Published online by Cambridge University Press: 27 March 2009
1. Attention is drawn to Mason's modification of Livingston's soilpoint method of directly estimating the water-supplying power of a soil in situ. Mason used ordinary lead writing pencils as soil-points.
2. This method, heretofore tested only in the laboratory, has been employed by the writer in an ecological field study. Details of the procedure adopted are described, and the reliability of the method is indicated by the presentation of a series of mean results with their corresponding probable errors.
3. It is concluded that the method is practicable; it should prove of considerable usefulness to workers in ecology.
page 355 note 1 Carnegie Inst. Wash., Pub. 204, p. 49, 1915.Google Scholar
page 355 note 2 Soil Science, 9, p. 469, 1920.CrossRefGoogle Scholar
page 355 note 3 A series of soils, comprising various mixtures of sand, loam, and humus, were brought to the same state of physiological humidity by growing plants in them until their moisture contents had been reduced to a stage when the plants exhibited permanent wilting.
page 356 note 1 West Ind. Bull. 19, p. 137, 1922.CrossRefGoogle Scholar
page 356 note 2 Koh-i-noor pencils, 4h, Hardtmuth, were used.
page 356 note 3 “Chicago” sharpener, Automatic Pencil Sharpener Co., Chicago, U.S.A.
page 357 note 1 Large pyralin tooth-brush oases, 7 inches long, by 1¼ inches diam. were used. The ventilating holes of these were closed by de Khotinsky cement. Cases and cement may be obtained from the Central Scientific Co., Chicago, U.S.A.
page 357 note 2 The object was to obtain average results for the water-supplying power of the soil in sections of fields running parallel to contour lines. Each determination involved the use of ten soil-points; by using five sets of pencils, five replicates of each determination could be obtained; from these, probable errors were calculated. In estimating the watersupplying power of the soil of plots laid out for manurial or varietal trials, different arrangement and spacing of the soil-points would naturally be chosen.
page 358 note 1 Wood, and Stratton, , Journ. Agr. Sci. 3, p. 417, 1910.CrossRefGoogle Scholar
page 359 note 1 West Ind. Bull. 19, p. 151, 1922.CrossRefGoogle Scholar
page 360 note 1 Mason used maize plants as indicators. Briggs and Shantz (Bur. Plnt. Ind., U.S. Dept. Agric., Bull. 230, 1912)Google Scholar have demonstrated that the variations exhibited by different species of plants, at least, of the commoner crop plants, in their ability to reduce the soil moisture to the point at which permanent wilting sets in are practically negligible, and, when significant, may be traced to imperfect root distribution rather than to specific differences in the magnitude of the force of inhibition at their absorbing surfaces.