Using Soil Amendments to Improve Infiltration, Reduce Runoff and Soil Erosion Dennis C. Flanagan Agricultural Engineer USDA-Agricultural Research Service National Soil Erosion Research Laboratory West Lafayette, Indiana

Problem with Intensive Agriculture: Water/Air Entry into the Soil

This is a typical midwest landscape showing the crop damage from ponding and runoff. Yield variation can be large, and there can be a great loss of production.

Reduced Water/Air Entry into soils by surface sealing results in reduced infiltration, increased runoff, and increased soil erosion.

Soil Tilth is Often Poor Due to: - Intensive Cultivation over past 200 years, depleting Organic Matter from soils. - Lower Organic Matter can result in smaller and weaker soil aggregate particles, soils with poorer structure, and reduced water holding capacity. - Soils with low Organic Matter can more easily seal and crust. - Frequent cultivation will reduce or eliminate large permanent pores in soil. - Shift in cation exchange complex from Calcium to more dispersive Mg or K.

Raindrop impact can destroy aggregates and contributes to surface sealing. However, there is also a chemical effect of the rainwater that disperses soil and enhances aggregate destruction and surface sealing.

Rain is derived from a natural distilling process and is low in electrolytes

Approaches are needed to control Physical destruction of soil aggregates by raindrop impact - Physical destruction of soil aggregates by raindrop impact - Chemical dispersion of soil particles because of low electrolyte concentrations in the rainfall and ponded surface water. - Slaking and destruction of soil aggregate particles due to rapid wetting and explosion of air out of micro-pore spaces in peds.

Physical Destruction of Soil Aggregates can be reduced by Use of mulches to protect the soil from raindrop impact. - Use of mulches to protect the soil from raindrop impact. - Reduced-tillage or no-tillage systems that can leave the soil in an aggregated and/or more porous state with crop residues to minimize raindrop impact directly on soil - Use of soil surface amendments (organic polymers) to strengthen the soil aggregates.

Use of Residues in No-till to Reduce Physical Destruction by Raindrop Impact

Chemical Dispersion of Soil Particles can be reduced by - Use of soil amendments that can rapidly produce large amounts of electrolytes (multivalent cations – Ca ++ ) in the surface water solution, which enhances flocculation and minimizes dispersion. - Balancing of the Calcium/Magnesium ratio in soils, towards higher Calcium. - Use of soil surface amendments (organic polymers) to strengthen the soil aggregates.

One way to prevent dispersion of the soil surface is to add a source of electrolytes such as gypsum. This is a cheap source of pure gypsum from the IPL power plant in Petersburg, Indiana.

This is the source of gypsum shown in the previous slide - from the scrubbing of high sulfur coal as required by the Clean Air Act.

DeWitt, Iowa Site Fayette silty clay loam Control Duration [min] mm/h Soil loss [g/m 2 /s] Rainfall Runoff Infiltration Soil Loss

Duration [min] mm/h Soil loss [g/m 2 /s] DeWitt, Iowa Site Fayette silty clay loam PAM + By-Product Gypsum Treatment Runoff Infiltration Rainfall Soil Loss

This is a corn plant growing in a soil with high Mg content and poor soil structure in South Dakota.

This shows the difference in production within 100 feet, between the existing high Mg soil control (left) and the same soil treated with Gypsum (right). Control With Gypsum

Differences in Soil Structure as affected by Gypsum Amendment With GypsumUntreated Control

These corn ears are from a similar on-farm treatment in Colorado. The 3 ears on the left were from an area treated with Gypsum. With Gypsum Amendment Control

Aerial View of Gypsum-treated field No-till field Treated with 1 t/A Gypsum every other year Fields near Van Wert, Ohio Untreated fields

This is a photo from a farm near Van Wert, Ohio on a Hoytville soil. There is a lot of crusting visible in this untreated Control.

This picture was taken just 10 ft away where Gypsum has been applied, and there is no crusting visible.

Slaking and Destruction of Aggregates by Rapid Wetting can be reduced by - Use of mulches or residues that absorb part of the rainwater and slow the wetting process. - Use of soil surface amendments (organic polymers) that strengthen the soil aggregates and also strengthen the entire soil surface.

Agricultural Field Study - Silt Loam Soil - 18 lb/A PAM was very effective Up to inflows of 16 Gallons/minute PAM Control Control

Steep (32%) slope study Untreated Control 71 pounds/acre PAM PAM t/A Gypsum

Natural Rainfall Study – 45% slope landfill embankment – silt loam soil PAM t/A Gypsum Untreated Control 71 lbs/A PAM

Stillwater, OK large flume study Untreated Control 71 lbs/A PAM Control PAM Inflows of Water up to 200 gallons per minute

Anionic Polyacrylamide (PAM) use Has been shown to be very effective at controlling soil erosion on a range of soils and slopes. - Has been shown to be very effective at controlling soil erosion on a range of soils and slopes. - Current cost of the material (~$3.00/lb) would make it impractical for general agricultural use for erosion control. - For certain types of applications, PAM may be a practical soil amendment, such as:  embankments  construction sites  critically-eroding regions  newly-seeded grass waterways or other channels

Summary Soil amendments that act at the soil surface can have dramatic effects on water infiltration, runoff and soil loss. - Soil amendments that act at the soil surface can have dramatic effects on water infiltration, runoff and soil loss. - These amendment effects can also subsequently improve crop stands and yields. - On many Midwest US soils that are subject to sealing and crusting, use of Gypsum or a Gypsiferous amendment may be of benefit. - Anionic Polyacrylamide may also be of benefit, especially in controlling erosion on critical areas during establishment of permanent vegetation.