RESEARCH ON THE GROWTH AND DEVELOPMENT OF TARO VARIETIES AND CULTIVATION TECHNIQUES FOR THE POTENTIAL VARIETY IN YEN BAI PROVINCE

MINISTRY OF EDUCATION AND TRAINING
THAI NGUYEN UNIVERSITY




LE VIET BAO




RESEARCH ON THE GROWTH
AND DEVELOPMENT OF TARO VARIETIES
AND CULTIVATION TECHNIQUES FOR THE
POTENTIAL VARIETY IN YEN BAI PROVINCE

Research field: Crop science
Code: 62.62.01.10




SUMMARY OF PhD THESIS

THAI NGUYEN - 2014
This thesis has been completed at:
AGRONO MY FACULTY, THAI NGUYEN COLLEGE
OF AGRICULTURE AND FORESTRY



Supervisor: Associate Prof. Nguyen Ngoc Nong




Examiner 1:
Examiner 2:
Examiner 3:




This thesis will be defended at the university panel meeting
At: College of Agriculture and Forestry, Thai Nguyen University
At dated month year 2014







This thesis is catalogued at:

- Thai Nguyen Learning Resource Centre
- Libraries at the College of Agriculture and Forestry
- National library
1


INTRODUCTION
1. Background of study
Taro plants, which scientific name is Colocasia esculeuta L. Schott,
is the monocot plants - belong to Colocasia gennus, Araceae family, is
also a species planted long ago in the world. In Vietnam, taro plants
are planted in many sub-ecological zones over the country such as Bac
Kan, Ha Giang, Lao Cai, Yen Bai, Nghe An, Da Lat, Tra Vinh, ; it is
grown on many different soil types from land farms in the plains to
slopping mountainous land (cultivation land) in mountainous regions.
Yen Bai is a northern mountainous province, with a total area of nearly
700,000 hectares of natural land. Its economy is mainly agricultural
and forestry production. Taro plants has been grown since a long time
in Luc Yen District, Yen Bai and the products of taro in Luc Yen now
became the speciality of this region. The policy of Yen Bai province
and Luc Yen district is that developing taro plant cultivation to grow
towards commodity production is not only effective in Luc Yen
district, on the arable land that traditional production development in
the districts of the province on different soil types in order to increase
the income of farmers.
Thus, the purpose of this study is to research on growth and
development of local taro varieties on single-crop farmland in Luc
Yen District and in lowland in Tran Yen District - where the
climate is similar to some other districts of Yen Bai such as Yen
Binh, Yen Bai city, Van Yen, Van Chan and it is also in the taro

development planning area of Yen Bai province in the upcoming
years. Initial research results will select the prospect varieties on
two types of soil to continue to study a number of cultivation
measures on fertilizers, planting density - season and preservation
techniques, which become urgently needed to expand the area,
develop taro cultivation towards commodity production, focus to
increase the income of people in the province, become the basis for
the expansion in some districts in the province aiming to plant
restructuring, and increase income for farmers.
From the above theory, we have implemented the study titled
"Research on the growth and development of taro varieties and
cultivation techniques for the potential variety in Yen Bai province".
2


2. The purpose of study
Through the activities of study and evaluating the growth and
development of some taro varieties on single-crop-land and lowland
in Yen Bai province, finding out the most potential and suitable
variety for the local;
Identifying a number of cultivation measures about fertilizers
(nitrogen, phosphorus, potassium and manure), density - season and
tuber preservation techniques for potential variety in single-crop-land
in Luc Yen District and lowland in Tran Yen District, which are the
basis for the area expansion, taro plants development towards
focusing on commodity production, contribute to improve incomes
for the local farmers.
3. Scientific and practical significance
3.1. Scientific significance
The results of the study has confirmed the scientific and practical

basis of the taro plant cultivation on single-crop-farmland in Luc Yen
district and lowland in Tran Yen district, Yen Bai province.
As a basis for the effective application of technical measures on
fertilizers, density, season and how to preserve taro tuber on single-
crop-farmland in Luc Yen district and lowland in Tran Yen district,
Yen Bai province.
3.2. Practical significance
The results of the study has added 1 taro variety (Bac Kan variety)
to taro variety system on Yan Bai province in addition to local
varieties and potential varieties; giving a plan for building the
specialized location for taro plant cultivating on single-crop-farmland
and lowland to meet the raw material site for the taro processing in
the future. Helping people to chang the crop system and improve the
incomes for people in some districts in the province of Yen Bai. The
result of the building taro cultivation model and results of taro plants
study have proven the scientific and practical basis of the taro plant
cultivation on single-crop-farmland in Luc Yen district and lowland
in Tran Yen district, Yen Bai province, thus it can be applied into
practice in Yen Bai.
3


