Background

This chapter illustrates another way in which science influences agricultural practice. Here there are few immediate, transparent connections between discoveries and new profitable practices. Instead there is a gradual and painstaking accretion of knowledge to provide a framework for the thinking of practical men and their advisers, to allow other work to be understood (cf. Chapters 6, 7, 8 and 9) and decisions to be taken in a rational and safe context.

Soil is the very foundation of agriculture. On it grow the plants needed as food for human society and its animals. The majority of soils derive from rocks and drifts, under the influence of climate and vegetation; they encapsulate, for the knowledgeable observer, centuries and even millennia of their history. Individual soils develop over long periods of time. Bare rock surfaces are comminuted by the action of water entering cracks and as a result of temperature changes the interspersed water breaks up the rock into smaller and smaller fragments. Drift material carried by wind, water or ice and deposited at a distance from the parent rock has already undergone the early stages of soil formation. The comminuted rock is further sorted, under the influence of surface water, into grades, with the smallest fragments collecting at the bottom of slopes. The process can be seen in miniature on any roadside cutting through soft rock. On a grander scale the same process leads to catenary sequences of soils down a valley slope to produce a series of soils.