AQUAPONICS SYSTEM

Aquaponics

Introduction

Aquaponics or pisciponics is a combination of hydroponics, the growing of crops in water rather than soil, and conventional aquaculture, the raising of aquatic animals such fish. The fish waste provides organic food for the growing plants and the plants naturally filter the water in which the fish live. This is a mutual relationship where the fish provide food for the plants and the plants provide a clean environment for the fish. Fish waste is used as fertilizer hence there's no need for buying chemical fertilizers.

Advantages of Aquaponics:

·            Water use is reduced significantly in recirculating aquaponics

·            No need for chemical fertilizers as fish waste is used in cycle

·            Less land space required – plants and fish are grown in close quarters.

·            Can grow food all year round depending on climate and the location of the aquaponics system (inside/outside)

·            Faster growth of plants (can exceed hydroponic plants growth by up to 4 times for particular vegetables and herbs.

·            Lower susceptibility to disease plants e.g. soil-borne bacterial disease. Fish in aquaponic systems are also less susceptible to pathogens that are common to aquaculture systems.

·            Saves labour and Money (no weeding, fewer pests, no watering, and fertilizing, bending, digging. Feeding the fish is what is important in aquaponics.

Disadvantages of Aquaponics

Cost of investment is higher than other forms of farming

Technologically requires more expertise to run properly.

How Aquaponics Works

The 2 major components of aquaponics systems are the fish and the plants. The natural characteristics and requirements of each of these components support the growth and health of the other.
 

Role of Aquatic Animals such Fish

·          Fish digest their food and create excrement which is released into the water where the fish is reared. This excrement is rich in nutrients that plants need to grow and produce.

·         In this process is there is ammonia in the fish waste which is toxic to fish in high concentrations and needs to be removed or the fish will die. The ammonia is broken down into nitrates and nitrites which are nutrients required by plants.

·         The invisible actors in this symbiotic relationship are the beneficial bacteria and composting red worms. The beneficial bacteria (Nitrosomonas and Nitrobacter) exist on every moist surface of an aquaponic system.  They convert the ammonia from the fish waste that is toxic to the fish and useless to the plants, first into nitrites and then into nitrates. The nitrates are relatively harmless to the fish and are important plant nutrient

·         The worms convert the solid waste and decaying plant matter in the aquaponic system into compost.

·         The water is reticulated from the tank through growing beds where the plants are grown. The plants take up the nutrients and use them to create energy for growth. The water flows back into the fish tank in a continuous cycle.

Hydroponically grown plant

·   Nitrate-rich water is introduced to the hydroponically grown plants.  These plants are placed in beds that sit on tubs filled with water, and the water is enhanced by the nitrate harvested from the fish waste. The plants' bare roots hang through holes in the beds and hang in the nutrient-laden water.

·   The hydroponic plants' roots function as a biofilter in that they strip ammonia, nitrates, nitrites and phosphorus from the water. The circulation of the water takes the nutrients away from the fish, to the plants. The water that returns to the fish tank is free from the nitrates and nitrites that are not required by the fish.

Site selection
Choosing the right environment in which to place the aquaponics farm is important. The amount of sunlight, ambient temperature, rainfall and wind are all crucial factors in producing a healthy plant. When growing outdoors, choose varieties of vegetables that will grow best in the environment. Most areas will require the use of a greenhouse, or you can always grow indoors.

Deciding What crop to Grow

• Different plants grow under different conditions. It’s important to consider which type of growing bed to use. This is determined by the type of root structure that plant tends to have.
• Plants with no root structure need floating beds, while root vegetables grow better in wicking beds.
• Most of the vegetables grow best in media beds. However plants such as lettuce, herbs or leafy greens, floating “raft” style beds are ideal. For root vegetables, wicking beds are a better choice. If you plan to grow tomatoes, peppers, beans or most other types of multiple yield plants, media beds are is the best option.

Selection of fish type

The choice of what to produce will be guided by:
1) Ecological requirements of the species- The different species have different biology and therefore different ecological requirements. They will therefore have different feeding, breeding and water quality requirements.

• Consider the temperatures at which they fish species thrive and survive. Tilapia, catfish are the main type of fish reared in Kenya for food. Other types are ornamental fish e.g. gold fish and koi carp that are not consumed.
• Nile tilapia and African catfish require warm water of more than 25- 28°C. In Kenya, such regions are to be found in low land areas. High sunlight intensity is also preferred for tilapia culture under semi-intensive production.
• Trout require cold water of less than 18°C for growing out and below 10°C for hatchery production. Such conditions in Kenya are to be found in high altitudes areas.
  2) Market preference

