The following points highlight the five main soil management practices of orchard. The practices are: 1. Soil Culture 2. Inter Culture 3. Weed Management 4. Manuring and Fertilization 5. Irrigation Systems.
Practice # 1. Soil Culture:
(i) Tillage:
It means ploughing and hoeing of the soil. The objective of the tillage is to loosen and pulverize the soil so that the roots of fruit plants may penetrate in the soil easily. It facilitates circulation of air and absorption of water. Tillage removes the weeds and helps in mixing manures and fertilizers. It releases the locked up plant food material through the activity of the micro-organisms.
(ii) Clean Cultivation:
It means keeping the land of the orchard always free from grasses or any other vegetation. It controls the weed growth and improves moisture retention in soil. Clean cultivation also improves the soil aeration and increases the nutrient availability. However, it causes soil compaction and deteriorates the soil structure. Soil becomes depleted of nutrients under continuous clean cultivation without the addition of organic matter or growing any leguminous crop.
(iii) Sod Culture:
It means the fruit plants are grown in permanent grasses without tillage and addition of any litter. This practice is common in hilly areas. Sod culture checks erosion. There is less damage to the fallen fruits. The disadvantage of sod culture is that water and available nitrogen is taken by the weeds. Hazards of fire are involved due to dry grass. Attack of rats and insect-pests is there.
(iv) Mulching:
Mulching is a system of soil management in which hay, straw, or cut grass is placed on the soil between the tree rows to conserve the soil moisture by checking surface evaporation. It is considered that cultivation and the maintenance of soil mulch are important as means of preventing the evaporation of moisture. If weeds are removed without disturbing the surface of the soil, very little water is lost by evaporation. Mulching, checks germination of weeds. However, mulching is susceptible to fire outbreak. Mulch also facilitates the hibernation of rodents.
(v) Clean Basin Management:
This practice is carried out manually by keeping the basin free of all weeds. It is the most common method of orchard floor management in apple. In this system 4-6 cultivations are given throughout the year to control weeds. The cultivation of basins after harvest facilitates the application of fertilizers in winter. It is recommended for young apple trees to develop deeper root system and to avoid any competition for nutrition or water by weeds with the plants. However, this system is not recommended for bearing trees due to its effect on feeding root system and soil moisture levels.
The chief objective of orchard soil culture is to provide the necessary conditions for the fruit plant to grow satisfactorily, utilising the moisture and nutrient supply in the soil to the best advantage. Manures can also be well incorporated into the soil only when the soil is loosened. This is also necessary to incorporate green manures and residues of cover, intercrops and mulches to help the process of decomposition.
On sloping land, the culture of the orchard soil is specially harmful. Growing of permanent cover crops on such land or planting of strips of grass between the narrow strips of clean tilled rows of fruit trees on the contours, are the usual practices which are aimed to prevent the soil from erosion.
The orchard cultural practices depend both on the kind of fruit and environments. In mango, soil culture is mostly done in the pre bearing age of the orchard. Raising of green manure, inter or cover crops is the common practice. As the trees grow and cover much of the ground, only an annual tillage is generally done, normally a month or two before flowering. In citrus, few shallow ploughings especially during June-July and October to December are necessary to keep down the weeds and mend the irrigation channels.
Practice # 2. Inter Culture:
(i) Intercrops:
Intercrops are raised in an orchard during pre-bearing period for increasing the income from land such as through raising of vegetables, pulses and short duration fruit crops.
When the new plants are set in the orchard, there is considerable area between the rows and trees which is not used by the fruit plants at that stage as the roots of the young plants are not spread to the whole vacant area around them but are limited to a short circular area extending not more than a few feet.
The space which is lying vacant can be utilized for planting for a few years, till the root system of the permanent tree is spread almost in the entire area. When the fruit tree in the orchard is young and has not started bearing fruits as yet, they may not be using all the area under them and as such the farmers can intercrop the orchard to supplement their income.
