Mineral nutrition and Fertilizer use of Cashew

2. The essential elements
• As with other plant species, Cashew requires 12 nutrient elements
for growth in addition to carbon (C), oxygen (0) and hydrogen (H).
• Plants cannot grow without a supply of these elements, and they
have thus become known as essential elements or nutrient
elements.
• To be considered an essential element, a particular element must
meet the following criteria:
• A deficiency of the element makes it impossible for the plant
to complete its life cycle
• A deficiency of specific for the element in question
• The element is directly involved in the nutrition of the plant.

3. • The essential elements, other than C, O and H, have been divided into
macronutrients (major nutrients) and micronutrients (trace elements)
because of the quantities that plants require.
Macronutrients
Iron(Fe)
Manganese (Mn)
Zinc(Zn)
Copper (Cu)
Boron(B)
Molybdenum(Mo)
Micronutrients
Nitrogen (N)
Potassium (K)
Phosphorus (P)
Calcium(Ca)
Magnesium(Mg)
Sulphur(S)

4. • In addition, some essential elements may reach levels that are delete to
plant growth.
• Examples include Mn toxicity in acid soils waterlogged soils (Labanauskas.
1966); B toxicity in alkaline soils through the application of irrigation water
high in B or the over application of B; and Cu and Zn toxicities, through the
excessive use of fertilizers containing these elements.
• Additionally, the application of one nutrient may reduce the absorption of
another nutrient to such an extent that a deficiency results.

5. Role of Nutrients
a. Nitrogen
• Nitrogen is an essential nutrient for plants.
• It is major constituent in many important compounds such as
proteins, nucleic acids, alkaloids and enzymes such as amino acids,
proteins, alkaloids and enzymes, and it seems, it forms a constituent
of every living cell in the plants.
• It also present in chlorophyll, through which the plants assimilate
carbon from atmospheric carbon dioxide and entrap solar energy.
• The air contains 78% nitrogen.
• Plants cannot use it directly.

6. Visual symptoms of deficient supply of nitrogen
• Nitrogen deficiency is very common and can easily be noticed during
harsh conditions.
• The usual symptoms are restricted growth in shoots and roots, small
size and yellowish green colour of the leaves in the early stages
• The symptoms are more obvious in the older foliage: this is due to the
mobility of nitrogen to the growing parts of plants.

7. • Premature defoliation of the older leaves, dormancy of buds and
of the growth of the plant, are also may occur as the deficiency
becomes acute
• When nitrogen containing fertilizers are applied as remedial
measures the responses are immediate and most pronounced
effect.
• Light sandy Soil of the coastal region where cashew is mostly
grown, is lacking in organic matter and the poorest in nitrogen
content.

8. Experimental evidence on N
The experiments conducted in India clearly indicated that nitrogen
content of shoot showed highly, significant positive correlation with
girth and height of seedlings.
It also showed that at low nitrogen level, the 2 year old cashew
seedlings were characterized with general yellowing of the older leaves
and soon spread to younger ones.
The leaves were also smaller than those of other plant (Mandal, 1997).

9. • It is also stated that lack of nitrogen of cashew seedlings became
visible 7 weeks after planting.
• Colour of the leaves changed gradually from dark to pale green and to
yellow, coincided with stunted growth and ultimately the seedlings
died after 4 months in case of severe nitrogen deficiency (Ohler 1979)

10. • Research conducted in India indicated that urea foliar sprays could be
used successfully on mature cashew at the time of new flush, flowering
and fruiting stages.
• The maximum absorption of sprayed nutrients occurs during the
young stages of the leaf when the leaf blade appears as brown- green
(Mandal, 1997).
• It is reported from Madagascar that during the vegetative stage of
cashew, nitrogen and phosphate were most important elements, but
later nitrogen in combination with potash become significant
(Mandal, 1997).

11. Phosphorus (P)
• Phosphorus is an essential component of every cell as a
structural component of membrane system of cell, the
chloroplast and the mitochondria.
• It also takes active pare in all type of metabolism of plants.
Several phosphate groups could be linked together by pyro-
phosphate Adenosine Tri Phosphate (ATP) is an important
compound of this complex found in plants.
• The pyrophosphate bond is very rich in energy complex
found during the hydrolysis of this bond 7600 cal/mol is
released.

12. • Formation and break-down of these bonds are seen during the
processes of photosynthesis and respiration.
• Phosphates also act as buffers in maintaining satisfactory
conditions of acidity and alkalinity in cells. Phosphorus is also
necessary for seed germination, metabolism, ripening of fruits,
fermentation, and the efficient utilization of nitrogen.

