Course soil and critical levels of nutrient elements in

Course objectives:

•     
To
strengthen understanding of various types of manures and fertilizers, their
manufacturing and application methodology.

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•     
To
focus on soil fertility and productivity with emphasis on nutrient deficiency
disorders and remedies.

•     
To
acquaint with the nutrient absorption mechanism, outcome of nutrient
fertilizers applied to the soil and critical levels of nutrient elements in
soil and plants.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Fertilizers

Fertilizer Classification

 

 

Manures:-

q  Manures are organic materials added to the
soil to increase crop production.

q  They are biological in origin.

q  The organic matter content is bulky and
large and the nutrient content is small. They have the following effect on the
soil.  

1.       They supply nutrients to the soil. Since
the manures contain nutrients in small quantities they have to be used in bulk
quantities.

2.       Since the manure contains a lot of organic
matter, it increases the water holding capacity in sandy soils and drainage in
clayey soils.

 

 

 

Farm yard manure

q  This is the decomposed mixture of excreta
(dung) and urine of farm animals like cow, horse, goat and sheep along with
leftover hay and fodder.

q   They are readymade manures and contain
nitrogen, phosphorus and potassium.

q  Farmyard manure when collected in the
field and stored in an exposed condition over a long period shows considerable
loss of ammonia which is a loss of fertilizing value. To prevent this loss the
dung is stored in pits which are about a metre deep. When the pits are filled to
the top, the surface is sealed with mud slurry. The manure is ready for use in
about 4-5 months.

q  This consists of a variety of farm wastes
such as farm weeds, straw, sugarcane refuse, rotting vegetables, kitchen
wastes, crop stubble, groundnut and rice husk.

q   Composting is a biological process in which
aerobic and anaerobic microorganisms decompose organic matter.

q   A
trench of suitable size 4-5 m long, 1.5 to 1.8 m broad and 1.0 to 1.8 m deep is
dug. A layer of well mixed refuse of about 30 cm thickness is spread in the
pit. A slurry of cow dung, earth and water is poured over this layer to keep it
moist. Another layer of the mixed refuse is spread in the pit till the heap
rises to a height of 45 to 60 cm above ground level.

Compost

N

P2O5

K2O

Farm Compost

0.5%

0.15%

0.5%

Town
Refuse

1.4%

1.0%

1.4%

Nutrient content of farm and town compost

GREEN MANURING

q  Green manuring is the practice of growing
and ploughing in, the green crops, into the soil.

q  It is a cheap and effective method that
increases soil fertility as it can supplement farmyard and other organic
manures and is more cost effective.

q  Green manures add nitrogen and organic
matter to the soil for improving crop productivity.

q  They also improve soil aeration and
drainage conditions.

Plants used as green manure are:

English and Hindi names

Botanical Name

Sunn hemp (Sanai)

Crotalaria juncea

Lentil (Masur)

Lens esculenta

Egyptian clover (Berseem)

Trifolium alexandrium

Sesbania (Dhaincha)

Sesbania aculeata

Cluster bean (Gaur ki phalli)

Cyamopris tetragonoloba

Cowpea (Lobiya)

Vigna sinensis

Horse-gram

Macrotyloma uniflorum

Senj

Melilotus parvifora

 

q  This type of manuring is used in fields in
which crops like rice, maize, sugarcane, cotton, wheat etc., which require high
nutrient input are raised. There is 30 – 50% increase in the crop yield by
using green manure.

q  The green manure crops are grown in the
field for about 6 – 8 weeks and ploughed into the soil during the flowering
stage. The plants are allowed to remain buried for about 1 – 2 months. During
this period, the plant gets totally decomposed. The soil is then tilled and the
next food crop is sowed. By alternating the green manure crop with food crop
the nitrogen and organic content of the soil is maintained.

