Earthworms as a Factor in the Reduction of Soil Crusting
1986
Kladivko, Eileen J. | Mackay, Alec D. | Bradford, Joe M.
Surface soil crusting after heavy rainfall is a problem on many cultivated soils. The objective of this study was to investigate the effect of earthworms (Lumbricus rubellus) on the aggregate stability and infiltration rate of a soil and then assess the susceptibility of this soil to surface crusting. The effect of 0, 15 (250 m⁻²), or 30 (500 m⁻²) earthworms pot⁻¹ on a Raub silt loam (Aquic Argiudolls) to which no, soybean [Glycine max (L.) Merr.] or corn (Zea mays L.) residue had been added was studied in 16-L pots over a 54-d period in the greenhouse. Earthworms increased both mean weight diameters (MWD) and water-stable aggregates > 2mm when determined on initially moist soil. In the absence of earthworms, steady-state infiltration rates on the Raub soil were 22 µm s⁻¹ (8 cm h⁻¹). Addition of 15 and 30 earthworms pot⁻¹ to soil containing crop residues, increased infiltration rates to 181 and 328 µm s⁻¹ (65 and 118 cm h⁻¹), respectively. The susceptibility of the undisturbed soil in the 16-L pots and of sieved, repacked soil to surface crusting under simulated rainfall was evaluated by measuring corn seedling emergence. Ten days after planting and simulated rainfall (6.25 cm h⁻¹), 85 to 100% of corn seedlings had emerged in the undisturbed soil in which earthworms were active, whereas in the absence of earthworms only 50 to 52% of seedlings had emerged. When the sieved soil that had received residues and earthworms was exposed to simulated rainfall, 40 to 73% of seedlings had emerged at 10 d, and by 16 d 80 to 88% had emerged. This compares with only 38% emergence in soil to which neither residue nor earthworms was added. Through their feeding, casting, and burrowing activity, earthworms are an important factor in the reduction of surface crusting.
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