Roots, tubers, plantains and bananas in animal feeding (2024)

INTRODUCTION

The sweet potato (Ipomoea batata L.) is one of the twelve principal plantspecies utilized as a human feed throughout the world.

It can be cultivated in many different climatic conditions, and as a resultlarge areas of sweet potato are cultivated in Asia, Africa, Europe,America and Oceania (Table 2). The various ways in which it can beused are shown in Table 1.

ECOLOGY

Sweet potato is a tropical and subtropical plant which can adapt to moretemperate climates providing the average temperature does not dropbelow 20°C and minimum temperatures stay above 15°C. In otherwords it can be cultivated between the 30 and 40° latitudes in bothhemispheres.

Temperature

For the cultivation of sweet potatoes a range of temperature between 15to 33°C is required during the vegetative cycle, with the optimumtemperature being between 20 to 25°C. The highest yields are obtainedwhen temperatures are high during the day (25 to 30°C) and low bynight (15 to 20°C); low temperatures during the night favour theformation of tubers, and high temperatures by day favour vegetativedevelopment. (Note: tubers development only occurs within a temperaturerange of 20 to 30°C, optimum 25°C and generally stops below 10°C).

Light

Sweet potato is a short day plant, that needs light for maximum development. However, the growth of the tubers appears not to be influenced byphotoperiod alone. It is probable that temperature and fluctuations intemperature, together with short days favour the growth of tubers andlimit the growth of foliage (Youg, 1962).

Altitude

In tropical regions it is possible to cultivate sweet potato from sea levelto 2500 m; for example in Bolivia, Peru and Colombia it is cultivatedfrom sea level to 2300 m. (Del Carpio, 1969).

Moisture

Moisture has a decisive influence on sweet potato growth and production.In this context it is relevant to note the water content of the leaf is (86%),stem (88.4%) and tuber (70.6%).

At planting it is important to have moist soils in order to achieve goodgermination. The soil must also be kept moist during the growth period(60–120 days), though at harvesting the humidity must be low in order toprevent the tubers rotting (Carballo, 1979).

Conditions that favour the development of the vegetative part of theplant include an 80% relative humidity and moist soils.

Soils

Sweet potato can be cultivated in a wide range of soils, with the bestresults obtained in ferralitic, brown humic and calcimorphologic soils.Ideally the soil should be friable, have a depth of more than 25 cm. andhave good superficial and internal drainage.

The chemical properties of the soil are less limiting than structuralproperties in obtaining good yields. For example, in sandy soils poor innutrients good yields can be obtained whereas in rich soils the vegetationoften becomes luxuriant and the roots large and irregular (in the sandysoils of Manacas Villa Clara, Cuba, yields of 28 t/ha. have beenobtained).

Other problems include the difficulty of using machinery on hilly landand drainage on flat land.

The sweet potato also prefers lightly acid or neutral soils, with theoptimum PH being between 5.5 and 6.5. Soils which are excessivelyacid or alkaline often encourage bacterial infections and negativelyinfluence yields (Cairo, 1980).

PHYSIOLOGY

Generally the growth cycle of the sweet potato is from 3.5 to 7 monthsand takes place in three phases; these are:

1. From planting to formation of tubers (40 to 60 days)

2. From formation of tubers to the time of maximum leaf development (60–120 days)

3. From maximum leaf development to the total development oftubers (45 to 90 days)

Normally the cycle is completed within 100 to 150 days at which timethe plant can be harvested.

MULTIPLICATION

Sweet potatoes are multiplied by both sexual and asexual means, thoughthe former is only of interest to geneticists and plant breeders.

Asexual reproduction using tubers and stems is the form of productionmost commonly used.

Propagation by stem

Of the two systems of multiplication of sweet potato, this form is thequickest and most economic and therefore the most commonly used. Thematerial to be used must be selected to avoid the transportation of eggsor larvae of Cylas formicarius elegantus S. to the new plantation and toavoid the use of unwanted crossbred varieties. In order to avoid this itis necessary to establish “seed banks”.

To maintain standards in Cuba it is necessary to obtain a certificate ofquality from the CEMSA (Experimental Centre for Improvement ofa*gamic Seeds), before seed material can be used.

Requirements for the production of “seed material” are:

1. The seed bank must not be planted in a field that has been used forsweet potato during the previous two years.

2. The irrigation system must be reliable.

3. The seed (stem) must be Cylas formicarius elegantus Summers andvirus free and less than 0.5% must be infested with the nematodeRotylenchulus remiformis Linfod y Olivera.

Other aspects to be considered are:

• The cut stems must be planted within four daysof cutting:

• The fertilisation applied to the soil at planting and after each cutwill be as follows:

Formula:

45 days after planting and after every cut, a 2% foliar urea spray (20 g/lwith a final solution of 500 l/ha) must be applied (Lopez and Alvarez,1971).

The first seed cutting to take place between 60 and 80 days afterplanting.

After each seed cutting, the following actions should be carried out:

• Weeding

• Fertilization

• Hilling

• Irrigation

Further cuts should be carried out every 60 days.

