The teart pastures of Somerset: II. Relation between soil and teartness

Abstract

1. Teart soils contain molybdenum in amounts varying from about 0·002 to 0·010% in the surface horizon and are neutral or alkaline in reaction and often calcareous. The contents of molybdenum increase down the soil profile. Teart soils are developed from Lower Liassic materials, but all soils formed from the Lower Lias are not teart. Those which are acid in reaction in the surface horizons are not teart even if their molybdenum content is high. Others which contain little molybdenum are also not teart; such soils cover a large area in Glamorgan.2. Molybdenum appears to be concentrated in the (uppermost) argillaceous component of the Lower Lias. The limestone contains little molybdenum. The soils of Somerset are largely derived from the upper, argillaceous component while those of Glamorgan are largely derived from the lower, limestone component. This may explain why the soils of Somerset contain much more molybdenum than those of Glamorgan.3. Somerset soils formed from Keuper, Middle Lias, Upper Lias and Cretaceous material generally contain little molybdenum and are not teart.4. How a knowledge of the relation between soil and teartness can be turned to practical advantage is briefly discussed.