Building Soils for Better Crops Sustainable Soil Management by Fred Magdoff and Harold Van Es - HTML preview

chAPter 16 reduCing tillage

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