agri

1. Soil profile, physical properties-soil structure and texture , Soils of Kerala-problem soils of Kerala
soil profile
A vertical section of soil through all its horizons and extending in to the parent material.
A vertical exposure of the horizon sequence is termed as “soil profile”.
A soil horizon is a layer of soil, approximately parallel to the soil surface,
differing in properties and characteristics from adjacent layers below or above it.
Practically, soil profile is an important tool for soil
classification which is applicable for thorough understanding of the soils.
Five master horizons are recognized in soil profile and are designated using
capital letters O, A, E, B and C.
O Horizons:(Organic)It comprises of organic horizons that form above the mineral soil. They
result from litter derived from dead plants and animals. ‘O’ horizons usually occur in forested
areas and aregenerally absent in grassland regions.
A - Horizon: It is the top most mineral horizon. It contains a strong mixture of decomposed
(humified) organic matter, which tends to impart a darker color than that of the lower horizons.
E - Horizon: It is an eluviated horizon. Clay and sesquioxides are invariably leached out, leaving
a concentration of resistant minerals such as quartz. An ‘E’ horizon is generally lighter in color
than the ‘A’ horizon and is found under ‘A’ horizon.
“B” – Horizon : (Illuvial) The sub -surface ‘B’ horizons include layers in which illuviation of
materials has taken place from above and even from below. In humid regions, the B horizons are
the layers of maximum accumulation of materials such as sesquioxides and silicate clays. In arid
and semi-arid regions Ca CO 3, Ca SO 4 and other salts may accumulate in the B horizon.
‘C’ – Horizon: It is the unconsolidated materialunderlying the ‘Solum’ (A & B). It may or may not
be the same as the parent material from which the solum formed. The ‘C’ horizon is out side the
zones of major biological activities and is generally little affected by the processes that formed
the horizons above it.
‘R’- Layer: Underlying consolidated rock, with little evidence of weathering.
SOIL PHYSICAL PROPERTIES: The physical properties include texture, structure, density, porosity,
consistency, temperature, colour and water content.
SOIL COMPONENTS
Mineral soil consists of four major components i.e., inorganic or mineral materials, organic
matter, water and air. In a representative loam surface soil, the solid mineral particles comprise
about 45% of the soil volume and organic matter 5%. At optimum moisture for plant growth, the
pore space is divided roughly in half, 25 %, of volume being water space and 25 % air. The
proportions of air and water are subjected to rapid and great fluctuations.
Mineral Matter: The Inorganic portion of soils is quite variable in size and
composition. It is composed of small rock fragments and minerals of various kinds.
Rock Fragments
2.0 - 75.0 mm - gravel or pebbles
Soil Particles
0.2 - 2.0mm - sand (gritty)
0.02 - 0.2mm - fine sand (gritty)
0.002 - 0.02mm - silt (powdery)
< 0.002mm - clay (sticky)
The proportion of different sized particles (texture) determines the nutrient supplying
power of the soil, considerably.
SOIL TEXTURE : Soil texturemay be defined as the relative proportion of particles of various
sizes ( Soil separates / Mechanical fractions ) such as sand, silt and clay. It is almost a permanent
property of the soil and may change slowly with time.
SOIL TEXTURAL CLASSES: Textural names are given to the soils based on each of the three
soil separates – sand, silt and clay. Soils that are preponderantly clay are called CLAY; those
with high silt content are SILT and those with high sand percentageare SAND. Three broad
and fundamental groups of soil textural classes arerecognized: SANDS, LOAMS and CLAYS.

2. Soil Structure may be defined as ‘thearrangement of primary particles (sand, silt and
clay), secondary particles (aggregates)and voids (pores) in to a certain definite pattern under
field conditions’.
Granular and crumb structures are characteristic of many surface soils (A horizon) particularly
those high in organic matter. They are best suited for growing crops. This structure is invariably subjected
to management practices.
 Governs the water and air permeability in to soils.
Influences water holding capacity, soil-water relationship and growth of
microorganisms.
Influences availability of plant nutrients.
SOIL COLOUR
Soil color is one of the obvious characteristics of soil and is frequently used to describe
soil, than any other. Soil color, as such, does not have any influence on plant growth.
Humus – brown or dark brown.
Iron oxides – red, rust – brown, or yellow depending upon degree of hydration.
Quartz Lime stones – white
SOIL REACTION
The soil reaction describes the degree of acidity or alkalinity of a soil.
The pH value represents the amount of free or active acidity and not the
total acidity. the pH value ranges from 0 to 14 where pH value of 0
represents the highest limit of active acidity; pH ‘7’ represents neutrality and pH
‘14’ represents the highest degree of alkalinity or basicity.
Classification of soils based on pH:
Based on the pH value of soil solution, the soils have been classified
into the following categories.
pH Range Category (Rating)
< 4.5 Extremely acidic
4.5 – 5.0 Very strongly acidic
5.1 – 5.5 Strongly acidic
5.6 – 6.0 Medium acidic
6.1 – 6.5 Slightly acidic
6.6 – 7.5 Neutral
7.5 – 7.8 Mildly alkaline

