between tropical and temperate zones, as there are between agricultural 
and non-agricultural systems. The breakdown rate of OM Powison 1976) to 
measurement of labile C with high can be significantly faster in the 
tropics, although there are no major differences in the pattern and 
products of breakdown (Jenkinson and Ayanaba, 1977). Correspondingly, 
the inputs of C to tropical systems can be much greater, which may 
explain the lack of a general difference in total organic C between 
temperate and tropical areas."

Organic Matter Dynamics in Soils of the Tropics-From Myth to Complex Reality
                Greenland, D. J. Wild, A. Adams, D.
SSSA SPECIAL PUBLICATION, 1992, VOL 29, pages 17

I am on the road currently and don't have access to this SSSA pub 
electronically but can send you a copy when I get back home.

Joel

Joel Gruver
School of Agriculture
Western Illinois University
jgruv@hotmail.com