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Plant analyses can be a powerful tool in the diagnosis of yield depressions. Critical plant composition data for corn, soybeans, wheat, and alfalfa are presented which can be useful in interpreting plant analyses. Data are also presented to indicate “normal” variations that may be expected to occur in plant composition resulting from variations in varieties, seasons and soil. For the corn plant, the nutrient composition of some elements change with the leaf sampled and the maturity of the plant.

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These studies show that a relationship exists between traffic volume, proximity t o the highway, engine acceleration us. constant speed, wind direction, and the amount of lead in the air. They also reveal that a marked effect of traffic on the lead content of the air is limited to a rather narrow zone bordering the lee side of the highways. Lead values can be expressed as a quadratic function in time and linear to traffic volume. Particle size studies reveal that 65 of the lead in the air between 30 and 1750 feet from a highway consists of particles under 2 p, and 85 % under 4 p in diameter. ead as a pollutant in the air, on plants, and in soils

Mineralization of an activated and a digested sewage sludge in soil was studied in laboratory incubations. The activated sludge had a much higher mineralization rate than the digested sludge, mainly due to a larger portion of active organic carbon and less stability of the organic matter. After around 2 months of incubation, the mineralization rates of both sludges approached a square foot function of time. The amount of active organic carbon is a characteristic of sewage sludge and is important in determining the aerobic‐anaerobic status of the system. The mineralization of sewage sludges was proportional to the rate of sludge application at least up to 8% in the digested sludge and up to 4% in the activated sludge systems at 22°C. Between 8 and 22°C, the mineralization rate of sludges in soil increased about 1.9 times for every 10°C increase in temperature. Moisture levels between 0.06 and 0.33 bars had no significant effect on mineralization of the sludges. A regression model was developed in the form of an exponential function among the cumulative organic carbon mineralized and factors of time, sludge rate, and temperature. The model requires a minimal number of parameters to define the system and was least biased in regression analysis over a wide range of conditions.

The relative efficiency of various fractions of a calcitic limestone was studied under greenhouse conditions. Pure calcium carbonate, a commercial sample of agricultural limestone, and 6 particle‐size fractions separated from this commercial sample were applied at different rates to 3 acid soils. The soils were sampled at various times and the pH determined. The changes in pH with time followed an expression of the form, pHf = pHo + b Log (1 + t). The factor b varied with rate of application, particle size, and soil. The limestone particles in the 10‐ to 28‐mesh size fraction were, in general, 14% as effective as those in the < 100‐mesh fraction, and particles > 10 mesh were essentially of no value. The efficiency of the commercial sample of agricultural limestone was approximately equal to that exhibited by the 40‐ to 60‐mesh fraction of the sample. The results indicate that, for practical purposes, a large portion of commercial limestone should be ground fine enough to pass a 40‐mesh sieve.