Cultivation of Mulberry
1. Selection of Mulberry Variety:
- Cultivation and harvesting of mulberry plants are called Moriculture.
- There are over 20 species of mulberry (Family-Moraceae) of which four are more common. They are: Morus alba, M. indica, M. serrata and M. latifolia. These plants grow both in tropical and temperate climates. An annual rainfall of 600-2600 mm is sufficient for its growth.
- The local species M. indica offers certain good features i.e. quick growing, hardiness, remaining fresh throughout the year, but its yield is rather low. Therefore, Central Silk Board have developed high yielding varieties such as Kanva-2, S-30, S-54 (suited for Karnataka, A. P., and Tamil Nadu states) and S-162, S-519, S-623 suited for Punjab, J and K, U. P. and W. Bengal states. These strains give 30-70% more leaves per hectare than the local strain.
- Mulberry is a hardy perennial tree species grown in temperate, tropical and sub-tropical regions of the world. The leaves of mulberry form the specific food for the silkworm, Bombyx mori. L.
- Among the food plants mulberry alone contributes about 90% of raw silk productions of the world, the other 10% is from non-mulberry (Tassar, Eri and Muga) food plants. It has been shown that about 75% of the protein directly derived from mulberry leaf is the primary source for the silkworm for bio-synthesis of its silk.
- Mulberry is propagated either through seeds or vegetatively. The vegetative method is mast common. In India, the most common method of propagating mulberry is through cuttings in multivoltine regions like Karnataka and West Bengal.
- Exotic varieties are propagated through root grafts. In univoltine areas like Kashmir, the mulberry is propagated through seedlings.
- Mulberry can be grown under various climatic conditions ranging from temperate to tropical.
- A perusal of the geographical position of the mulberry growing countries of the world indicates that all of them except Brazil is located north of the equator. Mulberry can be grown in all types of soil and climatic conditions.
(a) Atmospheric Temperature: It is found that mulberry requires a temperature ranging from 24°C to 28°C for better growth and leaf yield. Mulberry plants do not grow well if the temperature is below 13°C and above 38°C because the growth and sprouting of buds cannot be obtained. In temperate regions, the plants remain dormant during the winter season. Thus, in temperate regions, mulberry leaves are available for rearing purposes only from May to October. In the tropics, the growth of mulberry is continuous throughout the year.
(b) Rainfall: Mulberry can be grown in places with rainfall ranging from 600 mm to 2500 mm. When the rainfall is low the growth is limited due to moisture shortage and result in low leaf yield. On average 50 mm once in 10 days is considered ideal for mulberry.
(c) Atmospheric Humidity: The ideal humidity for mulberry leaf yielding is ranging in between 65 to 80 percent. The quality of leaf produced during the rainy season is better than the leaf produced during other seasons because, during the rainy season, the soil contains high moisture and high atmospheric humidity.
(d) Sunshine: This is also one of the important climatic factors which regulate the growth of mulberry. In temperate countries, mulberry grows with a sunshine range of 5.0 to 10.2 hours a day while in the tropics; it grows well with a sunshine range of 9.0 to 13.0 hours a day.
(e) Elevation: In Japan, mulberry cultivation is practiced at altitudes from 22 m to 1735 m above MSL, while in the U.S.S.R. it is practiced 400 to 2000 m. Under tropical conditions and in India, mulberry is cultivated at altitudes between 300 to 800 m above MSL. However, up to 700 m, MSL is ideal for the good growth of mulberry.
- Mulberry can be grown in all types of soil which maintains the mulberry plants for sustained maximum productivity of quality leaves. It has to supply the following constantly:
(a) The essential major and minor plant nutrients.
(b) Oxygen for root respiration.
(c) Mechanical support or anchorage.
(d) As a storehouse for water.
- Since, mulberry is a deep-rooted, perennial, long-standing, hardy, and monoculture crop. The soil should be deep, fertile, well-drained, clay loam to loam in texture, friable, porous, and with good moisture-holding capacity.
- But it thrives exceedingly well in red loamy soil with a pH ranging from 6.5 to 7.0. It can tolerate slightly alkaline and acidic conditions in the soil. However, the alkalinity can be corrected by applying gypsum/sulphur and the acidity by adding lime to the respective soils.
- The soil quality has an influence not only on the leaf yield but also on their quality which are reflected on the growth of silkworms resulting in high cocoon yield with better quality.
- In lands, where mulberry is grown as a rainfed crop the organic content of the soil is naturally poor and the water holding capacity is less. The rain water therefore percolates very fast and goes underground so that very little moisture is left on the strata where roots spread.
- This hazard can be overcome by adding organic matters like farmyard manure and compost. It is also by growing a mulch crop such as a leguminous species and subsequent mulching of the same into the soil. It works in two ways first by providing the humus required and secondly, by fixation of atmospheric nitrogen through the bacterial root nodules.
(a) Location and Topography: Mulberry plantation should be established near the rearing house it is convenient for quick transport and immediate use of leaves for feeding because after harvesting mulberry leaves loss considerable moisture and wither during transport, especially in summer, will lead to wastage of leaves and economic loss to the farmers.
