Coconut

Nutrient Management

Introduction General Aspects Of Manuring Principles Of Manuring Schedule Of Manurial And Cultural Operations Bulky Organic Manures Common Salt In The Nutrition Of The Coconut Palms Liming Of Coconut Soils Time And Method Of Application The Effect Of The Nutrients Nutrient Mixtures

Introduction

  • The coconut is a perennial crop and is unique in that once it starts flowering, the production phase lasts almost throughout the year and all through its life.
  • A normal tree produces an inflorescence (flower bunch) which finally gives rise to mature nuts in about twelve months after the date of opening of the flower, in the successive leaf axils, at intervals of about twenty eight to forty days.
  • In a normal tree growing under suitable conditions, there is a continuous process of fruit production right from the primordial stage of the flower to the final mature nut which becomes ready for harvest at intervals of about thirty to forty days.
  • This will be evident from a close examination of the crown of a normal bearing palm, where one could see nuts at different stages of maturity in the successive bunches or inflorescence.
  • Therefore, there is bound to be a steady utilization food material by the coconut tree and consequent depletion of plant foods from the soil.
  • Different estimates of the average annual loss of the important plant foods from a hectare acre of coconut garden yielding about 5,000 nuts per year have been reported.
  • The quantities of nutrients removed per hectare will be 62 kg of nitrogen, 25 kg of phosphoric acid and 93 kg of potash.
  • For the proper maintenance of coconut plantations and obtaining good yields, manuring has to be done judiciously and regularly.
  • It has to be noted that in coconut, the effect of manuring or other agronomic practices on the yield of the trees will be noticed only after a period of about two and a half to three years since this period is required for the development of the nuts from the primordial stage to full maturity.
  • Therefore, manuring has to be carried out regularly and systematically every year to maintain the condition of the trees and obtain good yields.
  • There is no gainsaying the fact that the coconut responds to the application of complete fertilizers-nitrogenous, potassic and phosphatic manures-especially when the plantations are located in less fertile or poor soils.
  • The response is particularly marked in the case of the application of potassic and nitrogenous fertilizers.
  • Application of potash (K2O) (to supply 0.75 to 340 to 680 gm per trees per year to the coconut, has been found to result in increased yields and greater resistance to disease.
  • Potash can be applied in the form of ash or muriate of potash.
  • Ash, particularly that obtained by burning coconut fronds, husks, etc., and stored properly without being subject to the leaching action of rain, may be applied, the quantity depending upon its potash content.
  • In the case of ash, it is considered desirable to apply in smaller doses at intervals during the course of the year rather than applying it in one large dose.
  • Application of nitrogenous fertilisers to supply 230 to 455 gm of nitrogen per tree per year has been found to result in increased yields of coconut.
  • This may be supplied in the form of ammonium sulphate, chilean nitrate or locally available oilcakes.
  • Oilcakes are best applied with the beginning of the monsoon rains, while it would be desirable to apply fertilisers after the severity of t he monsoon rain is over and when there is sufficient moisture in the soil.
  • Although coconut palms have not shown as much response to phosphoric acid as to nitrogen and potash, it is considered desirable to apply 115 to 230 gm of this nutrient per tree per year to maintain the fertility status of the soil.
  • It may, therefore, be supplied in the form of bonemeal or superphosphate or rock phosphate.
  • This may be applied fairly deep in the soil in plough furrows just before the monsoon rains, with the sowing of the green manure seeds or later along with the other manures.

The general recommendation for the manuring of seedlings in India is the following

Year after transplanting
Quantity (kg) of manures per seedling per annum
Ammonium Sulphate
Super-phosphate or bone-meal
Muriate of potash
I year
Nil
Nil
Nil
II and III years
0.25
0.25
0.25
III and IV years
0.50
0.25
0.50
V and VI years
1.00
0.50
0.75
VII years onwards
1.50
1.00
1.00

