Soil cover conserves moisture, intercepts raindrops to reduce a destructive impact, suppresses weed growth, and provides surroundings for members of the soil food web that spend at least some of their time above ground. This is true regardless of the land use — cropland, pasture, or range. If improving soil health is your goal, you should not see the soil very often.
Soil should always be covered by growing plants and/or their residue and it should rarely be visible from above. Soil cover cannot be taken for granted. Even in a no-till system, there are times when soil cover may be lacking because of crop harvest methods, amounts of residue produced, and low carbon/nitrogen ratios of some crop residues that make them decompose quickly.
Soil cover protects soil aggregates from taking a beating from the force of falling raindrops. Even a healthy soil with water-stable aggregates held together by biological glues, which can withstand wetting by the rain, may not be able to withstand a pounding from raindrops. When water stable soil aggregates are covered by crop residue or living plants, they are protected from crumbling by the hammering energy of raindrops. When soil aggregates remain intact at the soil surface, water infiltrates the soil and is available to plant roots. The above mentioned has been demonstrated, by using NRCS's artificial raindrop simulator exhibit.
A cover of crop residues on the soil surface suppresses weeds early in the growing season giving the intended crop an advantage. They also keep the soil cool and moist which provides favorable habitat for many organisms that begin residue decomposition by shredding residues into small pieces. If these shredders have good residue habitat they can increase residue decomposition, and therefore nutrient cycling.
Keeping the soil covered while allowing crop residue to decompose so their nutrients can be cycled back in the soil can be a bit of a balancing act. Producer must give careful consideration to their crop rotation, including any cover crops and residue management if they are to keep the soil covered and fed at the same time.