of fruits. Orissa, Kerala, Assam, West Bengal, Karnataka, Madhya Pradesh and Gujarat are major papaya-growing states, the highest productivity being 87.16 tonnes/ha in Karnataka followed by Andhra Pradesh (75.57 tonnes/ha), Tamil Nadu (56.0 tonnes/ ha), Madhya Pradesh (47.78 tonnes/ha), Gujarat (41.38 tonnes/ha), West Bengal (33.2 tonnes/ha), Rajasthan (31.80 tonnes/ha), Bihar (30.82 tonnes/ha) and Uttar Pradesh (23.75 tonnes/ha). The lowest productivity is from the north-eastern region including Kerala.
1,2 Senior Scientist (Hort.), Division of Crop Improvement and Production, Central Institute for Subtropical Horticulture, Lucknow 227 107, India
12
Approaches and Strategies for Precision Farming in Papaya
Selection of Varieties
A large number of varieties are cultivated in India. As a matter of fact many of them are not real varieties since these cannot be relied upon to reproduce the parental characters in their progenies. Based on sex expression, papaya varieties can be classified either as dioecious or gynodioecious. The dioecious varieties produce male and female plants in a 1:1 ratio when propagated from seeds. However, gynodioecious varieties produce female and bisexual (hermaphrodite) in a 1:2 ratio. Seven varieties (CO1, CO2, CO3, CO4, CO5, CO6 and CO7) have been released from TNAU, Coimbatore. Of them, CO2 and CO5 are recommended for papain extraction, while CO3 and CO7 are suitable for table purpose. Pusa Delicious, Pusa Majesty, Pusa Giant, Pusa Dwarf and Pusa Nanha have been released from IARI regional station. Of these, Pusa Majesty is recommended for papain extraction, while Pusa Nanha for kitchen gardening and high-density planting. Other gynodioecious variety Surya developed from IIHR, Banglore, having pink flesh colour is good for table purpose.
Propagation and Nursery Production
Papaya is normally propagated by seeds. To ensure genetic purity, seeds should be procured only from reliable sources. For planting one hectare area, about 500 g seed is required. The seedling can be raised in 3 m x 1 m x 10 cm nursery-beds or in polythene bags. The seeds should be sown 10 cm apart and one cm deep in rows and covered with fine compost or leaf-mould. Light irrigation may be followed in morning hours. The nursery-bed may be covered with polythene sheet / paddy straw / dry straw mulch to protect it from adverse weather conditions. Apart from nursery-beds, seeds are also sown in polybags of 20 cm x 12 cm size at the rate of 4 seeds/bag. The pot mixture should consist of one part each of sand, top-soil and FYM/vermicompost. The seeds should be sown not deeper than 1.5 cm. Regular watering with water-can should be done gently in morning and evening until seeds germinate.
The soil in bag should be treated with 100 ml of 0.1 per cent copper oxychloride to prevent damping-off, a fungal disease, which affects young papaya seedlings. Repeat after one month. Thin out seedlings to 2/bag 30 days after germination. Tender seedlings must be protected against heavy rainfall. The most serious disease in the nursery is ‘damping off’. Treating seeds with 0.1 per cent Monosan (phenyl mercury acetate) before sowing is the best preventive measure against this disease. Drenching with fungicide, copper oxychloride (0.3 per cent) prevents fungal rots at nursery stage. The optimum temperature for germination of papaya seeds is 35oC and temperatures below
23oC and above 44oC are detrimental. The seedlings become ready for transplanting
Vegetative Propagation
Since papaya is commercially propagated by seed, this leads to variation and a varietal name becomes misnomer. Even after six or seven generations of inbreeding only a maximum of 90 per cent homozygosity is attained (15). Hence, to perpetuate papaya true-to-type, utilisation of easy method of vegetative multiplication is necessary. The multiplication of papaya through budding has been attempted by Singh et al. (16).
Preparation of stock seedlings: Seedlings are raised by sowing papaya seeds
before 60 days of budding and transferred to pots/polybags/field when they attain a height of 8 cm. The seedlings of 1-1.5 cm diameter are ready for budding.
Selection of scion: For scion
material, vigorously grown female plant is headed back well in advance of budding (about 45 days), to induce axilliary growth (Fig. 1). Side shoots emerging from below the cut point, having a length of 24 cm and 1.2 cm diameter, are taken for bud wood. In this regard juvenility of the plant has to be given due consideration. It has been observed that female plant cut at a height of 30 -60 cm gives rise to shoots which have vegetative buds.