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General Aspects Of Manuring

  • There is general response to the application of potash and nitrogen, while response to phosphoric acid is seen only in certain restricted situations.
  • The response to manuring is conditioned to a large extent by the availability of nutrients in the soil, but there is no clear idea as to the threshold values below which response could be expected.
  • The non-response to manuring in the heavy coastal clay soils of Malaya is probably due to their high natural fertility.
  • Potash content is reported to reach as high as 0.8 per cent.
  • A minimum of three years appears to be a reasonable period for the first response of the trees to manuring to become manifest.
  • There is general agreement that initially high yielders do not respond as much to manuring as low and medium yielders.
  • This indicates the possibility of selective manuring of the trees especially when the prices of fertilisers are high.
  • Broadcast application of manures is seen to be as good as the application in circular basins or in trenches.
  • Application in linear trenches in between rows of trees is not as good as the other two.
  • It should, however, be realised that the experiments have been carried out in gardens where the palms have been planted as a pure crop.
  • This situation is never obtained in small holdings where the palms would be irregularly planted among miscellaneous other forms of vegetation.
  • Under these conditions, application of manures in circular basins or trenches is to be preferred for the following reasons:
  • The highest concentration of roots being close to the palms would result in maximum utilisation of nutrients.
  • There is less fixation of phosphates in the soil as the ratio of soil to fertiliser is less than when broadcast over the soil.
  • When manure is applied broadcast, the entire area has to be ploughed or harrowed to cover the manures. Loss of fertiliser applied to the surface is possible through run off.
  • Surface manuring may encourage surface rooting which may make the palms susceptible to drought.
  • There may be rank growth of weeds competing with the palms for plant food, which will cost more to control.
  • This method, largely in favour with the growers, has stood the test of time.
  • Much difference of opinion however still remains in the matter of response by coconuts to manurial applications.
  • The absence of uniform experimental material, and clear knowledge about the appropriate nutritional requirements, and the long lag period before results of indicative value could be obtained are responsible for this state of affairs.
  • Probably the use of radioactive tracers in investigations on coconuts would give quicker and more accurate assessment of some of these problems.

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Principles Of Manuring

  • The capacity of soils to supply plant nutrients deteriorates on continued cultivation.
  • Fertiliser practices in coconut gardens after a few years of cropping thus need occasional revision to meet the changing conditions of the nutrient status of the soil.
  • Thus, for practical manuring, it is important to know how far the effect of the plant nutrient depends on the presence or absence of another and to what extent cumulative excess of a major nutrient may adversely affect palm growth.
  • The coconut palm is unique in that once it starts flowering, the production phase lasts almost throughout the year and all through its life.
  • Therefore, there is bound to be a steady utilisation of food material by the coconut tree and consequent depletion of plant foods from the soil.
  • For the proper maintenance of coconut plantations and obtaining good yields, judicious and regular manuring is necessary and this has to be an annual practice.
  • It is known that the drain of manurial constituents by a heavily producing palm is very considerable and when that has taken place over a series of years, such effects are sure to influence adversely the growth characteristics of the palms and even to mask the most favourable hereditary characters.
  • A great majority of the soils in which coconuts are grown in India are found to be deficient in organic matter which is considered very necessary for the proper maintenance of soil structure, and moisture conservation and for obtaining maximum benefit out of the application of fertilisers.
  • Attempts have, therefore, to be made to ameliorate these conditions and this can be done by incorporating into the soil bulky organic manures like farm-yard manure, composts, or by a regular system of applying green manures grown in situ.
  • In loose coastal sandy soils, the application of manures and fertilisers should not be expected to give very good results since the nutrients are likely to be leached and carried away depriving the coconut palms of the best benefit if they are not applied at the proper time and supplemented by bulky organic matter.
  • Laterite soils on which there is a good acreage of coconuts in India, are of inherently low fertility and tend to be deficient in all plant nutrients.
  • Here there is need to supply all N,P and K ingredients in the form of manures.
  • Bulky organic manures with top dressing of N. P and K will suit this soil best.
  • Coconut plantations on laterite areas during the initial years appear to be highly productive but unless adequate manuring and soil management practices are given, the plantations deteriorate steadily.
  • Alluvial soils are naturally rich in plant food factors.
  • Sandy soils are not.
  • Peaty soils as a rule contain more organic and less of mineral matter.
  • Soils, which have received adequate quantities of ameliorative supplements such as silts or press mud, etc., need not receive heavy fertilizer additions.
  • It appears to be the view of some coconut growers that the long continued use of artificial fertilizers exhausts a coconut palm and that the palm would suffer severe set-back when the fertilizer application is discontinued.
  • Careful and judicious application of both organic manures and chemical fertilizers ensure both soil conservation and increased yields.
  • Fertilizer application to a large extent depends upon the method of application or any catch crops are grown what they remove from the soil or contribute to it.
  • These aspects are described under catch crops. Soil exhausting crops, particularly potash loving, such as sugarcane, pineapple, banana, tapioca, etc., should not be grown in coconut gardens due to the possible competition for their potash needs.
  • Therefore, should not be grown mixed together unless they are liberally manured, particularly with potash.

