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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
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Problem with Intensive Agriculture: Water/Air Entry into the Soil
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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.
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Reduced Water/Air Entry into soils by surface sealing results in reduced infiltration, increased runoff, and increased soil erosion.
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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.
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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.
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Rain is derived from a natural distilling process and is low in electrolytes
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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.
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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.
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Use of Residues in No-till to Reduce Physical Destruction by Raindrop Impact
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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.
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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.
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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.
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DeWitt, Iowa Site Fayette silty clay loam Control 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 51015202530354045505560 Duration [min] 0 20 40 60 80 mm/h Soil loss [g/m 2 /s] Rainfall Runoff Infiltration Soil Loss
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0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 51015202530354045505560 Duration [min] 0 20 40 60 80 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
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This is a corn plant growing in a soil with high Mg content and poor soil structure in South Dakota.
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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
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Differences in Soil Structure as affected by Gypsum Amendment With GypsumUntreated Control
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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
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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
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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.
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This picture was taken just 10 ft away where Gypsum has been applied, and there is no crusting visible.
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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.
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Agricultural Field Study - Silt Loam Soil - 18 lb/A PAM was very effective Up to inflows of 16 Gallons/minute PAM Control Control
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Steep (32%) slope study Untreated Control 71 pounds/acre PAM PAM + 2.2 t/A Gypsum
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Natural Rainfall Study – 45% slope landfill embankment – silt loam soil PAM + 2.2 t/A Gypsum Untreated Control 71 lbs/A PAM
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Stillwater, OK large flume study Untreated Control 71 lbs/A PAM Control PAM Inflows of Water up to 200 gallons per minute
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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
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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.
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