Agriculture Reference
In-Depth Information
C
of n s e r v a t i of n
a
g r i C u L t u r e
Conservation agriculture (CA) is one approach to farming that can help meet food
needs while using energy, inputs, and natural resources more efficiently. It is based
on three pillars: minimal soil disturbance, permanent soil cover, and crop rotations
(Hobbs et al., 2008).
Farming practices in the early 1900s often featured intensive plowing of soils.
This led to minimal soil protection for lack of plant cover and excessive soil ero-
sion by wind and water. Conservation tillage (minimum tillage and the use of crop
residues for soil cover) was introduced in the United States in the 1930s to counter
“dust bowl” land degradation. As energy costs increased and better no-till sowing
equipment was developed, many U.S. farmers switched to CA, doing away with till-
age altogether.
CA is adopted by farmers because it reduces production costs without reducing
yields. Even under these conditions, however, there is often a long lag period between
when the system is first introduced to farmers and when rapid adoption occurs. This
is partly a problem of information transfer and availability of good equipment, but
also overcoming the mindset of farmers who firmly believe that tillage is essential for
good crop production. Farmers typically need to experiment, hear about, and see the
technology and discuss it with fellow farmers before they are willing to risk investing
in something as strange and unusual as no till (Harrington and Erenstein, 2005).
However, once this lag phase has been breached, widespread adoption can occur
very rapidly. For example, no-till cropping was first introduced into Brazil to over-
come erosion problems on sloping land in Parana and other southern states. No-till
practices combined with residue retention reduced the soil erosion problem to accept-
able limits. Farmers were able to visually see the benefits and reacted by purchasing
improved no-till equipment. Information about CA spread very rapidly from one
group of farmers to another. Ten years after its introduction, area under no till rose
to 1 million ha. By 2005, more than 25 million ha of farmland in Brazil were under
CA. This is a large proportion of the global area currently covered by CA, estimated
at about 100 million ha (Derpsch, 2005). Apart from Brazil, CA is concentrated in
the United States, Argentina, and Paraguay but is steadily increasing elsewhere, for
example, South Asia.
The adoption of no till in South Asia has many parallels with the experience in
Brazil. In northern India, the introduction of short-duration rice and wheat varieties
allowed rice-wheat double cropping. Late planting of wheat after the rice harvest,
however, caused by late harvest of the previous rice crop and poor and excessive
land preparation, severely constrained wheat yields (Hobbs et al., 1997). In addition,
Phalaris minor
, a major weed in wheat, developed resistance to the herbicide (iso-
proturon) used by farmers for its control (Malik et al., 1998). Zero tillage was intro-
duced in the mid-1990s to enable timely wheat planting and to reduce wheat land
preparation costs. The idea was that the money saved by farmers on land preparation
could be used to buy the new but expensive herbicides for
Phalaris
control.
Farmer experimentation showed that zero till did indeed allow earlier wheat sow-
ing and higher yields, but it also resulted in reduced
Phalaris
germination because
less soil disturbance meant fewer buried weed seeds were brought to the soil surface
