Increased Water Retention
Cover crops dramatically reduce surface water runoff and increase soil moisture retention as a result. Period.
Rain on bare soil does not penetrate the soil. Upon impact, rain drops compact the particles on the soil surface. This forms something like a crust through which more rain does not penetrate. It runs off instead.
What appears to the untrained eye as a saturated field shedding excess water can actually be a field of dry soil shedding water that plants desperately need.
Soil is Meant to be Covered
Cover crops allow rainfall and snow melt to be absorbed, and allows the soil to hold plant available water longer–like a spongy reservoir in the porous root zone.
Cover crops create good soil structure, with a good mix of micro and macro pores that take in and release water and air like a healthy living organism.