Peter Bilson Obour


Peter Bilson Obour


Project title: Predicting soil workability and fragmentation in tillage


Tillage plays an important role in agricultural production. It improves soil tilth for crop establishment and development. Response of soil structure to tillage operations varies across space and time due to differences in soil characteristics such as soil type, texture and soil water content. Nevertheless, in practice, conditions for tillage activities are based on farm managers’ experiences which are often standardized across seasons and fields. The risk is that tillage operations could be executed at periods when the soil is not workable. Soil workability in tillage refers to the ability of soils to produce adequate friable aggregates (seedbed) for crop establishment without smearing or compaction (Müller et al., 2011). Soil workability is governed by the mechanical and hydrological state of soil (Mueller et al., 2003). The range of water content most suitable for tillage operations is located between the upper tillage limit (wet limit) and the lower tillage limit (dry limit). Tilling soils under too wet conditions destabilizes soil structure and results in formation of clods, particularly in heavy textured soils, while tillage operations under too dry soil conditions result in the formation of clods with rough surfaces and increases energy/fuel requirement for tillage operations. It has been recognized that quantitative information on soil workability limits is important for planning and scheduling tillage and other field operations based on field readiness. In other words, quantitative information on soil workability limits can be used to predict the ‘go and no-go’ days on the field (Simalenga and Have, 1992).
The purpose of the project is to improve prediction of soil workability limits and fragmentation in tillage, which is needed for improving decision support on scheduling and planning of tillage operations. Specifically, the aim is to evaluate the use of the soil water retention curve for predicting soil workability and fragmentation, and to quantify the effects of soil texture, soil organic matter content and compaction on workability limits and soil fragmentation.

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