frost tILLAGe!
Readers from temperate regions may have heard of frost seeding legumes into a pasture, hayfield, or winter wheat crop in very early spring, but perhaps not of tilling a frozen soil. It seems a strange concept, but some farmers are using frost tillage as a way to be timely and reduce unintended tillage damage. It can be done after frost has first entered the soil, but before it has penetrated more than 4 inches. Water moves upward to the freezing front and the soil underneath dries. This frozen state makes the soil tillable as long as the frost layer is not too thick. Compaction is reduced because equipment is supported by the frozen layer. The resulting rough surface is favorable for water infiltration and runoff prevention. Some livestock farmers like frost tillage as a way to incorporate or inject manure in the winter without concerns for compaction from heavy equipment.
heavy cover crop, which is mowed or rolled to create a
although matching wheel spacing and tire widths for
thick cover mulch (figure 16.7).
planting and harvesting equipment is sometimes a chal-
Farmers need to be aware of potential soil compac-
lenging task, as we discussed in chapter 15.
tion problems with reduced tillage. If a strict no-till
For organic farms, as with traditional farms before
system is adopted on a compacted soil, especially on
agrichemicals were available, reduced tillage is chal-
medium- or fine-textured soils, serious yield reductions
lenging, and full-field tillage may be necessary for
may occur. As discussed in chapter 6, dense soils have a
mechanical weed control and incorporation of manures
relatively narrow water range in which plant roots can
and composts. After all, the two greatest challenges
grow well, compared to their ability to grow in uncom-
of organic crop production are weeds and nitrogen.
pacted soil. When a compact soil is completely dry, roots
Organic farming on lands prone to erosion may, there-
have a difficult time making their way through the soil,
fore, involve trade-offs. Erosion can be reduced by using
and when a compact soil is wet, roots tend to have less
rotations with perennial crops, gentler tillage methods
air. Crops growing on compacted soils are more suscep-
like spaders and ridgers, and modern planters that
tible to inadequate aeration during wet periods and to
establish good crop stands without excessive second-
restricted root growth and drought stress during drier
ary tillage. Soil structure may be easier to maintain on
periods. Compaction, therefore, reduces plant growth
organic farms, because they use organic inputs heavily.
and makes crops more susceptible to pest pressures.
Livestock-based farms face special challenges related
In poorly structured soils, tools like zone builders,
to applying manure or compost to the soil. Some type
strip tillers, and zone-till planters provide compaction
of incorporation usually is needed to avoid large losses
relief in the row while maintaining an undisturbed
of nitrogen by volatilization, and losses of phosphorus
soil surface. Over time, soil structure improves, unless
and pathogens in runoff. Transitions from sod to row
recompaction occurs from other field operations. Crops
crops are also usually easier with some tillage. Such
grown on fields that do not drain in a timely manner
farms can still use manure injection tools with zone and
tend to benefit greatly from ridging or bedding, because
strip tillage, thereby providing compaction relief while
the sensitive seedling root zone remains aerobic during
minimizing soil disturbance. As with organic farms,
wet periods. These systems also use controlled traf-
livestock operations apply a lot of manure and compost
fic lanes, which greatly reduce compaction problems,
and naturally have higher soil health.
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Building SoilS for Better CropS: SuStainaBle Soil ManageMent