In mango orchard, pear, plum, phalsa and papaya may be planted as filler trees. They come into bearing quite early and yield good income before the permanent mango plants start bearing commercial crop. These temporary plants are kept well away from the permanent tree so that their roots do not compete with one another. When the permanent trees grow and occupy more space and their root system extend towards the filler trees, these should be removed.
Vegetables and some of the leguminous crops are also preferred as intercrops. The cereals are not grown because they are quite exhaustive thereby harming the fruit plants. The truck crops can be grown successfully as annual cash crops. If the orchards are situated near towns and cities, the vegetables as intercrops are best suited.
In the orchards which are far from the market, intercrop only those vegetables/crops which can be transported to distant markets, or stored for some period. When the fruit plants do not start bearing good commercial crop, the vegetables grown as intercrops should be fertilized adequately so that the fruit trees are not adversely affected for want of nutrients needed by them for their proper growth.
Gram and dwarf peas are the best intercrops for orchards where the trees have been budded on a rootstock requiring a well drained soil. The gram can be grown successfully as intercrop for the first 3-4 years after planting the orchard. It not only gives good return but also enriches the soil. Gram and peas intercropped in rabi season are harvested by the first week of April and thereafter in kharif season for a short duration, legume crop like Moong should be grown. Being a leguminous crop, it also enriches the soil. Guara grown for seed has also proved a good intercrop.
Crops like barseem which require lot of irrigation should be grown in guava and pear orchards because these trees can tolerate wet soil condition to a greater extent. Avoid creeper type vegetables in the orchard. Tall and exhaustive crops like cotton, bajra, maize, chari and bhindi should be avoided in the orchard.
(ii) Cover Crops:
These crops are raised mainly in the beginning or in advance of the rainy season, so that these may provide the necessary protection to the soil when damage by soil erosion is the greatest e.g., cowpeas, moong and soya-bean. Cover crops help to improve the physical condition of the soil by adding the organic matter to the soil. Retention of cover crops during summer months is undesirable as it will compete with the main fruit trees for soil moisture. Cover crops may also serve to draw off surplus moisture during monsoon.
(iii) Green Manuring Crops:
These crops are raised during the rainy season and buried into the soil after a few months of growth for incorporation of the organic matter, e.g., guara, senzi, daincha and cowpeas. To facilitate rapid decomposition of all green matter, it is necessary to plough down the same while still tender or succulent. The green manure crops are generally cut down and incorporated into the soil just when they reach the blooming stage. Green manuring crops also help to improve the physical condition of the soil by adding the organic matter to the soil.
When leguminous crops are used as inter, cover or green manuring crops, these are able to fix nitrogen from the atmosphere. Regular use of green manure may also help to reduce the expenditure on manuring and fertilization in the orchard.
Practice # 3. Weed Management:
The weeds should be eradicated from the orchards as they compete with fruit trees for water and nutrient. Bathu, pohli, piazi, pit papra etc. are the commonly found growing winter weeds. Motha, kahi and baru are the common weeds found growing during the rainy season. Cultivation of orchard land can help to kill weeds. Cultivation with tractor or ploughing rather helps their further spread. The orchard infested with such obnoxious weeds should be dug up and all rhizomes/bulbs collected with a rake/fork should be burnt.
The weeds in orchards can be best controlled by spraying pre-emergence herbicide like Hexuron 80 WP (diuron) or post-emergence herbicide like Glycel 41 SL (glyphosate) or Gramoxone 24 WSC (paraquat).
Practice # 4. Manuring and Fertilization:
Application of manures and fertilizers to the fruit trees constitutes a very important cultural practice. For successful orcharding, one has to apply organic manures as well as chemical fertilizers at the right time, in proper dose and in a right manner. Fruit trees remove large amount of nutrients from the soil than most other farm crops.
