Water Infiltration Complexities: Cover vs No Cover

By Brindle Harper (Texas 4-H Water Ambassador)

Soil infiltration refers to the soil’s ability to transport water into and through the exposed layer of soil. Infiltration allows the soil to temporarily store water, making it available for plants and soil organisms. The infiltration rate is a quantifiable measurement of the velocity at which water enters the soil, commonly expressed in inches/hour. A slow infiltration rate inevitably leads to ponding in level areas, surface runoff, and soil erosion. This will increase the likelihood of flooding, wasted resources, poor crop yield, soil nutrient loss, and economic loss. Sufficient water application is a must to ensure optimum crop yield. Water enters recharge zones and travels through porous soils, revitalizing groundwater aquifers and streams.

Water passes back and forth through the topsoil due to evaporation and percolation. Generally, the soil consists of a combination of clay, sand, silt, and other sediments. This layer of soil acts as a natural filter, leaving minerals to accumulate on the ground’s surface. In dry and hot climates (such as Lamb County), a hard, dry, and salty crust forms on bare surfaces. The salt sits on the surface as a white film. When the rain comes, the salt absorbs the water. The crusty layer absorbs most of the moisture, preventing infiltration and reducing water availability for plants and groundwater. Farmers must then plow to break through this layer, leading to a higher infiltration rate. A high infiltration rate can result in the leaching of nitrate nitrogen or pesticides and reduce phosphorus levels in soils. This leads to farmers over-irrigating and wasting water. In a heavy rainstorm, water droplets harshly meet bare soil, creating mini explosions, interrupting sediment particles, and causing erosion.

Alternatively, well-managed land averts these issues by achieving an ideal infiltration rate. An ideal infiltration rate is reached when the hydrologic cycle is at a steady state with no hindrances. Research shows that cover is the greatest asset to farmers and ranchers. Cover crops can include wheat, rye, barley, triticale, and turnips. In addition, cover can be debris left over from the last growing cycle. Field residues are materials left in an agricultural field or orchard after the crop has been harvested. These residues include stalks, stubble (stems), leaves, and seed pods. Live vegetation offers an easy avenue for the water to work into the soil because of a plant’s smooth leaves, stem, and root system. Furthermore, vegetation holds sediment in place as a firm foundation for this ecosystem to thrive. Well-covered land intercepts the explosions/erosions, —reducing the rain particles’ energy in the chain of transportation events. Excellent management practices, such as the use of no-till cropping systems, high residue crops, and cover crops, can improve infiltration rates, irrigation efficiency, and erosion control by increasing the soil organic matter content. There are no perfect solutions. However, we must do the most good—with what we have—for the most people.

“We still do not know one-thousandth of one percent of what nature has revealed to us.”—Albert Einstein

My Resources:
nrcs.usda.gov
sare.gov
Texas 4-H20 Academies