The present invention relates to a system for determining a soil characteristic, in particular, a system for analysis of the size of individual particles to determine characteristics of soil samples over a geographic area for agricultural applications. 
An agricultural field generally includes a variety of soil characteristics.  It is particularly useful to evaluate the soil to determine the optimum crops for maximum yield potential and for treatment methods available. 
Reference is made to U.S. Pat.  No.  4,630,773, entitled, Method and Apparatus for Spreading Fertilizer; U.S. Pat.  No.  5,355,815, entitled, Closed-Loop Variable Rate Applicator; and U.S. Pat.  No.  5,887,491, entitled, Soil Analysis Assembly and System. 
All documents cited herein, including the foregoing, are incorporated herein by reference in their entireties for all purposes. 
The present invention relates to a soil analysis system for determining: 1) a percentage of particles within certain size ranges in a region of interest in a soil sample, for example, size ranges comparable to sand, silt, and clay; and 2) a general soil characterization of the soil sample as a function of the percentage of the particles in each size range. 
Although soil type can include particular characteristics such as the physical nature of the soil, e.g., average particle size of sand, silt, clay, and the like, and their respective relationships, a general reference to the term soil type can include a variety of other characteristics and properties of a soil sample. 
The soil analysis apparatus determines a particular soil characteristic of a soil sample, in particular, the general physical nature of particles and the percentage of particles having generally common physical features.  The soil analysis system is configured to determine a soil sample as one of generally sand, silt, clay, sandy clay, silty clay, sandy clay loam, clay loam, silty clay loam, loamy sand, sandy loam, loam, and the like. 
With the soil analysis system, a series of soil samples can be analyzed to advantageously determine the relative soil makeup over a geographic area.  Sand, silt, and clay each have a generally distinct size range relative to one another and their respective percentage in a soil sample can determine a general soil character.  For example, sand is generally characterized by large particle size; silt by medium particle size; and clay by small particle size.  The relationship of each soil sample to another can be used to map soil characteristics over a geographic area. 
The soil analysis system includes an image analysis assembly coupled to an image sensor to isolate particles and calculate individual particle size to advantageously determine characteristics of a plurality of soil samples throughout a geographic area.  The soil information may be further analyzed to determine a treatment plan as a function of the soil characteristics and the respective location of each soil sample in a geographical area. 
In sum, the invention relates to a soil analysis system.  The soil analysis system includes a sensor device and an image analysis assembly.  The sensor device produces information corresponding to an image of at least a portion of one or more particles in one or more portions of a soil sample.  The image analysis assembly is operatively coupled to the sensor device and determines a category for each of the one or more particles.  The category is based on a function of size or surface area of each particle.  The soil analysis system may determine a category for the one or more portions of the soil sample.  The category may include clay, sandy clay, silty clay, sandy clay loam, clay loam, silty clay loam, sand, loamy sand, sandy loam, loam, and silt.  The image analysis assembly may further include a particle size calculation assembly for determining the size of the one or more particles and a soil determination assembly for determining at least one category of soil.  The soil analysis system may further include a first light source positioned at an angle relative to the soil sample on a first side of the sensor device and a second light source positioned at an angle relative to the soil sample on a second side of the sensor device.  The first light source may have a first wavelength and the second light source may have a second wavelength different from the first wavelength.  The sensor device may distinguish at least a portion of one or more edges of the one or more particles.  The particle size calculation assembly may determine an average radius of the one or more particles.  The image analysis assembly may determine if a particle has been substantially isolated.  The image analysis assembly may compare the size of the one or more particles in the soil sample to data relating to sand, silt, and clay and categorize the one or more particles as one of sand, silt, and clay.  The image analysis assembly may determine the percentage of sand, silt, and clay in the soil sample and categorize the soil sample.  The image analysis assembly may be operatively coupled to a controller for operation of an apparatus for treatment of a geographic area.  The image analysis assembly may be operatively coupled to a mapping system.  The image analysis assembly may be operatively coupled to a map analysis system for analyzing one or more data maps.  The mapping system may integrate one or more soil type maps with one or more data maps.  The controller may functionally cooperate with one or more maps relating to characteristics of a geographic area. 
The invention also relates to a soil imaging assembly including a sensor device and a soil image assembly.  The sensor device produces at least one form of an image corresponding to one or more portions of a soil sample including a plurality of particles.  The sensor device has sufficient resolution to distinguish the plurality of particles.  The soil image assembly functionally cooperates with the image sensor.  The image sensor and the soil image assembly communicate with one another to determine at least one of: a) one or more categories of particles in the soil sample; b) a percentage of each category of particle in the soil sample; and c) a category of soil representative of the percentages of the one or more categories of particles in the soil sample.  The sensor device may include a photosensitive imaging device.  The photosensitive imaging device may include a charged coupled device.  The charged coupled device may includes color capability.  The soil imaging assembly may further include a first and second light source.  Each light source has one or more wavelengths corresponding to at least one of red, green, and blue. 
The invention also relates to a method for analyzing soil including: positioning a photosensitive imaging device adapted to convert light intensity to an image in a functional relationship with one or more portions of a soil sample, the soil sample including one or more particles; producing information corresponding to an image of at least a portion of the one or more particles; isolating at least a portion of the one or more particles; calculating a size of the one or more particles; comparing the size of the one or more particles to data relating to at least one of sand, silt, and clay; classifying the one or more particles as one of sand, silt, and clay; determining the percentage of the sand, silt, and clay in the one or more portions of the soil sample; comparing the percentages of the sand, silt, and clay to data relating to at least one category of soil; and classifying the one or more portions of the soil sample as at least one of clay, sandy clay, silty clay, sandy clay loam, clay loam, silty clay loam, sand, loamy sand, sandy loam, loam, and silt.