Vermicompost:-

q  Vermicompost is a type of compost made by
earthworms and microorganisms as they feed on organic wastes.

q  The compost thus produced is mainly worm
excreta and finely ground soil.

q  Organic wastes can be collected and fed on
by worms so that the end product is the broken down version of the original
organic wastes.

q  Worm castings (excreta) in the
vermicompost have nutrients that are 97% utilizable by plants.

Biofertilizers:-

q  The biofertilizers containing biological
nitrogen fixing organisms are of utmost importance in agriculture Advantages Of
Biofertilizer

                               
i)           
They
help in the establishment and growth of crop plants and trees.

                              
ii)           
They
enhance biomass production and grain yields by 10-20 percent.

                            
iii)           
They
are useful in sustainable agriculture.

                            
iv)           
They
are suitable in organic farming.

                             
v)           
They
play an important role in Agrotorestry/ Silvi- pastaural system.

TYPES OF BIOFERTILIZERS

q  Rhizobium:-Most widely used biofertilizer is
Rhizobium which colonizes the roots of specific legumes to form tumor like
growths called root nodules. These nodules act as factories of ammonia
production. The Rhizobium – legume association can fix up to 100-300 KG/N. in
one crop season.

q  Azotobacter:-Application of azotobacter has been found
to increase yield of wheat, rice, maize, pearl-millet and sorghum by 0-30 p.c.
over control. Apart from nitrogen this organism is also capable of producing
antifungal and antibacterial compounds, hormones.

               

                To acquaint the students with
manure and fertilizers, their classification and manufacturing.

Simple
fertilizer or Single nutrient (“straight”) fertilizers:-

q  These are the fertilizers which supply
only a single plant nutrient.

ü  The main nitrogen-based straight
fertilizer is ammonia or its solutions. Ammonium nitrate (NH4NO3) is
also widely used. Urea is another popular source of
nitrogen, having the advantage that it is a solid and non-explosive, unlike
ammonia and ammonium nitrate, respectively.

ü  The main straight phosphate fertilizers
are the superphosphates. “Single superphosphate” (SSP)
consists of 14–18% P2O5, again in the form of Ca(H2PO4)2,
but also phosphogypsum (CaSO4 · 2 H2O). Triple superphosphate (TSP) typically consists of 44-48%
of P2O5 and no gypsum. A mixture of single superphosphate
and triple superphosphate is called double superphosphate

Complex
fertilizer or Multinutrient fertilizers:-

q  These fertilizers are the most common.
They consist of two or more nutrient components.

q  Fertilizers such as binary
fertilizers(NP,NK,PK),NPK fertilizers,micronutrient fertilizers comes under
complex fertilizers.

1.Binary
(NP, NK, PK) fertilizers:-Major
two-component fertilizers provide both nitrogen and phosphorus to the plants.
These are called NP fertilizers. The main NP fertilizers are monoammonium phosphate(MAP) and diammonium phosphate (DAP). The active ingredient in MAP
is NH4H2PO4. The active ingredient in DAP is
(NH4)2HPO4. About 85% of MAP and DAP
fertilizers are soluble in water.

2.NPK
fertilizers:-

•      
NPK
fertilizers are three-component fertilizers providing nitrogen, phosphorus, and
potassium.

•      
The N
represents the percentage of nitrogen in the product; the P represents the
percentage of P2O5; the K represents the percentage of K2O.

 Fertilizers do not actually contain P2O5 or
K2O, but the system is a conventional shorthand for the amount of
the phosphorus (P) or potassium (K) in a fertilizer

 

3.
Micronutrients:-

•      
The
main micronutrients include sources of iron, manganese,          molybdenum, zinc, and copper.

•      
The micronutrient
needs depend on the plant. For example, sugarbeets appear to
require boron, and legumes require cobalt

Composting

Biological process in which aerobic and
anaerobic microorganism decompose organic matter and narrow down the C/N ratio
of substrate used.

Final product formed is amorphous brown to
dark brown humified material known as compost.

