Figure 16.4. Left: A heavy disk (disk plow) can be used for primary and secondary tillage (photo by Mark Brooks). Right: A finishing disk.
helps decrease negative aspects of full-field tillage.
rougher soil often has much higher water infiltration
Compacted soils tend to till up cloddy, and intensive
rates and reduces problems with settling and hardset-
harrowing and packing are then seen as necessary to
ting after rains. Weed seed germination is also generally
create a good seedbed. This additional tillage creates a
reduced, but pre-emergence herbicides tend to be less
vicious cycle of further soil degradation and intensive
effective than with smooth seedbeds. Reducing second-
tillage. Secondary tillage often can be reduced through
ary tillage may, therefore, require greater emphasis on
the use of modern conservation planters, which cre-
post-emergence weed control.
ate a finely aggregated zone around the seed without
In more intensive horticultural systems, powered
requiring the entire soil width to be pulverized. A good
tillage tools, which are actively rotated by the trac-
planter is perhaps the most important secondary tillage
tor power takeoff system, are often used (figure 16.5).
tool, because it helps overcome poor soil-seed contact
Rotary tillers (rotovators, rototillers) do intensive soil
without destroying surface aggregates over the entire
mixing that is damaging to soil in the long term. They
field. A fringe benefit of reduced secondary tillage is that
should be considered only if the soil also regularly
Figure 16.5. Powered tillage tools used with horticultural crops: rotary tiller (left), and spader (right).
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Building SoilS for Better CropS: SuStainaBle Soil ManageMent
