agroforestry and ox power

[Guest guest]

Dear all,

 

I am including below the basics of agroforestry which

can be found at ICRAF - International Centre for

Research in Agroforestry.

 

 

A few comments first:

 

Agroforests, using protected or un-protected animals,

are an ancient way of life. To reinstigate an

agroforest landscape with the use of farm animal draft

power could well be a viable lifestyle option. Its

feasability lies in the complexity and diversity of

the systems. Agroforests, or there variant names of

agroecology, home gardens and permacultural landscapes

are a mirror negative of the present percentages of

land and tree cover. Presently, tree cover could be

from 10-20% in many developed areas. The concept here

would be for the opposite to be the case and have a

80-90% tree cover with only a few areas of the

opposite. So, whereas now there are islands of trees

and fields of space, in the agroforests there will be

islands of space in a field of trees, of all sizes and

all ages abuntant in their biodiversity.

 

 

 

http://www.icraf.cgiar.org/ag_facts/ag_facts.htm#systems

 

Agroforestry-the basics

Put simply, agroforestry is using trees on farms.

ICRAF defines agroforestry as a dynamic, ecologically

based, natural resources management system that,

through the integration of trees on farms and in the

agricultural landscape, diversifies and sustains

production for increased social, economic and

environmental benefits for land users at all levels.

 

Trees can provide many products, such as

 

timber

food

fruit, nuts

fodder

fuelwood

poles

fibres

mulch

medicines

cosmetics

oils

resins

and services, such as

provide food security

conserve soils

enhance soil fertility

improve microclimates

provide living fences for crops and fruit trees

demarcate boundaries

sequester carbon

stabilize watersheds

protect biodiversity

reclaim degraded lands

control weeds

Using trees on farms is an ancient art. For millennia,

farmers have nurtured trees on their farm and pasture

lands and around their homes. Neither the concept nor

the practice of agroforestry is new. But agroforestry

researchers are developing that ancient art into a

science.

 

 

Agroforestry systems

There are two basic categories of agroforestry

systems: simultaneous and sequential.

 

In a simultaneous system, trees and crops or animals

grow together, at the same time on the same piece of

land. These are the systems in which trees and crops

compete most for light, water and nutrients.

Competition is minimized by spacing and other means.

Trees in a simultaneous system should not be growing

fast when the crop is growing rapidly, to minimize

competition. Trees should have roots that reach deeper

than the crop roots. They should have a small canopy,

so they do not shade out too much light from the

crops.

 

In sequential systems, crops and trees take turns in

occupying most of the same space. The systems

generally start with crops and end with trees. The

time sequence keeps competition to a minimum. Trees in

a sequential system should grow rapidly when crops are

not growing, recycle nutrients from deep layers, fix

nitrogen and have a large canopy to help suppress

weeds.

 

Simultaneous systems

boundary plantings

contour hedges

live hedges and fences

hedgerow intercropping (alley cropping)

parklands systems

silvopastoral systems

agroforests

shaded perennial crops

windbreaks

Sequential systems

shifting cultivation

relay intercropping

improved fallows

taungya systems

multistrata systems (this system can also be

simultaneous)

A brief primer of terms describing these systems

 

Simultaneous systems

 

Many simultaneous systems are linear arrangements; the

trees or shrubs all appear in a row, or in strips if

there is more than one row. Boundary plantings are

trees used to delineate plots or farms. The trees

forming the boundary can also provide wood, fodder or

other products. Contour hedges are planted to prevent

erosion and form biological terraces. Living hedges,

live fences and woody strips are all variations on the

technique of using shrubs or bushes to form a

continuous barrier. They are used to form animal

paddocks, but they can provide feed and various other

products as well. Windbreaks or shelterbelts are used

to protect crops or animals. These techniques also

conserve soil moisture, give shelter to the farm home

and beautify the landscape.

 

In hedgerow intercropping or alley cropping trees are

planted on land along with crops; the crops are grown

in alleys between the rows of trees. The aim is to

maintain soil fertility by planting nitrogen-fixing

leguminous shrubs in areas where shortage of land

makes long fallow periods difficult or impossible.

