1. Chaudhary Sarwan Kumar Himachal Pradesh Krishi
Vishvavidyalaya
College of agriculture

2. Principles and Practices of Organic Farming
AGRON 513, (2+1)
Course instructor:
Dr Janardan Singh
Professor (Agronomy)
Presentation by:
Akarsh S G
A-2017-030-019
I year MSc (Agronomy)

3. NUTRIENT CYCLESNUTRIENT CYCLES
IN ECOSYSTEMSIN ECOSYSTEMS

4. NUTRIENT CYCLES: ECOSYSTEM TO ECOSPHERENUTRIENT CYCLES: ECOSYSTEM TO ECOSPHERE
 Nutrient cycling occurs at the local level
through the action of the biota.
 Nutrient cycling occurs at the global level
through geological processes, such as,
atmospheric circulation, erosion and
weathering.

5. NUTRIENT CYCLESNUTRIENT CYCLES
 The atoms of earth and life are the same; they just find themselves in different places
at different times.
 Most of the calcium in your bones came from cows, who got it from corn, which took
it from rocks that were once formed in the sea.
 The path atoms take from the living (biotic) to the non-living (abiotic) world and back
again is called a biogeochemical cycle.

6. Nutrients: The Elements of LifeNutrients: The Elements of Life
 Of the 50 to 70 atoms (elements)
that are found in living things, only 15
or so account for the major portion
of living biomass.
 Only around half of these 15 have
been studied extensively as they
travel through ecosystems or
circulate on a global scale.
Na SODIUM
M nMANGANESE
Fe IRON
C lCHLORINE
P PHOSPHORUS
AlALUMINUM
S SULFUR
M gMAGNESIUM
S iSILICON
K POTASSIUM
C a CALCIUM
N NITROGEN
H HYDROGEN
C CARBON
O OXYGEN

7. A GENERALIZED MODEL OF NUTRIENT CYCLING IN ANA GENERALIZED MODEL OF NUTRIENT CYCLING IN AN
ECOSYSTEMECOSYSTEM
 The cycling of nutrients in an ecosystem are interlinked by an a
number of processes that move atoms from and through organisms
and to and from the atmosphere, soil and/or rocks, and water.
 Nutrients can flow between these compartments along a variety of
pathways.

8. A GENERALIZED MODEL OF NUTRIENT CYCLING IN AN ECOSYSTEM

9. Nutrient Compartments in a TerrestrialNutrient Compartments in a Terrestrial
EcosystemEcosystem
 The organic compartment consists of the living organisms and their detritus.
 The available-nutrient compartment consists of nutrients held to surface of
soil particles or in solution.
 The third compartment consists of nutrients held in soils or rocks that are
unavailable to living organisms.
 The fourth compartment is the air which can be found in the atmosphere or in
the ground.

10. Uptake of Inorganic Nutrients from the SoilUptake of Inorganic Nutrients from the Soil
 With the exception of CO2 and O2 which enter
though leaves, the main path of all other
nutrients is from the soil through the roots of
producers.
 Even consumers which find Ca, P, S and other
elements in the water they drink, obtain the
majority of these nutrients either directly or
indirectly from producers.

11. The Atmosphere Is a Source of InorganicThe Atmosphere Is a Source of Inorganic
NutrientsNutrients
 The atmosphere acts as a reservoir for carbon dioxide (CO2), oxygen (O2) and water
(H2O).
 These inorganic compounds can be exchanged directly with the biota through the
processes of photosynthesis and respiration.
 The most abundant gas in the atmosphere is nitrogen (N2);about 80% by volume. Its
entry into and exit from the biota is through bacteria.

12. Some Processes By Which Nutrients AreSome Processes By Which Nutrients Are
RecycledRecycled
 Cycling within an ecosystem involves a
number of processes.
 These are best considered by focusing
attention on specific nutrients.

13. CARBON, HYDROGEN AND OXYGEN CYCLES INCARBON, HYDROGEN AND OXYGEN CYCLES IN
ECOSYSTEMSECOSYSTEMS
 C, H & O basic elements of life; making up from about 98% of plant biomass.
 CO2 and O2 enter biota from the atmosphere.
 Producers convert CO2 and H2O into carbohydrates (CH2O compounds) and
release O2 from water.
 Producers, consumers and decomposers convert CH2O compounds, using O2, back
into CO2 and H2O.

14. CARBON, HYDROGEN AND OXYGEN CYCLES IN ECOSYSTEMSCARBON, HYDROGEN AND OXYGEN CYCLES IN ECOSYSTEMS
 Carbon and oxygen cycle come out of the air as carbon dioxide during photosynthesis and are
returned during respiration.
 Oxygen is produced from water during photosynthesis and combines with the hydrogen to
form water during respiration.

