1. Name : Bisma shakeel
Roll number : 610
Gomal university Dikhan
Nitrogen fertilizers and their fate in soil
2. Fertilizer
Material of natural or synthetic origin added to the soil
to supply one or more plant nutrient
Fertilizers which supply N to plants in available form is
called N fertilizers.
There are four types of nitrogen fertilizers
1.nitrate,
2.ammoniacal,
3.both nitrogen and ammoniacal
4.amide.
4. Fate of N fertilizers in soil
Applied N
Unused by
plants
Microbes
Immobilization
Atmosphere
Ammonia
volatilization Denitrification
Ground water
Leaching
Used by
plants
5. Immobilization
Applied N is used by microbes in the need for their
growth.
However this will be mineralized and available to
plants sooner or later.
When N uptake is low.
6. Ammonia volatilization
NH4 ⁺ + OH⁻ → NH3 + H2O
when pH of soil is high
calcareous soils
losses can be high when high-N
organic wastes, such as manure, are
permitted to decompose on the soil
surface;
is greater in soils of low CEC, such as
sands
7. Denitrification
anaerobic soil conditions
presence of denitrifying bacteria (Thiobacillus
denitrificans, Micrococcus denitrificans)
presence of high carbon compounds
Loss of N in the form of N2 gas, nitrous oxide
(N2O), nitric oxide (NO), or one of the other gaseous
nitrogen oxide (NOx) compounds
8. Leaching
Loss of N especially Nitrate loss is high by
leaching.
Leaching is taken away of N by ground water
or run off or erosion.
erosion of surface soil having nutrients also
causes nutrient losses.
9. Biological N Fixation
Fixing the atmospheric N as ammonia (NH3) form of N
and then into amino acids and other
nitrogenous compounds that are nutritionally
useful to the chlorophyll-containing organism.
N2 + 8H+ + 8e- + 16 ATP 2NH3 + H2 + 16ADP + 16 Pi
nitrogenase
10.
11. Types of BNF and BNF organisms
Free living organisms
associative N fixing organisms
Symbiotic
Free living Symbiotic with plants
Aerobic Anaerobic Legumes Other plants
Azotobacter Beijerinckia
Klebsiella (some)
cyanobacteria (some)*
Clostridium (some)
Desulfovibrio
Purple sulphur bacteria
Purple non-sulphur
bacteria*
Green sulphur bacteria*
Rhizobium Frankia Azospirillum
12. Factors affecting N fixation
Temperature
each plant and soil condition have optimum
temperature for better function of microbes
most of the conditions optimum temperature
lies
between 30 – 40 degree celcius
Soil pH stress
Rhizobium nodules does not fix N or
their fix in
lower rates in Acid conditions.
13. Soil water stress
nodule formation is poor in conditions when there is
low water available.
reduction
condition
Soil nutrients
of microbial population in dry
The nutrients Co, Mo, P, Fe, B, and Zn
are considered to be directly involved in symbiotic
N2- fixation
Correcting deficiency of nutrients such as
calcium (Ca), cobalt (Co), copper (Cu), Mo, P, and
Zn has been shown to increase N2-fixation
14. Nitrogen use efficiency
Nitrogen use efficiency (NUE) is the fraction of
applied nitrogen that is absorbed and used by the
plant.
Improving NUE is important for improving crop yield
N uptake by plant in fertilized plot – N uptake in no fertilizer plot
100
N applied
15. Management Practices to Improve Crop
Nitrogen Use Efficiency
Nitrogen Application Rates
applying recommended rates split application of N
fertilizers applying based on soil analysis
Timing of Nitrogen Applications
Apply N fertilizers at crop uptake growth stages, it will
reduce loss of N.
16. Nitrogen Application Methods
Banding or dribbling liquid nitrogen fertilizer on the
surface rather than broadcasting or spraying it over
the surface can significantly reduce ammonia
volatilization from the N fertilizer.
Use of a urease inhibitor (enhanced efficiency
fertilizer) minimizes the volatilization loss of N from
urea fertilizer applied on the surface with no or
delayed incorporation.
Incorporate manure where practical.
Immediately incorporate urea-containing
nitrogen fertilizers
17. Spatial Variation
Differences in soils, production history, soil
management techniques, movement of water and
nutrients that imposing spatial variability
Topography is an important factor explaining spatial
variation in grain yield. Topography and slope
helped to explain 30% and 85% variability in the
yield of corn and soybean.
higher N fertility levels have been observed in
foot slopes and depressions due to the flow of
water and soil deposition of clay and organic matter
18. Nitrogen Management Using Site-Specific
Technologies
Remote sensors include ground-based active
optical sensors, satellites imagery, aerial imagery
or photography, ground-based reflective sensors
and leaf chlorophyll sensors.
Remote sensing techniques are now utilized to
determine the spatial crop N status in-season.
These technologies successfully used to measure
spatial variability in crop canopies.
