Three soils of the Atlantic Coastal Plain were compacted into steel drums with a vibrating probe. The physiological responses of barley and snap beans to changes in soil physical properties due to compaction were measured.On Galestown sand an increase in bulk density from 1.3 to 1.6 g. per cc. resulted in a 50% increase in yield of barley which was linearly and significantly correlated with increased available water. A 37% barley yield decrease with increasing bulk density from 1.3 to 1.65 g. per cc. on Freehold loamy sand was attributed to increased mechanical impedance. Compaction reduced barley yield on Penn silt loam, the response being correlated with oxygen diffusion.Density-yield relations were not clear in the case of snap beans, but significant differences in concentration of maturity of the beans were observed on the Penn and Freehold soils.Hydraulic conductivity and available moisture on the sandy soils and hydraulic conductivity and oxygen diffusion rates on the finer textured soil, were found to correlate best with plant response.

Synopsis The roots of a rye cover crop were primarily responsible for an improved physical condition of a Nixon sandy loam. Organic matter additions consisting only of the rye top growth had no measurable effect. Three years of cover cropping were necessary before any soil physical differences could be measured.

Daily changes in soil moisture under snap beans were computed on a daily basis by the Thornthwaite equation, with various adjustments to account for decreasing water loss with increasing water deficit. These values are compared with data obtained by extensive gravimetric sampling. Statistical analysis indicates that when moisture tensions over the rooting zone are less than 1 atmosphere, actual evapotranspiration is essentially equal to potential evapotranspiration but that it falls sharply when tensions exceed this limit. The accuracy and practical feasibility of water balance computations on a short‐term basis are emphasized.

During the growing seasons 1951–53, the moisture used by 2 grasses and 2 legumes was determined by use of Bouyoucos blocks. Stage of crop development had more effect than weather on water use. Water use appeared to reach a maximum around July 1. The peak water use per day was 0.13 inches. The average was considerably less. Most of the water used from the profile by all crops was removed from the surface 9 inches (the depth of the Ap layer). Very few grass roots extended below 30 inches. The consumptive use of water under fescue sod was less than under bluegrass. Frequent clipping of the grasses resulted in less total water use but a greater percentage use from the surface layer. There was a very good correlation between the amount of water used from a horizon during a drying‐out period and the amount present in the horizon at the beginning of that period. The correlation decreased with depth. It appears that the water was removed from the horizon where it was most abundant.