13. Symptoms under deficient supply of phosphorus
• Like most of other perennial crops, visual symptoms of phosphorus
deficiency are not very common in cashew plantations.
• Therefore it is always advisable to diagnose this deficiency by leaf
analysis.
• However it was observed that root and shoot growth was restricted
and plants become thin and spindly with no P in sandy soils.

14. c. Potassium (K)
• Unlike other macro-elements, potassium does not enter in to the
composition of any important constituents such as proteins,
chlorophyll, or carbohydrates.
• But it acts as traffic controller, root booster, food former, stalk
strengthener, sugar and starch transporter, protein builder, breathing
regulator, water stretcher and as disease retarder.

15. • Potassium is very mobile in plants and almost in all plants
potassium is present soluble forms.
• This element is involved in many important functions as control
of osmotic pressure, opening and closing of stomata,
photosynthesis, and translocation of assimilates and enzyme
activation.

16. Symptoms under deficient supply of potassium
• The growth of potassium deficient plants is rather slow.
• The older leaves develop chlorosis i.e. yellowing of leaves and leaf
scorch start from tips or margins of lower leaves.
• In older trees, leaves exposed to sun light show clear symptoms
of the deficiency.

17. Experimental evidence on K
• Potassium deficiency symptoms may develop in cashew
seedlings within 2 months.
• Lowest leaves turn yellow, starting at apex and along margins.
showing necrosis.
• Symptoms spread rapidly from lower part of leaf towards the
top (Ohler, 1979).

18. • While potassium is applied to grown up cashew trees, the K
content of leaves was at its peak at 14 days after application
(Harishu Kumar and Nagabhushanam, 1979).
• They observed that cashew responded only up to
150g/tree/year and potassium deficiency occurs mostly on light
sandy soil, while poor drainage decreases K absorption

19. d. Calcium (Ca)
• Calcium as calcium pectate is an important constituent of cell wall
and required in large amounts for cell division.
• It is a structural component of chromosomes.
• Excessive amounts of calcium can decrease the availability of many
micro nutrients.

20. • Since it is a phloem-immobile nutrient the first symptoms appear in
the growing points of the plant.
• Once it is supplied externally, the new shoot and root growth
would become normal and would reappear with lack of external
supply.

21. Symptom under deficient supply of calcium
• The normal growth of plant is arrested as the young of leaves of
terminal buds die back at the tips and margins. Root may become
short, stubby and brown.

22. Experimental evidence on Ca
• Kamal et al. (1979) reported that in Malaysia, application of lime
(5t/ha) and phosphorus (70 kg P20/ha) increased the pH of sandy
soil and the N and P content of the young leaves of cashew plants.
• They also found that lime application did improve the K content of
young leaves.

23. e. Magnesium (Mg)
• Magnesium is an essential constituent of chlorophyll.
• Several photosynthetic enzymes present in chlorophyll, requires
magnesium as an activator.
• It is usually needed by plants in relatively small quantities.
• Hence, its deficiency in soil is experienced later than that of
potassium.

24. Symptoms under deficient supply of magnesium
• Deficiency symptoms are initially seen in the older leaves and then
progress onto young leaves.
• A common symptom is interveinal necrosis, or the golden yellow
colouration of the edges and the interveinal areas of the leaf blade.
• Thus the veins blade.
• Thus the veins are seen as a green herring bone. This disorder could
be remedied by applying correct fertilizer mixtures and recovery is
quick

25. Experimental evidence on K
• Potassium deficiency symptoms may develop in cashew
seedlings within 2 months.
• Lowest leaves turn yellow, starting at apex and along
margins. showing necrosis.
• Symptoms spread rapidly from lower part of leaf towards
the top (Ohler, 1979).

26. • While potassium is applied to grown up cashew trees, the K content
of leaves was at its peak at 14 days after application (Harishu Kumar
and Nagabhushanam, 1979).
• They observed that cashew responded only up to 150g/tree/year
and potassium deficiency occurs mostly on light sandy soil, while
poor drainage decreases K absorption

27. d. Calcium (Ca)
• Calcium as calcium pectate is an important constituent of cell wall
and required in large amounts for cell division.
• It is a structural component of chromosomes.
• Excessive amounts of calcium can decrease the availability of many
micro nutrients.
• Since it is a phloem-immobile nutrient the first symptoms appear in
the growing points of the plant.
• Once it is supplied externally, the new shoot and root growth would
become normal and would reappear with lack of external supply.