However, because of the competition between hedge and

crop for moisture and nutrients, alley cropping has

proved practical only in limited circumstances.

 

Parkland systems include combinations of trees and

crops in which the woody component is a permanent

upperstorey. The tree cover can be quite open, as it

is in the Sahel where sorghum is grown under

Faidherbia albida. It can also be almost closed, as

shade trees in a coffee or cocoa plantation.

Multipurpose trees, such as fruit trees, may be

scattered on the cropland.

 

Silvopastoral systems also incorporate a discontinuous

tree storey, over a continuous grass cover. Animals,

the chief beneficiaries of these combinations, can

graze in pastureland under trees or they can feed off

tree fodder or browse. The fodder from the trees can

also be cut and carried to livestock penned elsewhere.

 

Agroforests are a special category of agroforestry. An

agroforest is a plant community that resembles a

natural forest in that it is generally multistrata and

contains large, mature trees and shade-tolerant

understorey plants. Agroforests are managed; an

example is the homegarden, well know in the humid

tropics. Usually grown near a homestead and smaller

than other agroforests, it contains many different

plant species of various sizes, types and growth

cycles. Homegardens are important in providing a wide

variety of foods and other domestic needs as well as

some commercial products.

 

Sequential systems

At certain times in the cycle of a sequential system,

trees are the only component. Crops or animals occur

in other parts of the cycle, either with or without

trees. Probably the best known system of this type is

traditional shifting or swidden cultivation, also

known as slash-and-burn agriculture, the most

extensive farming system in the humid tropics. Farmers

cut, let dry and burn the forest vegetation, then

plant crops or pastures, using the ash as fertilizer

to enrich (temporarily) the nutrient-poor soil. They

stay for as long as the soil can support their

crops-usually two or three cycles-and then let a

forest fallow grow for 15-30 years until sufficient

nutrients accumulate in the biomass. Then farmers

return, slash and burn the site, and the cycle

continues.

 

This traditional practice works well and was

sustainable for millennia-but it depends on low

population pressures, where the farmers are few and

the forests vast. With increasingly dense populations

and shrinking forests, the cycles become shorter and

shorter until they are no longer sustainable. The

forest does not have time to accumulate enough

nutrients in its biomass-the fallow period is just too

short.

 

Relay cropping is a very promising system for areas

with only one rainy season a year. Both crops and

trees are planted at the beginning of the rains, but

the crops grow rapidly and the trees slowly, thus

minimizing competition. The trees grow rapidly after

the crop is harvested, forming a short-term fallow

during the dry season. Before the next rainy season,

trees drop their leaflets, providing mulch; they are

then cut and harvested for poles or firewood. The crop

is planted again, benefiting from nutrients and

improved soil physical properties, while the trees

begin to coppice and resprout from seeds.

 

Multistrata systems also involve planting annual crops

with several species of trees, both at definite

spacings. Crops are dominant while the trees get

established and grow. Tree species of different

eventual size, shape and use (fruit, timber) form two

or more strata or canopies, with or without

simultaneous cropping. A leguminous ground cover is

often planted to control weeds and is sometimes grazed

by cattle or small ruminants.

 

Improved fallows are used in the humid tropics as an

improvement of shifting cultivation by shortening the

fallow period and increasing its biomass and nutrient

accumulation. Improved fallows are also used in

sub-humid tropics to occupy land that is not cropped

for a few months or for two to three years, to

accumulate biomass and nutrients as well as to smother

weeds. Improved fallow species are normally planted

shortly before or after the crops are harvested.

Fast-growing, nitrogen-fixing species are used, as

they do not compete with crops.

 

In the taungya system, the forest service allows the

farmer to use land in a forest plot planted to young

trees. The farmer cares for the trees and at the same

time grows crops for several seasons until the trees

grow big enough to cover them; then the forest service

takes over the plots again.

 

 

 

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