4. Subjects and scopes of study
4.1. Subjects of study
5 local varieties of taro plants which were collected in Bac Kan,
Ha Giang and Yen Bai (3 varieties) were characterized by different
biological-agriculture characteristic. Chemical fertilizers (nitrogen,
phosphorus, potassium) and organic fetilizer (local manure), tuber
preservation methods by the local people and other methods that
were studied and mentioned before by Nguyen Ngoc Nong, Nguyen

Thi Ngoc Hue.
4.2. Scopes of study
The experiments were studied on the single-crop-land in Luc
Yen district and lowland in Tran Yen district, Yen Bai province in
2011-2013.
5. New findings of the study
The study has evaluated the characteristics of growth and
development of 5 taro varieties collected in some northern
mountainous provinces (Bac Kan, Ha Giang, Yen Bai) which is
cultivated on single-crop-farmland in Luc Yen district and lowland in
Tran Yen district, Yen Bai province. This also selected the taro
variety of YB1 is the potential variety for Yen Bai province.
The study has identified technical measures on fertilizers
(nitrogen, phosphorus, potassium, manure), density, seasona and taro
tuber preservation techniques for potential variety (Yen Bai 1) on
single-crop-farmland in Luc Yen district and lowland in Tran Yen
district, Yen Bai province.
6. Structure of the dissertation
The dissertation consists of 5 parts, with Introduction: 4 pages;
Chapter 1: Literature review: 35 pages; Chapter 2: Content and
methodology: 16 pages; Chapter 3: Results and discussion: 63 pages;
Conclusions and recommendations: 3 pages. Reference includes 111
Vietnamese and English items.
4


Chapter 1
LITERATURE REVIEW
1.1. Scientific theory of the study
Yen Bai province has a tropical monsoon climate, with high

temperature difference between day and night, average annual
temperature of about 20 - 23
0
C, average annual rainfall of about
1500-1600 mm/year; relative humidity of about 84-86%. The main
type of soil in here are Red-brown soil on limestone (Typic
HAPLUDOX) and yellow-red ferralit soil, brown-red soil on acid
macma-stone with pH ranging from 5.0 to 6.0. There is a relatively
consistent between the natural conditions of some District in Yen Bai
province with the ecological requirements of the taro plan when
taking into comparison; On the other hand, taro plants were
cultivateded a long time ago, the large area of unused land with
mainly in single-crop Riceland (passived irrigation) and lowland,
which have been the theory of taro planted area expansion.
1.2. The origin, classification and distribution of taro growing
areas - (Colocasia esculenta (L.) Schott)
Taro plants commonly grow in the tropics and subtropics. In some
countries, taro plant (Colocasia esculentavar. Esculenta) is used for
food, especially in Asian and Oceania countries. Taro plats was
originated from Southern Centre Asia, such as India or Malaysian
peninsula. Some scientists also believed that taro plants originated in
Southeast India. In Vietnam, taro plants, especially water taro plants
were cultivated before rice plants, which about 10,000-15,000 years ago.
There is a various ranges of renetic resources in natural conditions: at
height 1.0 m to 1,800 m above sea level, some varieites can grow in
water, in humidity or arid land. Taro plants are planted in gardens, from
mountains to plains due to the ease of growing and adapting, whereas
taro plants are grown mainly in midland and mountainous regions.
Tuber crops that belong to Araceae Family (English name "Taro"),
include some types, such as Giant Taro in forest (Alocasia macrorrhira),

Swamp Taro (Cyrtosperma chamissonis), Tannia (Xantosoma
agittifolium), Elephant Ear-Giant (Colocasia gigantea ), taro (Colocasia
esculenta var. escullenta) and taro (eddo) (Colocasia esculenta var.
5


antiquorum). Among the plant species mentioned above, the taro species
have highest economic value.
1.3. Biological characteristics of taro plants
1.4. Natural condition requirements of taro plants
1.5. Taro production situation in the world and Vietnam
In 2012 the total planted area of taro in the world was 1,316,985
ha, the average yield worldwide in 2012 was 7.5681 tons/ha yield
and production reached 9,967,198 tons, whereas 7,360,196 tons in
Africa (the highest due to the largest area), then 2,195,042 tons in
Asia, followed by Oceania and the Americas.
In Vietnam, the total planted area of root crops in 2012 was
741,300 ha, which taro and other starchy crops contained 33,100 ha.
Root crops grown in almost provinces in the country.
1.6. Taro Research and Production Situation in the world and
Vietnam
In Vietnam, it only started in 1998 in research in taro varieties by
the Center for Plant Genetic Resources. There have been some
promising varieties are being tested in production currently. Up to
2010, there were 545 varieties of taro plants have been maintained
and preserved in group in national gene bank and described in 53
criteria of morphology, agronomic characteristics. The cultivation
measures in varieties, season, fertilizer, density, preservation
measures for plant taro have been studied by scientists in recent
years, however, these research mainly focused on taro plants in plain.