28. Symptom under deficient supply of calcium
• The normal growth of plant is arrested as the young of leaves of
terminal buds die back at the tips and margins. Root may become
short, stubby and brown.
Experimental evidence on Ca
• Kamal et al. (1979) reported that in Malaysia, application of lime
(5t/ha) and phosphorus (70 kg P20/ha) increased the pH of sandy soil
and the N and P content of the young leaves of cashew plants.
• They also found that lime application did improve the K content of
young leaves.

29. e. Magnesium (Mg)
• Magnesium is an essential constituent of chlorophyll.
• Several photosynthetic enzymes present in chlorophyll,
requires magnesium as an activator.
• It is usually needed by plants in relatively small quantities.
Hence, its deficiency in soil is experienced later than that of
potassium.

30. Symptoms under deficient supply of magnesium
• Deficiency symptoms are initially seen in the older leaves and
then progress onto young leaves.
• A common symptom is interveinal necrosis, or the golden yellow
colouration of the edges and the interveinal areas of the leaf
blade.
• Thus the veins blade.
• Thus the veins are seen as a green herring bone.
• This disorder could be remedied by applying correct fertilizer
mixtures and recovery is quick

31. Experimental evidence on Mg
• Ohler (1979) stated that the above symptoms of Mg deficiency on
cashew seedling could be observed within 30 days and the deficient
seedling may die within 75 days.
• Harishu Kumar (1978) reported that magnesium deficiency combined
with manganese-iron toxicity resulted in deficiency toxicity syndrome in
acid-soil complex where yellow leaf spot symptoms of adult cashew
trees are mostly observed.

32. f. Sulphur (S)
• Sulphur exists in two important essential amino acids methionine and
cystenine, which are also component of protein.
• It has specified role in initiating synthesis of protein.
• It is an essential constituent of many proteins enzyme.
• It is also found in some vitamin molecules and in Coenzyme A.

33. Symptoms under deficient supply of sulphur
• Hunger signs of sulphur in many ways resemble those due to nitrogen
deficiency.
• But sulphur deficiency is most pronounced in young tissues whereas
nitrogen deficiency is most evident in older parts of the plant.
• This could be accounted for by the differences in mobility of S
compounds.

34. g. Manganese (Mn)
• Mn is an essential constituent of chlorophyll and act as a catalyst in
enzyme system involving in oxidation-reduction reactions.
• Mn takes part in oxidation-reduction processes and decarboxylation
and hydrolysis reactions in the formation of oil and fats.

35. Symptoms under deficient supply of manganese
• Interveinal chlorosis first develop in younger leaves.
• The veins usually remain green and the pale yellow appear in
between veins.
• This is quite similar to that magnesium deficiency but first appear in
younger leaves.

36. Symptoms under abundant supply of manganese
• The manganese toxicity symptoms are necrotic mottling and
necrotic lesions on leaves, mainly along the veins.
• The necrotic spots enlarge as the leaves mature and the leaves
coupled with brown spotting of margins along with mottled
bands

37. h. Copper (Cu)
• Copper helps in the utilization of iron during chlorophyll synthesis.
• Act as electron carrier in enzymes.
Symptoms under deficient supply of copper
• Chlorosis first develop in young leaves resulting in the Die back
terminal point.

38. Boron (B)
• Boron involes in many matabolic activities as it regulates
carbohydrate metabolism, translocation of sugars, root development
and synthesis of amino acid and proteins.
• Pollen formation and in development and differentiation of important
tissues.

39. Symptoms under deficient supply of boron
• Boron deficient plants fail to expand young leaves which are
distorted and remain rolled and the growing points die.
• It causes barren plants and poor seed development due to
sterility and malformation of reproductive organs.

40. Experimental evidence on B
• Boron deficiency has caused 'gumming' in a nut crop like Almond.
• It is suspected that "gummosis in cashew might be due to boron
deficiency.
• It is reported that 10 to 15 kg Borax/ha will provide adequate boron
to balance the nutrient status of boron deficient cashew plants
(Mandal, 1997).

41. j. Zine (Zn)
• Zinc is a constituent of enzymes which involve in activities of
dehydrogenase enzymes.
• It also influence the formation of some growth hormones such as
Auxin in the plants and associated with water uptake.
Symptoms under deficient supply of zinc
• Chlorosis first develop in young leaves and the leaf blade turn pale in
acute deficiency.
• Shortening of internodes and delay in flowering, fruit setting would
also result due to lack of Zine supply.

42. Experimental evidence on Zn
• Ohler (1979) reported that, in Zn-deficient soils, the leaves of
cashew about 2.5 months old, change to, pale-yellowish green with
reddish brown pigmentation and become small and narrow in size.

