Page 70 - Soil Degradation, Conservation and Remediation

56 2 Physical Deterioration of Soil

compaction can be physical and physiological constraints to overall plant growth
and yield through poor development of root system (Iijima et al. 1991 ; Grzesiak

et al. 2002 ) since high soil impedance influences root elongation and proliferation.
Acquisition of water and mineral nutrients is primarily determined by dimension of
root zone and distribution of roots.

2.2.3.3 Management of Compacted Soils

The problems associated with soil compaction are low infiltration, high runoff, poor
root penetration, low available soil moisture, and poor aeration. So, the principles of
compacted soil management should include:

• Avoiding to make the soil more compact
• Avoiding excessive tillage

• Avoiding to till the soil when it is too moist (at or slightly higher than fi eld
capacity)

• Making and keeping the soil loose and friable
• Increasing infi ltration
• Reducing runoff
• Reducing evaporation
The techniques may involve reduced tillage, building up of organic matter, con-

trolled trafficking, and mulching.
Subsoiling : Subsoiling with heavy duty shanks to depths of 35–60 cm or even
deeper and usually spaced about 30–75 cm apart has been tried with mixed
results. Subsoiling is an expensive operation requiring about 30 hp per shank. Its

greatest benefits appear to occur in the southeastern USA, where soil is subject

to little or no freezing. Short-term benefits have been measured, but some scien-
tists think that subsoiling may, in the long run, make compaction worse. Subsoiled

fields may recompact to a greater degree from normal operations than without
any such subsoiling treatment. Apparently, subsoiling reduces the soil’s capacity
to support loads of equipment without compacting.
Reducing Tillage : The less the soil is tilled, the less it is compacted. Tillage con-
tributes to the breakdown of soil structure by compressing and breaking the
aggregates, necessary for aeration and root growth. Tillage also increases
decomposition of organic matter needed for aggregate stability. Organic mat-
ter depletion goes hand-in-hand with structure depletion. Reduced tillage
leaves higher amount of plant residues on the surface which prevent surface
sealing.

Controlled Traffi c Farming ( CTF ): Controlled trafficking is adopted in Australia to
reduce the risk of soil compaction since the early 1990s involving production of
grain crops under a production system where the high-powered tractors, large
harvesters, and heavy trucks all have the same track settings of 3 m. In the fi eld,
the width of the combine harvesters and planters is matched at perhaps 9 m,