The research on taro plants in mountainous and technical measures
for the local varieties in the mountainous northern province has been
limited. Therefore, it is very essential to study of the varieties and the
technical methods for prospect variety on single-crop land in Luc
Yen District and lowland in Tran Yen.
The technique measures of taro plants have been concerned in the
country in recent years. Many varieties of taro has been studied in
terms of growth characteristics, and techniques, such as density, crop,
fertilizer, pest in some sub-ecological zones in Ha Noi, Hoa Binh in
the Red river delta region. The same studies and technical measures
for local varieties of taro production have been limited in some
provinces such as Yen Bai, Ha Giang and Bac Kan. In particular,
there is almost no study of taro on a number of different types of land
6


including: single-crop land and lowland in the river bank. Therefore,
the study of growth and development of taro some selected local
varieties then finding out the promise one to study the technical
measures on singlecrop farmland and lowland will be completely
new, will contribute to complete the procedure of taro cultivation for
promising variety on singlecrop farmland and lowland in Yen Bai -
where has the similiar climate to 2 studied area named Luc Yen and
Tran Yen District.

Chapter 2
MATERIALS, CONTENT AND METHODOLOGY
2.1. Materials of the study
2.1.1. The studied taro varieties
Consisting of 5 varieties of taro: Yen Bai 1 taro variety (KMYB1)

(control), Yen Bai 2 taro variety (KMYB2); Yen Bai 3 taro variety
(KMYB3); Ha Giang taro variety (KMHG); Bac Kan taro variety
(KMBK);
2.1.2. The fertilizers used in study
Chemical fertilizers: Urea (46% N); SSP-superphosphate (16%
P
2
O
5
), Potassium chloride (56% K
2
O),
Organic fertilizers: Local Manure.
2.2. Location, duration of study
- Study area: Lieu Do Commune - Luc Yen District; Dao Thinh
Commune - Tran Yen Distict, Yen Bai province.
- Duration of study: 2011-2013.
2.3. Content of study
- Content 1: Studying the effect of climatic and land conditions to
develop taro plant production in Yen Bai province.
- Content 2: Studying the growth and development of several taro
varieties on single-crop-land in Luc Yen District and lowland in Tran
Yen District, Yen Bai province.
- Content 3: Studying on some technical measures appropriate
including fertilizer (nitrogen, phosphorus, potassium, manure),
density - season for promising taro variety (KMYB 1) on single-crop-
land in Luc Yen District and lowland in Tran Yen District, Yen Bai
province.
7

- Content 4: Studying on tubes preservation methods for potential
taro variety (KMYB 1) in Luc Yen and Tran Yen district, Yen Bai
province.
- Contents 5: Building model of taro cultivation in Luc Yen and
Tran Yen district, Yen Bai province.
2.4. Research methodology
2.4.1. Survey and data collection methodology
Using survey and collection of data methodology on climatic and
land conditions in Yen Bai Province that affects to taro plant
development in Yen Bai province through inheritance of secondary
data in the local agency units. From these data, it wil be synthesized,
evaluated and compared with taro plants to have a scientific theory
for the development of production. Using survey methodology,
directly interview people about techniques which have being applied
in a number of areas to synthesize, evaluate and compare.
2.4.2. Methods of field experiment design and agricultural norm
monitor
* Experiment 1: Studying the effect of climatic and land
conditions to develop taro plant production in Yen Bai province
- Experiment design: The experiment was arranged with 5
treatments, 3 replications arranged in randomized complete block
design (RCBD), 15 plots in total. Each experimental plot layouted in
area of 22 m
2
, 10 m in length, 2.2 m in wideth, single rows, 4 rows
per bed, bed trench 0.2 m. The total area is 330 m
2
each plots
(excluding the protected areas).

