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Go to start Pig Feed Improvement through Enhanced Use of Sweet Potato Roots and Vines in Northern and Central Vietnam
Contents:
INTRODUCTION
PART I -SELECTING AND GROWING SWEET POTATO FOR LIVESTOCK
1 Technology for growing dual-purpose and forage-purpose sweetpotato in the Northern Midlands of Vietnam
2 Technology for growing dual-purpose and forage-purpose sweetpotato in the Red River Delta of Vietnam
3 Technology for growing dual-purpose and forage-purpose sweetpotato in North-Central Vietnam
PART II - SWEETPOTATO ROOT AND VINE PROCESSING AND FEEDING TO PIGS
1 Sweetpotato vine and root ensiling methods and use of silage as pig feed
2 Feed crops and their processing and storage methods
3 Composition of concentrate feed mixtures (basal feed) and the rations for pigs for various weight categories
Technical supplement: Some principles of pig nutrition in the tropics

PART I SELECTING AND GROWING SWEETPOTATO FOR LIVESTOCK


1 Technology for growing dual-purpose and forage purpose sweetpotato in the Northern Midlands of Vietnam

1.1 Characteristics of the Northern Midlands of Vietnam

1.1.1 Soil characteristics

The agricultural land of the Northern Midlands of Vietnam consists of the old alluvial bed area and valleys of the plain areas. Erosion-has led to soil acidity and low soil organic matter, phosphorus and nitrogen. This restricts yield potential of cultivated crops.

The plains areas of the valleys are more fertile, with soil composition from loamy to less loamy and mixed sandy soil, suitable for sweetpotato as well as for corn, beans, and groundnut. The plains areas are 30 m above sea level and the slope varies from 10-30 %. There is mainly one crop a year, and the utilisation rate of agricultural land is low.

1.1.2 Climatic conditions

Climate of the Northern Midlands of Vietnam is a monsoon tropical climate. The dry season lasts from November to April, with early north-east winds. It is considered the coldest area of the country. Therefore, winter crop sweetpotato needs to be planted early with cold-tolerant varieties.

Rainy season is from May to October, with the greatest concentration between June and September. There is potential for flood during this period. Heavy rains and floods cause serious erosion. On the other hand, dry season runs from October/November to March/April, and the drought and low temperature tend to stunt crop growth. The most serious drought usually happens at the end of December and the beginning of January.

1.1.3 Population and density

The population density of this area is fairly low, ranging from 70 to 140 persons/km2, with Kinh people occupying more than 60% and various ethnic minority groups occupying the other 40%. The main income comes from crop production, mostly from a single food crop, yielding relatively tow living standards. The food/head/year averages between 220 kg and 302 kg. Low income leads to low investment and poor cultivation technology. Irrigation and water systems are not well developed, especially in the upland and mountainous areas. It is necessary to select varieties suitable for these conditions.

1.1.4 Crops and production systems

For crop purposes, the Northern Midlands of Vietnam is divided into two parts: upland and plain fields. The following crop rotations are recommended:

- On upland:

Sweetpotato or autumn corn
Spring sweetpotato - Winter rice (upland rice) - Winter soybean
Spring-Summer bean - Winter rice (upland rice) - Winter sweetpotato
Sweetpotato under permanent fruit trees

- On the plains:

Spring sweetpotato - Winter rice
Spring-Summer bean - Early winter rice - Winter sweetpotato
Late spring rice - Early winter rice - Winter sweetpotato
Spring sweetpotato - Early winter rice - Winter corn

1.2 Geographical location

The Northern midlands of Vietnam consist of the following provinces: Quang Ninh, Bac Giang, Bac Ninh, Vinh Phuc, Phu Tho, Thai Nguyen, Ha Tay, Hoa Binh. The following recommendations also apply to some neighbouring provinces that share similar topographical, soil and planting characteristics.

1.3 Recommended sweetpotato varieties suitable for root and vine dual-purpose and their characteristics

1.3.1 The characteristics of yield, agronomic performance, and growing period

Distinguishing characteristics
Variety
 
Hoang long
KB1
K51
TQ2
KL5
Root yield (ton/ha)
21-35
13-17
14-29
11.94
20-22.5
Vine yield (ton/ha)
18-35
29-40
19-32
28.70
20-36
Root DM yield (ton/ha)*
2-7
1-2.5
1.51
2.85
1-5.2
Root starch yield (ton/ha)*
1.4-4.9
0.7-1.75
1.05
2.14
0.7-3.5
Season suited to planting
Winter
Winter
Spring
Spring
Winter,spring
Tolerance performance:
  • Drought tolerance
Good
Good
Medium
Medium
Good
  • Submergence tolerance
Medium
Bad
Fair
Fair
Good
  • Cold tolerance
Medium
Good
Medium
Medium
Fair
  • Leaf insect tolerance
Good
Medium
Fair
Good
Medium
  • Weevil tolerance
Poor
Poor
Medium
Good
Medium
Growing time (days)
140
150
150
120
120