3. 7.9 – 8.4 Moderately alkaline
8.5 – 9.0 Strongly alkaline
> 9.1 Very strongly alkaline
Importance of soil pH on nutrient availability of plant nutrients
Soil
reaction is the important factor which governs the availability of various
nutrients by influencing the soil properties like physical, chemical and biological
etc. Bacteria and actinomycetes prefer near neutral to slightly alkaline
reaction (pH 6.5 – 8.0).Fungi work satisfactorily at all pH ranges.
nitRogen and Phosphorus availability is high in the neutral pH range. The availability
of micronutrients like zinc, iron, copper and
manganese are more in the acidic range.
SOIL MOISTURE CONSTANTS
Soil moisture constants are expressed in terms of the energy with which the water is held at
that moisture cont ent and the relationship is a continuous function with out break.
Soil moisture constant Soilmoisture potential
Oven dry soil -10,000 bars
Air dry soil -1,000 bars
Hygroscopic coefficient -31 bars
Wilting coefficient -15 bars
Field capacity -1/3 bars
Saturation Almost “O”
SATURATION :
Saturation water content is the amount of moisture present, when all the pores
are filled with water.
FIELD CAPACITY:
After heavy rain or irrigation to the soil the water drains off rapidly for the first
few hours and then starts to drain slowly. After two or three days, this rapid movement
becomes slow and negligible later. The soil is said to be at field capacity. At this
condition water moves out of macro pores and air occupies their places. The micro pores
are still filled with water, which is available to plants. But generally 1/3 bar
tension is frequently used to describe field capacity.
WILTING POINT: (wilting coefficient or Permanent wilting percentage):
It is the soil moisture content at which plants show wilting symptoms and can’t
recoup or recover even though it is kept in humid chamber. Sometimes, plants exhibit wilting symptoms
but recover with
the addition of water or when placed in humid chamber. The water content at this
condition is called the temporary wilting point.
Available water : Water held by soil at potential ranging between -15 bars to -1/3 bars, is
considered as plant available water.
SOIL BIOLOGY
The soil is teeming with millions of living organisms which make it a living and a dynamic
system. The organisms in the soil, not only help in development of soils but carryout a number of
transformations facilitating the availability of nutrients to the plants.

4. Benefits of soil organisms
Organic matter decomposition
Nitrogen fixation
Solubilisation of plant nutrients
Production of soil enzymes, growth promoting substances and antibiotics
Protect plant roots from invasion by soil parasites and pathogens.
IMPORTANCE OF SOIL ORGANIC MATTER / HUMUS
Influenceof Humus / Organic matter on soil physical, biological and chemicalproperties.
1 Imparts dark color to soils
2 Supplies polysaccharides for binding soil particles for formation of aggregates(genesis of
good soil structure)
3 Increases infiltration rate of water and provides better drainage
4 Increases water holding capacity
5 Reduces plasticity, cohesion, stickiness etc in clay soils
6 Reduces bulk density, there by influence porosity favorably
7 Through granulation, reduces wind erosion losses
8 Provides mulching (raw organic matter) and lowers soil temperature during summer.
Acts as an insulator and retards heat movement between atmosphere and soil
9 Reduces alkalinity in soils by releasing organic acids and CO2
10 With high adsorption capacity, it accounts for 30 -90% of the adsorbing power of mineral
soils ( Carboxylic group – 54% ; phenolic & enolic groups – 36%; imide group – 10%)
11 Acts as a buffering agent and reduces the likelihood damagefrom acids and alkalis.
12 With its solubilising effect, increses the availability of nutrients
13 Acts as a store house for nutrients. Organic matter is the source of 90-95% of nitrogen in
unfertilized soils. Also supplies available ‘P’, ‘S’ and micro nutrients like Fe, Mn, Cu and
Zn etc.,
14 Adsorbs temporarily the heavy metal pollutants and cleans the contaminated waters.
15 Serves as a source of energy for macro and micro organisms in soils and helps in
performing various beneficial functions in soils (N - fixation, mineralisation etc.)
16 Acts as a chelate and increases the availability of micro nutrients
17 Various organic substances like vitamins, antibiotics and growth promoting substances
namely auxins are produced by different micro organisms during decomposition of
organic matter. Also some fungi-toxins are produced to control diseases.
Soil Fertilityand Productivity