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Schedule Of Manurial And Cultural Operations

  • The following is a schedule of manurial and intercultural operations followed at the Central Coconut Research Station, Kasaragod, in Cannanore District of Kerala State.
  • The main soil type of this station is deep reddish loam with a mean annual rainfall of 3407.3 mm received mostly during the South-west monsoon period.
  • This can, with slight modifications, be adopted elsewhere to suit local conditions of soil, rainfall, availability of manure, cost of labour etc.

March-April

  • One ploughing with an iron plough to prepare the land to receive the summer showers.

May-June

  • After a soaking rain is received, sow a green manure crop using proper seed rate and cover it properly by working a light plough It would be desirable to give a basal dressing of ash at 20 pounds (10 kg) and cattle manure at hundred pounds (50 kg) per tree just before the sowing of the green manure crop If bonemeal or superphosphate is proposed to be applied, it may be incorporated into the soil before the sowing of the green manure crop.

August-September

  • Slash or cut down the green manure crop and plough it into the soil with a suitable iron plough.
  • If ammonium sulphate or muriate of potash or other manure mixtures are proposed to be applied, they may be broadcast and ploughed in with the green manure crop at the first or second round of ploughing.
  • If cattle manure has not been applied, they may be placed in shallow basins as already recommended.
  • If wild sunnhemp or similar green manure crop is grown, it may be buried in shallow trenches in between rows of trees.
  • The position of the trenches has to be shifted every year so as to cover the whole area in a few years.

October

  • A second dose of ash may be broadcast and a cultivator worked to incorporate it into the soil. Bunds washed off during rains may be rectified.

December

  • Work a cultivator (harrow) to create soil mulch.

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Bulky Organic Manures

  • A great majority of soils, in which the coconut is raised in India, is found to be deficient in organic matter which is considered very necessary for the proper maintenance of soil structure and moisture and for obtaining maximum benefit out of the application of chemical fertilisers.
  • Attempts should, therefore, be made to ameliorate this condition.
  • The application of farmyard manure, compost manure and green leaves in sufficient will increase the organic matter in the soil.
  • Where farmyard or cattle manure is available, it can be applied at about one hundred pounds (45 kg) per tree, per year.
  • But in view of the limited supplies of farmyard or cattle manure available in the country, one has to resort to other available sources like compost, green leaves etc.
  • In localities where green leaves are available in plenty, they may be collected and applied at about 45 kg per tree per year.
  • The leaves may be buried in shallow basins about eight feet (2.5 m) in diameter dug round the base of the trees or in trenches in between rows of trees and covered with soil.
  • In all cases of application of bulky organic manures, care should be taken to incorporate them properly into the soil, so as to prevent the breeding of the rhinoceros beetle (Oryctes rhinoceros) pest, which causes serious damage to the coconut palms.

Green Manure crops

  • Growing a green manure coop in situ and incorporating it into the soil is probably the easiest and most economical method of augmenting the organic matter in the soil.
  • Therefore it should be the endeavor of coconut planters to grow green manure crops wherever possible and practicable.
  • The green manure crop selected for cultivation should be a leguminous one, which will renovate the soil and come up well in the shade of the coconut trees.
  • Green manure crops cowpea (Vigna unguiculata), sun-hemp (Crotalaria juncea) Dhaincha (Sesbania aculeata) and wild sun-hemp (Crotalaria striata) may be grown depending upon local conditions.
  • Crotalaria striata which is a leguminous weed growing wild in most of the coconut tracts in particular, has been found to be a very suitable green manure crop for West Coast conditions.

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Common Salt In The Nutrition Of The Coconut Palms