*Root DM yield=Root yield x Dry Matter (DM) content in root
* Root starch yield=Root DM yield x starch content in DM


1.3.2 The characteristics of utilization, vine, root and storage

 

Distinguishing characteristics

Variety

Hoang long

KB1

K51

TQ2

KL5

Root palatability1:

  • For human (boiled)
  • For pigs (cooked)

High DM
Good

High DM
Good

Low DM
Fair

Low DM
Fair

Med DM
Good

Vine palatability:

  • For humans (boiled)
  • For pigs (fresh)

 

Bitter
Bitter

 

Not sweet
Not sweet (Should be cooked)

 

Sweet
Sweet
(Should be cooked)

 

Not sweet
Not sweet

 

Sweet
Sweet
(Should be cooked)

Method of storage:

  • Time (month)
  • Way to store

 

3-4
Fresh, dried

 

3-4
Fresh, dried

 

3-4
Fresh,dried

 

3
Dried

 

3-4
Fresh, dried

Root morphology:

  • Color of skin
  • Color of root flesh
  • Shape of root

Red-pink
Yellow Roundish

White
White
Roundish

Pink
Yellow
Slender

White
White
Slender

Light red
White
Slender

Vine morphology:

  • Shape of leaf
  • Color of tender leaf
  • Color of adult leaf
  • Color of stem

 

Heart shape White
Dark blue
Violet

 

Heart shape Violet
Green
Purple green

 

Heart shape Violet
Green
Green

 

Saw-tooth Green
Dark green Purple green

 

Lobe
White
Green
Green

1 For human consumption as a staple, instead of a vegetable, in which the level of DM is important to establish palatability. Palatability for pigs, on the other hand, was established by pigs' reaction when fed with certain varieties.


1.4 Sweetpotato varieties suitable for forage purpose and their characteristics

1.4.1 The characteristics of yield2, agronomic performance and growing period

Distinguishing characteristics

Variety

Rau muong

KL5

TQ1

T2

SN16

Fresh vine yield (ton/ha)

42

50

37.83

63.61

47.58

Fresh leaf yield (ton/ha)

10.72

7.6-13.5

11.99

13.25

14.01

Leaf DM yield (ton/ha)*

2.48

2.99

2.22

2.74

2.59

Leaf CP yield (ton/ha)*

0.55

0.58

0.49

0.53

0.47

Season suited to planting

Spring

Winter, spring

Spring, winter

Spring

Spring

Tolerance performance:

 

 

 

 

 

  • Drought tolerance

Good

Good

Fair

Medium

Medium

  • Submergence tolerance

Fair

Good

Fair

Fair

Fair

  • Cold tolerance

Fair

Good

Fair

Medium

Medium

  • Leaf insect tolerance

Good

Good

Good

Good

Fair

  • Twisted leaf virus tolerance

Good

Good

Good

Fair

Fair

Branching and regrowth

Strong

Strong

Strong

Strong

Strong

* Leaf DM yield=Fresh leaf yield x leaf DM content (excluding vines)
* LeafCP (crude protein) yield = Leaf DM yield x CP% in DM

2 The vine yield of the same variety grown for forage-purpose would be higher than that which was grown for dual-purpose which was not cut frequently in order to allow for root development.



1.5 Technologies that can be applied to increase vine and root yield

1.5.1 Selecting the appropriate variety

Growing purpose

Spring crop

Winter crop

Dual purpose

TQ1,K51,KL5,KB1

TQ2,KB1,Hoanglong,KL5,SN3

Vine purpose

Raumuong,T2,KL5,TQ1,SW6,KB1

TQ2,SN3,KB1,KL5,Hoanglong

1.5.2 Planting season

 

Spring crop

Winter crop

Planting season

  • 20 February-15 March
  • For vine purpose, it can be planted whenever the soil is moist.
  • 20 September-5 October
  • For vine purpose, it can be planted whenever the soil is moist.

Favorable conditions

  • From planting to harvesting the temperature and moisture is rather suitable.
  • During planting time, moist soil and high temperature provide good conditions for vines to grow.

Unfavorable conditions

  • Need to prevent flooding at the end of the season and too much vine growth.
  • At the end of season, soils are dry and temperatures low, roots may not develop well.