5. A productive soil hastobe fertile,while a fertile soil may or may not be productive. A soil is said to
be fertile if itcontainsandcan supplyall the thirteenessential plantnutrients (N, P, K, Ca, Mg, S, Fe,
Mn, Zn, Cu,B, Mo, Cl) inadequate amounts needed by the growing crop plants. However, for good
plant growth and productivity also needed are adequate amounts of water and air in soil.
Furthermore forrelease of several plantnutrientsagoodactivityof manysoil microorganismsisalso
required.Thusfora soil to be productive good soil physical and microbiological properties are also
neededinadditiontoitbeingfertile.Also a soil to be productive must also needed in addition to it
beingfertile.Alsoa soil to be productive must also be safe from natural hazards such as floods and
associated erosion.
Problem soils
Problem soils are the soils whose productivity is lowered due to inherent
unfavourable soil conditions viz., salt content and soil reaction.
saline soils : Saline soils contain neutral soluble salts of
chlorides and sulfates of sodium, calcium and magnesium.
Reclamation of salt affected soils: Leaching : The main objective in reclamation
of these soils is to leach the
salts below the root zone (hence, drainage system should be installed if
necessary). Leaching requirement (LR) has been defined as that fraction of water
that must be leached through the root zone to control soil salinity at a specified
level.
This is achieved by flooding and draining.
alkali or sodic soils: soils with pH
more than 8.5
Acid soils :soils with pH < 6.5 can also be categorized as acidic soils.
Plant nutrition: Plant nutrition is defined as the supply and absorption of chemical
compounds required for plant growth and metabolism. It is the process of
absorption and utilization of essential elements for plant growth and reproduction.
Nutrient: Nutrient may be defined as the chemical compound or ion required by an
organism. The mechanism by which the nutrients are converted to cellular material
or used for energetic purposes are known as metabolic processes.
Essential Plant Nutrients
Arnon and Stout (1939) suggested the following criteria for the essentiality of a plant nutrient:
(i) A deficiency of the essential element makes it impossible for a plant to complete its life cycle,
(ii) The deficiency is specific to particular essential element,
(iii) An essential element is directly involved in the nutrition of the plant.
Based on the these criteria 16 elements have been so far considered as essential plant nutrients.
These are : C, H, O, N, P, K, Ca, Mg, S, Fe, Mn, Zn, Cu, B, Mo and Cl.
Of these 3 elements (CHO) are taken from air and soil water, while the rest 13 are taken from
the soil through soil solution.
Classification of nutrients
On the basis of the amounts of these nutrients taken by plants they are classified as: (i)
macronutrients and (ii) micronutrients.
3.1.1 Macronutrients (taken up in large amounts, generally in kg per hectare). These can be
further sub-divided as
(i) Primary nutrients (taken up in large amounts): N, P, K.
(ii) Secondary nutrients (taken up in lesser amounts than N,P and K) : Ca, Mg, S

6. 3.1.2. Micronutrients : These are taken up in very small amounts, generally expressed in g or mg
per hectare, these include Fe, Mn, Zn, Cu, B, Mo, Cl.
Ionic forms in which taken up by plants, functions and deficiency symptoms of essential
plant nutrients.
Nutrients
(ionic forms)
Functions Deficiency symptoms
N (NH4+, NO3-) Synthesis of protein,
component of chlorophyll,
enzymes, nuclei acids
Light green colour of leaves,
older leaves show the
symptoms first.
P (H2PO4-, HPO4-) Component of ATP and ADP
and hence involved in energy
transfer in photosynthesis,
helps in root development
Leaves show purplish to red
coloration
K (K+) Control stomata opening for
photosynthesis, neutralizes
organic acids
Scorching and burning of leaf
margins
Ca (Ca++) Component of cell wall,
involved in cell division and
cell growth, co-factor for
enzymes
Failure in the development of
terminal buds, dead spots in
the mid-rib of leaves. In maize
the tip of the new leaves may
have a sticky material that
causes them to adhere to one
another
Mg (Mg++) Component of chlorophyll Light green veination in
leaves, cupping of leaves
S (SO4-) Component of proteins – S
containing amino acids cystine
and methonine
Similarly to N deficiency but
seen on top leaves as a
contrast to N deficiency
symptoms which first appear