43. k. Iron (Fe)
• Iron is an important constituent in the synthesis of chlorophyll and
helps he absorption of other nutrients.
• It is a structural component of chromes, heamin, ferrichrome and
leghemoglobin which involve in oxidation-reduction in respiration and
photosynthesis.
• As a constituent of enzymes like cytocrome oxidase, catalase,
peroxidase, nitrogenase, Iron helps in carrying out enzymatic
reactions in plants.

44. Symptoms under deficient supply of Iron
• Deficiency symptoms first develop as chlorosis in younger leaves.
• The veins usually remain green and the pale yellow appear in
between veins with acute deficiency the whole leaf blade
becomes pale yellow colour.
• Leaves become dry and papery and fall.

45. Molybdenum (Mo)
• Molybdenum is an essential component of two enzymes in plants,
nitrogenase and nitrate reductase.
• Mo is important in nitrogen transformation and it is a structure and it
is a structural component of nitrogenase and also plays an essential
role in iron absorption and translocation in plants,

46. Symptoms under deficient supply of molybdenum
• With Mo deficiency, leaves become yellow and leaf margins
roll in Leaves are often small and covered by necrotic spots.
• With extrema deficiency, the leaf lamina is not formed and
probably only the midrih present (Mengel and Kirkby, 1987).
This appearance may vary with the plant species.

47. Diagnosis of nutritional disorders
a. Visible symptoms
• Nutrient deficiencies and toxicities often produce characteristic
visible symptoms on leaves, stems, roots or fruits, which can be
used in the diagnosis of nutritional disorders in the field.
• The use of visible symptoms has the advantage on direct field
application as it is not dependent on costly laboratory equipment
or time-consuming chemical analysis.
• Unfortunately once symptoms become visible, considerable crop
loss may have already occurred.

48. • Additionally, some disorders produce rather similar symptoms or
no symptoms at all, and the effects of insect pests and diseases
may produce symptoms similar to those of nutritional disorders.
• To complicate the situation even further, plants may suffer even
multiple nutrition disorders producing complex symptoms and the
application of one nutrient to overcome a deficiency may result in
another nutrient becoming deficient.
• Thus, confirmation visible symptoms requires experience; and in
any event should be seen a first step in diagnosis to be confirmed
by soil or tissue analysis.

49. • In addition to the appearance of a particular symptom, the position
or location of that symptom must be noted (Asher er at., 1980).
• Nutrients are absorbed by the root system, and distributed among
various plant parts.
• Some of these nutrients may be redistributed to younger parts the
plant during times of shortage either readily, more slowly, or hardly at
all.
• Thus, when a deficiency of N, P, K or Mg occurs, plant tend to
withdraw these elements from the older leaves and redistribute them
to the growing parts where they are needed most (Robinson and
Snowball, 1986).

50. • These elements redistributed via phloem.
• Hence, the first and foremost the deficiency symptoms of the phloem-
mobile elements generally occur on older leaves.
• Certain elements which come under hardly mobile group in the plant
such as Ca, Fe, Mn and B are not redistributed and are referred as
phloem-immobile elements (Robinson and Snowball, 1986).
• The first symptoms of deficiency of phloem- immobile elements occur
on the actively growing parts of the plant.
• When a deficiency occurs with these types of elements, the plant
must have continuous external supply of particular element for the
growth and maintenance.

51. • The nutrient elements S. Zn, Cu and Mo often have variable mobility
in the phloem.
• Under some conditions, they appear to be phloem-mobile while
under another condition they behave as phloem-immobile elements
(Robinson and Snowball, 1986).
• Hence, for these elements, symptoms may appear on young or older
depending on the plant species or other factors such as moisture
supply, temperature and light, which may affect the appearance and
severity of nutrient disorders.

52. • Elements in excess amounts continue to be accumulated in the
leaves.
• Thus, there will be a tendency for toxicity symptoms to appear
first on the older leaves where accumulation has been occurring
for the longest time.
• In spite of the difficulties and the need for caution, visible
symptoms of nutrient deficiencies and toxicities remain an
important tool in the diagnosis of nutritional disorders.

53. b. Plant Tissue analysis
• Tissue analysis is also an important technique in the diagnosis of
nutritional disorders.
• In perennial crops like cashew, coconut and rubber plant tissue
analysis is often used in both trouble shooting and in the
recommendation of fertilizer rates.
• The method of tissue analysis is based on an established relationship
between crop yield and nutrient concentration in plant tissue.

54. • Critical concentrations for deficiency and toxicity have been defined
as those concentrations associated with 90% of maximum yield
(Ulrich and Hills, 1973).
• Between these concentrations is a range of concentrations required
for healthy growth.