1.5.3 Soil characteristics

 

Spring crop

Winter crop

Proper soil type

Sandy-light loamy soil

Loamy soil, light loamy soil, sandy mixed soil

Land type

High land, upland, bedy land

Upland, low land, low land

1.5.4 Soil preparation

 

Spring crop

Winter crop

Requirements

Prepare the soil deeply, porous and friable, well ploughed, good water drainage by the end of season

Prepare the soil in order to maintain moisture during growing season

Size of bed

Width: 1 .1-1 .2 m; height:40-45 cm.

Width: 1.0m; height: 35-40 cm

Distance btwn beds

10-20cm

10-20 cm

Direction of beds

Depending on the plot, but East-West direction is recommended

East-West direction


1.5.5 Planting method

 

Spring crop

Winter crop

Vegetative multiplication

  • The stems from winter crop or garden crop can be multiplied.
  • Choose the stems that are not infested with viruses or insects. No nitrogen fertilisation before cutting
  • Multiplication season is the end of June and beginning of July
  • Plant in mounded beds or flat beds. Irrigate, cut tops early to pro­ mote multiple branches.

Multiplication method of planting material from root

 

  • Choose the small or medium roots with no scratches, no virus, or insect infestation
  • Prepare the soil well, the soil clods must be as fine as for veg­ etables. The top of the bed is flat, with 1.2 m width, 20 cm height, fertilise 10 tons of manure/ha before planting as basic fertiliser.
  • Planting density: 40 x 40 cm/hole, the big root should be cut into parts then dipped into ash, planting depth is about 3 cm, cover the surface of the bed with chopped rice straw, water them to keep the plants and soil moist.
  • After the shoots have grown out of the soil surface about 5 cm, cut off weak shoots, leave only 2-3 shoots in a hole. When the shoots are 20- 25 cm long, cut the top to allow branching, 50 - 60 days later cut the stem to plant.

Preparation before cutting planting material

7-10 days before cutting, apply additional P and K fertiliser (1-2 kg K/ sao*), do not water or apply nitrogen

Standards of good planting material

Adult stem, thick and hard, with no root, no virus and insect infestation

Method of cutting planting material

Cut the 1st and the 2nd section, avoid damaging the stems and leaves

Length of stem (cm)
Node number/stem

25-30
6-8

20-25
5-7

Planting method

Put the stem horizontally in the direction of the bed, exposing the top 3-5 cm, cover with soils from both sides and pat down the soil next to the stem. Lay the stem down flat and no need to leave space between plantlets. Keep the stem fresh. Better plant in the evening. In winter, avoid planting during the north-east windy days.

Planting density
(stem/m of bed)

5-6 stem/ m

4-5 stem/m

* sao : An area unit of northern Vietnam, 1 sao equals 360m2


1.5.6 Fertilization

 

Spring crop

Winter crop

Ratio and total amount of fertilizers (kg / sao*)

300 -400 kg manure
3 kg urea (N)
10 kg superphosphate(P)
6 kg potassium chloride (K)

300-400 kg manure
4-5 kg urea (N)
10 kg superphosphate (P)
4.5 kg potassium chloride (K)

Basic fertilization

All manure
All P fertilizer
1 kg urea

All manure
All P fertilizer
1 kg urea

Frist additional fertilization
Timing
Amount (kg/sao)


15-20 days after planting
2 kg urea
2 kg potassium chloride


20-25 days after planting
2-2.5 kg urea
2-2.5 kg potassium chloride

Second additional fertilization
Timing
Amount (kg/sao)


45-60 days after planting
The remaining potassium chloride (4 kg)


45-60 days after planting
The remaining amount:
1-1 .5 kg urea
2-2.5 kg potassium chloride

* sao : An area unit of northern Vietnam, 1 sao equals 360m2


1.5.7 Cultivation technology

 

 

 

 

 

Spring crop

Winter crop

Pinch off young shoots

  • At 20 days after planting pinch off the tops to promote branching and optimize vegeta­tive development.
  • At 80-90 days after planting, if vegetative development is too strong, cut 30-40 % of vine.
  • At 20 days after planting pinch off the tops to promote branching and optimize vegetative development.
  • No cutting

Weed control,
re-mounding the bed

  • Link with the 1st additional fertilization
  • Dig small holes on both sides of the bed, let the soils dry for 1 day. Fertilize 2 kg of potassium chloride in holes, cover fertiliser with soil. During this process, excess roots are cut off to promote better root growth.
  • Mulch to protect the plants from cold and drought while keeping the soil surface moist.
  • Use rice straw to cover both sides of the bed when it is dry and cold.

Irrigation

  • Water while applying 1st additional fertilization. Drain to avoid the crop sub­ merged in water.
  • Water while applying 1st additional fertilization. During drought, irrigate rows between beds to keep soil moist.

