Introduction
First introduced in the early 1990s, precision agriculture technologies, or site-specific management, were considered by many to be perhaps the most significant development in production agriculture focused on improving farm profitability.
The initial focus was on fertility, and treating the variability that we all knew existed from our experiences with soil sampling. However, to a large extent this application still required laboratory analyses of manually collected soil samples resulting in data sets that were either too expensive, or too sparse, to benefit the producer. More recently the focus in precision agriculture has shifted to real-time sensing of soil structure and non-intrusive sensing of crop stress. And while these efforts continue within the research community, the machinery manufactures and software developers have been quietly enhancing the capabilities of field machinery.
Precision agriculture provides detailed records of farm activities. It often utilizes computer-based technologies where records can be automatically generated and stored. This gives farmers the potential to provide both the regulator, as well as the consumer, with a detailed record of (and justification for) their management decisions, without duplication. The promotion of sustainable management of natural and physical resources is a primary function of Precision agriculture. Precision agriculture has been described as “doing the right thing, at the right time, in the right place, with the least impact on the environment”
Soil Compaction
Compaction, a soil physical property, is a concern in crop production and environmental pollution. Soil compaction often restricts root development and growth due to increased bulk density and/or strength of the soil, reduces the biological activity of plant roots and organisms in the soil due to reduced aeration, and limits water infiltration.
Soil compaction management, relies heavily on the use of annual deep tillage, usually to a uniform depth (20 to 40 cm.) that it is an expensive application and it cause soil structure distribution at a long time. There are several drawbacks to this approach to manage soil compaction. Farmers do not usually know if annual sub soiling is required, where it is required in a field, nor the required depth of sub soiling. In addition, there is a great amount of variability in depth and thickness of hardpan layers. Studies have shown that the depth of this root-restricting layer varies greatly from field to field and also within the field. Applying uniform depth tillage over the entire field may be either too shallow or too deep and can be costly.
An alternative approach to estimate the state of soil compaction is to measure soil strength, since soil strength is strongly associated with compactness, packing density, relative bulk density, and drainable porosity. Using common methods to measure soil mechanical resistance is not a precise method. Moreover, it's time-consuming, labor-intensive and not practical method to determine soil compaction in a large-scale field. Therefore, there is a need for continuous and time-cost efficient method to identify the compacted zone.
A high-energy input is required to disrupt the hardpan layer to promote improved root development. Variable depth tillage, which modifies the physical properties of soil only where and what depth the tillage is needed for crop growth, could achieve significant savings in tillage energy, fuel consumption and CO2 emission caused by tractors. Raper, (1999) estimated that the energy cost of sub soiling could be decreased by as much as 34% with site specific tillage as compared to the uniform-depth tillage. Fulton et al., (1996) reported that fuel consumption could be reduced to 50% by site-specific tillage compared to sub soiling the entire field. Site-specific tillage can be implemented either with a pre-tillage map technology, or a real-time sensor. The real-time sensor would provide a one-step system to control tillage implement location and depth.