- Experiment treatments: 1: KMYB1 (control); 2: KMYB 2; 3:
KMYB 3; 4: KMHG; 5: KMBK.
- The norms and monitoring methods:
+ Norms on growth and biological characteristics: Emerging time
(Date); Growing percentage (%); Uniformity (%): Evaluation based
on 5 point scale: 1-5; Growing time (days); number of leaves/plant
(leaf/ plant); plant height (cm). Each plots was monitored diagonally
5 points, 3 plants each points, total of 15 plants; morphological
observations of stems, leaves and colors.
+ The level of pests and diseases infestion: Late blight disease
(Phytophthora Infestans); Insects: Aphids, cutworms, beetles in
the growing periods.
8


+ Indicators measure the components of yield and productivity,
tube quality assessment through sense, people's opinions and
laboratory analysis.
- The indicators measure yield and yield components; Preliminary
accounting of the economic efficiency of taro variety in the
experiment.
- The indicators of evaluating the quality of tubes through senses
and analysis.
- Some technical measures applied to experiments: planting date:
January 15, 2011 and the different seasons of the experiment. Tillage
techniques, making clean of grass, making bed of 25-30 cm (with
single-crop farmland), 10-15 cm (with lowland), 2.2 m wide surface.
Distance, density: 0.5 m between plants, 0.6 m between rows
(planting density of 33,000 plants / ha (rounded figures). Fertilizers:
0.5 tons of lime and 20 tons of manure, 80 N, 100 P

2
O
5
, 100 K
2
O.
Fertilizer applying: Base: 100% manure + 100% phosphate; First
Sidedressing (4-5leaves): 60% N + 40% K
2
O, combined with
weeding, digging, Apply 5-6 cm in depth, then filled with soil;
Second Sidedressing (7-8 leaves): 40% N + 60% K
2
O, combined
with weeding, digging, Apply 2-3 cm in depth, then filled with soil.
* Experiment 2: Studies on the growth and development of several
varieties of taro on lowland in Tran Yen district, Yen Bai province.
- Experiment designs: As Experiment 1.
- Formula experiments: CT 1: KMYB1 (control); CT 2: KMYB 2;
CT 3: KMYB 3; CT 4: KMHG; CT 5: KMBK.
- Norms and monitoring methods: As Experiment 1.
- Some technical measures applied to the experiment: As
Experiment 1
* Experiment 3: Effect of nitrogen doses on KMYB1 taro yield on
single-crop farmland in Luc Yen District, Yen Bai Province
- Experiment designs: The experiment was arranged with 5
treatments, 3 replicates arranged in randomized complete block
design (RCBD) with a total of 15 plots. Each experimental plot
layouted in area of 22 m
2

, 10 m long and 2.2 m wide. The total area is
330 m
2
each plots (without protective areas)
- Experiment treatments: CT 1: 0 N; CT 2: 40 N; CT 3: 80 N
(control); CT 4: 120 N; CT5: 160 N, with same base fertilizers.
9


- Norms and methods of monitoring: Monitoring of yield and the
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer was different in each treatments.
* Experiment 4: Effect of nitrogen doses on yield varieties
KMYB1 on lowland at Tran Yen district, Yen Bai province
- Experiment designs: As experiment 3.
- Experiment treatment: CT 1: 0 N; CT 2: 40 N; CT 3: 80 N
(control); CT 4: 120 N; CT5: 160 N. Common base fertilizer.
- Norms and methods of monitoring: Monitoring of yield and
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, with same base fertilizers
* Experiment 5: Effect of dose of phosphate to KMYB1 taro yield
on single-crop farmland in Luc Yen District, Yen Bai Province
- Experiment design: The experiment was arranged with 6
treatments, 3 replicates arranged in randomized complete block
design (RCBD), a total of 18 plots. Each experimental plot layouted
in area of 22 m
2
, 10 m long, 2.2 m wide. The total area is 396 m

2
in
each plots (excluding the protected areas).
- Experiments treatments: CT 1: 0 P
2
O
5
; CT 2: 30 P
2
O
5
(control);
CT 3: 60 P
2
O
5
; CT 4: 90 P
2
O
5
; CT 5: 120 P
2
O
5
; CT6: 150 P
2
O
5
. With
same base fertilizers.

- Norms and methods of monitoring: Monitoring of yield and
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer is different in each treatments.
* Experiment 6: Effect of dose of phosphate to KMYB1 taro yield
on lowland in Tran Yen district, Yen Bai province
- Experiment: As the experiment 5.
- Nutrition for 1 ha and treatments as experiment 5.
- Norms and methods of monitoring: Monitoring of the elements
of performance and productivity: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer for each treatments is different
10


* Experiment 7: Effect of dose of potassium to KMYB1 taro yield
on single-crop farmland in Luc Yen District, Yen Bai Province
- Experiment designs: The experiment was arranged with 6
treatments, 3 replicates arranged in randomized complete block
design (RCBD), a total of 18 plots. Each experimental plot layouted
in area of 22 m
2
, 10 m long, 2.2 m wide. The total area is 396 m
2

each plots (excluding the protected areas).
- Experiment treaments: CT 1: 0 K
2
O; CT 2: 30 K
2

