‘Agriculture not only gives riches to a nation, but the only riches she can call her own'. The growth in the demand for food, feed and fiber globally is anticipated to grow by 70 percent. At the same time the demand for crops in the production of bio-energy and other industrial use is also expected to rise. The rising demand for agricultural produce will put tremendous pressure on the limited resources available. The increase in urban settlement areas will force agriculture to compete for land and water. At the same time, agriculture has to adapt itself to the changing conditions and also has to address the issues related to climate change, help in the preservation of natural habitats and in maintaining the biodiversity . To meet these demands, farmers will need to equip themselves with new technologies so as to produce more with limited number of resources.
Sustainable resource management is the need of the hour. Conservation of soil quality is crucial to sustainability in agriculture. This has led to a shift from the use of traditional agricultural practices to modern agricultural practices so that the available resources are utilized in a sustainable manner. The modern technique of farming known as precision farming is based on the concept of site specific crop management. This method takes into consideration variability exhibited by the soil and accordingly inputs are applied based on the local requirements within a field. Soil sensing plays an important role in precision farming. Large numbers of soil sensors are being developed all around the world to measure different soil properties. Some of which are still in the research and development stage and some of which are commercially available.
Based on their principle of working these soil sensors can be classified as follows:
‘ Electrical and Electromagnetic sensors: Depending on the composition of soil under test, electrical resistivity or conductivity, capacitance or inductance of the soil is measured. The response time of these sensors is very fast, they have high durability and are of low cost. These sensors are commercially available.
‘ Optical and Radiometric sensors: These sensors, through the use of electromagnetic waves, measure the amount of energy that is either absorbed or reflected by the soil particles depending on the soil composition. The properties of the soil are measured using visible and near-infrared wavelengths . They can be used for the estimation of soil texture, moisture, CEC and other soil parameters with the help of proper data analysis techniques.
‘ Mechanical sensors: they are used to measure soil resistance with the help of a tool engaged with the soil. The amount of resistance offered by the soil is related to the compaction of the soil which is a spatially varying property of soil.
‘ Acoustic sensors and Pneumatic sensors: Though these are a class of mechanical sensors, they can be used as an alternative means for the differentiation of mechanical and physical characteristics of soil. Measurements taken using acoustic and pneumatic sensor have been used to correlate soil texture and compaction. The application of acoustic sensors in characterizing the physical state of soil is not very clear and requires more research work.
‘ Electrochemical sensors: These sensors produce an output voltage through the use of ion selective membranes, depending on the activity of ions under study such as H+, K+, NO3 ‘, Na+, etc. Soil pH sensors using this technique are already commercially available. The real time extraction of ions such as potassium is still not possible even though the concept appears to be simple.
There is a need to develop fast, real time and portable soil sensors which can generate soil report instantly. Thus, the problem of designing and developing a smart soil monitoring system was formulated using a reconfigurable embedded system platform.
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