•      
Compost is a microbiologically
well decomposed black to brown  amorphous
organo-mineral product.

–     
More stable and well rotten
material

–     
High organic matter

–     
High proportion of major
nutrients

–     
Free from pathogens                                           

 

 

                                                                             

 

 

Phases
of composting

Mesophillic / Low active phase

Thermophillic phase

Cooling phase

Maturity / Stabilization phase

 

 

Factors affecting rate of composting

•      
Temperature

•      
pH

•      
Moisture content

•      
C/N ratio

•      
Aeration

•      
Inoculants

 

C- energy source

N- cell building

30:1 to 35:1

Addition of nitrogen source such as legume residue,
aquatic weeds, slaughter house waste and green leaves etc enhance microbial
activity and thus increase decomposition rate

FARM YARD MANURE

FYM is a mixture of the solid and liquid
excreta of farm animals along with the litter (i.e. the materials used for
bedding purposes of cattle) and left over material from roughages or the fodder
fed to the cattle.

Nutrient
Deficiency in Plants

Macronutrients

•      
Macronutrients are needed in
relatively large amounts by plants.

Element

Symbol

Source

Oxygen

O

Air/Water

Hydrogen

H

Air/Water

Carbon

C

Air/Water

Nitrogen

N

Soil

Phosphorus

P

Soil

Sulfur

S

Soil

Potassium

K

Soil

Calcium

Ca

Soil

Magnesium

Mg

Soil

 

Micronutrients

•      
Macronutrients are needed in
relatively small amounts by plants.

•      
They are usually supplied by
fertilizers.

Element

Symbol

Source

Iron

Fe

Soil

Manganese

Mn

Soil

Boron

B

Soil

Molybdenum

Mo

Soil

Copper

Cu

Soil

Zinc

Zn

Soil

Chlorine

Cl

Soil

 

Nutrient Deficiency Symptoms

•      
Nutrient deficiency symptoms usually appear on the plant when one
or more nutrients are in short supply.

•      
In many cases, deficiency may occur because an added nutrient is
not in the form the plant can use.

•      
Deficiency symptoms for specific elements are included on the
“Key to Nutrient Disorders”.

Soil
fertility- approaches to soil fertility evaluation, critical level of nutrients

•      
Soil
fertility : is concerned with the inherent capacity of soil to provide nutrients
in adequate amounts and in proper balance for the growth of specified plants
when other factors such as light, moisture, temperature and the physical
condition of the soil are favourable.

•      
 

Approaches
for soil fertility evaluation : The
wide variety of diagnostic techniques used so far can be broadly grouped into

•      
1) Soil Analysis

•      
2) Plant Analysis

•      
3) Biological methods

•      
4) Visual symptoms of nutrient deficiency
or toxicity.

Essential, functional and beneficial elements

Nutrient

A nutrient element is one that is required to complete the life
cycle of the organism and its relative deficiency produces specific deficiency
symptoms.

Beneficial Element

Beneficial elements are the mineral elements which at very low
concentrations and often under specific conditions have been shown to stimulate
growth of certain plants, but are not essential or which are essential only for
certain plant species or under specific conditions. Eg. Selenium, nickel,
cromium.

Functional Nutrient

This term is defined as an element that play a role in plant
metabolism, whether or  not its role is
specific. Eg. Na, Co, Si, V + 17
essential nutrient element

Trace Element

Trace element is an element found in low concentration, perhaps
less than 1 ppm or still less in soil, plant and water.

Essential Nutrient

Elements needed by the plant without which it will not be able to
survive are called essential nutrients.

Criteria of essentiality

For an element to be regarded as an essential nutrient, it must
satisfy the following criteria:

    as propounded by Arnon & Stout(1939):

A deficiency of an
essential nutrient element makes it impossible for the plant to complete
the vegetative or reproductive stage of its life-cycle.
The deficiency is specific
to the element and can be prevented or corrected only by supplying that
element.
3. The element is involved
directly in the nutrition of the plant, quite apart from its possible
effects in correcting some microbiological or chemical conditions of the
soil or other culture medium.

