Effect of Organic Soil Amendments in Dispersive Soils on Soil Quality

摘要

The soils in Harris County vary widely, and each seems to present a unique challenge to the Harris County Flood Control District (HCFCD) in its infrastructure maintenance and improvement efforts. Many of the soils have low fertility, especially with respect to available macronutrients. Micronutrient deficiencies can also be a problem with soils exhibiting pH values in excess of 7.8. Nitrogen, phosphorus, potassium, sulfur, iron, manganese, boron and zinc deficiencies are found within the HCFCD right of way. However, the most pervasive and pernicious problem faced by the District is the presence of highly erodible and dispersive soils. Thus, the objective of this study was to determine which organic amendments were best at enhancing the stability of earthen channel banks by establishing sustainable vegetation and reducing erosion. The selected organic materials that were included in the study were blended, pelletized newsprint and chicken litter (Ckn), moderately composted yard wastes mulch (YWM), coarse-ground native wood chip mulch (CWM), double-ground native wood chip mulch (DWM), mushroom compost (Msh) and composted cotton gin trash (CGT). Results of the study indicated that the runoff water was decreased from 2 to 9 times over the control in all treatments except DWM and Ckn. Based upon the number of acres of channel and the amount of runoff water from the channel, this means a reduction of 13.6 to 24.2 million L/min that Houston does not have to move or store during a storm of 9.6 cm/hour. The sediment load was reduced by all treatments over the control by 2 to 5 times. The reduction of sediment that would not get into Houston's channels and surface water bodies would be between 0.6 to 2.9 ×10~6 kg. The total P was reduced by 0.3 to 8 times over the control in all treatments except Ckn and the dissolved P was reduced by 2 to 3 times over the control except for CGT and Ckn and these were actually higher than the control. The reduction in total P over the control that would not have the potential to contribute to eutrophication of surface water bodies around Houston would be 908 to 2942 kg and the dissolved P would be 145 to 218 kg. Thus, by adding organic amendments to the channel during construction or renovation, the potential for the channels contribution to runoff water, sediments and P is greatly reduced compared to their current methods.