55. • The relationship between crop yield and nutrient concentrations in
plant tissue may be determined by means of solution culture
experiments (Asher and Edwards, 1983), glasshouse pot experiments,
and field experiments.
• Generally, field experiments are considered the best method (Bates,
1971), but are considerably more expensive than solution culture and
pol experiments.
• They also depend on the availability of sites at which each of the
problems to be studied is well developed.
• A certain part of the plant rather than the whole plant is usually
selected for analysis, leaves being considered the most satisfactory
parts (Bates, 1971).

56. • Since leaves may continue to accumulate some nutrients with
increasing age, it is important that nutrient concentrations in
leaves of the same physiological age be compared.
• In most perennial crops.
• The blade of the youngest fully expanded leaf of the new flush is
most often selected as the index tissue for plant tissue analysis.

57. • Knowledge of the relationship between crop yield and nutrient
concentration in the index tissue is essential for interpretation.
• Two main approaches have been used to quantify the response curve
in terms of yield-nutrient concentration relationship:
a) the use of "Critical Nutrient Concentration" (CNC) (Ulrich 1952
Ulrich and Hills, 1967. Bates,1971)
b) the use of "Sufficiency Ranges" (Lockman, 1972, Jones and Eck,
1973).
•

58. • Ulrich and Hills (1967) defined Critical Nutrient Concentration (CNC)
as the concentration corresponding to 90% of maximum yield and
always represented a single value.
• However, since there are many factors govern the nutrient
concentration of plant tissue, some scientist suggested that a range
would truly represent the situation (Dow and Roberts, 1982; Smith,
1986).

59. e. Soil analysis
• The total amount of nutrient in the soil does not reflect the quantity
available for uptake by plant roots.
• Thus, chemical methods have been developed, and continue to be
developed, to estimate that quantity of a nutrient that is available to
the plant.
• In addition to the requirement that the method provide a good
estimate of nutrient availability, soil analysis methods must be rapid,
accurate, and reproducible to be accepted for routine use in soil testing
laboratories.

60. • The results of soil analyses must be interpretable, i.e. based on
previously established relationships between crop yield and soil
test.
• These relationships may be established by means of glasshouse
pot experiments or field experiments.
• Further, relationships need to be established between soil test
values and fertilizer applied order that recommendations on
fertilizer rates may be made.

61. • One advantage of soil analyses is the fact that they can be conducted
and fertilizers applied before a crop is planted.
• Disadvantages of soil analyses include the difficulty of obtaining
methods suited to varied soil types: problems in sampling due to
variability in fertility across a field; and problems in estimating the
likely effects of environmental conditions in the forthcoming season
(Melsted and Peck, 1973).

62. Correction of nutritional disorders
• Once a nutritional problem has been correctly diagnosed, it is usually
possible to correct the disorder.
• Often, a fertilizer containing the particular nutrient will be applied
either to soil or as a foliar spray to overcome a deficiency.
• In other cases, an amendment or amelioration may be applied to
correct a soil problem causing disorder.

63. Fertilizer use in cashew plantations
• Cashew tree obtains carbon, hydrogen and oxygen from air and
water; and all the other nutrients along with water are taken up from
the soil through the root system.
• The growth of a plant is determined not only by balance nutrient
supply from the soil it stand but also by such factors as texture,
structure, cation exchange capacity (CEC), reaction of the soil (pH),
moisture holding capacity and the parent material from which the soil
is derived.

64. • Regular application of plant nutrients in appropriate combinations is
essential for healthy growth and production.
• Under conditions in Lanka, the nutrients required by the cashew tree,
have been recognized as nitrogen (N), phosphorus (P), and potassium
(K). In addition Magnesium (Mg) is another major plant nutrient that
should be applied at regular intervals.
• Research conducted in dry zone of Sri Lanka indicated that adult
cashew respond well to the application of N and K fertilizers in Red
Latasol soils.

65. • The cashew seedlings grown in poly bags showed increased dry
matter to the application of fertilizer mixture of NPK (4:3:2) and
also to organic foliar fertilizer application (Wijeratne and
Fernandopulle,
2002; Fernandopulle, 2002).
• The type of fertilizer required by the cashew varies with its
physiological age.
• In general, young trees needs more of N and P for their vegetative
growth and as they reach the reproductive phase they need more
N and K for the production of new flush, flowers and fruits along
with it.

