Page 275 - Nutrient Management Planning Guide

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Chapter 8.1

Raindrop Buffering Effect. • Plants or plant residues reduce the impact of raindrops on the soil by intercepting raindrops and absorbing much of the energy. When raindrops strike bare soils, they can fracture soil aggregates and cause smaller particles to wash into and effectively plug soil pores. This reduces the permeability of surface soil layers resulting in reduced water infiltration.

Soil Channelling Effect. • Small channels created by intact stems and roots can serve as tiny “pipelines” that facilitate water movement into the soil. This effect is enhanced when a living canopy of leaves is present as these serve to direct precipitation towards the stem in a process referred to as “stem flow”.

Reservoir Effect. • Ground cover serves as a sort of in-field “reservoir” delaying the movement of water off the field and allowing more time for water to infiltrate. The stems of plants or standing crop residues serve as a physical barrier to water movement while vegetative debris on the surface may absorb some of the water and release it gradually so that it can be absorbed over a longer period of time.

Figure 8.1.6 Ground Cover Enhances Water Infiltration and Control Runoff

Crop Residues and Soil Temperature

Crop residues reduce the severity of runoff in the spring by serving as a barrier against runoff as well as improving runoff infiltration into the soil. Crop residues left on the soil surface also trap snow, which serves as an insulation buffer against extremes in soil temperature. The cooler, moister conditions that result can delay seeding in direct seeding or reduced tillage management systems since the soil warms more slowly in the spring.