Introduction

Sericulture, or silk farming, is the rearing of silkworms Bombyx mori. for the production of raw silk.  Mulberry leaves, particularly those of the white mulberry, are ecologically important as the sole food source of the silkworm (Bombyx mori, named after the mulberry genus Morus), the pupa/cocoon of which is used to make silk. Silk is a way of life in India. Over thousands of years, it has become an inseparable part of Indian culture and tradition. No ritual is complete without silk being used as a wear in some form or the other. Silk is the undisputed queen of textiles over the centuries. Silk provides much needed work in several developing and labor rich countries. Sericulture is a cottage industry par excellence. It is one of the most labor intensive sectors of the Indian economy combining both agriculture and industry, which provides for means of livelihood to a large section of the population i.e. mulberry cultivator, co-operative rarer, silkworm seed producer, farmer-cum rarer, realer, twister, weaver, hand spinners of silk waste, traders etc. It is the only one cash crop in agriculture sector that gives returns within 30 days. This industry provides employment nearly to three five million people in our country. India is the second largest silk producer in the World followed by China. Germany is the largest consumer of Indian silk. The sericulture industry is land based as silk worm rearing involves over 700,000 farm families and is concentrated in Karnataka, Tamilnadu and Andhra Pradesh (Southern states of India). Assam and West Bengal states are also involved to certain extent¹.

Mulberry foliage is the only food for the silkworm (Bombyx mori) and is grown under varied climatic conditions ranging from temperate to tropical. Favorable soils for mulberry cultivation are sandy loam and clayey loam. Slightly acidic are ideally suitable. Mulberry leaf is a major economic component in sericulture, since the quality and quantity of leaf produced per unit area have a direct bearing on cocoon harvest. In India, most states have taken up sericulture as an important agro-industry with excellent results. The total area of mulberry in the country is around 2, 82,244 ha. Though mulberry cultivation is practiced in various climates, the major area is in the tropical zone covering Karnataka, Andhra Pradesh and Tamil Nadu states, with about 90 percent. Area under mulberry in Karnataka is 166 000ha².

As the civilization develops and economy of the people elevates, there is a lot of demand for silk based products. Hence there is a scope for increasing the production of silk products and in turn to increase the rearing of silkworms.

Diluted spentwash increase the uptake of nutrients, height, growth and yield of leaves vegetables^3,4 and yields of condiments⁵ , yields of some root vegetables in untreated and spentwash treated soil⁶ , yields of top vegetables (creepers)⁷), yields of tuber/root medicinal plants⁸   yields of leafy medicinal plants⁹, yields of leafy medicinal plants in normal and spentwash treated soil¹⁰, However, no information is available on the yields of cocoons of silkworms CSR2, CSR4 and CSR18 reared using M5 mulberry leaves cultivated by irrigation with distillery spentwash. Therefore, the present investigation was carried out to study the influence of M5 mulberry leaves cultivated by irrigating with different proportions of spentwash on the yields of cocoons of silkworms CSR2, CSR4 and CSR18 reared using M5 mulberry leaves. 

Experimental

M5 variety of mulberry plant selected for rearing of silk worms. The land was ploughed repeatedly (3 to 4 times) to loosen the soil and all gravel, stones and weed were removed to get the fine soil. The ridges and furrows are made at a distance of 1.0 m, sets were planted at a distance of 0.6 m (set to set) along the row and irrigated (by applying 5-10cm³/cm²) with raw water (RW), 50% and 33% SW at the dosage of once in fortnight and rest of the period with raw water (depends upon the climatic condition), without the application of any external fertilizer (either organic or inorganic). Harvesting of the leaf is done by plucking individual leaf during cooling hours of the day which is 50-60 days old. Silk worms are fed with fresh leaves.

Silkworm varieties selected for the present study were CSR2, CSR4 and CSR18, reared by shelf method. Trays rectangular in shape measuring 0.9m x 1.2m and depth of 7.5cm and are arranged in stands of 2.5m high 1.5m long and 1m wide and have 10 shelves with a space of 20 cm. using M5 mulberry leaves cultivated by irrigation of distillery spentwash. At the end of 5^th age i.e., 7^th day, the matured ready spinning worms are picked and mounted on bamboo mountages.  The spinning of the cocoon starts immediately after mounting and completed in 48-72 hours. Then cocoons were collected after harvest and cleaned by removing litter. Trials were conducted thrice, yields were recorded by taking the average weight (Table- 1).

 Table 1: Weight of cocoons at different irrigation (kg) (Average weight is taken from 100 Cocoons)

RW – Raw water:  PTSW- Primary treated distillery spentwash

Figure 1: Yields of cocoons.   Click here to View figure

Results And Discussion

The yields were very high in all the three types of  cocoons reared using M5 variety mulberry plant leaves  cultivated by 33% SW irrigation, and moderate in 50%, while comparatively poor in RW (Table-1). In our previous studies also found that 33% SW irrigation favours the growth, yield and nutrients of plants. This could be due to the maximum absorption of NPK by the plants at 33% dilution. 33% diluted spentwash can be conveniently used as irrigation medium.

Enrichment of nutrients in M5 mulberry leaves cultivated by 33% influence healthy growth of silkworms contains comparatively high proportion of natural protein fibre secreted by silkworms in the form a thread, Fibroin – inner core comprising 75% of silk, Sericin – outer gum comprising 25% of silk. However, the percentage yield is maximum in the case of CSR4 (26.6%) and minimum in case of CSR18 (19.0%) and moderate in CSR2 (22.77%). The yields of CSR4, CSR18 and CSR2 in 50% SW irrigation were found to be 15.0%, 11.95% and 16.0% respectively.

Conclusion

It was observed that the yields of all the three varieties cocoons produced by rearing the silk worms using M5 variety of mulberry leaves cultivated by irrigation in 33% SW were maximum and moderate in 50% SW and minimum in RW irrigations. It concludes that, in 33% SW irrigation the plants are able to absorb maximum amounts of nutrients (NPK) both from the soil and the spentwash resulting high yield and enhance the nutrients in plants leaves which in turn influence the better growth of silk worms containing higher proportion of silk proteins yields spinning of long silk threads in cocoons resulting in increased weight of cocoons, minimizes the cost of cultivation, and increase the yield of cocoons resulting in high silk production, this elevates the economy of the farmers  since cultivation of mulberry is made without using fertilizer.

Acknowledgement

The authors are thankful to, The General Manager, N. S. L. Koppa, Maddur Tq. Karnataka, for providing spentwash.

References

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