7. in lower leaves. In rapeseed
mustard young leaves of S
deficient plants become pale,
chlorotic and cupped
Zn (Zn++) Formation of auxins &
chloroplasts; carbohydrate
metabolism
Stunted growth, pale to white
coloration of young leaves
(white bud disease of maize);
browning and scorching of
leaves (khaira disease of rice)
Nitrogenous fertilizers
A large number of fertilizers containing nitrogen are available. These can be broadly grouped
into four classes, namely ammonium, nitrate, ammonium and nitrate and amide containing
fertilizers. These are given in Table 4.
Table 4. Nitrogen content and other characteristics of nitrogenous fertilizers
Fertilizers Total N (%) Other nutrients
(%)
Equivalent
acidity/
basicity
(kg Ca/CO3)
Other
characteristics
Ammonium fertilizers
Anhydrous
ammonia
82.2 - 147 Marketed as
compressed
liquid gauge
pressure –75
pounds/sqm at
50oF and 197
pounds/sqm at
100oF
Ammonium
sulphate
20 24% S 107-110 Marketed in fine
to medium fine
crystals, non-
hygroscopic
Ammonium
chloride
26 - 128 Not widely used,
manufactures in
white, crystalline
form, non-
hygroscopie
Nitrate fertilizers
Sodiumnitrate
16 20% Na 29 Naturally
occurring
chemical. In
early 20th
century it was
prime source of
nitrogen. Very
hygroscopic,
marketedingrey

8. granules
Calciumnitrate
15 19% Ca 21 Available in
white crystalline
highly
hygroscopic and
not marketed in
India
Ammonium and nitrate fertilizer
Ammonium
sulphate nitrate
26
(19.25% NH4&
67.5% NO3)
5-6% S 93 Slightly
hygroscopic
Calcium
ammonium
nitrate
25
(12.5% NH4 &
12.5% NO3)
81% Ca Neutral Slightly
hygroscopic but
excellent
handling
qualities
Amide fertilizers
Urea
46 - 80 Most popular,
cheap. Free
flowingfertilizer.
It comes in
white prilled
form
Calcium
cynamid
20 54% Ca - It is no longer
produced
Bulky organic manures: These include FYM, rural compost, town compost, biogas compost,
night soil, sludge, green manures and other bulky sources of organic matter.
6.5.2. Concentrated organic manures: These include oil cakes, blood meal, fish manure, meat
meal and wool waste.
The application of organic manure improves the physical, chemical and biological conditions of
soils besides providing plant nutrients. The humus of organic manures is a colloidal material
with negative electric charge and is coagulated with cations. With organic manures soil particles
form granules. Soil with more granules is less sticky, have a better permeability, and greater
water holding capacity. Organic manures also increase buffering capacity of soils. Soils with
higher buffering capacity are capable of regulating the soil pH. Thus addition of organic manures
create a good environment for crop growth.
Compo
sition
Phosphorus (P2O5) Nitrogen Calciu
m
Magne-

9. of
phosph
atic
fertiliz
ers
Fertiliz
ers
(%) (%) (CaO)
(%)
sium
(MgO)
(%)
Total Availabl
e
Water
soluble
T
o
t
a
l
A
m
m
o
n
i
a
c
a
l
N
i
t
r
a
t
e
A
m
i
d
e
Singl
e
super
phosp
hate
18-20 16.5-
17
16 - - - - 25-30 0.5
Triple
super
phosp
hate
46 43 42.5 - - - - 17-20 0.5
Diam
moni
um
phosp
hate
46 41 41 18 18 - - - -
Amm
oniu
m
phosp
hate
sulph
ate
(16:2
0:0)
20 19.5 19.5 16 16 - - - -
Amm
oniu
m
phosp
hate
sulph
ate
20 20 17 20 18 2 - - -