The 17 nutrient recognized essential for plant growth are:
Carbon(C) , Hydrogen (H), oxygen (O), Nitrogen(N), Phosphorous(P),
Potassium(K), Calcium(Ca), Magnesium(Mg), Sulphur (S),Iron(Fe), Manganese(Mn),
Zinc (Zn), Boron(B), Molybdenum(Mo), Chlorine(Cl) and Nickel (Ni).

Hidden hunger

It may be defined as to a
situation in which a crop requires more of a given nutrient element without
exhibiting deficiency symptoms on plants. The concentration of an element is
above the deficiency level but still considerably below that required to permit
the most profitable crop performance.

Forms of nutrient element
absorbed by the plants

Essential plant nutrients

Forms of uptake

Biochemical functions

1st group
C, H, O, N, S

CO2, HCO3, H2O, O2, NO3, NH4,
N2, SO, SO2

Major constituents of organic
material, essential elements of atomic groups which are essential in
enzymatic process, assimilation by oxidation-reduction reaction

2nd group
P, B, Si

Phosphates, boric acid or
borate, silicate from soil solution

Esterification with native
alcohol groups in plants, the phosphate esters are involved in energy
transfer.

3rd group
K, Na, Mg, Ca, Mn, Cl

K+, Na+, Mg+2, Ca+2, Mn+2,
Cl-

Non specific functions
establishing osmotic potentials, more specific reactions in which the ion
bring about optimum confirmation of an enzyme protein. Bridging of reaction
partners, balancing anions, controlling permeability and electro-potentials.

4th group
Fe, Cu, Zn, Mo

Fe+2/Fe+3, Cu+2, Zn+2,
Molybdate ion or in the form of chelates

Present predominantly in
chelated  form incorporated in
prosthetic groups, enable electron transfer by valency change.

 

Soil Health

•      
Capacity of a soil to function
within ecosystem boundaries to sustain biological productivity, maintain
environmental quality and promote plant and animal health.      

•      
In the context of agriculture,
it may refer to its ability to sustain productivity. 

•      
A healthy soil would ensure
proper retention and release of water and nutrients, promote and sustain root
growth, maintain soil biotic habitat, respond to management and resist
degradation

Food grain production and
fertilizer use

 

 

Declining Fertilizer Response

 

 

 

 

 

 

Declining Nutrient Response

 

 

 

 

 

 

 

 

 

 

Integrated Nutrient Management (INM) – Panacea
for soil health and productivity

•      
INM envisaging conjunctive use
of chemical fertilizers, organic manures and biofertilizers enhances nutrient
use efficiency, soil health, crop yields and profitability

•      
Need to augment supplies of
organic manures, fortified, coated & customized fertilizers supplying
secondary and micronutrients, biofertilizers and soil amendments to have INM on
a sound footing.

•      
Site specific nutrient
management.

 

Fertilizers Policy Measures

•      
Nutrient Based Pricing and
Subsidy :
The pricing of fertilizers and subsidy on them to be fixed as per nutrient
content and not product wise.

•      
The move to encourage use of complexes
and broaden the basket of fertilizers for balanced fertilizer use

•      
The new pricing mechanism would
reduce dependence on DAP.

•      
The SSP containing 11% sulphur
to be promoted to correct wide spread sulphur deficiency in soils besides a P
source.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Course Outcome:

•     
To acquaint the students with manure and
fertilizers, their classification and manufacturing.

•     
To provide the basic knowledge of soil
fertility and productivity, nutrient deficiency and toxicity  symptoms in plants along with remedial
measures.

•     
To acquaint the students about forms of
nutrients, their absorption mechanisms and transformation of nutrient
fertilizers after their application in soil.