O; CT 3: 60
K
2
O (Control); CT 4: 90 K
2
O; CT 5: 120 K
2
O; CT 6: 150 K
2
O.
- Norms and methods of monitoring: Monitoring of yield and
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer is different in each treatments.
* Experiment 8: Effect of dose of potassium KMYB1 taro yield in
lowland in Tran Yen district, Yen Bai province
- Design of the experiment, the base fertilizer and fertilizer
treatments as experiment 7.
- Norms and methods of monitoring: Monitoring of yield and
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer is different in each treatment.
* Experiment 9: Effect of dose of manure on KMYB1 taro yield on
single-crop farmland in Luc Yen District, Yen Bai Province
- Design of the experiment: The experiment was arranged with 6
treatments, 3 replicates arranged in randomized complete block
design (RCBD), a total of 18 plots. Each experimental plot layouted
in area of 22 m
2
, 10 m long, 2.2 m wide. The total area is 396 m

2
in
each plots (without protected areas).
- Experiments treatment: CT 1: 0 tonnes manure (Control); CT 2:
5 tons of manure; CT 3: 10 tons of manure; CT 4: 15 tons of manure;
CT 5: 20 tons of manure; CT 6: 25 tons of manure.
- Norms and methods of monitoring: Monitoring of yield and
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer is different in each treatment.
11


* Experiment 10: Effect of dose of manure on KMYB 1 taro yield
on lowland in Tran Yen district, Yen Bai province
- Design of the experiment, the base fertilizers and fertilizer
treatments as experiments 9.
- Norms and methods of monitoring: Monitoring of yield and
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer is different in each treatment.
* Experiment 11: Studying in different density and seasons for on
KMYB1 taro variety on single-crop farmland in Luc Yen District, Yen
Bai Province
- Design of the experiment: The experiment was arranged in 2
factors design (Split - Plot Design) with 4 treaments for different
planting time (sub-factor) and 4 treaments for density (main-factor)
with 3 replicates. Each experimental plot layout in area of 10 m
2
, 10 m

long, 1 m wide, arrange 2 rows /beds, 0.6 m between rows but plants
depending on density, 0.2 m trench beds. Total number of plots is 48,
the total area is 480 m
2
in each plots (without protected areas).
+ The growing time treatments: T1: Growing 15/12/2011; T2:
Growing 30/12/2011; T3: Growing 15/01/2012 (control); T4:
Growing 30/01/2012.
+ The density treatments: M1: 4.2 plants/m
2
(rounded figures);
M2: 3.3 plants/m
2
(Control); M3: 2.8 plants/m
2
; M4: 2.4 plants/ m
2
.
- Norms and methods of monitoring: Monitoring of yield and
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer is different in each treatment.
* Experiment 12: Studying in different density and seasons for
KMYB1 taro yield on lowland in Tran Yen district, Yen Bai province
- Design of the experiment: As 11 experiments.
- Norms and methods of monitoring: Monitoring of yield and
yield components: As Experiment 1.
- The technical measures: As Experiment 1, planting date January
15, 2012, the amount of fertilizer is different in each treatment.
12

* Experiment 13: Research on some technical measures to
preserve KMYB1 tubes in Yen Bai province
Experiment was Layouted completely random, the treatments
include: CT 1: Store in wet sand on the cement floor; CT 2: Store in
bamboo scaffolding with cover; CT 3: Store in a covered ground
(floor) (Control); CT 4: Store in a covered cement floor.
2.4.3. Methods of soil sampling and soil analysis indicators,
manure analysis
According to current standards and method.
2.4.4. Methods of analysis and data treatment
The data are summarized and analyzed by IRRISTAT 4.0
software; Excel 2007 (Regression); LSD comparison by field
research methodology (Do Thi Ngoc Oanh et al, 2012, Pham Tien
Dung, 2008).
2.4.5. Methods of estimating the optimum amount of fertilizer in
cultivation and in economic efficiency; fertilizer efficiency and
VCR coefficients of fertilizers + The maximum amount of fertilizer
techniques:
+ The optimum amount of fertilizer for cultivation:
x
=
b
2a
+ The optimum amount of fertilizer for economic efficiency:
x
’
=
y’ - b

-2a
Whereas: a and b are coefficients of the regression equation. y 'is
weight of taro tubers (both main and small tubers) for sale to buy 1
kg of fertilizer (N, P
2
O
5
, K
2
O, manure).
- Fertilizer efficiency is the increased number of harvested
products with each unit of fertilizer applied.
- The VCR (Value Cost Ratio) coefficients: the profits with each 1
VND of fertilizer expenses = Profit coefficients when applying
fertilizer.
VCR
=
Value of increased products (by applying fertilizer)
Cost of fertilizer applied
13


