A lasting injury is done by ploughing land too wet.
—s.l. dana, 1842
We’ve already discussed the benefits of cover crops,
plant canopy forms to protect the soil from direct rain-
rotations, reduced tillage, and organic matter additions
drop impact. Certain soil types, such as sandy loams and
for improving soil structure. However, these practices
silt loams, are particularly susceptible to crusting. Their
still may not prevent compacted soils unless specific
aggregates usually aren’t very stable, and, once broken
steps are taken to reduce the impact of heavy loads
down, the small particles fill in the pore space between
from field equipment and inappropriately timed field
the larger particles, making very dense crusts.
operations. The causes of compaction were discussed
in chapter 6, and in this chapter we’ll discuss strategies
to prevent and lessen soil compaction. The first step is
to decide whether compaction is a problem and which
type is affecting your soils. The symptoms, as well as
remedies and preventive measures, are summarized in
table 15.1, p. 162.
cRUSTINg AND SURFAcE SEAlINg
Crusting and surface sealing may be seen at the soil
surface after heavy rains in the early growing season,
especially with clean-tilled soil, and in the fall and
spring after a summer crop (figure 15.1). Keep in mind
Figure 15.1. Rainfall energy destroys weak soil aggregates and creates
that crusting and surface sealing may not happen every
a surface seal that increases runoff potential. Photo is of soil in the
wheat-growing Palouse region of Washington State. When it dries, the
year, especially if heavy rains do not occur before the
seal turns into a hard crust that prevents seedling emergence.
161
Building SoilS for Better CropS: SuStainaBle Soil ManageMent