PHOSPHATIC MANURES.

Dominion, Volume 6, Issue 1558, 30 September 1912, Page 8

PHOSPHATIC MANURES.

TUEIB PE2COLATIOX THROUGH' . •THE SOIL. Mr. E. H. Lougbridge. Professor Emeritus in Agricultural Chemistry, in the University of California, recently instituted a series of experiments to ascertain to what extent phosphoric acid, added in the form of pkosphutic is carried deep into tho soil by the action cl the rain in different types of soil in that Stale. The experiments were, wade primarily for.the purpose of finding out v.iie(her these Manures, when added in the orchard, are carried down to tho roots oi the trees, but the results thus far (the experiments being incomplete) are of interest. Professor Loughridge says tho results are emphatic, and show that, e:;ccpt in very sandy soil, the phosphoric acid, decs not reach the roots ot trees, but is retained in the upper few inches, oven in the presence of a heavy rainfall. Using a high-grade superphosphate,* carrving T, per cent. of-.soluble phosphoric acid,.it was found that heavy my'soils would'retain' 10001b. per cere in the upper 3 inches, that a loam soil would hold that amount in 0 inches, while a sandy soii would allow jt to pass quito d«p. Ho adds that ho was struck by this "locking-up" of phosphoric acid at tho surface in the examination of the soil of au orange orchard where liberal applications of phosphates had bean made for many years. The examination of- the soil (black clay) showed that the amount of phosphoric acid' iu the upper 6 inches was .30 per cent., while in. the next C inches, and still deeper, the percentage was only .05. Evidently the upper I! 'inches had retained all "the phosphate that had been added in many years.