3) Production technology of the species
4) Resources available to produce

Management Challenges

• Water quality is a high priority and insures the growth of healthy fish and plants. There are several factors that go together to create the perfect water environment. They include the pH, Ammonia, Nitrite, Nitrate, Bacteria levels, Temperature, Oxygen levels and Alkalinity and Source. An imbalance of any one of these factors can cause the water quality to drop to harmful conditions for the fish and/or the plants.
• If waters get too hot especially when exposed to the sun during hot days, there will be a lack of oxygen for the fishes.
• Ammonia is very toxic to fish and a build-up of it in the fish tank will kill them (dead fish will also produce ammonia).
• The size of your fish tank and the amount of fish in the aquaponics system will affect the efficiency of the system e.g. having a dense population of fish can result in the bigger fish feeding on the smaller fish or too much fish waste for the biofilter to effectively convert to nitrates.
• The most common diseases in fish are bacterial infections, fungal infections and parasites. Aeration and water movement are critical for keeping fish healthy, as well as keeping the water clean and free from buildup of solids. Different fish suffer from different diseases. If problems with pests occur, no pesticides can be used, as they affect the health of the fish. Pest/diseased affected plants are removed from the system, and replaced.  

Word of Advice to potential Aquaponic Farmers

Potentially an aquaponics system is more productive than a traditional system, but it is also susceptible to greater risks.  There is need to prepare well, and to be properly informed before risking a considerable investment in money and time.

PAWPAW PRODUCTION

PAWPAW (Carica papaya)

Introduction

Pawpaw is widely cultivated fruit tree in the tropics and subtropics. It is grown in Kenya as a domestic fruit and small-scale cash crop. The fruits are low in calories and rich in vitamins A, B1, B2 & C, iron and potassium. Papayas enzymes promote digestion easing constipation. Sale of fresh papaya provides regular income for farmers since the fruits are produced through out the year.  

Utilization

Pawpaw fruits are sold and eaten locally as fresh fruit, with high demand from the hotels, local grocery, fruit salad vendors, supermarkets and export market. The fruits are dried and exported as part of a dried fruit mixture.

It can be used to make ice-cream flavour, refreshing drinks, jam, jelly, wine, marmalade, candies and crystallized fruits.

The latex produced by the unripe fruit is harvested and used in the production of papain, used in the brewing industry, canned meats and pharmaceutical industries.

Green fruits are pickled or cooked as a vegetable.

Young leaves are sometimes eaten as vegetables.

Potential for Pawpaw farming

Pawpaw production can be very profitable and rewarding for a farmer even on a small parcel of land. There are a number of processing opportunities for the fruit and export market.

Tree types

The pawpaw has three tree types based on the flowers are arranged; female, male and hermaphrodite. These can only be differentiated after it flowers. The characteristics are described below:

Pistillate (Female plants)

They produce female flowers only. These are large, situated singly or in clusters near the trunk of the tree and close to the base of the leaf stalk. There are no stamens (Male flowers), so cross pollination is necessary for the fruit to set. They produce good fruits.

Staminate (Male plants)

They produce only male flowers, which are borne in large numbers in long, drooping branches of up to 1m in length. The true male flower produces pollen only and it is essential for the development of fruit from the female flower. Occasionally male plants will produce 2 hermaphrodite flowers and set fruit on the ends of the branches; however, these fruits are usually of poor quality or no fruit production.

Hermaphrodite plants

They produce flowers which have both male and female parts and are capable of self- pollination. Bisexual fruits are usually long and narrow, and although the eating quality may be excellent, the shape presents some problems for commercial handling.

Pollination

Pollination is a key component of productivity that also plays a role in determining fruit set and fruit quality. Hence it is important to balance the tree types.

Varieties

Most of commercial varieties grown in Kenya are derived from Hawaii. A few are from India and some known as 'Mountain varieties'.

Honey Dew -This is an Indian variety of medium height that produces oval juicy medium size fruit.

Kiru- This is a Tanzanian variety that produces large fruits.

 It is a high yielder of papain.

Mountain-This is a variety that grows at high altitudes with very small fruits only suitable for jam and preserves.

Solo- This is a Hawaiian variety that produces small round very sweet fruits with uniform size and shape. It is hermaphroditic. It is popular for both export and local markets.

Solo Sunrise- Hawaiian variety that produces smooth pear shaped fruit of high quality, weighing 400 to 650 grams. The flesh is reddish orange. This variety is high yielding.

Sunset- Hawaiian variety is a dwarf high yielding plant with red flesh and having same characteristics as ‘Solo’ variety. It is very sweet

 Solo sunset- The fruit is red/pink in color and very sweet. Average fruit size is 425 grams. Hermaphrodite fruit is pear shaped, with a small neck at the stem end. Fruit sets at average 1 meter above the ground.

Sunrise (Strawberry pawpaw) - Has a deep red-flesh. Variety is resistant to the ring spot virus disease. Fruit has a freckled greenish-yellow skin that turns yellow as the fruit ripens.

