livestock traffic, and rainfall.
In hayfields, where heavy traffic
loads are frequent, soil particles can
break down and be squeezed together.
In this scenario, soil pore space is
reduced, and water and air cannot
freely move through the soil.
Poor grazing management can cause
cattle to overgraze one area of a pasture.
Even though livestock can break
up the upper layer of soil through
hoof action, deep soil compaction
can occur over time. Soils high in clay
content are more susceptible to hoof
compaction than sandier soils.
Heavy rain can disturb the smallest
soil particles found on the soil surface.
This can result in crust layers. In pastures
with adequate ground cover, rainfall
compaction is usually minimal.
In pastures, three primary types of
soil compaction are common: surface
compaction, tillage pans (hardpans),
and subsurface hardpans.
Sustained heavy equipment or livestock
traffic can result in surface compaction
in the upper three inches of the
soil. In this area, growth is usually limited
to seedlings. Surface compaction is
easily corrected with a light disking.
Tillage pans, or hardpan compaction,
are generally the result of
repeated soil disturbance by the
same equipment at the same depth
(plow, disk, or chisel plow). When
this occurs, soil permeability rates are
decreased and soil layers seal and pack
tightly. Roots in this condition only
have access to moisture and nutrients
above the compacted layer.
Subsurface hardpans develop over
time as leached minerals and clays
are deposited at a specific soil depth.
Unless they are broken and mixed
with porous soil, subsurface hardpans
tend to re-form after a few seasons.
Breaking a subsurface hardpan is only
beneficial if it allows well-developed
plant roots to use moisture available
at deeper profiles.
The most accurate process for assessing
soil compaction is by combining
penetration resistance with visual
observation of a forage root system.
Look for restricted growth of the roots,
both vertically and horizontally.
A penetrometer can be used to measure
penetration resistance. Producers
should also note soil moisture and
changes in soil density (bulk density).
Soil bulk density is determined
by dividing the dry weight of soil by
its volume. Volume accounts for both
soil particles and the pores between
particles. Bulk density could affect
BRING IN THE MACHINE
Aeration is a mechanical process by
which soil is disturbed. Soil aeration
is often used to renovate established
pastures. It can reduce soil compaction
and increase water infiltration.
Machines used to aerate soils
include colters, which make narrow
slits in the soil; rollers with spikes that
make indentations in the soil; and
prongs, which function as a mini subsoiler.
These machines can be used for
28 I WORKING RANCH I NOVEMBER / DECEMBER 2020