VARIETIES

Table 3 demonstrates the yields of 6 of the best varieties, grown in threedifferent soil types and harvested at different times. Two of thesevarieties have only recently been produced. Note: the recently developedvariety, CENSA, 85–48 which is a short cycle variety (90 to 100 days)has given excellent results in experimental conditions in terms of bothtops and tuber yield (40 ton/ha).

TIME OF PLANTING

In Cuba sweet potato can be planted all the year round if you haveirrigation and appropriate varieties.

Where the soils are sandy or clay and irrigation is not available it isadvisable to plant at the beginning of the spring, (April to May) thoughgood yields can usually be obtained from July to January.

As indicated, time of planting depends upon the variety used; forexample, the variety Cuba 3 gives better yields when planted during thedry season, with irrigation, than when it is planted during the rainyseason with the same soil moisture content. Other varieties, like Haiti,give the same yields either when planted during the dry season withirrigation or during the rainy season with or without irrigation. Theyield of this variety depends upon the soil moisture content which is theprincipal factor limiting the growth and development of tubers, and isindependent of the time of planting.

DENSITY OF PLANTING

The distance between plants in any crop is a factor which can affectyields, however, in the case of sweet potato no significant responses havebeen obtained with the different distances studied.

At CENSA the effect of planting distance between plants (22.5 to 30cm.) and between rows (70 to 90 m.) under irrigation were studied; thebest results (i.e. 30 ton/ha) were obtained planting at 90 × 22 cm and 70× 30 cm.

In experimental work carried out at the Central University of Las Villaswith different distances between plants and location of stems, i.e.perpendicular or across the hill, no significant yield differences wereobtained. The distances studied were 90 × 30 cm and 90 × 15 cm.

On the basis of these studies, the planting density recommended byCENSA is 37000 plants/ha with the following distances of planting:Sept.-Feb. 0.90 × 0.23 m and March-August 0.90 × 0.30 m (Ministry ofa*griculture, 1990).

FORMS OF PLANTING

1. In the furrow

2. In the upper part of the hill

3. On one side or on both sides of the hill.

METHODS OF PLANTING

Manual

In Cuba planting is generally done by hand, putting the stem on the hillor in the furrow and covering it with earth using a spade.

Mechanical

In Cuba planting is done with a TR4 planter made in Bulgaria or anothersimilar Trakia planter made in the USSR.

In order to obtain the best results the following planting procedureshould be taken into account:

1. - stems should be 25 to 30 cm in length

2. - the depth of planting should be between 7 to 10 cm

3. - planting should be on the hill

4. - 2/3 of the stems should be buried

Cultivation

Cultivation activities depend on a series of factors including: variety,time of planting, type of soil, planting distance, etc. The objectiveshould be to carry out as many operations as necessary to optimisevegetative development of the plants (Rodriguez Nodal and MoralesTejon, 1990).

CONTROL OF WEEDS

In this crop, weeds can be controlled by manual, mechanical-manual orchemical means.

Manual control alone is used only for small areas. Mechanical—manualcontrol consists of a combination of between row and between plantcultivations, as follows:

1. Mechanical cultivation using an inter row harrow and a manualcultivation between plants within 10 to 15 days of planting.

2. Hilling up around plants, 25 to 30 days after planting with the aimof reconstructing the hill to eliminate weeds and the incorporatefertilizers. If necessary, hand hoeing between plants should bedone at this stage.

In Cuba a second mechanical cultivation might be necessary for dryseason planting.

Use of chemical products

There are many products on the market which can be used and their usewill depend upon the chemical to be used.

FERTILIZATION

Due to the sweet potato's great yield potential (foliage and tubers) itrequires a considerable amount of fertilization; this varies according tovariety and soil type. The percentages of N.P. and K in the organicmatter of sweet potatoes are as follows:

When 15 ton/ha of sweet potato are harvested approximately: 70 Kgof N; 20 Kg of P₂O₅ and 110 Kg of K₂O are extracted from the soil (Jacoband Uexkull, 1968).

Method and timing of fertilizer application

There are several different ways of applying fertilizer, including:

1. In the furrow.

   1. Placing the fertilizer in the furrow and covering with soil fromthe hill.

   2. Planting the stem in a new hill after opening the furrow at ahigher level than the fertilizer.

2. In the hill. The fertilizer is placed at points 30 cm apart within thefurrow.

3. At 30 days after planting. The fertilizer is continuously spreadalong the the length of one side of the hill, following which it iscovered using a double mould—board plough passed down thecentre of the furrow.

4. At 20 or 30 days before planting (in sandy soils). After spreadingthe fertilizer it is incorporated using a harrow.

The ratio and amount of fertilizer to be used in sweet potato productionhas been established in different countries. Examples are shown in Table4.

IRRIGATION

Overall the sweet potato plant requires soils with a high moisture content.For vegetative growth its needs are moderate, though during the firstmonth of growth when the tubers are developing the moisture requirement increases. During the final days of the cycle the moisture requirement reduces.