Chapter 3
RESULTS AND DISCUSSION
3.1. Climatic and soil conditions affect to the taro production in
Yen Bai
The natural conditions of climate and soil in Yen Bai province is
relatively suitable for taro plants grow and develop. With large
agricultural land area, the taro plants can grow well on a variety of
crop land such as single-crop farmland, lowland, or upland in Luc

Yen, Yen Binh, Yen Tran, Van Chan District to constitute the
accomodity production of goods. However, most of the land is high
terrain, steep, complexly dissected and diversed. Climatic conditions
are so different an, there is also some extreme climates that difficult
to develop agricultural production in general and plant taro in
particular.
3.2. The growth and development of taro varieties on single-crop-
farmland in Luc Yen district and lowland in Tran Yen district,
Yen Bai province
3.2.1. Some biological characteristics of taro varieties on two soil
types
Studied taro varieties had different characteristics on roots and
tubes, especially KMYB1 and KMYB2 had similiar features such as
stems with purple color, purple veins, however KMYB1 taro variety
have distinctive characteristics that are dark purple stem, wavy leaf
margins, purple tuber.
3.2.2. Germination ability of taro varieties on two soil types
Taro varieties on farmland and lowland have high germination
rate that reached 100% at 40 days after planting; the germination rate
was higher On single-crop farmland in Luc Yen district than on
lowland (Tran Yen District).
3.2.3. Period of growth and development of taro varieties on two
soil types
There were no significant differences in total time of growth and
development. From planting to harvest, growth time ranged from
235-240 days on farmland and 225-230 days on lowland. After
harvesting it can be planted by winter crops with the agricultural
system of taro plants + winter crops.
14

3.2.4. Plant height, number of leaves and the uniformity of taro
varieties on two soil types
On singlecrop farmland in Luc Yen District, taro varieties have
the final height (was measured at the time of July) reached 127.5 to
147.2 cm, the highest was KMYB 1 variety, the lowest was KMBK
127.5 cm. The number of leaves/plant reached 17.3 to 18.6
leaves/plant. Plant Height of taro varieties on lowland ranged from
129.8 -143.4 cm; the highest was Ha Giang taro varieties reached
143.4 cm, the lowest was KMBK reached 129.8 cm. The number
leaves peaked at 18.2 leaves (KMYB 3), the lowest was KMBK (16.6
leaves). The highest uniformity on 2 types of soil belonged to KMYB
1 taro variety.
3.2.5. The composition and level of pest and diseases infestion of
taro varieties on two soil types
In general, on both 2 types of soil in Tran Yen district, there were
aphids, cutworms, beetles attacked taro fields, but in different levels.
Bac Kan taro variety generally have higher rates of damage than
other varieties. Late blight disease appeared in all varieties of taro,
and increase at the period of 13-15 leaves (18.5 to 25.5%) whereas
KMBK was the highest (on single-crop farmland).
3.2.6. The yield components and yield of taro varieties in two soil
types
Table 3.9a. The yield components and yield taro varieties on
single-crop farmland
No.
Variety
Main tubes
Sub-tubes
E.Y

(tons/ha)
A.Y
(tons/ha)
Weight
(Kg)
E.Y
(tons/ha)
A.Y
(tons/ha)
Tubes/plant
Weight
(kg)
E.Y
(tons/ha)
A.Y
(tons/ha)
1
KMYB1(Control)
0.77
25.41
21.85
10.2
0.029
9.76
8.46
35.17
30.31
2
KMYB2
0.75

24.75
21.04
6.9
0.028
6.38
5.48
31.13
26.52
3
KMYB3
0.72
23.76
20.55
8.1
0.028
7.48
6.44
31.24
26.99
4
KMHG
0.78
25.74
21.62
7.4
0.031
7.57
6.46
33.31
28.08

5
KMBK
0.46
15.18
12.86
12.2
0.032
12.88
11.25
28.06
24.10

CV (%)


1.5



7.7

2.7

LSD
0,05


0.54

1.11

1.40
On single-crop farmland in Luc Yen District, the Actual yield
(A.Y) of taro varieties ranged from 24.10 to 30.31 tons/ ha, the
highest was KMYB 1 which reached 30.31 tons / ha, higher than the
other varieties at the 95% confidence level; the lowest was KMBK
15


only which reached 24.11 tons / ha, 6.20 tons/ ha lower than the
control; KMYB 2 was 3.79 tons / ha lower than the control; these
value were 3.32 tons/ha, 2.23 tons/ha with KMYB3 and KMHG,
respectively at 95% confidence level.
On the lowland at Tran Yen district, taro varieties had Actual
yield ranged from 24.61 to 29.04 tons / ha, the highest was KMYB 1
* 29.04 tons / ha), higher than KMYB2, KMYB3, KMHG at 3.86,
3.99, 2.03, 4.43 tons/ ha, respectively at 95% confidence level.
Table 3.9b. The yield components and yield varieties of taro
plants on lowland
No.
Variety
Main tubes
Sub-tubes
E.Y
(tons/
ha)
A.Y
(tons/

ha)
Weight
(Kg)
Tubes/
plant
Tubes/
plant
Tubes/
plant
Tubes/pl
ant
E.Y
(tons/
ha)
A.Y
(tons/
ha)
1
KMYB1
(Control)
0.76
25.08
21.95
8.5
0.029
8.13
7.09
33.21
29.04
2

