2. Fertilizer use efficiency
• When a fertilizer is applied all of its nutrient(s) are not absorbed
by the crop. Only a fraction of the nutrient(s) is utilized by the
crop.
• Fertilizer use efficiency is the output of any crop per unit of the
nutrient applied under a specified set of soil and climatic
conditions.
3. FERTILIZER USE EFFICIENCY
• Based on the nutrient supplying power of soils as
determined by soil test values, fertilizer
recommendations are made.
• The aim is to get maximum economic yield with
minimum inputs.
• Of the various inputs fertilizer is the costly input.
This costly input must be efficiently used and
utilized.
4. Fertilizers are considered as efficient when maximum yield is
obtained with minimum possible amount of fertilizer application.
• It is indeed difficult to quantify the efficiency of a particular
fertilizer since it depends on:
1. Losses due to leaching
2. Losses in gaseous forms
3. immobilization by chemical precipitation, adsorption on
exchange complex and microbial cells.
4. chemical reactions between various components in fertilizers
during mixing, before application to soil.
5. physical properties of soil
6. chemical properties of soil
7. Fertilizer characteristics.
5. 1. Leaching losses:
• Nitrate fertilizers are easily lost in leaching.
• The extent of leaching is more in sandy soil than in clayey soils.
• The loss is more in bare soil than cropped soil.
• The losses can be reduced to and extent by suitable method and timing of
application.
• Losses in leaching also occur when ammoniacal calcium cyanamide and urea
fertilizers are applied to soils.
• In extreme acid soils or sandy acidic soils, ammonium fertilizer are lost because
ammonium ions cannot easily replace the aluminium ions in exchange sites.
• When urea mixed with neem seed crush is applied to paddy soil, the efficiency of
urea is more.
6. 1. Leaching losses: contd
• During summer losses from the ammoniacal, calcium cyanamide and
urea are more because they are rapidly oxidized by nitrifying
organisms.
• The activity of nitrifying organism is reduced and thereby the leaching
loss is minimized.
• There are also some chemical compounds when applied with nitrogen
fertilizers inhibits the nitrifying organisms and reduces the leaching
loss.
Examples:
• N- Serve (2–chloro–6–trichloromethyl pyridine) @ 0.15 – 0.5 kg/ha
• AM (2–Amino-4-chloro-6-methyl pyridine) @ 0.3 – 0.4% (of applied
fertilizer)
• Thiourea @ 1.5 – 2.5% (of applied fertilizer)
7. 1. Leaching losses: contd
Loss of potassic fertilizer:
• Applied potassic fertilizers are easily lost in drainage water in
sandy soils and acid soils. However in clayey soils there is no
appreciable loss.
• The loss can be minimized by adjusting the time of application to
synchronise with maximum plant uptake period and also
applying the fertilizer in 2 or more split doses.
• There are some slow release potassic fertilizers which are not
subjected to leaching losses easily.
E.g. potash frits, potassium metaphosphate and fused potassium
phosphate.,
Practically no leaching loss occurs from phosphatic fertilizers
8. 2. Gaseous losses due to Volatilization:
• The nitrogen compounds present in the fertilizer are
lost as gases under certain soil condition.
• The following kinds of gaseous losses are noted.
1. Loss as ammonia under high pH conditions i.e. under
alkaline conditions.
2. Loss as N₂, N₂O, NO due to denitrification.
The above losses are determined by soil pH, fresh organic
matter, moisture, temperature and type of
microorganisms present in soil.
9. Volatilization can be controlled by
• Proper placement of urea.
• As far as possible ammonium fertilizer should be
avoided.
• If there is no alternative to ammonium fertilizers,
the fertilizer should be placed at least 4-6 below
the surface.
• Urea should be used instead of ammonium and
nitrate fertilizer.
10. 3. Immobilization of fertilizer
nutrients :
• Nutrient elements may be immobilized or fixed
or converted into unavailable forms by one or
more of the following three means:
1. chemical immobilization
2. physicochemical immobilization
3. microbiological immobilization
11. 3. Immobilization of fertilizer
nutrients : contd
• In acid soils, the efficiency of water soluble phosphorus is very low. The water soluble
phosphorus is immediately converted into insoluble phosphorus compounds. In such
soils insoluble phosphatic fertilizer like rock phosphates should be utilised. Further a
thorough mixing of the phosphorus with soil increases the efficiency of the fertilizers.
