ABCD on Pawpaw (papaya) farming in Kenya
English: Pawpaw; Swahili: papayu
Pawpaw is a widely cultivated fruit tree in the tropics and subtropics. It is a popular fruitinKenya.
General Benefits of Pawpaw
- Ripe papaya is a favorite breakfast and dessert fruit that is available year-round.
- It can be used to make fruit salads, refreshing drinks, jam, jelly, marmalade, candies and crystallized fruits.
- Green fruits are pickled or cooked as a vegetable.
- Young leaves are sometimes eaten. In some countries, seeds are used as vermifuge and to induce abortion (abortifacient).
- Carpaine, an alkaloid present in papaya, can be used as a heart depressant, amoebicide and diuretic.
- Some countries grow pawpaw so that they can extract papain which is used in beverage, food and pharmaceutical industries: in tenderizing meat, chill- proofing beer, drug preparation for digestive ailments and to treat gangrenous wounds.
- Papain is also used treating hides, degumming silk and softening wool.
Types of Pawpaw
They are distinguished on the basis of their flowers: Female (pistillate), male (staminate) and hermaphrodite (bear both male and female flowers). These groups are only distinguishable at flowering stage. Fruits from female flowered trees are usually sweeter and of more round shape than fruits from hermaphrodite trees.
Suitable Growth Condition
- Papaya thrives in warm areas with adequate rainfall and a temperature range of 21-33°C.
- Its altitude range is similar to that of the banana, from sea level to elevations at which frosts occur (often around 1600 m). However they grow best in areas below 1000 m.
- The quality and yield are low at higher altitudes. Frost can kill the plant, and cool and overcast weather delays fruit ripening and depresses fruit quality. Fruit tastes much better when grown during a warm sunny season
- Evenly distributed annual rainfall of 1200 mm is sufficient if water conservation practices are employed.
- They need to be planted in sheltered locations or surrounded by windbreaks; strong winds are detrimental, particularly on sandy soils, as they cannot make up for large transpiration losses.
- Papaya grows best in light, well-drained soils rich in organic matter with soil pH of 6.0-6.5. It can tolerate any kind of soil provided it is well-drained and not too dry.
- The roots are very sensitive to waterlogging and even short periods of flooding can kill the plants.
Papaya grows best when planted in full sunlight. However, it can be planted as an intercrop under coconut, or as a cash crop between young fruit trees such as mango or citrus. Low growing annual crops such as capsicums, beans, onions and cabbages are suitable good intercrops.
Clean cultivation is standard practice and weed control, particularly around the small plants, is very important. If weeds are only slashed – resulting in a grassy weed cover – papaya plants suffer severe competition. Experimental work shows a very good response to mulching.
Irrigation is needed to minimise the abortion of flowers and maintain growth during the dry season. There should be watering every once a week. Papaya is a fast-growing crop that requires a lot of nutrients. The use of manure and mulch steadies the release of nutrients. Calcium deficiency depresses growth and fruit set and enhances fruit drop; liming (to a pH of about 6) is the remedy.
The stage of physiological development at the time of harvest determines the flavour and taste of the ripened fruit.
The appearance of traces of yellow colour on the fruit indicates that it is ready for harvesting. Fruits harvested early have longer post harvest life, but give abnormal taste and flavour. The fruits also tend to shrivel and suffer chilling injuries when refrigerated. The fruit is twisted until the stalk snaps off or cut with a sharp knife. Yields per tree vary from 30 to 150 fruits annually, giving 35 to 50 tons of fruit per ha per year. A papaya plantation can be productive for over 10 years but the economical period is only the first 3 to 4 years. It is therefore advisable to renew the plantation every 4 years.
For papain production, latex is collected by tapping the green unripe fruit. Four longitudinal incisions, skin-deep and 2 to 3 cm apart are made with a sharp, non-corrosive rod (glass, plastic or horn). Latex is collected in a clean glass or porcelain container and dried, or a canvas covered tray fixed onto the trunk of the tree. The latex is later scraped off the canvas with a wooden scraper and dried. Fruits may be tapped once a week, until they show signs of ripening. The operation is best done early in the morning (before 10:00) because the latex flows slowly in hot weather. Tapping results in ugly scars on the fruit, although quality is unaffected. Tapped fruit can be processed or used as animal feed. The papain producing trees are productive for 2 to 3 years, with the first 2 years being the most productive. If kept longer production is uneconomical.
Propagation and planting
Papaya is propagated by seed. To reproduce the desired characteristics it is best to get seeds through controlled pollination. The fleshy outer layer of the seed coat (sarcotesta) enveloping the seed is removed because it inhibits germination. This is achieved by rubbing the seed together against a fine-meshed screen under running water. Thoroughly dried seeds stored in air-tight containers remain viable for several years. Seeds are sown in small containers (tin cans, plastic bags or paper cups) at the rate of 3-4 seeds per container. Use of sterilized soil minimizes losses resulting from nematodes and damping-off fungi. Germination takes 2-3 weeks. Another practice is to sow the seeds in sterilised nursery beds and to prick out at the 2-3-leaf stage, transferring 3-4 seedlings to each container. Seedlings are transplanted about 2 months after sowing when they reach the 3-4-leaf stage or 20 cm height, preferably at the onset of the rainy season. During transplanting, take care not to disturb the roots. Older seedlings recover poorly after planting out.
Papaya needs adequate drainage and is often planted on mounds or ridges. Transplants must be watered regularly until they are established. Field spacings are in the order of 3 x 2 m to 2.50 x 1.60 m, giving densities of 1667 and 2500 plants/ha respectively. The same densities are obtained by planting in double rows spaced (3.25+1.75) x 2.40 m or (2.50+1.50) x 2 m. Thinning to one female or one hermaphrodite plant per hill is done when the plants reach the flowering stage. In the absence of hermaphrodite plants, 1 male plant per 25 – 100 female plants is retained as pollinator.
Papaya plants grown from seed produce fruits of different shapes, sizes, colour and even taste. Vegetative propagation of papaya provides a solution to most of these problems. The clone is selected for higher productivity and good quality fruits besides agronomic qualities such as dwarfness for easy harvesting and good resistance to diseases. Propagation of papaya using tissue culture is fast gaining popularity, mainly because tissue culture has numerous advantages over other conventional methods of propagation. Tissue culture facilitates rapid production of disease free plants. In Kenya such plants are available from Kenya Agricultural Research Institute (KARI), Thika as well as several private companies.
Planting holes of 60 x 60 cm and at least 50 cm deep are prepared with 1 bucket of compost and a handful of rock phosphate is mixed in with the dugout soil and returned around the plant. Firm the soil and water liberally and add mulch around the young plant.