The manurial requirements of a fruit trees are governed by multiplicity of factors like age of the fruit tree, type of soil, climatic conditions, cultural practices being followed etc. An orchard can be maintained in commercial bearing only by adding adequate manuring. Plants require N, P, K, Ca, Mg, S and traces of Mn, Bo, Cu, Fe, Zn and Mo from the soil for its normal growth. Orchards are manured both by organic manures and inorganic fertilizers.
(i) Organic Manures:
Farmyard manure, poultry manure, compost, oil cakes and green leaves are the chief organic manures. Organic manures improve the physical condition of the soil and also add some quantity of nutrients to the soil. The percentage of nitrogen contained in common organic manures ranges from 0.5 per cent in the low grade fresh cattle manure to a little over 2.5 per cent in the poultry manure. Farmyard manure is the most popular manure and is widely used in orchards. If properly maintained, it may contain about 1.5 per cent nitrogen, 0.9 per cent phosphorus and 1.3 per cent potash. The farmyard manure to be used in the orchard should always be well-rotten as otherwise its application may attract white ants.
Poultry manure is also very rich in nitrogen which ranges from 1.0 to 1.8 per cent. Its phosphorus content is 1.4 to 1.8 per cent and potash is 0.8 – 0.9 per cent. Green manure or ploughing in a cover crop is another form of organic manuring and is better done during a dormant or semi-dormant period of the trees. Oil cake is a rich source of nitrogen and is being used chiefly for its nitrogen content. Daincha, guara and sanhemp are also good source of nitrogen and contain 0.62, 0.34 and 0.75 per cent nitrogen, respectively. Sanhemp also contains 0.12 per cent phosphorus and 0.51 per cent potash.
(ii) Inorganic Manures:
Use of fertilizers in the present agriculture is indispensable. To achieve the desired goal, the farmers have to use varying amounts of a variety of fertilizers supplying nutrients essential for successful fruit production. It is, therefore, important that the growers are well familiar with the different fertilizer materials they use in their orchard.
a. Urea:
It is available in the form of white round pills which are free flowing. It is highly hygroscopic because of which it has to be packed in moisture proof bags. It can be mixed with phosphatic and potassic fertilizers provided the mixture has to be used immediately after preparation. It contains 46 per cent nitrogen in amide form. It is highly soluble in water. Therefore, if applied under extensively wet conditions, it may be leached to deeper layers of the soil. As such it is desirable to apply it to soil under moderately wet conditions followed by mixing it thoroughly with soil. It has highly acidic reaction in soil. It is also suitable for foliar application in the form of a solution in many fruit crops.
b. Ammonium Sulphate:
It is available in the form of white or grey coloured crystalline salt. It absorbs very little moisture from air i.e. non-hygroscopic and possesses excellent physical properties owing to which it can be easily mixed with phosphate and potassic fertilizers while applying to soil. It keeps well during storage and transport. It has 20.6 per cent nitrogen in ammonical form. It is quickly soluble in water. It is not susceptible to leaching. In addition to N, it contains 24 per cent sulphur also and thus supplies sulphur in the sulphur deficient fields. It has an acidic residual effect in soil.
c. Calcium Ammonium Nitrate (CAN):
It is available in the form of grey or light brown granules which are free flowing. Because of being highly hygroscopic in nature, it has to be stored in moisture proof bags like urea. It can be mixed with phosphatic and potassic fertilizers provided the mixture has been used immediately after it is ready. It contains 25 per cent nitrogen, half of which is in ammonical and half in nitrate form. It has neither acidic nor alkaline residual effect on soil.
d. Di-Ammonium Phosphate (DAP):
It is available in the form of granules of light grey colour and contains both nitrogen (18%) and phosphours (46-48% P2O5). It is totally water soluble in nature. Di-ammonium phosphate is non-hygroscopic and slightly hard in nature. Its physical properties are the best among most of the fertilizers and can be mixed with nitrogen and potassic fertilizers before application. The quality of this fertilizer does not deteriorate much on storage but it tends to caking with prolonged storage in airy and humid stores. It is neutral in reaction.
