Page 126 - Soil Degradation, Conservation and Remediation

114 4 Wind Erosion

Fig. 4.4 Ridging of soil for wind erosion control (Photo courtesy of USDA-NRCS)

pitting machines can be used to bring compact clods to the surface. Emergency tillage
is most effective when done at right angles to the prevailing wind direction. Because
clods eventually disintegrate (sometimes rapidly), emergency tillage offers, at best,
only temporary wind erosion control (Woodruff et al. 1972).

4.6.4 Residue Management

Residues of the harvested crops protect soil against wind erosion. Standing crop
residues provide non-erodible elements that absorb much of the shear stress in the
boundary layer. When crop residues are sufficiently high and dense to prevent
intervening soil surface drag from exceeding threshold drag, soil will not erode.
Standing stubble effectively protects the soil from wind erosion. Stubble mulching
is a crop residue management system using tillage, generally without soil inversion
and usually with blades or V-shaped sweeps (McCalla and Army 1961; Mannering
and Fenster 1983). The goal is to leave a desirable quantity of plant residue on the
surface of the soil at all times. Residue is needed for a period of time even after
the crop is planted to protect the soil from erosion and to improve infiltration. The
residue used is generally that remaining from a previous crop. Figure 4.5 shows a
ridged field retaining sufficient residues of the previous crop, and Fig. 4.6 shows
that the residues of the past wheat crop have formed an effective cover mulch.
Any crop residue, either grown in place or hauled in and spread, can control wind
erosion. Last year’s wheat or corn residues are uniformly spread over the field; they