Friday, January 23, 2009
Thursday, January 22, 2009
Drip Irrigation
Drip irrigation, also known as trickle irrigation or microirrigation is an irrigation method which minimizes the use of water and fertilizer by allowing water to drip slowly to the roots of plants, either onto the soil surface or directly onto the root zone, through a network of valves, pipes, tubing, and emitters.
Modern drip irrigation has arguably become the world's most valued innovation in agriculture since the invention of the impact sprinkler in the 1930s, which replaced flood irrigation. Drip irrigation may also use devices called micro-spray heads, which spray water in a small area, instead of dripping emitters. These are generally used on tree and vine crops with wider root zones. Subsurface drip irrigation (SDI) uses permanently or temporarily buried dripperline or drip tape located at or below the plant roots. It is becoming popular for row crop irrigation, especially in areas where water supplies are limited or recycled water is used for irrigation. Careful study of all the relevant factors like land topography, soil, water, crop and agro-climatic conditions are needed to determine the most suitable drip irrigation system and components to be used in a specific installation.
Advantage / Disadvantages of Drip Irrigation
The advantages of drip irrigation are:
Minimized fertilizer/nutrient loss due to localized application and reduced leaching.
High water application efficiency.
Leveling of the field not necessary.
Ability to irrigate irregular shaped fields.
Allows safe use of recycled water.
Moisture within the root zone can be maintained at field capacity.
Soil type plays less important role in frequency of irrigation.
Minimized soil erosion.
Highly uniform distribution of water i.e., controlled by output of each nozzle.
Lower labour cost.
Variation in supply can be regulated by regulating the valves and drippers.
Fertigation can easily be included with minimal waste of fertilizers.
Foliage remains dry thus reducing the risk of disease.
Usually operated at lower pressure than other types of pressurised irrigation, reducing energy costs.
The disadvantages of drip irrigation are:
Expense. Initial cost can be more than overhead systems.
Waste. The sun can affect the tubes used for drip irrigation, shortening their usable life. Longevity is variable.
Clogging. If the water is not properly filtered and the equipment not properly maintained, it can result in clogging.
Drip irrigation might be unsatisfactory if herbicides or top dressed fertilizers need sprinkler irrigation for activation.
Drip tape causes extra cleanup costs after harvest. You'll need to plan for drip tape winding, disposal, recycling or reuse.
Waste of water, time & harvest, if not installed properly. These systems requires careful study of all the relevant factors like land topography, soil, water, crop and agro-climatic conditions, and suitability of drip irrigation system and its components.
Germination Problems. In lighter soils subsurface drip may be unable to wet the soil surface for germination. Requires careful consideration of the installation depth.
Salinity. High application efficiency often results in a failure to meet the leaching requirement, therefore salts build up in the root zone. This is a significant problem in areas where seasonal rainfall is not sufficient to drain salts from the profile.
Pine Apple
This familiar dessert fruit came under domestication prior to the visit of Christopher Columbus to South America and has since become naturalised in some areas. According to S.W. Pursglove, its centre of origin is in the Pavana-Paraguay river drainage area. The culinary pineapple has always been known in cultivation and is thus termed a Cultigen. There are five species of pineapple in all and the cultivated form was selected by the Tupi-Guarani Indians. Europeans were introduced to the pineapple after the second voyage of Columbus (1493-1496) when he landed on the island of Guadeloupe on the 4th November, 1493.
The fruit’s resemblance to a pine cone gives the fruit its Spanish name pifia, and the English name pineapple. The generic name Ananas is derived from the Tupi Indian name ‘Nana’.
The fruits you purchase in the shops are all cultivars, of which ‘Cayenne’ is the most popular, and this was introduced into England in about 1835 owing to the qualities of good flesh colour and a fine flavour.
The cultivar ‘Cayenne’ is a perennial or biennial herb reaching 1.5 metres in height and has a wide leaf spread of about 130 to 150 cm and a terminal inflorescence which develops into the fruits. Growth continues after fruiting, producing the familiar bushy rosette which is situated on top of the fleshy fruit.
1 Crown of leafy bracts borne on an extension of the peduncle.
2 Fruitlet.
3 Fleshy tissue of carpels.
4 Loculus with abortive ovules.
5 Leafy bract of fruitlet.
6 Central fibrous axis.
7 Rind or shell.
8 Peduncle with bracts.
Inflorescence and Fruit Formation of the cultivar ‘Cayenne’
The apical meristem broadens to form a tightly packed inflorescence approximately 450 days after planting. The Stout peduncle (stalk of the inflorescence) bears 100 to 200 flowers which are arranged in a spiral manner and each flower is subtended by a floral bract. The flowers open from the base upwards over a period of about 20 days with 5 to 10 flowers opening each day.
At fruit formation 100 to 200 flowers change to 100 to 200 berry-like fruitlets which fuse tightly together, each subtended by a familiar leafy bract.
Growth by cell division is completed during flowering and increase in fruit size is caused by development and enlargement of existing cells.
On close examination of the pineapple it will be observed that the fruitlets are born in two series, one turning to the left in gradual slopes of 8 rows, and the other turning to the right in a steeper slope of 15 rows. As is well known, each fruit is surmounted by a crown rosette of leaves (mentioned earlier). This crown can be cut off and used for propagation. I have managed to root the crown successfully, but I have never achieved fruiting of my rooted plant. Pursglove claims shortening days hastens flower production and as long as you have a high temperature, between 21°C and 36°C, fruiting should be achieved. There is a cultivar ‘Queen’ that can be grown at a lower temperature.
In the New World, Humming Birds are the principal pollinating agency, and bees also obtain nectar from the base of the flowers, but are unable to pollinate the flowers themselves. The fruits will form without pollination (parthenocarpic), but, of course, no seed will be formed.
The pineapple is a Sorosis, because it is a fleshy, multiple fruit formed from an entire inflorescence. Those of us who struggle to draw or paint a pineapple will need to be aware of the geometric formation of the individual pineapple fruitlets.
The pineapple belongs to the Family Bromeliaceae, which includes the familiar vase-like pot plants Bilibergia, Cryptanthus, Tillandsia, Guzmania and Vriesea.
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