🧫 PERMANENT MANURIAL

Permanent manurial experiments provide long-term evidence on how continuous nutrient and manure application changes crop yield and soil health over time.

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PERMANENT MANURIAL EXPERIMENTS

OPM, NPM, LTFE, Findings

Permanent Manurial Experiments

Permanent manurial experiments are conducted to study the long

term effect of continuous application of plant nutrients either singly or in

combination and with or without organic manure on crop yield, nutrient

uptake, and physico-chemical and biological properties of soil.

The first one started was the classical field experiment at

Rothamsted Experimental Station, Harpenden in England in 1854 by

Lawes and Gilbert.

Most of PMEs test common treatment combinations like: Fertilizer N

or P or K alone, Fertilizer N and K, Fertilizer N and P, Fertilizer NPK,

Farmyard Manure (FYM), Residual effect of FYM, Hand weeding, Zn or S

addition, Control (no manure), tillage, irrigation, etc.

Similar to Rothamsted experiment, in India PME was started at

Coimbatore in 1909 and this was the first of its kind in our country. This

called as Old Permanent Manurial experiment ( OPM ) is being conducted in

red soil (Alfisol) with cereal-cotton crop rotation under rainfed conditions.

Subsequently in 1925, a second experiment was started with the

same treatments and called as New Permanent Manurial ( NPM ) experiment

to test the effect under irrigated conditions.

In OPM and NPM a uniform fertilizer dose of 25-60-75 kg N, P2O5 and

K2O/ha is being applied in all these years. As these are designed with very

low dose of fertilizers and manures without any replication and

randomization, they do not match to the present day use pattern of fertilizer/

manure and statistical analysis.

Therefore, to study the effect of intensive cropping and manuring

new set of experimental design was implemented all over India by ICAR by a

coordinated scheme on Long Term Fertilizer Experiment ( LTFE ). During

1972, LTFEs were started at 11 centres and later further expanded at seven

more centres.

Under this scheme, a third experiment was started in 1972 at Coimbatore

called as Long Term Fertilizer Experiment (LTFE) in medium black soil

(Inceptisol) to test intensive cropping system with Ragi-maize cropping

system.

The major findings in these experiments are:

• Application of single nutrient (N or P or K) alone resulted in lower crop

yield. Combination of NP and NPK gave higher yield.

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• Phosphorus became a limiting nutrient when it was not applied and it

reduced the yield to the extent of 50-60 per cent. Application of P

along with N, K, and FYM raised the available soil P from low to

medium status.

• Potassium was depleted even when it is applied continuously.

• Continuous use of N fertilizer alone reduced the soil productivity.

Addition of FYM with NPK significantly increased the crop yield to the

tune of 15-20 per cent over NPK alone. Addition of organic manure

improved pore space and water holding capacity of soil. Combined

application of organic manure and inorganic fertilizer not only

increased the yield of crops but also improved the soil productivity.

• Population of bacteria, fungi, Actinomycetes and Azotobacter were

increased due to organic manure incorporation. The activities of

enzyme urease, dehydrogenase, cellulase, and amylase were favored

by organic manure application.

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Summary Cheat Sheet

Key Recall Points

• PERMANENT MANURIAL 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