e. Superphosphate:
Superphosphate is available both in powder and granulated form. Single superphosphate contains 16% P2O5, double superphosphate contains 32% P2O5 and triple superphosphate contains 46% P2O5. Whole of phosphorus in these fertilizers is water soluble. It is prepared by adding sulphuric acid to rock phosphate and gypsum is added as filler in it. It is greyish in colour. It does not absorb moisture from soil and had little tendency to caking. It is acidic in nature. Superphosphate has best physical conditions and can be mixed with other fertilizers before adding.
f. Muriate of Potash:
It is available in the form of pinkish crystalline salt and absorbs very little moisture from air i.e. non-hygroscopic in nature. It possess excellent physical properties and can be mixed with other nitrogenous and phosphatic fertilizers while adding to soil. Muriate of potash contains 60% K2O. It keeps well during transportation and storage. It is highly water soluble and is neutral in reaction.
Applications of Fertilizers and Manures:
In order to obtain maximum benefits and to minimise possibilities of any adverse effects it is important that fertilization should be done at appropriate time in a suitable manner.
Time of Application:
In north India where summer and winter seasons are well marked, there are definite periods of growth and dormancy or rest for the fruit trees. From February to April the fruit trees have the highest requirements of nutrients for vegetation, flowering and fruit setting. To be effective, the nutrients must be readily available at a time when these are needed the most.
The best time for applying N fertilizers is about two weeks prior to the initiation of growth and flowering. If the quantity is small, the application can be made in a single dose. However, if it is large, split the quantity in two equal doses i.e. one before the initiation of growth and second after fruit set. The P fertilizer should be applied along the N fertilizers. The K fertilizer should be applied in spring or in some fruit trees about 4-5 weeks prior to the fruit maturity as it improves fruit quality. Organic manures should be applied about 3 months ahead of the spring flush so that by that time nutrients are converted into readily available form.
The time of application of micronutrients depends upon the kind of fruit tree and the severity of deficiency. If the deficiency is mild, one spray in April may be enough, but if it is acute 4-5 repeated sprays at monthly intervals may be needed to correct the deficiency. Usually the sprays are more effective than soil applications. However, in soils with neutral pH, soil application may be attempted either with pure chemicals or with chelated compounds. The time of soil applications is same as for other fertilizers.
Method of Application:
The method of application should be appropriate taking into consideration the age of trees, their root extensibility, type of orchard management, kind and amount of fertilizers to be applied.
The different methods are as follows:
i. Broadcasting:
It consists of spreading the fertilizer uniformly over the entire field. This is applicable in full bearing or closely planted orchards.
ii. Band/Strip Placement:
This placement can be made either in bands or in trenches around the trees or fertilizers are drilled or injected into the soil. This method is commonly used when fertilizers are applied in small quantities to young trees and when P and K fertilizers need to be incorporated into the root zone or in case of plants with poorly developed root systems.
iii. Foliar Application:
The spraying entails applications either with manually operated or with power sprayers. Generally foliar sprays include micronutrients application or nutrient which cannot easily be supplied through soils. This is followed as a means of fertilizer application in fruit trees, which must be sprayed at regular intervals to affect the growth and fruit quality.
This fertilizer may also be applied either as injections to tree trunks or as dabs to cover the pruning wounds as is done in grapes. Applications of concentrated fertilizers should not be applied too close to the trunks. Each fertilizer application should be followed by a copious irrigation.
iv. Fertigation:
Fertigation involves the application of fertilizers with irrigation water at a slow and controlled rate to meet nutritional requirements at different stages of crop growth. Under fertigation, the fertilizers can be applied in ten splits as compared to one-two splits. Such applications result in increased crop yields with substantial savings in fertilizer and irrigation water.
The application of liquid fertilizers makes the nutrients continuously available to the plants. Fertilizers containing one or more elements can also be applied by injecting them through suction side of the pump or by injecting under pressure in the irrigation pipes or by injecting in the irrigation pipes through a ventury. Easily soluble fertilizers should be applied to avoid precipitation, clogging and damage to the components of the system.