(b) Preparation of the Land: When once the land is selected for mulberry cultivation, the field has to be leveled and the fertility level improved. Leveling of the land depends upon its topography such as flat, incline, and terrace type of fields. While leveling, the level of the underground water must be taken into consideration. In case the water table is nearer the surface, proper drainage must be provided. If it is a hilly area, smaller terrace gardens with contour bunds have to be formed and proper drainage has to be provided for the water to move out. After leveling deep plowing is necessary to remove the weeds and the soil has to be made into a fine tilth before the pits are prepared for planting. Wherever mulberry has to be planted the land should be free from weeds as they are unwanted plants in the field of any crop. They compete with the crop for sunlight, water, and nutrients. Some of the weeds are known to release root exudates which render the soil unfit for the growth of the crop, as they are mainly phenolics and have adverse allelopathic effects. Some weeds also act as secondary hosts for many plant diseases and insect pests that destroy the crop. Hence, it is very important that mulberry cultivation should be taken up only in a land that is free from weeds like species of Cynodon and cyperus. Periodic weeding is a must for the better growth of mulberry.
(c) Planting Season: Early spring and late autumn seasons are best suitable for mulberry plantations. Planting in the winter and summer seasons should be avoided. Planting should not be delayed in spring, if delayed the sprouted buds fall off and the plants do not grow well. In India, the planting season varies in different parts. In Karnataka, mulberry is planted during July-August with the onset of the South-Western monsoon. Subsequent rains help the proper establishment of the crop. In West Bengal, cuttings are planted during November (Late autumn). Planting during the rainy season will result in the rotting of the cuttings.
(d) Direction of Planting: In temperate regions, the direction of the rows of planting is important. Depending upon the light intensity (sunshine hours) and wind direction, mulberry seedlings are to be planted in rows either in North-South or East-West direction; making the rows parallel to the direction of wind. In tropics, where the sunlight is not a limiting factor, mulberry rows can be planted in any direction. In sloppy lands, the rows should be parallel to the contour lines.
(e) Planting Distance: The planting distance depends upon, the agroclimatic conditions (sunshine, temperature, precipitation, etc, soil fertility level, intensity of cultivation practices adopted including the training and harvesting methods and also the variety of mulberry planted. Regarding the plant spacing considerations like number of branches, and branching habits of the variety methods of training and fertilizer practices and moisture status in the soil should be kept in view.
The general pattern under rainfall conditions is known as ‘Pit system’ of cultivation and under irrigation the row planting is known as ‘Kolar system’. In this system, ridges and furrows are made at distance of 0.30 to 0.45 m. On either side of ridges, mulberry is planted at a distance of 0.10 to 0.50 m. In West Bengal, where rainfall is heavy, a close planting called “strip system” is followed. In this method, spacing of 0.6 m between the strips is made, in each strip, 2 to 3 rows are planted at a distance of 0.15 m.
(f) Selection of Planting Material: Stem cuttings are obtained from 6-8 month old branches. Fully grown thick main stems and branches which are free from insects and diseases should be selected. These should be generally one and a half-centimeter thick. The stem is cut into pieces with 3 to 5 buds of about 20 cm long. Cuttings should not be too woody or tender. The cuttings should be clean cut at an angle of 45° with a sharp tool without any split in the bark.
(g) Planting Method: Three methods of planting have been practiced in India.
1. Planting cuttings directly in the field.
2. Raising saplings in the nursery and planting in the fields.
3. Raising saplings in the plastic bags and transplanting.
- If the cuttings are directly planted in the field there is bound to be atleast 20-30% gaps as the sprouting in any of the commercial varieties will be anywhere between 70-80%.
- Further, one cannot be sure of 100% sprouting when these gaps are planted again by fresh cuttings. This kind of planting will not give the farmer uniform leaves as the plants differ in their age which will result in poor cocoon yield. Hence, direct planting of cuttings is not recommended.
- After preparation of land, pits of standard size of 40 cm width, 40 to 50 cm depth are made where interplanting distance is over 1.2 metre, trenches of 45 cm x 45 cm are opened in the planting row.
- Farm yard manure or compost is applied in the pits or trenches, at the rate of 15 tonnes per hectare, over which leaf mould upto a thickness of about 10 cm is added, chemical fertilizers at the rate of 80 kg N, 100 kg P20, and 50 kg K2O per hectare are also applied.
- After applying the fertilizers, the soil is filled to a depth of 5 to 10 cm and the saplings planted with the spacing as stated earlier.
- Although mulberry can be propagated both by cuttings and saplings; planting of saplings is recommended as their survival and establishment is better.
- At least 3 to 5 months before the pits are ready; one should plan for the nursery. Nursery bed must be prepared before the cuttings are ready.
- The nursery bed should be 4-5 metres x 1.5-2 metres and about 30 cm above the ground level and it should be preferably in shade. The nursery bed has to be prepared with equal quantities of red soil, sand and manure.
