🧫 FERTILITY SURVEY

Soil fertility surveys convert laboratory and field observations into actionable nutrient-status maps for advisory and planning use. This lesson outlines survey procedures and village fertility index-based interpretation.

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LECTURE 18

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FERTILITY SURVEY AND MAPPING

Survey, village indices

Soil Fertility Survey

Soil survey essentially aims at taxonomical classification of soils in

well-defined units. The properties studied in the survey are ultimately used

to plot the extent of boundaries on a map. The maps are referred for various

purposes particularly for predicting yields based on soil fertility.

Fertility surveys are carried out in profile studies. Profiles in

representative locations in each soil series are opened and thoroughly

examined. From samples collected at different depthwise layer, soil

physical, chemical, and biological properties are thoroughly studied. The

factors limiting crop growth are identified in field and laboratory estimations.

Parameter on the depth of soil, rooting depth, bulk density, particle

density, porosity, water holding capacity, possible profile moisture storage,

soil reaction, salinity, total and available nutrients, presence of hard pans.

By interpretive analysis the fertility, data are grouped and used for mapping.

The division of Soil Survey and Land Use Planning of State

Department of agriculture, which is operating in selected districts of the

Tamil Nadu compiles the information and publish them as a Report. The

reports are available on cost basis to needy persons and institutions. The

results of survey are further classified and mapped by National Bureau of

Soil Survey and Land Use Planning located in Nagpur, Bangalore and in

many other locations in India. The Maps are distributed on cost basis for

their effective use. Soil Maps of Agro-climatic regions, fertility status,

irrigability, soil depth, crop suitability, salinity, etc are available.

Besides, the State Agricultural Universities and other national

Institutes conduct soil surveys and prepare maps on nutrient status marking

the macro and micronutrient deficient soils for ready recognition. The

remote sensing tools are also used in Mapping.

Village Fertility Indices and Mapping

In our country, the soil testing laboratories are functioning in all the

states. In Tamil Nadu, the soil testing and mobile soil testing laboratories

are functioning in almost all the districts.

One of the major functions of these laboratories is to analyze the soil

samples collected from the farmers for available N, P and K status. For

every year few taluk will be adopted. After analyzing the soil samples for

available NPK, they are grouped as low, medium and high based on the

soil test value as follows.

After grouping soils as low, medium or high, Village Fertility Index

25 (1/2) 3 (4/4)

(VFI) will be worked out for every revenue village.

NL + 2 NM + 3 NH VFI =

NL + NM + NH

Where NL, NM, NH are the number of soil samples falling under

the category low, medium and high, which are given weight of 1,2,3

respectively. Arbitrarily an index below 1.5 is low, between 1.5-2.5 is

medium, and above 2.5 is high.

Using these fertility indices, the current area wise fertilizer

recommendation for each crop can be modified. A soil fertility map may be

prepared in any outline map of block / taluk by plotting the index values

within the boundary of villages.

25 (2/2)

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Summary Cheat Sheet

Key Recall Points

• FERTILITY SURVEY is exam-relevant for SSAC122 and objective questions in soil science.
• Use soil-test based interpretation with focus on pH, CEC, and nutrient availability.
• Apply the 4R principle: right source, right rate, right time, and right method.

Exam Traps

• Do not mix up soil fertility concepts with fertilizer quantity alone.
• Numerical and term-based questions often test definitions, units, and threshold values.
• In problem-solving, interpretation must follow soil reaction, crop stage, and management context.

References

3 sources • [1] [2] [3]

[1]

ICAR e-Course: Soil Chemistry, Soil Fertility and Nutrient Management

Official

[2]

Brady and Weil, The Nature and Properties of Soils

Book

[3]

Indian Council of Agricultural Research

Official