Waimanalo- Hawaiian variety that produces smooth, shiny round fruits with short neck and is of high quality.The flesh is orange yellow, thick, sweet and firm. It is recommended for fresh market & processing.

Kapoho- Solo type with yellow to orange flesh colour. Fruits are smaller than that of sunrise.

Mexican Red- A rose-fleshed pawpaw that is lighter in flavor. It is a medium to very large fruit. However it is not as sweet as Hawaiian types

Ecological Requirement

Altitude

They grow best in areas below 1500m above sea level. The quality and yield are low at higher altitudes.

Rainfall

Evenly distributed annual rainfall of above 1000mm. Pawpaw trees cannot withstand prolonged drought. In low rainfall areas irrigation is necessary to facilitate vigorous growth.

Soils

Pawpaw grows best in light, well-drained soils rich in organic matter with soil pH of 6.0-7.0. It can tolerate any kind of soil provided it is well drained and not too dry. The roots are very sensitive to water logging and even short periods of flooding can kill the plants.

Temperature

Pawpaw thrives in warm to hot areas with adequate rainfall and a temperature range of 21-33°C. Fruit tastes much better during warm sunny seasons. Cold temperatures below 120 C cause the tree to grow poorly. Frost can kill the plant; Cool and overcast weather delays fruit ripening and depresses fruit quality.

Starting Production

·         Variety selection-For commercial production, it is important to select high yielding varieties

·         Choose variety as per market demand and environmental adatability.

·         Site should be suitable with the required production requirements

·         Market for produce should be readily available since the fruits are highly perishable.

Land preparation

The field should be cleared of bushes, tree stumps and leveled out. Deep soil cultivation is recommended thus ploughing and harrowing should be done before planting.

Propagation

·         Pawpaw is propagated by seed. To reproduce the desired characteristics it is best to get seeds through controlled pollination.

·         Seeds are extracted from healthy fruits selected from healthy plants. 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.

·         The seed may be sown directly in the field or nursery beds, seed boxes or polythene bags then transplanted.

·         Raising seedlings in seed bed

·         Prepare either raised or sunken beds 1m wide and of convenient length.

·         Water the beds thoroughly before and after sowing until seeds germinate.

·         Sow seeds at a depth of 1cm in rows that are 15 cm apart.

·         Seeds germinate in 2-3 weeks.

·         Continue watering until they are ready for transplanting in containers.

·         Prick out at the 2-3-leaf stage, transferring 3-4 seedlings to each container 1 week after emergence.

Raising seedlings in containers

·         Plants propagated in containers are less susceptible to stress and subsequent loss than those produced in seed-beds.

·         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 disease.

·         Germination takes 2-3 weeks.

·         Seedlings are transplanted about 2 months after sowing when they reach the 3-4-leaf stage or 20cm height, preferably at the onset of the rainy season.

·         During transplanting, care must be taken not to disturb the roots. Older seedlings recover poorly after planting out.

Direct Planting

·         Sow 6 seeds per planting hole.

·         Thin to 4 plants after germination and later to 1 plant per hole after it is possible to establish the sex of the plant.

·         For hermaphrodite varieties, plant 2 seeds per hole and thin to 1 seedling per hole after 1 month.

Field establishment

Dig Planting holes of 60 x 60 x 60cm.

Spacing and plant population

·         2.5 m x 2.5 m (1,600 plants/hectare)

·         2.5 m x 3 m (1,332 plants/hectare)

·         3 m x 3 m (1,110 plants/hectare)

Transplanting in the field

·         Transplant seedlings to the field 4-5 weeks, when they are 10-20cm in height. Young plants have higher survival rates than older plants.

·         Mix 40kg of well rotten manure with 100-120g of DAP and the top soil and fill the hole with the mixture.

·         Plant 4 seedlings per hole for varieties that have male and female flowers on different plants.

·         Thin to one female or one hermaphrodite plant per hill when the plants reach the flowering stage (after 6-8 months).

·         In the absence of hermaphrodite plants, 1 male plant per 25-100 female plants is retained as pollinator. Most of the male plants should be removed since they bear no fruit.

·         For hermaphrodite varieties plant 1 seedling per hole.

·         Transplanting should be at the same depth as the seedlings were previously growing; deeper planting may cause some loss due to stem rots.

·         Plants that have been grown in seed beds should, in addition to being hardened off (reduce irrigation), be provided with some simple cover when transplanted to the growing site.

·         It is good practice to reduce the leaf area of the plant at transplanting, so that transpiration is reduced while the root system is re-established. If possible planting should be done in the late afternoon.

·         Plants propagated in containers are less susceptible to stress and subsequent loss than those produced in seed-beds. However, these will still require attention until they are established.

·         Whichever method is used, seedlings should be planted into moist soil and watered as soon as possible afterwards. Daily watering will be required for some time. 