  • Either as a direct manure or as an indirect soil ameliorant.
  • The addition of common salt in coconut gardens is a very old and popular practice among coconut growers.
  • It is very widely applied to the soil as well as to the top of the palm often admixed with a little wood ash.
  • In lateritic soils, the addition of common salt in the pits for planting seedlings is known to soften the laterite bed and help early penetration of the tender roots.
  • The view that common salt helps to conserve soil moisture has not yet been proved by experiments.
  • The results of several studies in different soil types have shown that the concentration at which common salt may exert a beneficial effect on soil moisture conservation is very high and in this concentration may adversely affect normal plant growth.
  • Whether sodium chloride can release available potash from the soil has also been not definitely proved by experimental data.
  • As a matter of fact, there is very little evidence that adding sodium salts to a soil increases the availability of the soil potassium.
  • Growers have a feeling that common salt when applied to the soil has an effect of bringing down the percentage of incidence of barren nuts.
  • In the case of coconut seedlings, moderate quantities of sodium chloride appeared to be invigorating, but a heavier application was rather harmful.
  • The coconut palm is a semi-halophyte, being able to live in situations where its roots come in contact with such salt concentrations as would be lethal to many other plants.
  • This shows that it can resist the action of salt but it need not be that it requires salt.
  • There appears to be a misunderstanding as to the actual amount of salt concentration prevailing on coastal sands on which the coconut palms thrive well.
  • The coastal soils are not at all saturated with salt on account of the fact that the underground water in the coastal areas flows seaward from higher inland regions.
  • In many parts of the coast, therefore, fresh water could regularly be struck on land within a few yards of the waves.
  • Salt sprays are liable to deposit small quantities of the substance on the soil surface, but due to the extreme mobility of the chloride ion these are leached into the subsoil especially when there is rain.
  • These consideration indicate that while the coconut palm can tolerate salt concentrations in the soil to a considerable extent and often absorbs salt into the system and removes it in the different products such as husks, it cannot be asserted that it has any special preference for it.
  • Its partiality for coastal soils thus appears to have little to do with the alleged salt concentrations of these areas.
  • Nevertheless, it has to be conceded that the use of common salt has been and still continues to be very popular among coconut growers as a beneficial agent in the health and productivity of the coconut palm.

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Liming Of Coconut Soils

  • In order that the best effects of fertilisers are derived by the palms, great care has to be exercised in liming the soils.
  • Over-liming of soils create potash and boron deficiency as well as the condition known as lime induced chlorosis in palms.
  • Where liming materials not containing magnesium are used, magnesium tends to become a limiting element and may be applied as magnesium compounds.
  • Lime is also said to have the effect of "sweetening" the soil which, if it is a coastal soil, rich in organic matter may be acid.
  • Many coral-derived soils under tropical conditions which have a vast acreage of coconuts are low in lime content due to excessive leaching of the surface layers.
  • This is a factors which leads to their stickiness and liability to water loging.
  • Disturbance in nutrient uptake under acid conditions may be compensated by increasing the Ca concentration in the soil.
  • Since the activity of polyvalent nutrient elements in soil is much reduced by the greater absorption on the soil colloids of divalent than monovalent ions, a good potassium status of exchangeable potassium per hectare requires ten times more calcium for adequate nutrient balance.
  • In addition to regulating base saturation and pH, and thus affecting weathering and humus formation, liming stimulates mineralisation of organic nitrogen and phosphorus, improves nitrification and reduces aluminum and manganese toxicity in very acid soils of low organic matter content.
  • The coconut thrives best at pH conditions just on the acid side of neutrality, though it appears to be a plant which needs a soil giving an alkaline reaction.
  • The fact has, however, to be conceded that the coconut palm can adapt itself to quite a wide range of pH conditions in the soil.
  • All the essential and beneficial elements of plant nutrition are available to the plants provided they are present in the soil, so long as the pH is in the range of 6.5 and 7.0.
  • When the biological regime in the soil is most satisfactory, nutrient conditions are favourable without being extreme and phosphorus availability at a maximum, while soils with higher pH tend to make the micronutrients unavailable with the exception of molybdenum.
  • Since lime serves a twofold function in the soil, firstly as a plant nutrient factor and secondly as the agent adjusting the soil reaction and hence the availability of other soil nutrients to plants, the liming of coconut soils appears to be rather important.
  • Indeed, the changes in the soil due to liming are so many, so complex, and so inter-related, that it is not possible to ascribe the influence observed to any one factor.

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Time And Method Of Application

  • The proper time for the application of manures is when there is sufficient moisture in the soil.
  • At the same time care should be taken to see that the manures applied are incorporated into the soil properly and not washed off by rain water running through the plots.
  • All precautions should be taken in plantations against soil erosion by previous levelling, terracing and erecting proper bunds, wherever necessary.
  • Weeds should not be allowed to rob the coconut palms of their manures and their growth should be checked and controlled properly.
  • The manures recommended are best applied after the receipt of heavy rains of the monsoon.
  • It is a common practice to apply manures to coconuts in trenches or in shallow basins dug round the tree or apply them broadcast and cover with a plough.
  • If a full dose of manures is given to all the trees regularly every year, it appears desirable to broadcast the manure and plough it in by using a heavy plough especially in closely-planted gardens.
  • Placement of the fertilisers, especially of phosphatic manures, at some depth in plough soles or by any other method is considered advantageous.
  • In young plantations and for under-planted seedlilngs, the manures are best applied round about the young trees till they attain the bearing stage.
  • In widely spaced coconut gardens (8 meters and above), applying manure mixtures in shallow basins of about 1.5 meters radius is desirable.
  • In opening trenches in basins, care should be taken to see that healthy feeding roots are not unduly cut.

