Soil Survey
Under the eighteenth amendment Soil Survey of Pakistan was devolved to the provinces. The mandate of Soil Survey was also devolved resultantly the responsibilities were put on the shoulders of Director General Soil and Water Conservation Agriculture department of this province. The objectives of the Soil Survey is to describe, analyze, classify and map the soils of the survey area and, through interpretation of the findings, evaluate the potential of the mapping units for improved land use and agriculture planning.
The Director Soil Survey of the province proposed to the Director General Soil and Water Conservation to allow for initial starting of the work with nominal staff and resources and to survey the soils of catchment and command area of the completed projects of Water Retaining Facilities in Khyber Pakhtunkhwa. The Director General agreed with the proposal and fix the target of 02 numbers of the water Retaining Facilities one each at Kohat and Swabi as a trial base. This report contains the material and information for the planning on individual farm. Therefore the survey methodology was of the detail soil survey. A final purpose of the report is to be describe the soils and their relationship to each other as well as to the soils of the world. Furthermore 02 numbers water retaining facilities at Karak and Malakand districts were studied in detail and the reports were completed accordingly.
What is meant by Water Retention?
Water retention is defined as the soil water content at a given soil water suction. By varying the soil suction and recording the changes in soil water content, a water retention function or curve is determined. This relationship is dependent on particle-size distribution, clay mineralogy, organic matter and structure or physical arrangement of the particles as well as hysteresis, i.e., whether the water is absorbing into or desorbing from the soil. The data collected in these methods are from water desorption. Water retention or desorption function or curves are useful directly and indirectly as indicators of other soil behavior traits, such as drainage, aeration, infiltration, plant-available water and rooting patron (Gardner, 1986).
Two desorption methods are commonly used to measure water retention, a suction method and pressure method.
Objectives of Soil Survey
Survey methodology
The soil series and soil properties and characteristics were studied in detail. Land capability, land use, land form and parent materials were also analyzed. For the recognition of individual soil series, phases and their variant, the criteria adopted was of the U.S Soil Taxonomy (U.S.D.A. 1951). Topographic maps at the scales of 1; 50,000 together with irrigation maps, were also used to guide the local point finding locations.
For detail soils observation a shallow pit, about 50 centimeter deep was dug and the top soil and sub-soil were described. The properties of the part of the profile below 50cm were examined by auguring in the bottom of the pit to a total depth of about 110 to 115cm. In each horizon the main properties and characteristics were listed which include colour, texture, structure and presence or absence of calcium carbonate etc. Soils were differentiated on the bases of theses differentiating criteria. In all pits a soil series have been recognized in the area. A soil series includes soils which are developed in the similar parent material and have the similar chemical and physical properties in the similar environment.
By the end of the survey concept of a model profile of soil series become clear. For complete profile description and soil sampling of these modern profiles, pits were dug at the representative site to a depth of about 150cm. All the horizons and sub-horizons were described in such a detail as they deserve on detail level survey, with additional information about consistence, roots, pores and horizon transitions. The information together with a detail of physiography, parent material, vegetation, crops and site location, was recorded on a data sheet. These descriptions were made according to FAO guidelines for soil descriptions. Samples of all horizons and sub-horizons were taken for analysis in the soil testing laboratory of agriculture research department Khyber Pakhtunkhwa.
The individual soil series were delineated on topographic sheets as soil associations or complexes. These soil boundaries were regularly transferred to topographic sheets in the course of survey for correlation purposes. On the completion of these field works, soil boundaries were transferred directly to topographic maps at a scale of 1; 50000. The resulting maps were reduced to a scale of 1: 25000 with a pinto-graph to form soil map.
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