66. • The total quantities of fertilizer that should be applied per tree will
depend on the age of the tree, the type of clone, and the soil type in
the locality.
• The cashew trees grown on light sandy soils need more frequent
applications of fertilizer than those in heavy clay loamy soils.
• Moreover, trees grown in wet localities require more split applications
while the trees in drier locations should receive fertilizer when the
soil is moist, preferably at the tail end of the monsoon if irrigation
facilities are not adopted

67. Interaction of N P and K in cashew plantations
• In general, cashew appears less demanding in its nutritional
requirements than many other plants.
• However, nitrogen fertilization significantly

68. Fertilizer mixtures
• The nutrient content of the most commonly used fertilizers in cashew
plantation are as follows.
• Separate fertilizer mixtures are recommended according to the growth stage
of cashew. Fertilizer application can be done either singly or mixed. Mixtures
provide all necessary nutrients and facilitate in application efficiency.
Urea 46% N
Sulphate of ammonia 21% N
Rock phosphate 28% P2O5 or 12% P
Muriate of potash 60% K2O or 50% K
Kiserite 24% MgO or 14% Mg
Dolomite 20% MgO or 12% Mg

69. Polybag nursery plants
• 30 g of the NPK mixture (4:3:2) and 10 g of kieserite/ poly
bag should be applied.
• The above rate should be thoroughly mixed with the soil
about 1 week prior to planting.

70. Basal dressing at planting
Each planting hole (2'x 2'X2') should be filled with top soil mixed
with the following amounts of fertilizer and allow to be
seasoned for about 1-2 weeks.
* Young plant mixture - 250 g
* Dolomite - 500 g

71. Young plant mixture (Approx. composition 4:3:2)
To make 100 kg of young plant mixture, the following fertilizer
ingredients should be mixed according to the given weights.
Urea - 38 kg
Imported Rock Phosphate - 47 kg
Muriate of potash - 15 kg 100kg

72. Rate of application (from seedlings up to 5 years)
• The Table gives the rates of fertilizer application (g /plant/yr)
as straight fertilizers or as the Young Plant Mixture
Type of Fertilizer(g) Time after transplant(years)
1 2 3 4 5
Urea 76 133 190 247 304
Imported rock Phosphate 94 165 235 306 376
Muriate of potash 30 52 75 97 120
Yung Plant Mixture(g) 200 350 500 650 800

73. • At early stages of growth, two split doses would be beneficial, first
in tail-end of South-West monsoon (Yala) and second in tail-end of
North-Eastmonsoon (Maha) rains.

74. Adult plant mixture (Approx composition 4:3:4)
• To make 100 kg of adult plant mixture, the following fertilizer
ingredients should be mixed according to the given weights.
Urea - 33.5 kg
Imported Rock Phosphate - 41 kg
Muriate of potash - 25.5 kg
100kg

75. Rate of application (from 5 years onwards)
• The rate of application of the adult plant mixture would vary with
yield of the plant.
• The following rates could be recommended accordingly.

76. Rates of adult plant fertilizer mixture for young cashew
Average
yield/plant recommended dosage
(kg/plant/year) (kg/plant/year)
5 -10 1.0kg
10 -15 1.5kg
15 -20 2.0kg
20 & more 2.5kg

77. Method of application
• Fertilizer should be applied only after weeding and cleaning the
base of the individual trees within 1-2m radius depending on the
canopy size, in order to avoid the competition for nutrients from
weeds.
Young plants:
• During early stages (up to 1 1/2 years) fertilizer should be
broadcast close to the plant covering entire full circle up to a
distance of 0.5 m from the base of the plant and incorporated in to
the soil.
• As the plant grows older this area should be gradually extended up
to 1.0 m (Figure 5. 2a).

78. Adult plants:
• Fertilizer should be broadcast in an about 1-12 m wide circular
strip. about 0.5-1 m away 3-1 m away from the base of the plant
and incorporated in to the soil.
• Area over which fertilizer is applied should approximately be
equal or more than 50% of the canopy area (Figure 5. 2b).

79. a) Young cashew tree b) Adult cashew tree

80. Figure 5.2: Method of fertilizer application
Frequency of fertilizer application
• Frequency of application of fertilizer has been recommended for
cashew
according to its maturity:
• Young plants: Half yearly application (biannually)
Adult plants: Annually
• Annual application of crushed dolomite is recommended at the rate
of 250g for a mature tree, as it will serve as a reservoir of Magnesium
for the healthy growth of the plant.

81. Time of fertilizer application
• Nutrients are absorbed by plants along with soil water;
therefore, fertilizers should not be applied during the dry weather.
• Periods of prolonged and heavy rain should also be avoided, for
then the fertilizer may be washed out of the soil and lost before
the nutrients can be absorbed by the plant.
• Therefore, fertilizer should be applied at the tail-end of the
monsoon rains.