KMYB2
0.73
24.09
20.72
5.6
0.028
5.17
4.47
29.26
25.19
3
KMYB3
0.71
23.43
20.07
6.3
0.028
5.82
4.99
29.25
25.06
4
KMHG
0.79
26.07
22.08
5.8
0.031
5.93
4.93

32.00
27.01
5
KMBK
0.48
15.84
13.80
11.7
0.032
12.36
10.81
28.20
24.61

CV (%)


2.4



6.4

2.7

LSD
0,05


0.88

0.78

1.35
3.2.7. The size of main tubers of taro varieties on two soil types
The taro varieties had the tube height on farmland averaged 12.3
to 17.6 cm, which KMYB 1 reached 15.1 cm. Diameter of the tubes
reached 6.6 to 8.9 cm, in which KMYB 1 was the highest (8.9 cm).
On lowland, the tube height ranged from 12.0 to 17.3 cm that KMHG
was the highest; The main-tube diameter was from 6.4 to 8.6 cm and
KMYB1 was the highest.
3.2.8. Quality of tube of taro varieties on 2 types of soil
Study Results of senses and analysis showed that KMYB1 and
KMBK was evaluated at a higher quality than other varieties. Although
KMYB 1 had not the highest quality indicators but had the advantage of
local varieties with large adaptability, high yield and thus have meet the
requirements for selection as potential variety to expand the
development area towards commodity production in Yen Bai.
3.2.9. The economic efficiency of taro varieties on two soil types
On the single-crop farm land KMYB1 had the highest economic
efficiency with the profit of 61.053 million VND. KMBK had the
16


lowest (21.649 million VND). On the lowland, KMYB1 had the
highest economic with profit of 58.8 million VND. KMBK was the
lowest (25.49 million dong).
3.3. Study on some technical measures affecting to the yield

components and yield of KMYB 1 in Yen Bai
3.3.1. Effect of nitrogen doses on yield of KMYB 1 on 2 types of soil

Figure 3.3. Effects of different levels of nitrogen fertilizer to yield
of KMYB1 taro variety on single-crop farmland
On single-crop farmland in Luc Yen: Actual yield at control
treatment reached 29.86 tons / ha, higher than treatment 1 and 2. The
control had equivalent yield with treatment 4 and lower than
treatment 5 at 95% confidence level. On lowland in Tran Yen
district: Actual yield of treatments ranged from 26.94 to 30.29 tons /
ha, the highest was the treatment 5, higher than the control at 1.09
tons/ ha.
The regression equation showed the correlation between yield and
nitrogen fertilizer on farmland, which was: Y = - 0,0001x
2
+ 0,0334x
+ 27,78.
- The optimal amount of nitrogen fertilizer (in techniques): 167.0
kg N / ha.
17


- The optimal amount of nitrogen fertilizer (in economic
efficiency): 137.5 kg N / ha.
The regression equation showed the correlation between yield and
nitrogen doses on lowland is: Y = - 0,0001x
2
+ 0,0356x + 26,94.
- The optimal amount of nitrogen fertilizer (in techniques): 178.0
kg N / ha.

- The optimal amount of nitrogen fertilizer (in economic
efficiency): 148.5 kg N / ha.


Figure 3.4. Effects of nitrogen doses on yield of KMYB1 on lowland
Nitrogen fertilizer use efficiency on farmland in Luc Yen
district reached from 18.7 to 30.0 kg tubes/kg N (including main
and sub tubes), highest performance at 40 kg N / ha; Increasing
the amount of nitrogen caused decrease the efficiency. The Profit
factor ranged from 2.6 to 4.0, the highest profit ratio was 3.9 when
applying 40 kg N / ha.
Nitrogen fertilizer use efficiency on lowland in Tran Yen district
reached from 21.0 to 32.3 kg tubes/kg N (including main and sub
18


tubes), highest performance at 40 kg N / ha; lowest was 160 kg N /
ha; The Profit factor differed at treatments and ranged from 2.9 - 4.3,
the highest profit ratio belonged to treatment of 40 kg N / ha; the
lowest was 160 kg N/ha.
3.3.2. Effect of phosphate on yield of KMYB 1 taro variety on 2
types of soil
On single-crop farmland in Luc Yen: Actual yield ranged from
28.03 - 30.35 tons/ha, whereas the highest yield was treatment 6 (150
kg P
2
O
5
/ha), lowest was treatment 1 (none applying phosphate
fertilizer). Treatment 1, 3 had the equivalent yield to the control.