15. NITROGEN CYCLE IN ECOSYSTEMSNITROGEN CYCLE IN ECOSYSTEMS
 Nitrogen (N2) makes up 78% of the atmosphere.
 Most living things, however, can not use atmospheric nitrogen to make
amino-acids and other nitrogen containing compounds.
 They are dependent on nitrogen fixing bacteria to convert N2 into NH3(NH4
+
).

16. Sources of Nitrogen to the SoilSources of Nitrogen to the Soil
 Natural ecosystems receive their
soil nitrogen through biological
fixation and atmospheric deposition.
 Agricultural ecosystems receive
additional nitrogen through fertilizer
addition.

17. Biological Sources of Soil NitrogenBiological Sources of Soil Nitrogen
 Only a few species of bacteria and
cyanobacteria are capable of
nitrogen fixation.
 Some are fee-living and others form
mutualistic associations with plants.
 A few are lichens.

18. Atmospheric Sources of Soil NitrogenAtmospheric Sources of Soil Nitrogen
 Lightning was the major source of soil nitrogen
until recent times when the burning of fossil
fuels became a major source of atmospheric
deposition.
 Nitrogen oxides come from a variety of
combustion sources that use fossil fuels.
◦ In urban areas, at least half of these pollutants
come cars and other vehicles.

19. Agricultural Supplements to Soil NitrogenAgricultural Supplements to Soil Nitrogen
 Various forms of commercial
fertilizer are added to agricultural
fields to supplement the nitrogen
lost through plant harvest.
 Crop rotation with legumes such as
soybeans or alfalfa is also practiced
to supplement soil nitrogen.

20. Biological Nitrogen FixationBiological Nitrogen Fixation
 Nitrogen fixation is the largest source of
soil nitrogen in natural ecosystems.
 Free-living soil bacteria and
cyanobacteria (blue-green “algae”) are
capable of converting N2 into ammonia
(NH3) and ammonium (NH4
+
).
 Symbiotic bacteria (Rhizobium) in the
nodules of legumes and certain other
plants can also fix nitrogen.

21. NitrificationNitrification
 Several species of bacteria can
convert ammonium (NH4
+
) into
nitrites (NO2
-
).
 Other bacterial species convert
nitrites (NO2
-
) to nitrates (NO3
-
).

22. Uptake of Nitrogen by PlantsUptake of Nitrogen by Plants
 Plants can take in either ammonium (NH4
+
) or
nitrates (NO3
-
) and make amino acids or nucleic
acids.
 These molecules are the building blocks of
proteins and DNA, RNA, ATP, NADP, respectively.
 These building blocks of life are passed on to
other trophic levels through consumption and
decomposition.

23. AmmonificationAmmonification
 Decomposers convert organic
nitrogen (CHON) into ammonia
(NH3) and ammonium (NH4
+
).
 A large number of species of
bacteria and fungi are capable of
converting organic molecules
into ammonia.

24. DenitrificationDenitrification
 A broad range of bacterial species
can convert nitrites, nitrates and
nitrous oxides into molecular
nitrogen (N2).
 They do this under anaerobic
conditions as a means of obtaining
oxygen (O2).
 Thus, the recycling of N is complete.

25. NITROGEN CYCLE IN ECOSYSTEMSNITROGEN CYCLE IN ECOSYSTEMS
 Molecular nitrogen in the air can be fixed into ammonia by a few species of
prokaryotes.
 Other bacterial species convert NH4
-
into NO2
-
and others to N03
-
.
 Producers can take up NH4
-
and to N03
-
use it to make CHON.
 Decomposers use CHON and produce NH4
-
.
 Recycling is complete when still other species convert N03
-
and NO2
-
into N2.

26. PHOSPHOROUS CYCLE IN ECOSYSTEMSPHOSPHOROUS CYCLE IN ECOSYSTEMS

27.  Phosphorus, as phosphate (PO4
-3
), is an essential element of life.
 It does not cycle through atmosphere, thus enters producers through the
soil and is cycled locally through producers, consumers and
decomposers.
 Generally, small local losses by leaching are balanced by gains from the
weathering of rocks.
 Over very long time periods (geological time) phosphorus follows a
sedimentary cycle.

28. Sulphur CycleSulphur Cycle
Plants can absorb directly the sulphur containing amino acids, e.g., cystine,
cysteine, and methionine but these amino acids fulfill only a small proportion or
requirements for sulphur.
To fulfill rest of the requirements of plants, sulphur passes through a cycle of
transformation mediated by microorganisms. It accumulates in the soil mainly as
a constituent of organic compounds and has to be converted to sulphates to
become readily available to the plants.

31. Sulphate-reducing bacteria have a key role in the sulphur cycle. They use sulphate
(SO42-) as a terminal electron acceptor in the degradation of organic matter, which
results in the production of hydrogen sulphide (H2S).
 Subsequently, the sulphide can be oxidized aerobically by chemolithotrophic
sulphur-oxidizing bacteria (for example, Thiobacillus or Beggiatoa spp.) or
anaerobically by phototrophic sulphur bacteria (for example, Chlorobium spp.) to
elemental sulphur (S°) and SO42-.
Sulphur transformations.Sulphur transformations.