Wind break

Paw paws do not tolerate strong winds and the establishment of wind breaks hedges is necessary.  

Mulching

This is recommended after sowing or transplanting. The mulching should not be so close to the stem of the seedlings, give an allowance of about 10cm from the stem. The mulch should be removed so that the development of the young plant is not hindered.

Weed control

Frequent hand weeding is essential and care need to be taken not to damage the roots of the young plants. Keep the area around the stem weed free. Slashing is not enough as the seedlings will still suffer from weed competition.

Intercropping

Pawpaw grows best when planted under full sunlight. Intercropping can be done when paw paws are young. Low growing annual crops such as capsicums, beans, onions and cabbages are suitable intercrops.

Manure and fertilizer

Apply manure at the rate of 40kg per tree before the rains begin every year.  It should be applied around the plant basin and incorporated well into the soil.

Apply 40g of CAN per tree two months after transplanting in the first year. If possible apply a split application of 60g CAN per tree at the beginning of the long and short rains. After which 200g of compound fertilizer can be applied per tree per year at the beginning of the rains.

Major Pests

Fruit flies -The flies usually deposit their eggs in ripe fruit. Developing larvae cause rotting of ripening fruits.

Control-Fruit should be harvested at the mature green stage. Over ripe and infested fruit should be buried.

Red Spider Mites- Mites suck the plant sap, leading to poor plant growth and blemishes on the fruit. Serious infestations occur during long dry periods

Control

Use recommended miticides

Root-knot nematodes- Cause root swellings or root galls, resulting in yellowing and premature abscission of the leaves. Infestation by nematodes reduces growth and yield.

Control

Do not replant pawpaw in the same field.

Birds- They feed on the ripe fruit.

Control

Harvest when the fruits are physiological mature)

Major Diseases

Damping-off and Foot rot- caused by soil-borne fungi, and result to rotting of roots, stem and fruits.

Ripe fruit rots- Several fungal pathogens are involved in fruit decay.

Powdery mildew- As the fruits develop, the white mould disappears leaving grey-scarred areas. (Use sulfur based fungicides)

Papaya ring spot virus (PRSV) - virus is spread by aphids and it is also mechanically transmitted.  Severely infected plants do not flower and they die young. Infected fruits develop characteristic line patterns, which form rings and remain green when fruits ripen. (Destroy infected plants, doo not intercrop with host plants e.g. cucurbits).

Anthracnose -causes fruits to rot and makes them unmarketable

Control

Immersing fruits in warm water at 400 C for 20 minutes can control the fungi infection).

Rhizopus- It is a common postharvest disease of the pawpaws and is important only during storage and transit (sanitation in and around the packing area).

*Integrated pest Management is the recommended method for control of pests and diseases that includes good cultural practices, biological and chemical control.

Harvesting

·         Pawpaw starts flowering after 6-8 months and fruits are ready for harvesting 8-10 months after trees have been planted.

·         The physiological development stage of fruit at the time of harvest determines the flavour and taste when the fruit is ripened.

·         Fruits harvested too early have longer post harvest life, but give abnormal taste and flavour. Fruits also tend to shrivel and suffer chilling injury when refrigerated.

·         Harvest when at least 2 yellow strips appear between the ridges of the fruit.

·         Harvest by cutting fruits from the tree, leave a stem 0.5-1 cm long on the fruit. The stem can later be reduced when packing the fruits.

·         Avoid latex flowing on the fruit by placing the stalks of harvested fruits facing downwards.

·         Place the fruits gently into the harvesting crates.

·         It is better to harvest the fruits early and leave them to ripen in shade.

Yields

Under good conditions fruiting starts within a year from planting and continues with a yield of 30-150 fruits per tree during its life span. A yield of 35-50 ton/ha can be realized per year. The fruits are available throughout the year provided water is adequately available. A pawpaw plantation can be productive for 4-5 years but the economical period is 3-4 years.

Post harvest handling

The fruits should be handled carefully and should not be stored for many days. Under ripe fruits may be stored for almost 3 weeks and then removed to room temperatures to complete ripening. Fully ripened fruit can only be stored for 2 - 3 days at room temperature.

Challenges in production

·         The major problem faced in papaya production is significant post-harvest losses along the marketing chain. Factors such as fungal diseases, physiological disorders, mechanical damage, or a combination of these are the leading causes of post-harvest losse

·         Lack of quality planting material/seed is a serious draw back in production Most often farmers plant poor quality pawpaw of low market value and in some cases diseased material is used hence reducing economic lifespan of the orchard.

Advice to potential growers

·         Papaya production is expected to grow based on increased domestic consumption of the fruit throughout the year and high markets prices. There is also opportunity to utilize the fruits in value addition. Pawpaws can be intercropped with other crops thus providing extra income. Quality fruits can be obtained by ensuring the recommended pre-harvest and post harvest practices are adhered to.