Improvement of the soil fertility of a volcanic indurate layer (Tepetate) by applying acid treated biosolids
Volcanic indurate matter produces low soil fertility when rises to the surface, reducing the agricultural potential of the land and distressing marginal zones that live from agriculture. The habilitation of these materials using biosolids has not been explored, although the problem exists in several countries around the world. This work evaluated the impact of the application of biosolids on the fertility of a fragmented volcanic indurate layer (Tepetate). Tepetate’s fertility was measured before and after biosolids application with three biosolids application rates: agronomic rate (AR), as well as 10 and 20xAR. Biosolids were mixed with Tepetate and kept in pots under green house conditions along with a control, during four months. One set of pots with and without vegetative species. Organic matter content increased between 180 and 470% compared to the control. Cation exchange capacity (21.8 to 42.3 Cmol+kg-) resulted adequate for keeping nutrients for plants. pH values were adequate for agricultural activities (5.9-7.2). Dry color of the Tepetate, becomes darker (grayish brown; 10YR 5/2) than the initial yellowish brown (10YR 5/4) because of the addition of stable organic matter from biosolids. Considering edaphologic characteristics it is suitable to habilitate volcanic indurate layer by the application of biosolids.
Tepetates of Central Mexico : paleogeographical background and functioning in modern agroecosystems
Volcanic soils with indurate subsurface horizons (having the local name tepetates), totally or partly cemented by silica, 1:1 clays, and iron oxides or calcium carbonates, cover about 660,000 km. In a number of earlier works, focused on identification of cementing agents and ecological significance of tepetates, they were considered as pedogenic phenomena; however, though they are often inter-layered with or overlain by paleosols, they were never related to the past soil forming processes and environmental conditions. We studied spatial distribution and properties of tepetates, associated soils and paleosols in Morelos State/ Central Mexico to understand the (paleo) environmental conditions and processes of their formation which pre-determinate their specific impact on the functioning of agroecosystems. In the key site of the Glacis de Buenavista, tepetates are overlain with thick profiles of welded Luvisols of the Late PleistoceneHolocene age. The Luvisol Bt horizons are characterized by extensive 1:1 clay accumulation due to in situ weathering and clay illuviation, high content of free iron oxides, and redoximorphic pedofeatures. All these properties indicate long-term pedogenesis under humid forest environments. Underlying tepetates have lower clay and free iron content. In tepetates thin sections, we observed a peculiar combination of the re-deposited material of Luvisol Bt horizons and fragments of fresh volcanogenic rocks and minerals. Materials, typical for the surface soil horizons – phytoliths and small charcoal fragments – were also found. Besides re-deposited illuvial pedofeatures, there are in situ clay coatings and infillings as well as ferruginous mottles and nodules. We interpret the observed combination of properties in the Luvisols and tepetates as result of interaction of long-term humid pedogenesis and regular catastrophic volcanic events. The period between eruptions was long enough for formation of Luvisols with Bt horizon rich in crystalline 1:1 clay. Association of re-deposited material of different soil horizons and fresh volcanic components in tepetates suppose that they are formed by mass movement processes, linked to eruptions: lahars and mud flows. The sediment, thus formed, contains sand and silt, mostly of volcanic origin, and clay from soil material, in proportions that are favourable for its structural collapse and hydroconsolidation when moistened and loaded. Further clay illuviation and redoximorphic segregation of iron oxides filled few pores left after primary consolidation, and thus contributed to tepetate induration. Presence of subsurface indurate horizons with low permeability promotes lateral soil drainage and could provoke erosion. Such Luvisol-Tepetate profiles are stable in the natural ecosystems, SOLLEIRO-REBOLLEDO ET AL. 17 WCSS, 14-21 August 2002, Thailand 1914-2 were dense forest vegetation prevents soil losses with runoff. Under cultivation the accelerated erosion could destroy quickly the upper part of the profile, exposing tepetates to the surface and causing advanced land degradation. High density that hampers root penetration and provokes strong surface runoff, very limited water availability and low cation exchange capacity cause the drop of agroecosystem productivity. Vast areas covered by tepetates are set aside as badlands.
Preparation and performance evaluation of swine manure bio-oil modified rubber asphalt binder
Abstract In order to study the effect of the preparation process of swine manure bio-oil modified rubber asphalt binder on the rheological properties of the binder, the matrix asphalt and asphalt rubber were used as the control group, and swine manure bio-oil modified rubber asphalt binders were obtained by three preparation processes. Then the rheological properties of five binders were evaluated by rotational viscosity, DSR, MSCR and BBR tests. The results show that the addition of swine manure bio-oil to asphalt rubber is beneficial to the workability, but cause negative effect on its high temperature performance, fatigue performance and low temperature crack resistance. The preparation method of premixing bio-oil and rubber powder can reduce the degradation of high-temperature performance of asphalt rubber caused by addition of swine manure bio-oil to a certain extent. The fatigue properties of the three bio-binders are close, and the critical temperature is less than 25 °C. The process of premixing bio-oil and rubber powder will increase the creep stiffness and reduce the low-temperature performance. However, the low-temperature performance of the binder obtained by this process is still better than that of the matrix asphalt and can meet the requirements of use. Therefore, it is recommended to use the preparation process of premixing bio-oil and rubber powder to prepare swine manure bio-oil modified asphalt rubber.