Conservation Agriculture (2003, Vol. 23 No. 1) - SIA
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CONSERVATION AGRICULTURE
by
Kenrick Chandon & L. Oliva Agra
It is well known that
‘virgin land” produces much higher crop yields than soils repeatedly
cultivated. While it may never be possible to fully maintain virgin land
productivity, it would be worthwhile trying to reduce the decline that comes
from continuous cropping. This is being attempted under a concept known as
‘conservation agriculture.’
MODERN FARMING METHODS
After viewing the
results of modern farming methods, scientists have come to conclude that
old-fashioned methods were indeed best for preserving soil productivity. Modern
methods tend to result in more rapid soil degradation and therefore less
sustainable agriculture. For instance, when the sugar industry turned to
pre-harvest burning of trash, in the early sixties, to facilitate mechanical
cane loading, this was the modern thing to do. That came at a cost however, as
organic matter, which used to be returned to the soil when the trash decayed in
green cane harvesting, was now lost. Soil became more exposed to erosion during
rains and tended to dry out more quickly during droughts. Gradually, such soils
became less productive.
SOIL EROSION AND
COMPACTION
Heavy machinery
simplified land preparation, making possible the ploughing of large areas more
thoroughly and in much shorter time than before. At the same time we were
loosening and exposing vast tracts of land to forces of erosion in a manner
unheard of when we were restricted to the use of the fork and hoe.
We sometimes make
matters worse by furrowing down-slope rather than along contours, speeding up
soil loss from erosion. Meanwhile the weight of machinery and equipment used in
cane cultivation and harvesting compressed the soil making it less suitable for
the passage of roots.
CONSERVATION AGRICULTURE
In summary, our
forefathers were practicing a form of agriculture that preserved the land far
better than we do now. Their careful management meant that we inherited soil
with inherent high yielding capability. That is a legacy we have largely
squandered.
Nonetheless, it would be
impractical to go back to the old fashioned methods. What conservation
agriculture seeks to do is to use modern methods to achieve the same end
results our forefathers did.
OBJECTIVES
The objectives of
Conservation Agriculture are:
1. to reduce soil degradation
2. to conserve, improve and make more efficient use of natural resources
APPROACHES
Conservation agriculture
is now rapidly gaining popularity across the world. The Sugar Industry Research
Institute has been approaching it by focussing on the areas of reduced tillage,
trash blanketing, crop rotation and the application of manures. In this issue,
reduced tillage technology will be discussed.
REDUCED TILLAGE
In conservation
agri-culture, crops are grown with minimal tillage of the soil. Typical land
preparation involves several passes of tractors and equipment to do ripping,
ploughing, harrowing and furrowing, often with some operations repeated. The
objective is to produce a seedbed of uniform tilth to a depth of at least 18
inches.
With reduced tillage,
the same depth and quality of soil tilth is achieved with far fewer number of
operations - often no more than one pass of equipment as against the typical
five or six passes in conventional land preparation. Cultivation is restricted
to only the strips of land in which the crop will be planted. However, these
strips are cultivated no less thoroughly. Reduced tillage therefore uses less
energy, disturbs less soil surface, retains the mulching effect of the crop
residue and, most importantly, is less costly.
Over the last five
years, SIRI has designed and developed special machines for reduced tillage.
The first was a single row machine, given the name RTM 1.5, Figure 1,
and the second a double row (RTM 3.0), Figure 2.
REDUCED TILLAGE STAGES
Old foliage killed by Roundup spray. Planting furrow opened by one pass of the Reduced Tillage machine
Land preparation completed
Sprouts emerged, old banks still present
Cane growth after 4 months - old banks destroyed by inter-row cultivation
Cane field at 6 months
REPLANTING WITH REDUCED
TILLAGE
The sequence of events
in replanting a field using the reduced tillage approach is as follows:
1. Destroy the old cane stools with a chemical (glyphosate) spray when the sprouts are about four weeks old
2. Prepare the seedbed with one pass of the Reduced Tillage Machine (RTM), which opens a furrow in the inter-row space (Figure 2)
3. Drop seed cane
4. Apply fertiliser
5. Cover with conventional tractor drawn covering tool
6. Inter-row cultivate when cane is sufficiently grown to destroy old banks and build up bank along new cane row (Figure 4)
EXPERIENCES
SIRI used the single row
machine (RTM1.5) to prepare a field at its experiment farm at Springfield in
1999. Without use of chemicals to kill the old stubble, the bank was split and
the new cane inserted. This field was furrow irrigated. Establishment was quite
good, as there was no need for supplying, but not all of the old stubble was
killed and there were volunteers (approximately 5%) of the old variety mixed
with the new. However, growth and yield were quite acceptable being at or above
farm average for plant cane and three ratoon cycles so far.
In August 2002, the
newly developed double row machine (RTM3.0) was used to prepare another field
at Springfield. This field was treated in the manner outlined where glyphosate
was used to kill old stubble and the seed planted in the inter-row spaces. Drip
irrigation tubes were laid along with the canes before covering. Figure 5 shows
that at 6 months this field looks as good as any planted in conventional
manner.
BENEFITS
Reduced tillage is
therefore important in conservation agriculture as it results in minimal
disturbance of the soil, thus reducing risk of soil erosion while producing an
adequate growth environment for the crop. At the same time, there are other
obvious benefits such as:
1. reduced fuel consumption during land preparation
2. reduced establishment cost of up to 50%
3. increase in land prepared in an hour
All this is achieved
with no appreciable difference in growth and yield between the reduced and
conventional tillage.
