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Purpose
This
web module is a forum for presenting and sharing information on
cover crops for the highland tropics.
Introduction
Green manure/cover
crops are crops that are grown around the world to enhance soil
fertility and protect the soil from erosion and other negative impacts
of bare ground. These crops have additional uses such as forage
for animals, or food for human consumption. Green manure/cover crops
are a recognized part of sustainable agriculture in both temperate
and tropical areas, and research has been devoted to documenting
and improving cover cropping and fallowing practices for the lowland
tropical areas of the world.
However, green
manure/cover crops for use in the highland tropics have been less
studied. Discussion lists for
green manuring in several languages (mulch-L,
coberagri-L, evecs-L)
have featured questions about multi-purpose soil improving crops
for the high altitude tropics. Exchanges have been especially lively
in sharing information about crops such as sweetclover (Melilotus
alba), tarwi (Lupinus mutabilis), and grass pea (Lathyrus
spp.). In the fall of 2001, CIDICCO,
the International Cover Crops Information Center in Tegucigalpa,
Honduras, made a request to students in a class at Cornell University
to assemble relevant information and expertise from Web and printed
sources on high altitude cover cropping. This module is the result
of that request. We hope that it will serve as a means to generate
even more information sharing on this subject.
Tropical
highlands
Tropical
highlands are areas in the tropics above 2000 meters in altitude.
Average day/night temperatures in highlands are cooler than in lowland
tropical areas and fall within the range of the temperate zone,
with extremes between day and night rather than from summer to winter.
When irrigation is unavailable, growing seasons are determined by
a the length and intensity of a rainy season. Rainfall in tropical
highlands ranges from seasonally wet to a mostly arid climate with
a brief rainy season that allows a short window for crop production.
In the Americas, highland Ecuador and Guatemala are examples of
more moist high altitude climates, while the inter-Andean valleys
of Peru and Bolivia, and many parts of highland Mexico, are examples
of the dry high altitude tropics.
Cover crop
roles
This range of climates, as well as the social, economic, and cultural
characteristics of different mountainous regions, define niches for
highland tropics green manure/cover crops that are similar to those
in temperate farming systems but also quite different. An ideal cover
crops for the highland tropics must:
- stabilize
highly erosible soils on slopes. Quick establishment
of soil cover and good root systems are important.
- improve the fertility and structure of soils that
may be eroded or degraded in other ways.
- have multiple roles including economic value within
in the livelihood of households and communities; for example,
provide fodder for livestock, food, or another product.
- resist frost at higher elevations
- be able to grow to maturity and set seed within
the local growing season, so that seed can be saved (Wheeler
et al. 1999).
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