Deficiency Symptoms of Some Essential Elements:
The major essential elements include C, H, O, N, P, K, Ca, Mg, S. The minor elements comprises of Fe, Mn, B, Zn, Cu, Mo required in smaller quantity. In addition, some elements are also essential, although they are required in traces by some of the fruit plants. The trace elements like N, CI, Al, Si, Co, etc. are required by some plants in a very minute quantity. Nutrients deficiency symptoms are one of the criteria of judging the nutritional status of the plant.
Leaf Sampling in Fruit Crops:
Leaf sampling in fruit crops is an essential tool for manipulation of manurial requirement of the plants. Plant analysis is the second criteria after soil testing that is critical to improving crop nutrition and yield. The plant analysis identifies how will the plants utilized the soil and applied nutrient. It allows the plant to tell us what nutrients it needs for proper growth. Leaf analysis can be used to diagnose nutrient problems after symptoms are found. This is achieved by identifying nutritional shortage or excesses before symptoms are developed and resulting in a more economical fertilizer schedule.
Sampling Procedure:
Collect 4-8 leaves per tree from each direction (North, East, South and West) at working height of one to two metres by taking one leaf per shoot. Sample along diagonals (X pattern), from about 10-20 per cent trees from selected blocks in the orchard. Collect leaf samples in polythene bags. Keep the bags in the ice-box and immediately send to the Leaf Analysis Laboratory.
In order to diagnose or confirm nutrient deficiencies or toxicities and to determine nutrient status of fruit trees, following leaf sampling procedures should be adopted.
Practice # 5. Irrigation Systems:
Irrigation is very important in fruit crops as sufficient moisture must be maintained in the soil for obtaining the optimum yield of good quality fruits. The aim of irrigating a fruit tree should be to wet the entire root zone without allowing any wastage of water beyond the root zone. The irrigation systems have to be properly devised so that the water requirements of the trees are met at the minimum expenditure without any wastage of water.
System of irrigation of fruit plants vary with the age of trees. Several methods are employed for the irrigation of fruit trees depending on the age of the tree, the soil topography and the availability of irrigation water. Thus the system of irrigation must be decided in relation to the varying orchard conditions.
Different systems of irrigation commonly adopted are as follows:
(i) Flood System:
In this system whole of the area is irrigated through one head i.e. without sub-division of the unit area into small plots. Irrigation water used in this case is excessive as the entire field is to be wetted to meet the need of the excessive root system. It provides fully saturation of root zone. The system is useful where intercrops or green manuring crops are grown in an orchard. In this system, the wastage of water is more and this also leads to excessive weed growth. There is a risk of bark diseases like collar rot or foot rot because the tree trunks remain in contact with water for long time. This system is suitable for orchards of more than 8-10 years old.
(ii) Furrow System:
This system is suitable in areas where the orchards are planted in sloppy land. In this system the water moves slowly in furrows in the area between tree rows. The trees are fed through the lateral movement of water. The consumption of water is less in this system and there is no risk of bark diseases. Saturation of root zone is comparatively less. Intercropping or green manuring is not possible in furrow system. This system is suitable for old orchard.
(iii) Basin System:
In this method, a small circular basin is provided around the tree trunk. These basins are linked directly with one another through straight channel. There is less wastage of water and it checks weed growth. Water passing through the channel touches the tree trunk directly and hence risk of bark diseases is involved. The water flow also draws away the manure from the tree basins and deposits it at the end of the channel. This system is suitable for young fruit plants below 1- 2 years of age.
(iv) Modified Basin System:
This system is an improvement over the basin system. In this system, main channel runs in between the tree lines and the basins are linked with it independently through small sub-channels. The only drawback of this system is that this needs more attention to block the sub channels after the basin has received adequate water. The size of the basin is increased with the extension of the leaf drip of each tree every year. Intercropping is not possible in this system. This is a good system of irrigation for the young orchard upto 6-8 years of age and also for the arid-irrigated areas where there is a shortage of water.