Furrow and sprinkler irrigation techniques can be used. It is best tocarry out one irrigation before planting if the soil is not moist. The netapplication of irrigation should be between 200 to 250 m³/ha every 7 to10 days. This should be stopped about 15 days before harvest (INRA,1972).

DISEASE AND PESTS

The sweet potato plant is not seriously affected by fungus diseases orvirus attacks. Though it can suffer from insect attack.

Tetuan (Cylas formicarius elegantulus S.) is the most important pestthat affects the sweet potato. The female lays its eggs in stems and rootsand the larvae make galleries in the tubers which affects flavour (DiasSanchez, 1980). In order to control this pest it is best to use “seed” fromareas free of the pest, though various insecticides can be used to combatthe pest; these are applied to the soil and stems.

Biological control

In Cuba the insect “Hormiga Leona” (Pheidole megacephala frabricio)has been used successfully to control the pest. This is achieved bydistributing its colonies or nests around the fields at a rate of 13 per ha.,30 to 45 days after planting. Distribution of the fungus (Blauberia bassiana Bal.) over the plants 15 days after planting has also been successful.

Nematodes in general do not constitute a serious problem. Theprincipal species are Rotylenchulus remiformis Lenford and Oliveira.

Overall, biological control, complimented by agronomic practices suchas crop rotation is the best way to achieve success in sweet potato cultivation.

HARVESTING

The time of harvest largely depends upon the variety and soil moisturecontent during the first month of plant development. However the actualcommercial varieties used take different times to harvest, for example:

• early varieties take 3 to 4 months

• medium varieties take 4 to 6 months

• late varieties take more than 6 months

The growth cycle of any variety can be altered by an excess of moisturein the first 3 months after planting. This produces an intense foliardevelopment and a late formation of tubers. Often in these cases thenumber of tubers are reduced.

Methods of harvesting

Harvesting can be carried out in 3 ways: manual, semi-manual andmechanical.

The manual method is the simplest. It is usually used by the smallscale producers and involves the use of a digging stick to lever the tubersout of the ground.

Semi-manual: This is the most frequently used method in Cuba andinvolves the removal of the foliage with the help of a harrow whichclears the foliage from the area to facilitate the final harvesting. Theelimination of foliage must be carried out 24 hours before harvesting.After the foliage is removed a double mould board plough is passeddown the centre of the hill leaving a ridge in between the original twoand ensuring that the soil does not cover part of the adjacent ridges. Thetubers exposed after the first pass are picked up by hand and removedprior to making a second pass. Tubers are then again collected by hand.

Mechanical: This system is not ideally suited to the conditions of Cuba.Where this system can be applied satisfactory results can be achievedwith a potato harvester. With this equipment the tubers can be collectedin bulk in the field or on a trailer running along side the harvester. Thepresence of foliage or inadequate soil preparation can make this type ofharvesting more difficult.

Conservation and storage

The tubers of sweet potato can be conserved in good condition for sometime if they are stored in good conditions; for example:

1. All tubers damaged by insects or fungus disease should beremoved.

2. All tubers with mechanical damage should be removed.

3. Storage should be carried out in 45 Kg bags in store rooms withgood ventilation and low humidity. The bags should be raised offthe ground on wooden pallets. Stacks should be no more than 10bags high with space around each for the circulation of air.

4. Once the tubers are bagged they should be transported within 24hours.

In countries such as USA, USSR and Japan some producers of sweetpotato store their products in refrigerators at a temperature of 13–15degrees C and with 80% relative humidity. In this way the tubers can bestored for 4 to 6 months.

Bibliography

Cairo, P. 1980. Soil. Editorial Puebloy Educacion Habana Cuba.

Carballo, N. 1979. Effect of soilhumidity on the sub - period ofgrowing in the cultivation of sweetpotato (Ipomoea batata L) I Forumcienific technic. Santa Clara,Cuba.

Del Carpio. 1969. The genetic improvement of sweet potato in Peru.Vida Agricola Peru.

Dias Sanchez, J. 1980. Determinationof the fly activity of Cylas formicarius elegantulus (F) using a lighttrap. Centro Agricola, CentralUniversity of Las Villas, Cuba.

FAO. 1987. Production Yearbook.FAO, Rome.

INRA. 1972. Irrigiation standards.Technical collective of Irigation.La Havana, Cuba.

Jacob, A. and Uexkull. 1968. Fertilization. Edicion revolucionaria.Instituto del Libro. La Havana,Cuba.

Lopez Zada, M. and Carmen Alvarez. 1971. Comparative study ofsweet potato yield with differenttimes of foliar nitrogen application.Centro Agricola Fac. de CienciasAgropecuarias. Universidad Central de las Villas.

Ministry of Agriculture. 1990. Recommendations for agamic multiplication of tropical crops. Cuba.

Rodriguez, Nodal, A.A. and MoralesTenon, T. 1990. Recommendationsfor agamic multiplication of tropical plants. Santo Domingo, Cuba.

Youg, C.K. 1962. Effects of thermoIpomoea batata under controlledconditions. Plant physiologyc 36No. 5 pp. 680–684, 1961.