• In calcareous soils applied phosphatic fertilizers invariably converted in to tricalcium
phosphate – a compound from which phosphorus is not easily available. Under such
conditions water soluble phosphorus are relatively more efficient than water insoluble P
like rock phosphate.
• Microbiological fixation of fertilizer N may be a serious problem when un-decomposed
organic materials of high C/N ratio is present in the soil. This type of immobilization is
of short duration only. It can be overcome by application of larger quantities of water
soluble N fertilizers or by allowing enough time for complete decomposition of
undecomposed organic matter.
12. 4. Interaction between different
fertilizers :
• It is often a common practice to mix fertilizers containing different nutrient carriers,
just prior to application.
• The efficiency of the following fertilizers will be lowered if mixed with the fertilizer or
amendment noted against them.
Ammonium sulphate - Basic slag
Ammonium sulphate - Calcium carbonate
Super phosphate - Basic slag
Ammonium phosphate - Basic slag
Ammonium phosphate - Calcium carbonate
Super phosphate - Calcium carbonate
Urea can be mixed with all fertilizers. Other fertilizers can be mixed just before use.
13. 5. Soil physical properties:
Soil compaction reduces the fertiliser efficiency.
Soil temperature affects the fertilizers efficiency by
changing solubility of fertilizers, concentration of
solubilized fertilizer cation exchange and also the ability
of the plants to absorb and use nutrients.
To an extent the soil temperature is modified by
common management practices like tillage, mulching
and irrigation.
14. Influence of soil temperature on Nitrogen:
• Variation in temperature causes differential response to
crop uptake, of NH4⁺ and NO3⁻⁻ - N fertilizers.
• Below 13°C the uptake of N from NH4 or NO3
fertilizers is almost nil.
• Maximum uptake of N by plants from NO3 and NH4
fertilizers is observed in the range of 19° - 24°C.
• The influence of temperature on the efficiency of
fertilizer is dependent on soil moisture.
15. Influence of soil temperature on
Phosphorus & Potassium :
• Phosphorus:
The efficiency of phosphatic fertilizers increases significantly with
the increase in soil temperature from 10-35° C as evidenced by
increased P uptake by many plants with increase in temperature.
• Potassium:
The effect of soil temperature on the uptake of K ions both from
soil potassium and fertilizer potassium is controversial. However, at
low doses of K fertilizers, there is possibility of increased uptake of
K by plants with increase in soil temperature up to 24 – 28°C.
16. Soil moisture:
One of the most singled out problem in agriculture is the
lack and excess of moisture.
Efficient water management is complementary to efficient
fertilizer management.
Maximum efficiency of fertilizers can be obtained only in
the presence of adequate soil moisture and vice versa.
Excessive moisture leads to leaching loss of added
fertilizers whereas lack of moisture results in poor
availability of the added fertilizer and high osmotic pressure
of soil solution due to concentration of fertilizers soils.
17. 6. Soil Chemical properties:
• Plant nutrient availability depends on the prevailing pH
of soil.
• In strongly acidic and alkali soils the efficiency of
phosphatic fertilizer is low.
• In such situations, efficiency of fertilizers can be
increased by correcting the soil condition, using suitable
amendments.
• Physiologically alkaline fertilizers like calcium
cyanamide basic slag etc. should receive priority on acid
soils and physiologically acid fertilizers like ammonium
sulphate etc. on alkaline soils.
18. 7. Plant characteristics:
• Different crops remove varied amount of plant nutrients from soils.
• There is also appreciable variation within varieties of same plants, between
dicots and monocots etc.
• Since the roots are the principal organs through which plants take up
nutrients, the rooting pattern and habit have an important bearing on the
nutrient removal.
• Plants which develop a vigorous deep-root system during their early stages of
growth require a large quantity of fertilizer as basal dressing.
• The fertilizer needs of deep rooted crops are generally lower than shallow
rooted crops.
19. 8. Fertilizer characteristics:
• The mobility of the fertilizer nutrients in the fertilizer, the
type of fertilizer and the time and mode of application
decide the efficiency of a fertilizer.