At a higher level, emerging shoots have reproductive buds only. Using the above
rootstock and scion material, patch and shield budding are done during July, August, September and October (Table 1). The top of seedling stock is removed after a week of budding. The buds sprouted after 15 days of budding attain sufficient length after a month (Fig. 2). The highest success of 90 per cent is obtained in patch budding if
Fig. 1. Axillary growth after heading back papaya plant
Approaches and Strategies for Precision Farming in Papaya
done in the first fortnight of September closely followed by 80 per cent in the second fortnight of August, whereas in shield budding good success is obtained (80 per cent) if done in the first fortnight of September (Fig. 3). There is earliness of flowering and increased yield in budded plants as compared to the control plants.
Table 1. Seasonal effect on success in different methods of budding in papaya
Time of budding Success (per cent)
Patch budding Shield budding
July 60.0 37.5
August 80.0 56.0
September 90.0 80.0
October 50.0 40.0
Source: R.N. Singh, Gorakh Singh and O.P. Rao (16 )
Planting Season
The season of planting has a great influence on growth and fruiting. Seedlings planted during monsoon, grow taller and bear fruits at higher level on trunk than those planted in other seasons (8), thereby increasing the cost of production. Allan et al. (1) reported various effects of environment on seedlings of papaya but the use of different planting times is desirable to obtain accurate information on papaya plantation. Muthukrishnan and Irulappan (7) observed that the best season of papaya planting was beginning of monsoon but transplanting could be continued from June to November. Singh and Singh (12) reported that September planting was more beneficial as it gave higher yield, better fruit quality and less incidence of papaya ring spot virus and can be recommended for end-users.
Spacing
Planting distance is determined by the integration of light interception, cultivar and economic consideration. In various papaya-growing tracts of India,spacings are recommended as per papaya cultivars (7). High-density planting of papaya has increased the productivity per unit area and considerable information has been published (6, 8 and 12). A spacing of 1.8 m x 1.8m is normally followed for most of the cultivars. A closer spacing of 1.33 m x 1.33m (5,609 plants/ha) is optimum for Coorg Honey Dew. The spacing of 1.4m x 1.4m or 1.4m x 1.6m is best suited for cv. Pusa Delicious under subtropical condition of Bihar. Spacing of 1.6m x 1.6m gives highest yield of fruits as
well as papain in Tamil Nadu. A closer spacing of 1.2m x 1.2m for Pusa Nanha is adopted for high-density orcharding, accommodating 64,000 plants/ha. Singh and Singh (13) suggested that 2.0m x 1.8m spacing is optimum plant density (OPD) for better canopy development, yield and fruit quality of papaya cv. Pusa Delicious under Uttar Pradesh condition (Figs 4 and 5).
Sex Expression and Thinning
Recent studies confirmed precocious separation of one pair of chromosome with complete 9 : 9 chromosomal separation. The karyological analysis indicates that there is a satellite chromosome in male plant. This satellite chromosome determines sex in papaya (10) but homologue chromosome is not a satellite. According to Chaudhary et
al. (5) leaves of male plants are rich in total carbohydrate, phosphorus and chlorophyll
a and b than those of female plants, which are rich in nitrogen and potassium. The prediction of sex of nursery seedlings by chlorimetric test of leaf extracts was provided correct up to 88 per cent in case of female and 61 per cent in male (14).
In dioecious varieties, male and female plants will be in a 1:1 ratio. Keeping 5 per cent male plants in the orchard for proper pollination, other male plants should be removed. Normally, male plants flower earlier than female ones and can easily be identified as they have pendulous, hanging and branched stalks. In gynodioecious varieties, stamens can be seen adhering to petals surrounding the ovary. Only one plant per pit should be retained.
Fertilizer Application
The development of nutrition management to maintain plant health and encourage successful fruiting in papaya depends on improving our understanding on the role of each nutrient on different components of growth. Papaya is a heavy feeder and adequate Fig. 5. Good yield of papaya can be obtained in
high-density planting Fig. 4. High-density planting in papaya
Approaches and Strategies for Precision Farming in Papaya
manuring of young and mature plants is essential to maintain the growth and vigour of tree for regular high yields. The petiole analysis methodology proved satisfactory in fertilizer recommendation to papaya. The petiole from sixth fully opened leaf from top, 6 months after planting is found best indicator for the nutrient status of papaya. Critical limits of N, P and K have been workout which are 1.01 - 2.50 per cent, 220-400 mg/ g and 3.30 - 5.50 per cent, respectively. The importance of N for the growth of papaya was demonstrated by Awada (2) and Awada and Long (3 and 4). Application of N, P and K increased the concentration of respective elements in papaya petiole (11). The Ca and Mg content of petiole was not related in any way to applied N, P and K. Before planting, each pit should be filled with 10 kg well- decomposed farmyard manure / compost, Azospirillium (20 g) and Phosphobacterium (20 g), neem cake (20 kg) and bone-meal or fishmeal (1 kg). The following dose of fertilizers (Table 2) has been standardized to achieve the objective of precision farming.