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The Effect Of The Nutrients

Nitrogen

  • The supply of nitrogen which is a constituent of plant cells as well as chlorophyll, the green colouring matter of leaves, is of great importance for the rapid development and growth of the trees.
  • Nitrogen deficiency is reflected in deficient leaf formation as well as in restricted growth.
  • Nitrogen promotes the development of the vegetative parts of the plant especially the leaves and shoots.
  • The complete effects of nitrogen in plant metabolism could be achieved only if phosphoric acid and potash also are provided.

Phosphorus

  • Phosphorus is found especially in leaves and seeds as well as in all parts of the plants where vigorous cell division is taking place.
  • Phosphorus deficiency results in deficient results in deficient root development and delayed ripening of the fruit.
  • Characteristic discolouration often occurs on the leaves where phosphorus is in short supply.
  • Excessive phosphorus dressings do not act unfavourably on plant growth because part of the phosphate gets fixed in the soil in forms not readily soluble.
  • Potash and phosphoric acid act jointly in many of their functions.
  • The two together help the formation of sugar, starch and fats as well as in protein synthesis.
  • They particularly promote flowering, fruit setting and root development, speed up ripening and increase resistance to certain diseases and pests.
  • Potassium in the presence of phosphorus improves the quality characteristics of the produce, such as flavour, keeping quality, fruit colour, grain weight and size.

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Nutrient Mixtures

  • Since the process of application of manure to coconut plantations, namely, spreading and covering is a costly operation, it is easier and more economic to mix the different manures (nitrogenous, phosphatic and potassic) just before application instead of applying them separately.
  • But in doing this, care should be taken to see that only suitable manures are mixed.
  • Ammonium sulphate should, in no case be mixed with ash or lime, since chemical action will set in and nitrogen will be lost in the form of ammonia.
  • These should, therefore, be applied separately with an interval of about a month.
  • Muriate of potash and sulphate of ammonia, if mixed, should be used immediately.
  • The mixture, if stored, will become damp in moist air and will cake up.
  • The manure mixtures approved by the Departments of Agriculture are 8:8:16 N:P:K respectively and these are available in the market under guaranteed analysis.
  • An application of about 2.5 to 3.5 kg of this mixture over a basal application of 50 kg of compost, farmyard manure or green leaf is recommended per year per adult palm, lower doses being used for younger palms in pre-bearing stage.

The newly planted young palms may be fertilised according to the following schedule

Age of plantation
Dosage (Per Palm Per Year)
After one year's growth 1/8 Of the adult palm dosage
After Two year's growth 1/4 Of the adult palm dosage
After Three year's growth 1/2 Of the adult palm dosage
After Four year's growth 3/4 Of the adult palm dosage
After Five year's growth and thereafter Full Of the adult palm dosage

  • It is expected that new plantations will attain the bearing stage in six to seven years after planting, if quality-planting material is used and properly cared for.
  • The effect of manuring will be more pronounced if it is combined with proper irrigation in areas where rainfall is not sufficient.

Mixtures for sandy soils

Mixture 1
Per tree per year
Cattle manure or compost
25 to 50 kg
Wood ash
10 to 20 kg
Bonemeal
1 kg
Mixture 2
-
Fish guano
7 kg
Muriate of potash
1 kg
Mixture 3
-
Prawn dust
7 kg
Muriate of potash
1 kg
Mixture 4
Oilcake
7 to 10 kg
Wood ash
10 to 20 kg
Bonemeal
1 kg

Note

  • Wood ash at 10 to 20 kg may be used instead of 1 kg of muriate of potash.
  • It is very necessary to grow and incorporate a suitable green manure crop to sandy and other soils deficient in organic matter.
  • Young palms have been found to respond well to the application of nitrogen and potash.
  • Nitrogen may be supplied in the form of ammonium sulphate 300 to 1000 gm per seedling per year depending upon the age of the seedling, preferably in two instalments.
  • Potash in the form of ash 5 to 10 kg or potassium sulphate or muriate of potash at 1 kg per seedling per year may be sufficient.
  • As the seedlings attain the bearing stage, the mixtures, recommended for adult trees may be adopted.
  • An occasional dressing of about 0.25 to o.5 kg of superphosphate per seedling is also desirable for healthy growth.

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