In improved modified basin system, the basins are linked with the channel passing through along the side of these basins. This system avoids the risk of bark diseases and intercropping is possible.
(v) Sprinkler System:
This system is used where water supply is not adequate. The water is pumped with pressure through the sprinklers attached to pipes and these sprinklers are adjusted in such a manner to overlap upto one fourth area covered by the other sprinklers. These are then moved to the next point after sufficient percolation has taken place. This system is very costly and is suitable in areas where the sub surface water is not fit and the soil is uneven or sloppy and the water supply is not regular from the canals. It is suitable for the full grown orchards.
(vi) Drip System:
The water is supplied with pressure after filtering it through the pipes with attached hoses designed to supply water in drops. These small hoses are placed around the tree in a circular pattern and the percolating water moves down and sideways wetting the root zone. This system of irrigation is very costly and most useful in areas with scanty rainfall for high density plantation. This system requires regular water supply. In this system, the loss of water due to evaporation and erosion of soil are nil but percolation and seepage losses are appreciable.
The pipelines and the sprouts are occasionally damaged due to growth of the root zone and un-prudent operation of machinery. The advantage of application of liquid fertilizer to the root system is available. High cost of operation, damage to pipelines and infestation of diseases to the underground parts of the plants starting from collar regions are the disadvantages of this system.
Proper Use of Drip System in Orchards:
The drip irrigation system has great potential to use irrigation water judiciously and efficiently along with improvement in the yield. Drip system supplies water near the root zone of the plants through dripper/emitters @ 2-10 litres per hour at a low pressure from 0.20 to 1.5 kg/ cm2, to meet daily crop consumptive use. Micro sprinklers are also used in place of drippers, which supply 20 to 40 litres water per hour depending upon the nozzle size and the working pressure. It is reported that drip systems allow irrigation of 50 to 200 per cent additional area enabling it to give additional produce.
The water for drip system may be available from canal, stored rainfall or tube-well. In case of tube-well irrigation, the water can be directly pumped through mesh filter into the drip system. In case of canal water, the water should be first stored in the storage tank and then pumped into drip system through sand filter and mesh filter. The storage tank should be lined. Its capacity should be according to the command area and availability of canal water. Water storage tank of 800 m3 capacity is sufficient for 10 acres of command area. The floating inlet should be adopted to reduce the sucking of silt load.
Components:
It includes:
(1) Control unit i.e. pumping, Alteration and fertilizer application unit
(2) The distribution network i.e. a network of main, sub main, lateral and emitters/micro sprinklers
(3) The miscellaneous components i.e. joints, flow and pressure regulating valves and water meters.
Working of the System:
The diameter of the main and sub-main (PVC) lines (25-75 mm) should be selected very carefully according to the size of the area to be irrigated. The mains and sub-mains are laid 45-60 cm below the soil surface to avoid damage during inter-culture and deterioration due to ultraviolet radiation.
The lateral lines (12-16 mm) are spread along the lines of trees and length of each line depending on length of the plant row. These laterals are joined with the main/sub-main line with the help of adopters. The discharge of the dippers may not vary more than 10 per cent of the specified one during working of the system.
When the system is to be operated in big orchard, the command area should be divided into two or four sub-units so that each sub-unit is not more than 10 to 15 acres. This will results in proper, judicious and economical utilization of irrigation water.
The planting distance can be kept closer in drip irrigated orchard due to less spread of the trees. Initial cost of drip system is more but is compensated through coverage of more command area under irrigation and thereby increasing the productivity.
Precautions:
In canal water supply, sand filter should be cleaned after every two to three weeks depending upon the silt load by back washing. Mesh filter should be closed every day. The emitter discharge should be measured periodically to check any clogging.
After 3-6 months any algae or bacterial formation should be removed from the drip pipes using one litre hydrochloric acid in 1000 litres of water. Pump this solution in the pipes by injection, keep it for 15-20 hours in pipes and then flush it out.