WATER-SUPPLYING POWER OF THE SOIL UNDER DIFFERENT SPECIES OF GRASS AND WITH DIFFERENT RATES OF WATER APPLICATION

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Abstract
The lawn grasses Kentucky blue, Chewing''s fescue and Washington bent were used. One plot received no water in addition to that falling as rain; a 2nd received an additional amount equal to 50% of the normal rainfall, a 3rd 100%, and a 4th 200%. The usual form of porous porcelain soil point was used (inserted 6 cm. and left in the soil for 1 hr.). The rainfall was only about 60% of the normal for May-Aug., thus disturbing the intended ratio of 1 to 1.5, to 2.0, and to 3.0 for the different plots. The evaporation rates were far above the average for the 2 preceding summers. Thus a very severe drouth was experienced. The water-supplying power of the soil on the three sections of the check plot was below the critical value of 100 mg. during most of the 3-month period involved and the grasses were brown and dry. The other plots were usually well over the value of 500 mg. above which most lawn grasses do not suffer from a lack of soil moisture, and each of the 3 species remained in good condition. The yields were nearly as good from the 1.5 N plot as from either of the others, indicating that amounts in excess of those which will maintain a water-supplying power of the soil at 500 mg. or above are not required to obtain good top growth of lawn grasses. The water-supplying power of the soil under the fescue was greater in nearly all of the 41 determinations involved. Its average value for 11 dates on the 1.5 N plot was about 60% greater than that for the Kentucky blue grass. The values for the latter and Washington bent were quite similar, the bent usually being slightly higher. These results suggest that the narrow-leaved fescue places a smaller demand on the available soil moisture than the other two broader-leaved forms. This, together with the fact that it enters a drouth period with a greater reserve of soil moisture, is probably a significant factor in enabling this species to survive drouth periods better than many other forms such as the bents and blue grasses.