32. Other transformations, which are carried out by specialized groups of
microorganisms, result in
•sulphur reduction (for example, Desulfuromonas spp.) and
• sulphur disproportionation (Desulfovibrio sulfodismutans).
 Organic sulphur compounds, such as dimethylsulphoxide (DMSO) can be
transformed into dimethylsulphide (DMS) and vice versa by several groups of
microorganisms. SH, sulfhydryl.

34. The sequential pattern of microbial degradation of complex organic matter in anoxic
environments in the presence and absence of sulphate.
Macromolecules, such as proteins, polysaccharides and lipids are hydrolysed by
hydrolytic bacteria. Subsequently, the monomers — amino acids, sugars and fatty
acids — are fermented by fermentative bacteria into a range of fermentation products,
such as acetate, propionate, butyrate, lactate and hydrogen.
In the presence of sulphate (a), sulphate-reducing bacteria consume these
fermentation products.
 However, in the absence of sulphate (b), hydrogen and acetate — the acetate having
been produced directly by fermentation or indirectly by acetogenesis — are consumed
by the methanogens.

35. GLOBAL NUTRIENT CYCLESGLOBAL NUTRIENT CYCLES
 The loss of nutrients from one ecosystem means a gain for another. (Remember the
law of conservation of matter.)
 When ecosystems become linked in this manor, attention shifts to a global scale. One
is now considering the ECOSPHERE or the whole of planet earth.

36. GLOBAL WATER CYCLEGLOBAL WATER CYCLE
 Oceans contain a little less than 98% of the earth’s water.
 Around 1.8% is ice; found in the two polar ice caps and mountain glaciers.
 Only 0.5% is found in the water table and ground water.
 The atmosphere contains only 0.001% of the earth’s water, but is the major
driver of weather.

37. GLOBAL WATER CYCLEGLOBAL WATER CYCLE
 Evaporation exceeds precipitation over the oceans; thus there is a net
movement of water to the land.
 Nearly 60% of the precipitation that falls on land is either evaporated or
transpired by plants; the remainder is runoff and ground water.

38. GLOBAL WATER CYCLEGLOBAL WATER CYCLE

39. GLOBAL CARBON CYCLEGLOBAL CARBON CYCLE
 All but a small portion of the earth’s carbon (C) is tied up in
sedimentary rocks; but the portion that circulates is what sustains
life.
 The active pool of carbon is estimated to be around 40,000 gigatons.
 Of active carbon, 93.2 % found in the ocean; 3.7% in soils; 1.7% in
atmosphere; 1.4% in vegetation.

40. GLOBAL CARBON CYCLEGLOBAL CARBON CYCLE

41. GLOBAL NITROGEN CYCLE IGLOBAL NITROGEN CYCLE I
 99.4% of exchangeable N is found
in the atmosphere; 0.5% is
dissolved in the ocean; 0.04% in
detritus ; 0.006% as inorganic N
sources; 0.0004% in living biota.
 Figure 54.19 in Freeman (2005)
gives major pathways and rates of
exchange.

42. GLOBAL NITROGEN CYCLE IIGLOBAL NITROGEN CYCLE II
 Humans are adding large amounts of N to ecosystems.
 Among the fossil fuel sources, power plants and automobiles are important
sources of atmospheric nitrogen deposition in the US.
 Investigations of native plant and natural ecosystem responses to nitrogen
deposition and global warming will be a focus of study.
 E.g. invasive species tend to be more devastating to ecosystems with high soil
nitrogen content

43. Reference :Reference :
 FUNDEMENTALS OF SOIL SCIENCE, Indian society of soil science ,revised edition
February 2012.
 THE USE OF NUTRIENTS IN CROPS PLANTS, N.K Fageria,CRC Press ,Taylor & francis
group.
 TEXT BOOK OF PLANT NUTRIENT MANAGEMENT, Indian society of Agronomy, New Delhi.
First edition Nov 2014
 Ghaly AE, Ramakrishnan VV (2015) Nitrogen Sources and Cycling in the Ecosystem and
its Role in Air, Water and Soil Pollution: A Critical Review. Journal of Pollution Effects &
Control Cont 3(2): 136. doi:10.4172/2375-4397.1000136
 F.H Bormann and G.E Likens (1967) Nutrient cycling, science ,vol 155
 B. Mukherjee , D. Mukherjee, M. Nivedita (2008) Modelling carbon and nutrient cycling∗
in a simulated pond system at Ranchi ecological modeling 437-448
 Patrick Lavelle, Richard Dugdale, Robert Scholes, Ecosystems and Human Well-being:
Current State and Trends 333-351
 Muyzer G, Stams AJM (2008) The ecology and biotechnology of sulphate-reducing
bacteria. Nature Review, Microbiology 6: 441-454