Titration Curves and Buffering Capacities of Hawaiian Soils

In the development of a liming program for the acid soils of the Hawaiian Islands, it was found that soils of the various great soil groups varied greatly in their lime requirement for correction of similar degrees of acidity. This variation in lime requirement appeared to be associated with the differences in the buffering capacities of the soils. Titration curves were made on more than a hundred soils selected from the typical profiles of the soil families belonging to the various great soil groups. The results of this study have justified the following conclusion regarding the nature of the titration curves and buffering capacities of the tropical and subtropical soils of the Hawaiian Islands: The buffering capacity of Hawaiian soils was much lower than that found for soils of the temperate regions. The buffering capacity of the soils of the different great soil groups varied greatly; however, there was very little variation in the degree of buffering exhibited by the soils of the different soil families of each group. Each soil group has a typical titration curve. The soils of the low humic latosol and humic ferruginous latosol have the lowest buffering capacity, and the soils of the hydroI humic latosol and brown forest groups exhibit the greatest degree of buffering. The organic matter fraction of the soil affects the degree of buffering above soil reaction of pH 5.5. It is most "active" in neutral and alkaline portions of the titration curves. However, the organic matter fraction does not influence the nature of the curve. The general character of the titration curve is determined by the nature of the clay minerals. The kaolinite and iron oxide clays give rise to titration curves having a low buffering capacity and montmorillonite and hydrated aluminum oxide clays give titration curves having a high buffering capacity. The silica-sesquioxide ratio of the clay fraction of the soil or the quantity of clay in the soil was not related to the degree of buffering exhibited by the titration curve of the soil. This is probably due to the large amount of "free oxides" found in these soils. There is a direct relation ship between the cation exchange capacity of the soil and its buffering capacity. The higher the cation exchange capacity the greater buffering would be exhibited by the titration curve of the soil

Chromium Distribution in the Latosols of the Hawaiian Islands

The Hawaiian Islands were formed from basaltic lavas, some of which have high concentrations of pyroxene and olivine. Since chromium is associated with the foregoing minerals, it is reasonable to assume that the element is present in the soils of Hawaii. The present study was designed to determine the presence and the dislribution of the element in the various great soil groups formed through the process of laterizarion. Other objectives were to determine the correlation, if any, between chromium concentration and the intensity of weathering in the soils and the influence of the parent material on the accumulation of the element. This study will attempt to show that both these factors play important roles in the concentration of chromium in the Hawaiian soils which were analyzed

Nature and Properties of the Soils of the Red and Black Complex of the Hawaiian Islands

A study was made of the mineralogical constitution of the soils of the red and black complex of the Hawaiian Islands. The application of differential thermal analysis established kaolin as the dominant mineral in the red soils and montmorillonite as the dominant mineral in the black soils. To aid in the understanding and interpretation of the experimental data a discussion of the differential thermal apparatus and the clay minerals was given. Four major variations in the soils of the red and black complex, differing in modes of formation, were recognized. The first type consists of black soils forming under low rainfall at low elevations adjacent to red soils forming under higher rainfall on upper elevations. Type II black soils may form under heavier rainfall than type I, but are stabilized by seepage waters from adjacent red soils. Type III comprises a number of black soils developing under restricted drainage, as a result of a high water table, near red soils having better internal drainage. Type IV consists of several profiles of alluvial and ash material, where a red top soil rests upon a black subsoil. In every case, except in a red and black profile from Molokai, kaolin was found to be the dominant clay mineral in the red soil and montmorillonite in the black soil, with a kaolin montmorillonite mixture in the transitionary zones. Under intense leaching and oxidation, kaolin formation was favored. In situations where retention of bases and silica was favored, montmorillonite formation occurred. The cause for the soil colors was reviewed. Hematite and goethite were listed as the main cause for the color in the red soils. Investigation of black soils low in organic carbon from Kunia road supports the view that the black color need not necessarily be associated with organic matter

The Comparative Effects of Calcium Carbonate and of Calcium Silicate on the Yield of Sudan Grass Grown in a Ferruginous Latosol and a Hydrol Humic Latosol

Several current field experiments in the Hawaiian sugar industry have shown that liming has increased both yield of sugar and phosphorus uptake by the plant. This interest led to the initiation of this study, which had as its objective a comparative study of the effects of application of calcium silicate and calcium carbonate on the growth of plants and on the availability of phosphorus when applied to a soil having aluminum oxides in a fairly good state of crystallinity against a soil in which aluminum exists in a highly hydrated colloidal oxide system

Vanadium Content of Hawaiian Island Soils

The vanadium contents in the surface horizons of the Hawaiian soils range from 190 ppm to a high of 1520 ppm, with an average of 450 ppm. The very high concentrations are confined to the Humic Ferruginous Latosol Group. Thus, the vanadium contents of the Hawaiian soils are higher than those of other arable soils reported in the available literature. The amount of vanadium in the soil is influenced by the amount found in the parent material but the concentration of the element is more clearly a reflection of the weathering processes. In the Hawaiian Islands, where the major soil-forming process is latosolization, vanadium accumulates in the soil profiles. This characteristic may be used to advantage to find lithologic discontinuities in soil profiles. The concentration ratios derived in this study reflected the weathering state of the soils. When these ratios were plotted against rainfall they fell into the natural soil grouping used by soil classificationists. A correlation between the concentration of vanadium and titanium was observed in the Humic Ferruginous Latosol Group

Nickel Content of Some Hawaiian Soils and Plants and the Relation of Nickel to Plant Growth

An investigation of the nickel content of some representative soils from the Great Soil Groups of the Hawaiian Islands and the plants growing on them was made to obtain more information on the distribution of nickel in local soils and plants. Furthermore, since various studies reported in the literature showed contrasting observations of either a stimulating or a toxic effect of nickel on plant growth, this investigation was extended to various water culture and soil pot experiments to determine the actual effect of varying concentrations of nickel on the growth of plants. There is a higher nickel content in Hawaiian soils and plants than in the normal soils and plants reported in the literature from other parts of the world. Symptoms of toxicity (chlorosis, necrosis, stunted growth, and sparse, brown, slimy roots) were exhibited by tomato plants grown in nutrient solutions containing 1.0 ppm Ni and more. The chlorosis, necrosis, and stunted growth exhibited by the injured plants in the water culture experiments were also manifested by the plants in the soil pot experiments