Studies on soil reaction V The depth-distribution of reaction and flocculation in continuously manured soils

The reactions of the unmanured and the limed and unlimed portions of the sulphate of ammonia plots on Eothamsted Park Grass and Woburn barley fields change steadily with increasing depth, and at 36 inches still show the same relations as in the surface soil. The difference in pH values between the limed and unlimed portions of the Rothamsted soil is substantially constant at all depths down to 36 inches. The reaction of the subsoil plays an important part in determining the effect of liming. The subsoils from the sulphate of ammonia plots at both centres are highly flocculated. Mixtures of 1 part of soil with 5 parts of water exhibit complete flocculation in the case of all samples below 9 inches and the velocity of sedimentation decreases and the volume of the final sediment increases regularly and markedly with the depth. Such changes in soil texture probably constitute important factors in the action of a high surface acidity.