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Cassava

Description

..CASSAVA

Cassava is locally known as Balingoy or kamoteng kahoy. In other countries it is known as yucca, manioc, and tapioca. It is a perennial shrub which sometimes reaches the size of a small tree. Its stems vary in color from pale to dirty-white to brown marked by numerous nodes formed by scars left by fallen leaves. Pale to dark-green leaves are fan-shape with 5 to 9 lobes.
Considered a vegetable and staple food specially during lean months and typhoon months. Cassava and sweet potato are the rootcrops commonly grown in Bicol. These commodities have special agronomic characteristics and performance that its potential cannot be undermined.Cassava is a perennial plant that thrives well even in poor soils.

Cassava can be processed into starch, noodles, seasoning and sweets. It is also used as a substitute in the processing of animal food. It can also be made into pellets, chips and pearl. The chips can be used for alcohol production. Cassava is now used to produce biodegradable plastics and some medical, horticultural and sporting good products.
(Source: Department of Agriculture – Bureau of Agricultural Research, Date accessed 24 March 2014)

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Cultural Management

 

Land Preparation

In general, one plowing and harrowing is adequate for areas just previously planted or regularly planted every year. For newly opened or fallowed areas, two to three plowings and harrowing may be necessary depending on soil tilth and weed incidence. In areas prone to water logging like in clayey soils, ridges or mounds should be constructed to prevent rotting of cuttings and storage roots.
Depth of plowing from 10 to 20 cm does not seem to affect yield in lighter soils. However, for heavier soils, plowing depth may affect root yield and deeper plowing most probably favor root production.

Crop Establishment

To insure good yields, only cuttings that are free from insect pests and diseases, mature, fresh and selected from vigorously growing plants should be used.
The length of the cutting varies from 20 to 30 cm depending on node number. There should be at least five nodes per cutting to have a better chance of sprouting and survival.

Cuttings should be taken from at least 6-month old plants. The best part of the stem to use is the middle part, the terminal part being too young (dries easily) and the basal part too old (lignified with little food reserve). When the age of the plant is uncertain, the size of the pith (central soft portion) may be used as a guide to maturity. The pith's diameter should be 50% or less than the total diameter.

Stems that are too thin should not be planted. As a guide, the thickness of the stems should not be less half the regular size of the variety. When the stems are thin, not because of poor growing conditions but due to cultural practices like density planting, the thin stems might be planted without affecting field performance.

Stems should be properly stored to maintain their viability and yielding ability. The stems to be stored should be mature, free from insects and diseases and at least 1 meter long. The stems are bundled, positioned vertically (buds facing up) in a well-ventilated area and protected from direct sunlight by covering them with protective materials like coconut fronds.

When using stored stems, only those with enough moisture should be planted. A stem has sufficient moisture if upon cutting, the white latex or sap appears within three seconds. The germinated and rooted parts should be discarded.

If water is available, cassava can be planted anytime. In the presence of a dry period lasting for several months, it is best to plant at the onset of the rainy season.

Plant horizontally in the furrow when rainfall is uncertain and vertically on the ridge when there is plenty of rain and water logging is a potential problem. Slant or diagonal planting is done when the conditions are neither too dry nor too wet.

There are other things to consider in deciding the position of planting to adopt. In vertical planting, the buds grow earlier giving a headstart over the weeds but harvesting is more difficult and planting takes more time since one has to be careful not to plant the cuttings in an inverted position. Cassavas planted vertically are also more resistant to lodging. On the other hand, those planted horizontally or diagonally are easier to harvest but lodge easily. Planting depth is shallower (5-8 cm) for horizontal planting and deeper for vertical or diagonal planting (10-15 cm). For dry and sandy soils, planting is deeper and for moist and heavier soils, planting is shallower.

Plant only one cutting per hill. When the soil is not fertile and the variety is not branchy, plant about 20,000 cuttings/ha (1 m x 0.5 m spacing). In fertile soil and with vigorously branching varieties, plant about 10,000 cuttings/ha (1.0 m x 1.0 m spacing).

Replant missing hills only if they exceed 30% of the total population and not later than two weeks after planting using longer cuttings when planting vertically.

Water Management

Although cassava is a drought-tolerant crop, yield is also reduced with limited rainfall. Under Philippine conditions, it is not economical to irrigate cassava because of its low economic value. The best way to evade moisture stress is to plant at the onset of the rainy season.

Weed Control and Cultivation

Control the weeds during the first two months after planting. This can be done by hand weeding in combination with off-barring and hilling-up. Cultivation, which loosens the soil aside from controlling the weeds, is beneficial to the expanding storage roots. Cultivation should not be done beyond two months after planting to prevent damage to the developing storage roots unless the canopy is still limited due to the poor growing conditions. To save on hand weeding, cassava can be planted in straight rows in two directions so that cultivation can be made perpendicularly.

Other methods of controlling weeds in plantations are: high population density planting, inter-cropping with short maturing crops like legumes and using herbicides and mechanical cultivators.

Pests Management

Spider Mites

Two species of spider mites of the genus Tetranychus are serious pests especially during the dry season. They suck the plant sap from the under-surface of the leaves causing the leaves to turn yellow then brown before falling off. The damage symptoms appear first among the lower leaves. Recommended control measures are stripping and burning of affected leaves, use of clean cuttings and resistant varieties and planting at the onset of the rainy season. There are a number of available acaricides but these chemicals are expensive and not recommended for practical use.

Scale Insects

The scale insects (Saisettia spp.) are another group, which are becoming serious especially under continuous cultivation. They suck the sap from the stems that make them unfit for planting. The use of resistant varieties and clean planting materials are recommended control measures.

Cassava Bacterial Blight

Among the cassava diseases, the cassava bacterial blight (CBB) is the most serious and destructive especially during the rainy season. Symptoms of the disease are angular leaf spotting and blight, wilting, die-back, gum exudation and stem and root vascular necrosis. The use of resistant varieties coupled with cultural practices like wider spacing, elimination of infected plants and the use of bacteria-free planting materials are the most promising control measures.

Brown Leaf Spot

The brown leaf spot is the most common disease infecting cassava but the yield loss is not so serious as that resulting from CBB. The disease occurs throughout the year but is most prevalent during the wet season. Spots are present on both leaf surfaces. The spots appear more or less circular starting from faded green to brown with darker borders. Eventually, the lesions turn somewhat irregular to angular due to the limitation by the leaf margins and the veins. In the advanced stage, infected leaves turn brownish and drop prematurely. The disease is usually not controlled in commercial planting.

Harvest Management

The right time to harvest depends on the variety. Some varieties can be harvested optimally from about 10 months for the early maturing to 18 months after planting for the late maturing. However, the eating quality of the roots also affects the decision when to harvest for the fresh market. To determine the best time to harvest, pull out a few (about 10 samples plants) randomly every 10 days starting 9 months after planting to evaluate the eating quality. If there is no further increase in yield and the eating quality is all right, the crop may be harvested.

For the fresh market, only the needed quantity should be harvested at any one time since the roots deteriorate very fast within 2-3 days after harvesting. In this case, staggered harvesting starting from one end of the field to the other end should be practiced so that the harvested area can be immediately used for other crops if desired.

To harvest, cut the tops leaving the stump, about 30 cm. for grasping when uprooting the plant. If the soil is hard, mechanical harvesting aids that grasp the stem as it is raised make harvesting operations easy.
If cassava is to be processed into chips for animal feed or for flour production, harvesting has to be done during the dry season since artificial drying is expensive and uneconomical.

Source: Department of Agriculture – Bureau of Agricultural Research, Date accessed 24 March 2014