Submitted to: Advances in Geoecology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 7/1/1997
Publication Date: N/A
Citation: Interpretive Summary: Erosion is produced when rainfall exceeds the capacity of the soil to take the water in. This causes land destruction and off-site damages such as floods. A rainfall simulator study was conducted to measure if the amount of water absorbed can be improved by adding materials to the soil surface. These materials were applied to the soil and the amount of water entering or running off was measured. We found that two materials (polyacrylamide and a gypsum like material) when applied together increased water intake rates and reduced erosion. The type of elements the soil contained (Ca vs Mg) also seemed to have an affect on the erosion process and the effectiveness of these materials. This type of erosion control methodology is a viable, low cost alternative to other more expensive ways, and will afford the opportunity for farmers to prevent erosion at a much lower cost and protect the environment.
Technical Abstract: Surface sealing causes a low water infiltration rate (IR) producing runoff and erosion. Structural instability and the low electrolytes in rainwater causes dispersion of clays producing IR <2 mm/hr for many soils of the USA low in Na. We hypothesize that exchangeable Mg (EXMg) behaves similar to Na causing dispersion and increased surface sealing. We conducted a rainfall simulator study to measure IR and erosion of 5 soils from the midwest USA containing a range of EXMg. Topsoils were sampled, air-dried and sieved to <2 mm. Interrill plots (0.14 m2) were packed and brought to saturation from below for 2 hours and rained on at 64 mm/hr at 5% slope with -5 cm tension for 1 hr randomly. Samples of IR and runoff were collected at 5-min intervals. Four replications each were run with no treatment, 20 kg/ha anionic polyacrylamide (PAM), 5,000 kg/ha fluidized bed combustion bottom ash (FBCBA) and PAM+FBCBA at the same rates surface applied. All soils developed surface seals when untreated at this rainfall intensity except for the sandy soil. Three soils had IR <7mm/hr regardless of clay type. A soil with a very low EXMg content had a IR >7X that of a similarly textured soil with a Mg:Ca ratio >1. Soil loss was also significantly less for the low Mg soil. Amending the soils with PAM+FBCBA increased the IR and reduced the soil loss for all soils except the sandy soil. PAM was less effective than FBCBA when added alone. Amending soils to reduce runoff and erosion seems to be a viable alternative for erosion control. More work is necessary to separate the effect of changing the Mg:Ca ratio and the release of electrolytes on increasing IR and reducing soil erosion.