Soil Testing Equipment

Referent and Standards Product for Soil Testing Equipment

Soil: The Living Matrix

Around the world, farmers are very intelligent and know the characteristics of soil. They know many  things about  the soil  that scientists do not, and scientists know many  things  that  farmers  do  not,  so  these  two  groups  of  workers  must  work together. This is true of North American, European, and Asian countries. Farming practices are based on empirical experience; some of these practices may not stand up to scientific testing, but others obviously must do.The importance of soil structure as a factor in soil fertility is becoming increasingly clear. If a plant is to grow, its roots must spread so that their delicate structures of root  hairs  can  get  access  to  plant  nutrients. They  also  only  thrive  if  there  is  an adequate supply of water and air. In several countries with plantations of sugarcane, the continuous high yields obtained through irrigation and the extensive application of manure  and  fertilizers  have  created  problems. Chemical  analyzes  of  the  soils
from such areas show that common plant nutrients are still present, but that something has happened to the soil that is interfering with its productivity. At first it was thought  that  the cane  itself  is deteriorating, but  this  is not  likely, as  it propagates vegetatively.  Instead,  unfavorable  conditions  for  beneficial  soil microorganisms may have been produced. The deterioration of  the  soil  structure  seems  to play a direct part in this, because soil microorganisms have an important influence on the soil structure. Soil organic matter – the formation, decomposition, and transformation of which are caused by microorganisms – is of great importance to sustainable soilfertility and soil structure.

More experiments on soil structure and other physical properties of soils, such as permeability,  porosity,  and  moisture  retention  capacity,  are  desirable.  Soil  fertility depends on a large number of complex factors, not all of which are known. Physical properties of the soil are no less important than chemical properties. The clay fraction determines many physical and chemical properties of soils. The properties of clays are determined by their mineralogical compositions. X-ray studies and differential thermal analyses of clays have now become necessities in soil laboratories. The electrochemical properties of clays are fundamentally important to understanding soil behavior. This chapter introduces the various types of soil and their functions, as well as the pollution of the soil with heavy metals, which is detrimental to the health of the soil

Soil Taxonomy and Classification

A soil  taxonomist distinguishes soils partly on  the basis of  the kind of diagnostic horizon(s)  present  in  each  soil.  The  current  soil  taxonomy  (classification)  was adopted  in 1965; a simplified account of  this classification system follows below(see US Soil Survey Report 1972, 1975). Order. This is the most general category. All soils fit into one of ten orders. Suborder. Suborders within a soil order are differentiated largely on the basis of soil properties  and  horizons  resulting  from  differences  in  soil moisture  and  soil temperature. Forty-seven suborders are presently recognized.
Great group. Soil great groups are subdivisions of suborders. The 185 great groups found in the US, and 225 worldwide, have been established largely on the basis of  differentiating  soil  horizons  and  soil  features.  The  soil  horizons  include those that have accumulated clay, iron, and/or humus, and those that have pans
(hardened or cemented soil  layers)  that  interfere with water movement or root penetration.
Subgroup.  Each  soil  great  group  is  divided  into  three  kinds  of  subgroups:  one representing the central (typic) segment of the soil group; a second that has prop-erties that tend toward other orders, suborders, or other great groups (intergrade group); and a  third  that has properties  that prevent  its classification as  typic or intergrade. About 970 subgroups are known in the United States.Family. Subgroups contain soil families, which are distinguished primarily on the basis of  soil properties  important  to  the growth of plants or  the behavior of soils when  used  for  engineering  purposes. These  soil  properties  used  include texture, mineral  reactions  (pH),  soil  temperature,  precipitation  pattern  of  the area,  permeability,  horizon  thickness,  structure,  and  consistency. About  4,500 families have been identified in the United States.Series. Each family contains several (similar) soil series. The 10,500 or more soil series  in  the United States have narrower  ranges of  characteristics  than  a  soil family. The name of the soil series has no pedogenic (i.e., related to soil formation) significance; instead, it represents a prominent geographic name of a river, town,or area near where the series was first recognized. Soil series are differentiated on  the  basis  of  observable  and mappable  soil  characteristics,  such  as  color, texture,  structure,  consistency,  thickness,  reactions  (pH),  and  the  number and  arrangement  of  horizons  in  the  soil  pedon  as well  as  their  chemical  and
mineralization  properties.  Terms  describing  surface  soil  texture,  percentage slope,  stoniness,  saltiness,  erosion,  and  other  conditions  are  called  phases. Mapping units are created by adding phase names to series names. All mappingunits are polypedons. Prior to 1971, soil type was a mapping unit that was used
to denote a subdivision of a series indicating the series name and surface texture. Soil type is no longer official nomenclature; it has been replaced by series phase.

The  prime  land  means  the  best  land.  The  definition  of  prime  land  will  change depending  on  the  use  of  the  land,  and  full  agreement  as  to  exactly  how  “prime” should be defined  is unlikely, even  for a  specific  land use. For  farmland use,  it  is proposed that prime land should meet all the followingrequirements: adequate natu-ral  rainfall  or  adequate  and  good-quality  irrigation water  for  intended  use; mean annual temperature >32°F (0°C) and mean summer temperature >46°F (8°C); lack of excessive moisture – flooding should not occur more often than once every two years; water table should be below the rooting zone; soil should not be excessively acidic, alkaline, or saline; soil permeability should be at least 0.38″  h−1 (1.0 cm h−1) in  the upper 20″  (51  cm);  the  amount of gravel,  cobbles, or  stones  should not be excessive  enough  to  seriously  interfere  with  power  machinery;  any  restricting layer  in  the  soil  should be deep  enough  to permit  adequate moisture  storage  and unhampered root growth, and; the soil should not be excessively erodible.The objectives of soil surveys and taxonomy are to facilitate growth on soils that have never been grown on before, and  to  learn enough about certain soils  to predict how they would respond when irrigated with a specific quantity of irrigation water of known quality. This objective also emphasizes  the  inclusion of a  rational means of transferring technology from one soil to another, interpretations that allow the predition of land use for every soil mapped, and that the survey should serve as a scientific database.  Soil  surveying  has  developed  into  a  specialized  subject. A  survey  report contains information on not only the characteristics of the soil and its profile, but also the  existing  and potential uses of  the  land,  the yields obtained by  the  farmer or by experimental stations under different systems of management, erosion and drainage conditions, and the potential for reclamation or its suitability for irrigation, where these are necessary. Soil maps and survey reports form the basis for planning the utilization of the land, and they have also been found useful in road and building projects.


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