10. (20+2
0+0)
Amm
oniu
m
phosp
hate
sulph
ate
nitrat
e
20 20 17 20 17 3 - - -
Urea
amm
oniu
m
phosp
hate
(28:2
8:0)
28 28 25,2 28 9 - 19 - -
Urea
amm
oniu
m
24 24 20.4 24 7.5 - 16.5 - -
phosphate (24:24:0)
Nitro
-
phos
phate
(20:2
0:0)
20 20 5.4 - - - - - -
Udai
pur
rock
phos
phate
20-
35
- - - - - - - -
Muss
oorie
rock
phos
phate
23-
34
- - - - - - - -
Jhab
ua
rock
phos
phate
31-
38
- - - - - - - -
Soil Fertility Evaluation and Fertilizer Recommendations

11. The selection of the proper rate of plant nutrients is influenced by a knowledge of the nutrient
requirement of the crop and the nutrient-supplying power of the soil on which the crop is to be
grown. The techniques commonly employed to assess the fertility status of a soil are : (i)
nutrient-deficiency symptoms of plants, (ii) analyses of tissue from plants growing on the soil,
(iii) biological tests in which the growth of either higher plants or certain micro-organisms is
used as a measure of soil fertility and (iv) chemical soil tests.
Nutrient-deficiency symptoms of plants
Tissue tests: Rapid tests for the determination of nutrient elements in the plant sap of fresh
tissue have found an important place in the diagnosis of the needs of growing plants.
Total analysis: Total analysis is performed on the whole plant or on plant parts. Precise
analytical techniques are used for measurement of the various elements after the plant material
is dried, ground, and ashed.
Biological tests
Biofertilizers
The bio-inoculants or preparations containing microorganisms that supply nutrients especially
nitrogen and phosphorus are known as biofertilizers. On the basis of nutrients supply, these are
broadly classified in four groups: (i) nitrogen fixers, (ii) phosphorus solubilizers, (iii) plant
growth promoters (iv) organic matter decomposers.
14.1. Nitrogen fixers
Certain micro-organisms like bacteria and blue-green algae have the ability to use atmospheric
nitrogen and made available this nutrient to the crop plants. Some of these ‘nitrogen fixers’ like
rhizobia are obligate symbionts in leguminous plants (Tilak and Saxena, 1996), while others
colonize root zones and fix nitrogen with loose association with plants. A very important
bacterium of the latter category is Azospirillum, which was discovered by a Brazilian scientist in
the mid 1970s. The third group includes free-living nitrogen fixers such as blue-green algae and
Azotobacter.
14.1.1. Legume Inoculants : The most widely used biofertilizer for pulse crops is Rhizobium
which colonizes the roots of specific legumes to form turmour like growth called root nodules.
The Rhizobium-legume association can fix up to 100-200 kg N/ha in one crop season and in
certain situations can leave behind substantial nitrogen for the following crop.
The range of nitrogen fixed per hectare per year by different legumes is 100-150 kg for clover,
53-85 kg for cowpea, 68-200 kg for pigeonpea, 46 kg for peas, 35-106 kg for lentil, 112-152 kg
for groundnut, 49-130 kg for soybean, 50-55 kg for mungbean and 37-196 kg for guar (Tilak,
1998). Stem nodulating legumes such as Sesbania rostrata, Aeschynomene sp. and Neptunia
oleracea have become popular in improving soil fertility. The N-fixing bacteria associated with
such stem nodulating legumes belong to Azorhizobium, a fast growing species of Rhizobium. The
N-acumulating potential of stem nodulating legumes under flooded conditions ranges from 40-
200 kg N/ha (Rao et al., 1994).
14.1.2. Azotobacter and Azospirillum : The beneficial effects of Azotobacter on cereals, millets,
vegetables, cotton and sugarcane under both irrigated and dryland conditions have been well
substantiated and documented. Application of this biofertilizer has been found to increase the
yield of wheat, rice, pearlmillet and sorghum by 0-30% over control. Apart from nitrogen, this
organism is also capable of producing antibacterial and antifungal compounds, hormones and
siderophores (Tilak, 1993).
Azospirillum, an associative microareophilioc organism living in association with diverse group
of plants consists of 5 species namely, A. brasilense, A. lipoferum, A. amazonense, A.

