A study was made of a Red‐Yellow Podzolic soil with particular regard to the properties of dioctahedral vermiculite, one of its major clay minerals. The soil, Nason silt loam, which is derived from a muscovite schist residuum, was found to be nearly devoid of exchangeable calcium and low in other bases. Although the cation exchange capacity of the B3 horizon was 25 me. per 100 gm. soil, this horizon contained only 0.08 me. Ca per 100 gm. Clay minerals present were kaolinite, dioctahedral vermiculite, and regularly and randomly interstratified illite‐vermiculite. The 14.7A basal spacing of vermiculite from the C1 horizon moved to 10.5A when the clay was K saturated, but the effectiveness of K saturation decreased from the C1 horizon through the A horizon where there was only slight collapse. Boiling the clay from the B1 horizon for 102 hours in 1N KCl caused a change of the 14.7A basal spacing to only 14.2A. However, treatment of the clay in 1N KCl plus 0.1N HCl or treatment with 1N NH4F altered this spacing to near 10A. The difficultly collapsed mineral had a high internal surface, high base exchange capacity, and low divalent cation content. Easily collapsed dioctahedral vermiculite was made difficultly collapsed by repeated Al saturation and drying. Heat treatment at 800°C. collapsed the 14.7A spacing of the mineral in all horizons to 10.3A. Glycerol solvation caused no increase of the 14.7A spacing. These results together with D.T.A. data support the theory that non‐exchangeable Al in the interlayer position in vermiculite restricts collapse of the mineral on K saturation.
The availability of residual phosphorus from long‐time superphosphate applications to Groseclose silt loam exceeded that of rock phosphate. Based on A values, residual phosphorus from superphosphate was approximately four times as available as that from rock phosphate. Data on total, Truog, and NaHCO3‐soluble phosphorus showed that: (1) more of the superphosphate had reacted with the soil than had rock phosphate; (2) more of the phosphorus applied as superphosphate had accumulated in the silt and clay factions of the soil and, based on solubility in NaHCO3, was relatively available; and (3) more of the phosphorus applied as rock phosphate had accumulated in the sand fraction of the soil and was relatively unavailable, as judged by solubility in NaHCO3. Apparently, some of the rock phosphate had not reacted with the soil and was still in its original molecular combination. X‐ray analysis revealed the presence of apatite or a mineral similar to apatite in the sand fraction of soil that had received rock phosphate. The mineral, which gave pronounced reflections at the same values obtained from rock phosphate fertilizer, was not found in soil receiving superphosphate. Approximately three‐quarters of the phosphorus applied over a 40‐year period from either source was present in the soil as residual phosphorus. This quantity nearly doubled the total phosphorus content of the soil. Crop yields on plots receiving the two fertilizers have been equal except for the first few years when superphosphate produced higher yields.
A study was made to determine the origin of the calcareous material found in certain floodplain soils of the limestone valleys of Virginia. The CaCO 3 in these soils was derived from the highly fractured and faulted limestone underlying the area. Groundwater, high in dissolved CO 2 , percolated through the crushed limestone, dissolving an appreciable amount of Ca and Mg carbonate. This water issued at the surface in the form of large springs and lost some of the dissolved CO 2 which resulted in a saturated solution with respect to calcium. The CaCOa depositing alga Oocardium stratum Nag was found below the point of saturation in the streams and was thought to be of major importance in the deposition of CaCO 3 . In a 200-foot section of stream channel beginning 450 feet below a spring having a rate of flow of 104 gallons/min, approximately 2.85 tons of CaCOa were deposited annually as tufa. Algal-deposited tufa is torn from stream channels during heavy rains and redeposited downstream by flood waters. Calcareous material occurs several miles from the source area and is a constituent of the flood plain soils along the creeks and rivers of the area.
Orchardgrass (Dactylis glomerata) grown on Davidson clay loam showed a yield response to N in 1949 and 1950, to N and K from 1951 to 1953 and to N, P and K from 1954 to 1962. During the latter period, yield response to a given nutrient occurred only if adequate amounts of the other two were applied. Lower yields were obtained with 171 than with 114 kg of N/ha in 1958 without applied K and in 1960 to 1962 with applied K. This apparently resulted from higher uptake of K with 171 kg of applied N and a cumulative depletion of available K in the soil.
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