Soil loosening processes in tillage : analysis, systematics and predictability

<p/>The soil movements and the inter-particle forces in the vicinity of an operating tool of a tillage implement may be called a soil tillage process. Examples are the tillage processes of tines, plough-bodies etc. (soil loosening processes) and the influence on the soil of land rollers, wheels etc. (load bearing processes). The report is limited to soil loosening processes. Modern farming requests that the energy consumption and the results (in terms of soil pulverization, soil configuration after tillage etc.) of soil loosening processes can be predicted. This necessitates not only prediction methods, but also a systematics of soil loosening processes.<p/>The report presents a systematics of soil loosing processes, which starts with the distinction between tines and plough-bodies. The latter group includes rotatiller blades, harvester lifting blades etc. The plough-bodies are considered to be composed of 3 parts; firstly, the part that loosens still firm soil; then, the part that induces a further tillage; and, finally, the part where the soil is leaving the sphere of direct influence of the tool. For a number of basic shapes of tines and plough-body parts, the process types that may be induced by these basic shapes are presented. Which process type will occur in a given situation, will depend on the soil type, soil porosity, soil moisture content, soil structure, and tool speed. The proposed basic shapes are not intended to keep a permanent place in the systematics; as the requirements of agricultural practice change and research advances, other shapes may become basic. In the current situation, the 2-dimensional curved blade with a small cutting angle and a small working depth-blade height ratio is an important basic tool. An investigation into this blade is reported in detail.<p/>The report also presents a systematic treatise of the methods that are available for the prediction of process aspects (such as the amount of energy consumption and the degree of soil pulverization), together with a discussion on the advantages and disadvantages of these methods, as well as directives for use in the development of new prediction methods. New contributions to the predictability of aspects of 2-dimensional blades are published in the report.<p/>When it is necessary to extend the systematics or to develop new prediction methods, experiments must be performed. A survey of aids to analysis is, therefore, included.