12. halopreference and A. irkense. Associative nitrogen fixation, capability to produce plant growth
promoting antifungal, antibacterial substances and their effect on root morphology are the
principal mechanisms responsible for the increase in crop yields (Tilak and Annapurna, 1993).
Inoculation with Azospirillum results in enhanced assimilation of mineral nutrients (N, P, K, Rb+,
Fe2+), and offers resistance to pathogens (Wani, 1990).
A new bacterium Herbaspirillum taxonomically closely related to Azospirillum has also been
isolated from forage grasses (Indira and Bagyaraj, 1996). Acetobacter diazotrophicus is a
saccharophilic bacterium and is associated with sugarcane, sweet sorghum and sweet potato.
Reports from Brazil indicate that this bacterium fixes around 150-250 kg N/ha/year in case of
sugarcane.
14.1.3. Blue-green algae : A judicious use of blue green algae could provide to the country’s
entire rice acrease as much nitrogen as obtained from 15-17 lakh tonnes of urea. Methods have
been developed for mass production of algal biofertilizers and it is becoming popular among the
rice growers in many parts of the country (Ventakaraman and Tilak, 1990). Recent research has
shown that algae also help to reduce soil alkalinity, and this opens up possibilities for
bioreclamation of such inhospitable environments. This area is of particular relevance, because 7
million hectares of arable land in our country are salt affected.
14.1.4. Azolla : Azolla is known as a floating nitrogen factory in low land rice fields and in
shallow fresh water bodies. The Azolla anabaena association use the energy from photosynthesis
to fix atmospheric nitrogen amount to 100-150 kg/ha/year from about 40-60 tonnes of biomass
(Singh, 1998). An integrated system of rice-Azolla-fish has been developed in China. We need to
give greater thrust on this system.
Phosphate solubilizers
14.2.1. Phosphorus solubizing bacteria : Bacteria such as Pesudomonas and Bacillus excrete
acids into the growth medium and hence solubilize bound phosphorus (Gaur, 1985). These
organisms are quite useful in the utilization of rock phosphate with low content of P. Field
experiments conducted with P-solubilizers like Aspergillus awamori, P. striata and B. polymyxa
significantly increased the yields of various crops like wheat, rice, cowpea, etc. Use of rock
phosphate with phosphate solubilizing bacteria resulted in a saving of 30 kg P2O5/ha (Gaur,
1985).
14.2.2. Mycorrhizae : Recent research has shown the possibility of domesticating mycorrhizae in
agricultural systems. They also ubiquitous in geographic distribution occurring with plants
growing in all environmental conditions. VA-mycorrhizal fungi occur over a broad ecological
range from aquatic to desert environments. These fungi belonging to the genera Glomus,
Gigaspora, Acaulospora, Entrophosphora, Modicella, Sclerocystis and are obligate symbionts.
These fungi have been cultured on nutrient media using standard microbiological techniques.
They are multiplied in the roots of host plants and the inoculum is prepared using infected roots
and soil.
Crop responses to VAM inoculation are governed by soil type, host variety, VAM strains,
temperature, moisture, cropping practices and soil management practices. The major constraint
for using VAM has been the inability to produce ‘clean pure’ inoculum on large scale. Field trials
indicated that VAM inoculation increased yields at certain locations and the response varied from
soil type, soil fertility particularly with available P status of soil and VAM culture (Tilak, 1993).
Mycorrhizal fungi assists in the uptake of phosphorus and trace metals and positively influences
water and nutrient status via hormonal influences. However, lack of suitable inoculum production
technology is the major limitation for the commercial exploitation of this system.
14.3. Plant growth promoting Rhizobacteria