82. Fertigation
• Where irrigation is practiced fertilizer could be applied by
dissolving with irrigation water (fertigation).
• For this only soluble fertilizer should be used and the rates
could be calculated for each application of irrigation, avoiding
the monsoonal rains.

83. Methods of fertilizer application
• The aim of fertilizer application is to bring the wide a spread of roots
as much as possible in contact with the fertilizer.
• The best way of achieving this would be by broadcasting around a
circle, that coincides with its canopy and incorporate the fertilizers into
the soil, in order to prevent losses by surface run off or as gaseous
form.
• During the first year after planting, the fertilizer should be applied in a
circle of weeded surface, a few centimeters from the base of the plant
to a distance of 6-9 inches (1220 cm) and lightly forked in.

84. • The radius of this circle should be increased with age.
• In mature cashew trees, fertilizer placement may be continued in
the weeded outer circle about four feet away from the base to
the end of its canopy.
• Mechanization of fertilizer application could be adopted if the
mature trees are trained to have their
lower branches from about 3-4 feet height.

85. After care
After application of fertilizer the area should be mulched with weeded
material. Mulch would be helpful to:
a) Keep down subsequent weed growth
b) Conserve moisture in the manure circle
c) Reduces soil temperature and prevents free wind circulation over
the surface.
d) Prevent run-off by sudden rains after application
e) Mulch when decomposed will add organic matter to the soil
thereby improve the structure, water holding capacity, nutrient
retention of the soil.

86. Commonly used inorganic fertilizers in cashew
plantations
• Ammonium sulphate
• Ammonium sulphate is a white to off white sugar like crystals.
• It is agronomically a good source of both nitrogen (21% N) and
sulphur (24% S). Owing to the SO4 ion ammonium sulphate is more acid
forming than other nitrogenous fertilizers.
• Therefore, under alkaline conditions, surface losses of ammonia (NH3
of ammonia (NH3) occur.
• Hence, this fertilizer should not be mixed with alkaline fertilizers, such
as Dolomite.

87. • Ammonium sulphate apparently reacts with carbonates to
form ammonium carbonate which decomposes and releases
ammonia.
• Under these conditions, separate applications of Ammonium
and alkaline fertilizers are recommended to the soil.

88. Urea
• Urea is a white even sized round free flowing crystals.
• The minimum N content should be 46 %.
• It is a synthetic organic fertilizer.
• During the manufacturing process of urea, the formation of a toxic
substance called biuret is inevitable.
• In fertilizer grade of Urea, the percentage of biuret should not
exceed more than 1.5%.

89. Advantages of urea
• Urea is the cheapest source of nitrogen fertilizer presently available
for use in plantations.
• As urea has a high nitrogen content (46% N), transport and handling
charges and even application costs are comparatively low.
• Urea has yet another advantage that it does not acidify the soil to
the same degree as some other nitrogenous fertilizers such as
ammonium sulphate,

90. Limitations of Urea as a fertilizer
Two major drawbacks are encountered in the use of this synthetic
crystalline urea. They are as follows:
i) Its hygroscopic nature and
ii) Presence of biuret at toxic levels.

91. • Because of high hygroscopic nature, crystalline urea, either
straight or in mixtures with other fertilizer components, would
become moist, caked up on storage or have poor handling
properties.
• This disadvantage has been minimized by the production of
prilled urea, which has better storage and
handling properties, and by packing it in moisture-proof bags.
• However, precaution has to be taken to tighten the half-used
bags of urea or area based fertilizer mixtures.

92. • The conversion of organic urea to inorganic ammonium carbonate in
the soil was a biological process initiated by microorganisms, which
contained the enzyme urease.
• In general, urease is present in all soils. The reaction is as follows:
CO (NH)2 Urease (NH4)2CO3 ----------> NH3 + CO2 + H20
• The rate and extent of hydrolysis of urea in the soil therefore depends
on the microbial activity in the soil, which in turn depends on factors
such as fertility, soil temperature, soil pH and soil moisture content.

93. Volatilization losses of nitrogen:
• The production of ammonium carbonate on hydrolysis causes a
temporary increase in soil pH.
• If the increase in pH exceeds seven (7), may cause the release of
ammonia from ammonium carbonate, with the formation of the more
stable ammonium bicarbonate.
• When urea is spread on the soil surface without being incorporated
into the soil, high losses of ammonia occur by volatilization results under
any type of soils.
• As a general rule therefore Urea should never be applied without
immediate incorporation.