• The nitrogenous fertilizer are highly mobile and subjected
both downward and sideward mobility.
• Phosphorus is highly immobile.
• Potassium is also mobile but compared to nitrogen its
mobility is lower.
• To get maximum efficiency N and K fertilizer should be
applied in frequent split doses and phosphorus as basal
dressing or near the root zone.
20. Type of fertilizer also decide the efficiency:
• Ammonium and Urea fertilizer are more efficient for
paddy under different Indian conditions than nitrate
fertilizers.
• Water soluble phosphorus materials are more efficient
for short duration crops and in soils which are neutral to
alkaline is reaction.
• There is also a certain amount of interaction noticed
among crops and fertilizers. For example paddy
performs better when ammonium sulphate is applied as
N carrier and tobacco when potassium sulphate is
applied as potassium carrier.
21. To get maximum benefit from fertilizer we
should follow the following practical points: 4R
concept
1. Right type of fertilizers with favourable chemical and
physical properties.
2. Right Time of fertilizers application (time of
application should synchronise with the rapid crop
uptake period and there should be only a minimum time
for soil fertilizer interaction)
3. Right Dose of fertilizers based on the nutrient
supplying power of soils and crop need.
4. Right method of application.
22. Certain practical approaches to
increase efficiency of fertilizers:
1. High yielding varieties of crops give higher yields than local varieties without
fertilization as well as a higher unit response to fertilizer even at the lower rate of
application. Therefore wherever possible, high yielding varieties should be
grown.
2. Optimum plant spacing and maintenance of optimum plant population are
essential to get maximum benefit from the applied fertilizers.
3. Ensure effective organic matter recycling, in order to maintain fertility and
productivity. Response for a nutrient is generally higher in soils supplied with
adequate amount of organic matter.
4. While applying organic manures having high C:N ratio ensure that adequate
amount of nitrogenous fertilizers are applied to soils to compensate biological
locking up of N in microorganisms.
23. Certain practical approaches to
increase efficiency of fertilizers:
5. Include a legume either in rotational sequence or as a
intercrop. Legumes besides fixing atmospheric N, transform
non-available native phosphorus and precipitated or fixed
fertilizer P into available forms.
6. Excessive irrigation should be avoided as it results in the
loss of N and K fertilizers. Further, there is also gaseous loss of
N under waterlogged condition. There should not be excess
water in the soil particularly at the time of fertilizer
application. Fertilizer application should be made after
draining the excess water.
24. Certain practical approaches to
increase efficiency of fertilizers:
7. Crop response to phosphatic fertilizers is generally more in dry seasons.
8. Balanced fertilization should be practiced based on the soil test values. Efficiency of a
straight fertilizer containing nutrient) depends on the sufficiency of other nutrient in the
soil.
9. The phosphates in general are more efficient when the entire dose applied as basal
dressing, potash entire quantity as basal dressing or part as basal and rest in split doses
depending on the soil texture and the nitrogen in 2-3 (or 4) split doses.
10. Water soluble phosphatic fertilizers should be placed 4-6 cm below the soil and 4-6 cm
away from the seeds to ensure maximum availability to plants. Insoluble fertilizers should
be thoroughly mixed in soil.
11. Sometimes it is better to cure the urea by mixing the urea with 5-10 parts of soil
thoroughly and keeping the mixture for overnight. This enhances the conversion rate of
urea into ammonia carbonate.
25. Certain practical approaches to
increase efficiency of fertilizers:
12. Efficiency of the N fertilizer can be increased by mixing the fertilizer
with crushed neem seed (5:1 parts).
13. Foliar application of fertilizers should be resorted to under certain soil
conditions and climatic conditions.
14. Zinc deficiency is becoming more and more widespread day by day.
In such cases application of zinc sulphate at the rate of 10-25 kg of zinc
sulphate as basal dressing, not only corrects the zinc deficiency but also
enhances generally the efficiency of the other applied fertilizers.
15. Adverse soil condition should be corrected by using appropriate
amendments, to get maximum benefit from fertilizer.
16. Absence of weeds, pest and diseases ensures the efficiency of fertilizer.