13. A group of rhizosphere bacteria (rhizobacteria) that exerts a beneficial effect on plant growth is
referred to as Plant Growth Promoting Rhizobacteria or PGPR (Schroth and Hancock, 1981).
PGPR belongs to several genera, namely, Actinoplanes, Agrobacterium, Alcaligenes,
Amorphosporangium, Arthrobacter, Azotobacter, Bacillus, Bradyrhizobium, Cellulomonas,
Enterobacter, Erwinia, Flavobacterium, Pseudomonas, Rhizobium, Streptomyces and
Zanthomonas (Weller, 1988). Bacillus sp. are appealing candidates as PGPR because of their
endospore producing ability which make them ideal inoculants for dry areas. Currently
Pseudomonas spp. are receiving much attention as PGPR, because of their multiple effects on
plant growth promotion.
PGPR are believed to improve plant growth by colonizing the root system and pre-emptying the
establishment of suppressing Deleterious Rhizosphere Micro Organisms (DRMO) on the root
(Schroth and Hancock, 1981). Inoculating planting material with PGPR presumably prevents or
reduces the establishment of pathogens (Suslow, 1982). Production of siderophores is yet another
molecular weight high affinity Fe+3 chelators that transport iron into bacterial cells and are
responsible for increased plant growth by PGPR (Kloepper et al., 1980). Under Fe-deficient
conditions, fluorescent Pseudomonas produce yellow-green fluorescent siderophore-iron complex
(Hohnadel and Meyer, 1986) which creates an iron deficient environment deleterious to fungal
growth.
Integrated Nutrient Management (INM)
The concept of INM is the rationalization of plant nutrient management in order to upgrade the
efficiency of plant nutrient supply to the crops through the adequate association of local and
external plant nutrient sources accessible and affordable to the farmers resulting ultimately in
higher productivity and income to the farmers. In INM, better management results in plant
nutrient gains, which are reinvested in the plant nutrient cycle in order to gradually upgrade the
plant nutrient capital on the farm (soil reserves, crop residues, manures etc.) in an economically
justified, socially acceptable and ecofriendly manner. This should also increase the cash flow for
the purchase of chemical fertilizer.
INM firstly operates at the field level, optimizing the stocks and flows of plant nutrients from the
diverse sources in order to increase the uptake of plant nutrients by the crops, the agronomic
and physiological efficiency and at the same time to reduce losses of plant nutrients from the
soil.
At the farm level INM is the combination of plant nutrition practices and allocation of plant
nutrient sources optimizing the flows of nutrients passing through the soil/crop/livestock
system and increasing both the stock of plant nutrients in the system and income of the
farmers. INM aims at the accumulation of the production capacity of the farmers through
accurate and profitable investments in external plant nutrient sources and amendments,
efficient processing and recycling of crop residues and onfarm organic wastes. An inventory has
to be made for the entire farming system involving seed, irrigation, manure, residues, animals
on the farm etc. Only a careful periodic study of the inventory permits the proper
implementation of INM.
The concept of INM can then be extended to the entire village or a district or a state. This will
then involve making of inventories beyond the cropped areas and should list the source and
amount of irrigation water, its quality including plant nutrient content, sediments provided by
floods, plant nutrients removed by cutting of trees, contribution of pasture land if any and loss

14. of gains of nutrients by rains, floods and storms. When planned and proceed well, INM leads to
the betterment of soils, pasture and forest lands animal stock, people and area as a whole.
15.1. Components of INM
The major components of INM are as follows:
15.1.1. Fertilizers: Fertilizers are concentrated source of one or more plant nutrients. The nutrient
supply through fertilizers during 2004-2005 was 18.4 million tonnes consisting of 11.7, 4.6 and
2.1 million tonnes of N, P2O5 and K2O, respectively (FAI, 2005). In contrast, nutrient removal by
crops was 8-10 million tonnes higher than nutrient addition through fertilizers. This gap needs to
be bridged through organics and biofertilizers.
15.1.2. Organic manures: Among the organic manures, the most common is the
compost/farmyard manure (FYM). Organic manures not only supply plant nutrients inbalanced
proportion but also improve, physical and biological properties of soil and thus make the system
sustainable.
15.1.3. Green manures: Green manuring with legumes has long been known to be beneficial for
sustainable crop productivity. In several studies conducted in India green manure was able to
replace 60 kg N/ha. A fertilized green manure crop would substitute more mineral fertilizer N
than an unfertilized green manure crop (Sharma and Mittra, 1988). A wide variability in N
substitution through green manuring to the order of 45-120 has been reported. However, most
commonly observed N additions through an array of green manures are in the range of 40-60 kg
N/ha.
15.1.4. Crop rotation: To overcome the ecological diseases of monoculture, the first
solution that man found was the changing of crops from one to another or from one
season to another. Even before the modern agriculture was established the farmer had
discovered the restorative power of legumes. For example, Vigil as early as 70-19 BC
advocated the application of legumes and indicated in the following passage.
“Or, changing the season, you will sow these yellow wheat, wherever before you have taken up
joyful pulse, with resulting pods”.
Thus the key to successful crop rotation was a soil restorer legume such as beans (Vicia faba L.),
clover, lupins (Lupinus album L.) and Vatch (Vicia savita L.). The famous English Norfold
rotation popular in 18th Century in England was turnip, barley, clover and wheat in a 4 year
sequence. Thomas Jefferson followed a 5 year rotation of wheat-corn/potato-pea (Pisum sativum
L.) – rye (Secale cereals L.)/wheat-clover/buck wheat (Fagopynum esculentum Moench). Even
today only 20% of the corn in the United States is grown in continuous monoculture, while the
remaining 80% is grown in a 2 year rotation with soybean or in short (2-or-3 year rotation) with
alfalfa, cotton, dry bean or other crop. The legumes restore soil fertility in many ways. Some of
them are: (i) they fix atmospheric N2 and leave part of it in soil, (ii) their deeper tap root system
absorbs moisture and nutrients from deeper soil layers and some of the nutrients absorbed are left
in the root mass in the surface soil, (iii) improve soil permeability, (iv) lesser disease and pest
problem and (v) better weed control.
15.1.5. Crop residues : Substantial amounts of crop residues are produced in India every year.
Five major crops namely rice, wheat, sorghum, pearlmillet and maize alone yield approximately
225 MT straw/stover with an average composition of about 0.5% N, 0.5% P2O5 and 1.5% K2O
Soil drainage: When rainfall intensity exceeds the infiltrability of soil or the amount of rainfall
exceeds the storage capacity of soil, the excess water accumulates at the soil surface and may