Vine lifting

  • When too much vegetative growth, lift up the stems to break off excess roots on stems to limit vegetative growth and allow nutri­ ents to concentrate in roots. Avoid damaging the stems and leaves.
  • No need to lift up the stems because this crop does not have much vegetative growth.


1.5.8 The vine-cutting method for forage varieties

Cutting method

Spring crop

Winter crop

First vine harvest

  • Time to start harvest
  • Harvest criteria

 

  • At 40-45 days after planting
  • Choose 2-3 longest stems of a plant, use a sharp knife to cut, leaving 10-1 5 cm.

 

  • At 45-50 days after planting
  • Choose 1 -2 longest stems of a plant, use a sharp knife to cut, leaving 15-20cm.

Subsequent vine harvest

  • Harvest interval
  • Stems and amount to cut

 

  • Cut stems every 10-15 days until the last harvest.
  • Depending on vegetative growth, cut 2-3 longest stems, up to 4 stems if much growth, leaving 1 5-20 cm. More stems can be cut near the end harvest.

 

  • Cut stems every 10-15 days until the last harvest.
  • Cut 2-3 longest stems of a plant, leaving 15-20 cm. Irrigate while applying addi­ tional fertiliser after cutting.


1.5.9 Main insects and protection

 

 

Spring crop

Winter crop

Weevil

 

  • The most serious for spring crop. The drier and hotter the weather is, the more weevil attack. Less serious in sandy soils than in loamy soils. Cracked soils are most susceptible to weevils. Storage roots are also often attacked, so it is necessary to cover the roots with nylon or sand.
  • Rotate sweetpotato with paddy rice and other crops. Use biological control such as introduction of natural enemies, manipulation of habitat, conserva­tion of natural enemies through avoidance of pesticide use or trap weevils to eliminate them.

Sweetpotato Hornworm (Agnus convolvuli)

  • The most serious attack is in spring when they eat all the leaves.
  • Protection by planting in rotation with other crops or pick them out by hand.

Borer

  • The larvae attack the main stems and petioles and decrease the vegetative growth. Vine yield is decreased. For dual-purpose varieties, in the case of too much vegetative development, borer attack is good because it limits vegetative growth, allowing the nutrients to go into roots. In this case, protection is not necessary.

Black rot

  • Plant sweetpotato in rotation with other crops such as paddy rice. Clear all the remaining parts of the previous crops, do sanitation of the field.
  • Plant sweetpotato in rotation with other crops. Do not use black rot- infected roots and stems for breeding material. Avoid damaging the roots during harvest. Clean fields after harvest.


1.5.10 Harvest

 

Spring crop

Winter crop

Methods of identifying the time for harvest

  • Most appropriate time for harvest depends on the timing of rotation with other crops.
  • Harvest when two thirds of the leaves have turned yellow or fallen off. Another indication is when tubers no longer have any roots attached.

Date of harvest

From 20 June to 5 July

From 5 February to 20 February

Methods of harvest

Sunny and dry days are best for harvesting. First, dig out both sides of the bed, then hoe to pick out the roots. Avoid damaging the roots, clean soils off of the roots and store in cool place.


1.5.11 Storage

 

Spring crop

Winter crop

Root storage
Root storage Methods

  • Put roots in a heap, cover the heap with a layer of sand before covering with a sheet of nylon. The roots can be stored up to 2-3 months.
  • Slice the roots with or without the skin to make dry chips <0.5 cm in thickness. Avoid molding. The experience of the farmers: soak slices in salt water (in concentration of 8-10% for 1 hour) before drying to avoid molding. When completely dried, put chips in nylon bags for storage.

Storage duration

From July to February

From March to June

Remarks during storage

Susceptible to rotting or weevil attacks. Check regularly to eliminate rotting or weevils or dry the slices again.

Due to high humidity, storage roots are often molded or rot­ ten.

Vines storage
Methods to store vines

  • Chop vines into 0.5-1 cm lengths, dry thoroughly and store in nylon bags and feed them to pigs regularly.
  • Chop vines into 0.5-1 cm lengths, pre-wilt, then ensile with additives*.

Storage duration

From July to February

From March to June

Remarks during storage

Susceptible to molding.

Due to high humidity, storage roots are often molded or rotten. Bags need to be air­ tight.

* Ensiling methods will be covered in Chapter 2.


1.5.12 Recommended utilization

 

Spring crop

Winter crop

Vine

Use dried or ensiled vine

Use fresh or ensiled vine or sell the surplus vine

Root

Big root, slice and dry to make chips or starch noodles

Small root, high moisture content, feed fresh or ensiled roots to pigs

 


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