- While planting cuttings in the nursery bed a distance of 15-20 cm from cutting to cutting and 10-15 cm from row to row has to be maintained. The cutting is pushed into the soil leaving only one bud exposed above the ground.
- If necessary, little fertilizers may be used after one month of planting to boost growth. It is important that the root system should not be damaged while uprooting the saplings. It is recommended that only 3-4-month-old saplings are transplanted in pits and water should be given immediately after planting.
- Raising of the sapling in plastic bags is more beneficial than rising in nursery bed. The plastic bags of 20 cm and 25 cm size must be used and the mixture of red soil, sand and manure is filled.
- In each plastic bag, a cutting of 20 cm length is planted deep in the mixture. Bags kept under the shade and watered regularly.
- The great advantage of this method is that the root system is not affected during transplantation and plants will be well established after some time and plants could tolerate the drought situation in case of failure of irrigation/rains.
- The importance of the application of fertilizers and manures for both increased productivity and improved quality of mulberry leaves has been well recognized. It is fully realized that the native soil fertility is not sufficient alone, so the application of manures and fertilizers is a must. The proper applications of manure are as follows:
1. Increases water retention capacity.
2. Improves the texture of soil helping in good rooting.
3. Increases microbial population.
4. Supplies micro-nutrients in addition to macro-nutrients.
- The common organic manures are used for mulberry are farmyard manure and compost. Sometimes neem cake and groundnut cake are also used to a limited extent.
- Introduction of leguminous cover crops between the rows of the main plantation not only protects the soil but also increases fertility due to the accumulation of nitrogen through symbiotic nitrogen fixation by bacteria.
- Of the three major elements of fertilizers viz. Nitrogen, Phosphorus and Potassium, nitrogen is the most major important and vital for increased production of good quality leaves.
- This is done to control weeds and simultaneously make the soil porous so as to allow water to soak deep in the soil and to ensure better aeration and enhance nitrification. All these can be achieved by manpower with tools or by bullock-drawn implements.
- First, weeding is required 30 days after planting. This can be done by manual labour. To remove weeds ploughing of inter-space between the rows periodically to a depth of 15 cm is necessary. Under rainfed conditions, periodical ploughing is essential to remove weeds and conserve moisture and nutrients. Inter cultivation should be done atleast 3-4 times a year.
9. Water Management / Irrigation
- Water is the most important single input which controls agriculture productions. There are different methods of irrigation.
(a) Furrow method: In this method, the field is laid out into a series of ridges and furrows. The basal part of the furrows is made wet by the flowing water and ridge is moistened by the capillary movement of the water. Advantages of this method are:
(i) It is suitable for widespread as well as close-spaced mulberry plantation.
(ii) Evaporation from the soil surface is relatively less.
(iii) The ridges carrying the plant root system are freely aerable helping root development.
(iv) Furrow serves as a drainage channel during heavy rains and thus water stagnation is avoided.
(b) Flatbed method: The field is divided into rectangular beds with bunds all around and channels on the sides. The bed size may vary from 3.5 x 2.0 m to 4.0 x 6 m.
The benefits are:
(i) It is suited for most soil types.
(ii) Relatively economic in use of water, their is low wastage of water due to run off.
(iii) The soil is not eroded.
(iv) Irrigation is quicker.
(c) Basin method: The basin method is suitable mostly for tree plantations. In this system, irrigation water from the supply source is laid into the basin around the trunk. The diameter of the basin may vary according to the age size of the tree from 1.0 to 1.5m.
(d) Overhead or sprinkler: Method of irrigation can be practiced in undulating lands where low and high bushes are cultivated.
The advantages are:
(i) Most efficient in economizing water use.
(ii) There is a uniform distribution of water on the foliage.
(iii) The percolation loss in porous and sandy soil is avoided.
(iv) Most suitable for emergency irrigation.
Pruning is judicious removal of undesirable branches of mulberry plant with the following objectives:
1. To give the plant a proper shape and size.
2. To improve the leaf yield.
3. To improve the quality of leaves.
4. To adjust the leaf production to synchronize with the requirement for silkworm rearing.
5. To facilitate easy leaf harvest and inter cultivation, also helps to divert the energy of the plant towards optimum leaf production.
- Since, mulberry is a perennial plant, periodical pruning is necessary to maintain higher leaf yield. It is very important that the first leaf harvest should be done only 8 months after planting and the first pruning should be done after the first harvest of the leaves to allow proper establishment of the plant. This will facilitate the plant to develop a sturdy stem and an efficient root system.
- The first pruning will be in May/June after the commencement of rains and it will be at 60 cm from the soil level. The second pruning will be in October/November after taking 2 or 3 successive leaf harvest and it will be at the same height as the first pruning for irrigated mulberry, but 90-100 cm (middle pruning) from the soil level for rainfed mulberry.
11. Quality of Leaves:
- The leaf which is dark green, turgid, soft, thick with good moisture content and high percentage of protein is considered to be excellent. Such quality leaves will yield better silk.
- Chlorotic and drooping leaves are due to nutritional deficiency or excess of moisture or both.