Saturday, 15 July 2006

Effectiveness of PAM in Controlling Soil Erosion in a Highly Degraded Soil of the Tropics Under Steep Slopes.

Gustavo Martínez and Rafael Ramos-Santana. Univ. of Puerto Rico, Po Box 129, Juana Diaz, PR 00795

High sediment loads from agriculture and construction sites are the major source of surface water impairment in Puerto Rico. The use of anionic polyacrylamide polymers is quickly gaining recognition as a cost-effective short-term erosion control strategy. In this study we evaluated the effectiveness of different dosages and formulations of PAM in a highly weathered soil (Corozal clay, Typic Hapludults) of the tropics under steep slopes (20%) conditions. A series of indoor box experiments were conducted according to guidelines of the National Research Project for Simulated Rainfall. Three formulations of PAM, namely: (SOILFLOCTM 300 E, SOILFIXTM LCD, and a synthetic formulation from Aldrich Chemical Company) were evaluated at the following rates: 0 (control), 20 kg ha-1, 80 kg ha-1, and 120 kg ha-1. A series of simulated rainfall (7 cm h-1) experiments were conducted at: 24 hours, 2 days, 8 days, 1 month, and 2 months after polymer application. At their highest rates, all PAM products reduced sediment production by > than 75% relative to the control in all events. There were no significant differences in sediment production control between the two highest PAM rates (80 kg ha-1 and 120 kg ha-1) evaluated. A month after PAM application sediment production was 1,272 kg ha-1 in the control treatment vs. 285, 70, and 100 kg ha-1 at the 120 kg ha-1 rate of SoilFloc, SoilFix, and Aldrich PAM respectively. A field experiment was established on experimental plots (18.6 m2) to evaluate PAM effectiveness and persistence under natural rainfall and complete sunlight exposure conditions. Results will be discussed.

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