94. • When incorporated the ammonia quickly changes into the
ammonium form reacting with H+ in the soils, which is then held
on to the colloidal surfaces, until depletion, through plan uptake,
cation exchange or nitrification.
• If properly applied, urea is an effective nitrogen fertilizer. It is not
inferior to any other nitrogen sources.
• Because of high hygroscopic nature, crystalline urea, either
straight or in mixtures with other fertilizer components, would
become moist, caked up on storage or have poor handling
properties.

95. • This disadvantage has been minimized by the production of
prilled urea, which has better storage and
handling properties, and by packing it in moisture-proof bags.
• However, precaution has to be taken to tighten the half-used
bags of urea or area based fertilizer mixtures.

96. Phosphate fertilizers
• Imported Rock phosphate
• This is a natural rock mineral found in deposits in many parts of the
world.
• Therefore, the minimum P205 content should be 27.5%.
• The relative effectiveness of rock phosphate varies with the origin,
fineness of grinding, soil type and farming system.
• Since the suitability of rock phosphate is low, it is recommended for
perennial but not for annual crops

97. Potassium Fertilizer
Muriate of Potash
• This is a pinkish colour crystilline fertilizer with 60% K20.
• The chemical womponent is potassium chloride and therefore soluble
in water.

98. Magnesium Fertilizers
• At present, Mg deficiency is not reported in cashew plantations of Sri
Lanka.
• However, experience with other plantation crops show that regular
use of NPK fertilizer could bring about the hunger signs of magnesium.
• Therefore like other plantation crops, ground dolomite should be
applied as preventive measure with regular use of NPK fertilizer.
• If and when the symptoms of Mg deficiency appear, kieserite should
be applied in addition to the preventive measures described above.

99. Dolomite
• This is also natural rock mineral, low in solubility.
• It contains about 8-10% Mg and 8-20% Ca.
• Therefore, ground-dolomite is recommended as a long-term
preventive measure, against magnesium deficiency. As dolomite is
alkaline in reaction, it should not be combined with fertilizer mixtures
containing ammonium sulphate as N will be lost.
• However it can be applied at the same time provided the fertilizers
are dug over well manage to the soil immediately after application.

100. • Dolomite is available locally and is therefore cheap.
• This makes it a convenient source both for corrective measures
and it ensures against development of Mg deficiency condition.
• At the same time it behaves as a soil amendment to correct soil
PH.

101. Kieserite
• This is an easily soluble fertilizer and contains 18-20% Mg.
• It is more expensive than dolomite.
• Therefore it is only recommended when visual Mg deficiency has
developed.

102. Use of Organic Manure in cashew plantations
• Organic manures contain low amounts of plant nutrients (Table 5.4)
therefore comparatively large amounts of these material needs to be
applied.
• For example, quantities of plant nutrients found in 1 kg of an
inorganic mixture (4:3:4 NPK) are obtained from 14 kg cattle manure
together with 130 g of rock phosphate and I kg of any kind of ash.

103. Chemical composition of some locally available organic
manure
Material
Moistur
e N % P2O3 % K2O%
Cattle dung(fresh) 40-55 0.4-0.8 0.2-0.4 0.3-0.6
Cattle dung(dry) 8-12 0.7-1.5 0.4-0.7 0.6-1.1
Goat dung 10-15 2-3 0.4-0.7 1-1.5
Pig dung - 0.53 0.55 0.4
Farmyard manure 5-8 0.7-1.6 0.3-0.6 1.1-1.5
Compost - 0.6 0.3-0.6 0.2-0.8
Fish refuse - 2-4 4-Feb traces
Kitchen or wood ash - Nil - 3

104. • Since this bulkiness would lead to an increase in the costs of both
transportation and handling of the manures, one should consider its
economics when considering the use of organic manures in cashew
plantations.
• Rates of organic manure for young cashew plants (plant /year)
Time period
Organic
matter(kg) Rock Phosphate
Potash(
g)
1 year 3 30 -
2 year 5.5 55 -
3 year 8 75 -
4 year 10 100 -
5 year 13 120 -

105. Table 5.6 Rates of organic manure for mature cashew plants
Weight of
nut
Organic
matter
Rock
Phosphate Ash
tree/year(kg) (kg) (g) (kg)
10 14 130 1
15 21 200 1.5
20 28 250 2
25 35 325 2.5

106. • It should be freely used when they are available in close proximity to the
land.
• The use of organic manures would be particularly beneficial on coarse
sandy soils which are poor in organic matter.
• Apart from adding plant nutrients, organic manure helps to:
1) Improve soil structure by improving soil aggregation
2) Improve water holding capacity of the soil
3) Improve nutrient retention
4) Promote, microbiological activity
5) Make phosphate more readily available
6) Improves buffering capacity of the soil.

107. Thank You..