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Comparative decomposition rates of alfalfa, wheat straw, and whole partridge pea, or its various plant parts taken separately, were determined by measuring weight losses during laboratory incubations. Effects of these plant materials on nitrification rates in soil were also determined. The alfalfa lost the most weight by decomposition during a 32‐week period. The loss in weight of straw also exceeded that of the whole plant of partridge pea. The nitrification rate with partridge pea added was lower than that with untreated soil. Partridge pea leaves increased nitrification, but the pods or stalks decreased it. The nitrate content of field plots previously grown to partridge pea was higher than that of plots without a legume, but not as high as in plots previously in sweet clover.

Kaolin and illite were identified in the clay fraction of Alonso soil. The relative concentration of kaolin to illite in the 2.0-0.2 µ fraction was greater than double throughout the profile, while in the less than 0.2 µ fraction, it was about the same for profile depths down to 3 feet. Illite seems to predominate over kaolin at lower profile depths. The total potassium content of the clay fraction less than 0.2 µ corresponded with the observed trend in illite variation. Illite was found to be the only soil mineral source of native potassium in Alonso soil.

Quartz, hematite, magnetite and maghemite were identified as the most prominent minerals present in the coarse fraction of a typical Alonso clay. Although plagioclase was an important constituent detected in the parent rock, only traces were found in the soil. There was no indication of the presence of orthoclase either in the rock or in the soil. The iron minerals appear to follow a rather uniform distribution throughout the profile, while the most intensive peaks of quartz were more prominent in the silt rather than in the sand fractions. A possible explanation for the particle-size distribution of quartz could be the original textural composition of the pedogenic material as would be encountered in quartziferous volcanic ashes. Inasmuch as the percent of silt in the soil decreased with the profile depth, it is reasonable to expect a concomitant decrease in the relative quartz content of the soil.

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