15. keep the soil under saturated condition for longer time.
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Drainagemeans removal of excess water from surface or sub-surface of soil body by
means of some water conveying devices.
Excess water may be due to 1) over irrigation 2) accumulation of monsoon runoff in low
lying areas for want of an outlet and 3) seepage from reservoirs, canals and ditches.
The drainage problem are two types : surface drainage problem and sub-surface
drainage problems. Surface drainage problems arise in the flat areas of land that aresubjected
to ponded water. Uneven land, low capacity of disposal channels, above ground level water
bodies are the chief causes for ponding of water in an area.
The sub-surface drainage problems may arise due to low soil permeability, humid climate and
rise of ground water causing development of a shallow water table.
In case of surface drainage, water is removed directly from the land by land smoothing,
land grading, bunding and ditching. Land surfaces arealso reshaped to eliminate ponding and to
createslopes so as to induce gravitational flow over land and channels to an outlet. The excess
water can also be diverted from the land by diversion ditches, dykes etc.
Subsurface drainage refers to the outflow or artificial removal of excess water from with in the
soil, generally by lowering the water table or by preventing its rise, using mostly the artificial
water conveying devices. An underground net work can be created for facilitating sub surface
drainage.
A mole drainagesystem: It is createdby pulling through the soil at the desired depth a pointed
cylindrical plug about 7-10 cm in diameter. The compressed wall channel thus formed provides
a mechanism for the removal of excess water. This is an easy system to install, but is easily
clogged after few years.
A perforated plastic pipe can be laid underground using special equipment. Water moves in to
the plastic pipe through the perforations and can be channeled to an outlet ditch. About 90% of
the underground drain systems being installed are of this type.
A clay tile system made up individual clay pipe units 30-40 cm long can be installed in an
open ditch. The files are then covered with a thin layer of straw, manure or gravel and the ditch
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is then refilled with soil. Tile drains were popular two decades ago, but high installation costs
make them less competitive than the perforated plastic systems.
IMPORTANCE OF DRAINAGE
1 Drainageis essential, as the crop growth will be drastically affected by continuous soil
saturation with water.
2 Soil saturation may encourage certain diseases and parasites.
3 Poor drainage leads to the development of salt affected soils.
4 High water table may limit root penetration.
5 Soil saturation stops the gaseous exchange causing oxygen deficiency and accumulation
of CO2 to toxic levels in root zone.
6 Wet soil requires more heat to warm up than dry soil, due to high specific heat of water,
the growing season for winter crops is shortened in poorly drained soils.
7 Under poor drainage conditions / anaerobic conditions many organic and inorganic
compounds will be reduced to toxic levels and inhibit crop growth.
8 Denitrification occurs in anaerobic conditions.
9 Some micronutrients will become unavailable.