Table 2. Fertilizer dose for papaya plants
Fertilizer Form Dose
(g/plant/year)
Nitrogen (N) Urea 250
Phosphorus (P) Single superphosphate 250
Potash (K) Muriate of potash 500
These fertilizers should be applied in five split doses (after 4 moths of age) at two- month intervals. Deficiency of lime and boron has often been observed in papaya orchards. Spraying of 0.5 per cent zinc sulphate (twice) and one spray of borax (0.1 per cent) may be done depending upon the nutrient status of soil.
Irrigation Management
Irrigation in papaya is empirical and not based on soil plant water relationship. It depends upon the soil and climatic conditions of specific region. Papaya is a shallow- rooted crop and is highly sensitive to fluctuation of soil moisture. Prolonged moisture stress affects the growth and development, encouraging the production of male flower, leading to poor fruit set. Fruits of papaya produced in high rainfall and humid regions are usually larger than those grown in low rainfall regions irrespective of varieties. Lower moisture level shifts plants towards sterility and male floral characters, while higher moisture conditions results in excessive production of undesirable carpelloid types in which the stamens fuse with developing ovary, resulting in mishappened fruits. Trials taken up have revealed that irrigation at 60-80 per cent available soils moisture depletion is found optimum for papaya.
The crop is extremely sensitive to collar rot under flood irrigation where water comes in direct contact with the trunk. In north Indian condition, papaya requires irrigation at 5-7 days intervals during summer and 15 days in winter. Low-volume, high frequency irrigation like drip irrigation is becoming increasingly popular in long-duration commercial crops and could be an alternative system of irrigation for papaya in order to efficient utilization of water which is becoming a scarce and costly input in recent years.
Replenishment of evaporation losses under basin irrigation up to 100 per cent increased the yields although the yield difference between 75 and 100 per cent were not significant. The evapotranspirational loss was around 3,510 mm with 75 per cent of evaporation replenishment (28 months crop) (17). Whereas drip irrigation of papaya with 60 per cent of evaporation replenishment was found to be optimum. The water use with 60 per cent replenishment was around 2,985 mm. Restricting the water flow under drip irrigation by allowing the water to flow in pipes embedded in soil 30 cm away from the trunk on either side of the plant resulted in higher yields (Table 3). Daily irrigation of papaya with 2 emitters/plant placed midway between the trunk and skirtline was found to be ideal for papaya growing (17). The relative performance in papaya with drip irrigation in comparision to traditional system of irrigation is given in Table 4.
Table 3. Growth, yield and water use of papaya in relation to irrigation frequency, number of emitters and their placement under drip irrigation
Treatment Plant height (m) Trunk girth (m) Fruit number / plant Average fruit weight (kg) Fruit yield (tonnes/ha) Total soluble solids (0Brix) Water-use efficiency (kg/ha/mm) Irrigation frequency Drip daily 2.46 0.36 36 1.32 116.5 12.6 42.4 Drip alternate 2.31 0.32 31 1.24 110.2 12.8 36.9 day Number of emitters 1 emitter/plant 2.25 0.33 30 1.21 98.2 12.1 32.9 2 emitters/plant 2.38 0.38 35 1.30 115.6 12.4 38.7 Emitter placement Skirtline 2.25 0.32 30 1.12 101.4 12.5 33.9 Midway between trunk
and skirtline
2.40 0.36 34 1.20 120.5 12.3 40.4
Approaches and Strategies for Precision Farming in Papaya
Table 4 Relative performance of papaya with drip irrigation in comparison with traditional irrigation method
Yield (q/ha) Irrigation
water (cm) Water-use efficiency (q/ha/cm) Advantage of drip irrigation Place
Surface Drip Surface Drip Surface Drip Saving of
water (%) Increase in average yield (kg/plant) Coimbatore 130.0 230.0 228.0 73.0 0.6 3.20 68.5 43.5 Kalyani 312.0 383.0 24.0 11.0 13.0 34.8 54.2 18.5
Source : Approaches for Sustainable Development of Horticulture. Singh, H.P., Negi, J.P. and Samuel, J.C. (Eds), pp. 81-91.
Drainage and Productive Life
Papaya plants are very much susceptible to waterlogging. Even 24 hours stagnation of water may kill the well-established orchard. Therefore, it is essential to make some furrows/ trenches for quick and complete drainage of water during rainy season. The profitable productive life of papaya is two-and-a-half years under north Indian conditions provided the crop is well-managed.
Intercrop
When papaya is grown as a main crop, all kinds of vegetables can be grown as intercrops for about six months from planting. Vegetables such as cowpea, tomato and clusterbean can be grown as intercrops. Papaya is itself grown as intercrop in combination with perennial fruit orchards where the spacing required for the main crop like mango, sapota, guava, lemon etc., is more than 5 m especially during early periods of orchard establishment.
PLANT PROTECTION