IF YOU’RE TRYING TO MAKE YOUR SOIL HEALTHIER, 

YOU SHOULDN’T SEE IT VERY OFTEN.

In other words, soil should always be covered by growing plants, their 

residues, or a combination of the two. Keeping the soil covered all the time 

makes perfect sense when you realize that healthy soils are full of life and 

that the microorganisms living in the soil have the same needs as other living 

creatures. They need food and cover to survive.

When you have a vegetative cover on the soil, especially a living cover, you 

offer those microbes both food and shelter. Some scientists say when you 

till the soil and remove crop residues, the effects are as devastating to soil 

microbes as a combination of an earthquake, hurricane, tornado, and forest 

fire would be to humans. From the perspective of the living creatures within 

the soil, a tillage tool like a chisel shank has the effect of ripping the ground 

like an earthquake; removing residue is like a tornado ripping the roof off a 

house; uncovered soil can be drenched and whisked away by gushing water 

and wind like that of a hurricane—or scorched in the hot sun like an out-ofcontrol fire.

STOP THE SPLASH, HARVEST THE BENEFITS

When a falling raindrop explodes as it hits bare soil, it dislodges unprotected 

soil particles, and begins the process of soil erosion. Cover crops and plant 

residue prevent that violent splash on soil, protecting soil aggregates from 

being pounded by falling raindrops. 

Safe from disintegration by the hammering energy of raindrops, the structure 

of healthy soils remains intact, which prevents soil crusting. In this protective 

environment, water infiltrates the soil and becomes available to plant roots. 

A mulch of crop residues or living plants on the soil surface also suppresses 

weeds early in the growing season, giving the primary crop a competitive 

covered all the time.

Uni

Dep

Agr

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HEALTHY SOILS ARE:

Natural Resources Conservation Service

Cover Saves 

Scarce Water

Extreme temperature changes 

and high winds characteristic of 

the semiarid, short-grass prairie 

of the the Great Plains can have 

drastic and devastating effects on 

exposed soil. In the High Plains 

sub-region of the Great Plains, 

more than 65 percent of the soil 

must remain covered to limit 

evaporation of water. Bare soil 

heats up quickly in direct sunlight; 

and the hotter it gets, the faster 

water evaporates from it. 

In this rainfall-limited area 

(average annual rainfall is 

10-20 inches), maintaining 

soil cover is a key to profitable 

agricultural production. 

The combination of high winds 

and hot temperatures wastes 

water if soils aren’t covered. 

However, ground cover (both 

living and residues) limits the 

drying effect of wind, shades 

the soil from hot sun, and 

traps snow during winter. All 

of which add up to more water 

infiltrating into the soil and 

less evaporating into the air.
advantage. This is especially the case if the cover crop is rolled prior to 

planting the main crop because the entire soil surface is covered 

and protected. 

Cover crops can build moisture reserves far better than row crops can by 

themselves. Cover crops open pores and small channels in the soil for 

better water infiltration, and the organic matter they build helps retain 

both moisture and nutrients.

The cool, moist soil of cover crops also provides favorable habitat for 

many organisms that decompose residues and recycle nutrients for the 

next crop. Providing a good habitat for these organisms can increase 

residue decomposition, and improve nutrient cycling, by up to 

25 percent.

LIVING PLANTS GO BEYOND COVER

While it’s easy to see the importance of giving the soil protection above 

the ground, it’s not always as easy to recognize benefits living covers 

provide below the surface. 

Through their roots, living plants offer soil microbes their easiest, most 

reliable food source. Because these soil microbes need a consistent food 

source throughout the year to thrive, cropping plans that include crop 

rotations with cover crops throughout the growing season (or perennial 

grasses and legumes) can help sustain them year-round. 

WANT TO LEARN MORE? 

VISIT WWW.NRCS.USDA.GOV

HEALTHY SOILS ARE: covered all the time.

Living in the Rhizosphere

Every soil organism has something it 

eats...and something that eats it. Each 

organism and each bit of plant residue 

is important to the complex food web 

under the soil surface. While each 

source of microbial food is important to 

a balanced food web in a healthy soil, 

there is no better food for soil microbes 

than the sugars exuded by living roots.

Living plants maintain a rhizosphere, an 

area of concentrated microbial activity 

close to the root. The rhizosphere is 

the most active part of the soil biology 

because it is where the most easy-toeat food is available for microbes. It’s 

also critical for plant growth and health, 

because those microbes, in turn, provide 

essential nutrient cycling for crops. 

Because living roots provide the easiest 

source of food for soil microbes, growing 

perennial crops or long-season cover 

crops is the key to feeding the foundational 

species of the soil food web—so 

they’ll be healthy and ready to perform 

throughout the primary growing season. 

rhizosphere