Treatment 4, 5, 6 (90-150 kg P
2
O
5
/ha) had higher yield than the
control at 95% confidence level.
On lowland in Tran Yen: Actual yield ranged from 27.63 - 29.98
tons/ha, whereas the highest yield was treatment 6. The control had
the equivalent yield to treatment 1, 3 and lower yield than treatment
4, 5, 6 at 95% confidence level.
The regression equation showed the relationship between yield of
KMYB 1 according to level of phosphorus fertilizer on farmland was
the corresponding parabolic function: Y = -0,0001x
2
+ 0,0241x +
28,03. The optimal amount of nitrogen fertilizer (in techniques):
120.5 kg P
2
O
5
/ ha. The optimal amount of nitrogen fertilizer (in
economic efficiency): 89.0 kg P
2
O
5
/ ha.
The regression equation showed the relationship between yield of
KMYB 1 according to level of phosphorus fertilizer on lowland was
the corresponding parabolic function: Y = -0,0001x
2

+ 0,0270x +
27,62. The optimal amount of nitrogen fertilizer (in techniques):
135.0 kg P
2
O
5
/ ha. The optimal amount of nitrogen fertilizer (in
economic efficiency): 104.0 kg P
2
O
5
/ ha.
Phosphorous fertilizer use efficiency on farmland in Luc Yen
district reached from 15.5 to 23.4 kg tubes/kg P
2
O
5
/ha (including
main and sub tubes), highest performance at 30 kg P
2
O
5
/ha;
19


Increasing the amount of fertilizer caused decrease the efficiency.
The Profit factor ranged from 1.9 - 2.6.
Phosphorous fertilizer use efficiency on lowland tended to higher
than on farmland although the lower yield. As on the farmland, the

highest performance was at 30 kg P
2
O
5
/ha (24.7 kg tubes/kg
P
2
O
5
/ha), lowest was 15.7 kg tubes/kg P
2
O
5
/ha when applying 150 kg
P
2
O
5
/ha. The Profit factor ranged from 2.1 - 3.2.
3.3.3. Effect of potassium on yield of KMYB 1 taro variety on 2
types of soil
On single-crop farmland in Luc Yen: the highest Actual yield
was treatment 6 (30.4 tons/ha), higher than the control at 1.34
tons/ha; lowest was treatment 1 (27.53 tos/ha, lower than the
control 1.53 tons/ha). Treatment 2,4 had the equivalent yield to
the control. Treatment 5, 6 had higher yield than the control at
95% confidence level.
On lowland in Tran Yen: the highest Actual yield was treatment 6
(30.16 tons/ha), higher than the control at 1.28 tons/ha; lowest was
treatment 1 (lower than the control 1.54 tons/ha). Treatment 2,4 had

the equivalent yield to the control. Treatment 5, 6 had higher yield
than the control at 95% confidence level.
The regression equation showed the relationship between yield of
KMYB 1 according to level of potassium fertilizer on farmland was
the corresponding parabolic function: Y = -0,0001x
2
+ 0,0302x +
27,53. The optimal amount of potassium fertilizer (in techniques):
151,0 kg K
2
O/ha. The optimal amount of potassium fertilizer (in
economic efficiency): 121.0 kg K
2
O/ha.
The regression equation showed the relationship between yield of
KMYB 1 according to level of potassium fertilizer on lowland was
the corresponding parabolic function: Y = -0,0001x
2
+ 0,0308x +
27,34. The optimal amount of potassium fertilizer (in techniques):
20


154.0 kg K
2
O/ha. The optimal amount of potassium fertilizer (in
economic efficiency): 124.0 kg K
2
O/ha.
Potassium fertilizer use efficiency on farmland ranged from 19.2 -

28.7 kg tubes/kg K
2
O /ha, highest at level of applying 30 kg K
2
O /ha.
The Profit factor ranged from 2.1 - 3.6. Increasing potassium made
decrease the profits, the lowest at 150 kg K
2
O/ha.
On the lowland, potassium performance ranged from 18.8 - 29.0
kg tubes/kg K
2
O /ha, highest at level of applying 30 kg K
2
O /ha;
lowest at 150 Kg K
2
O/ha. The Profit factor ranged from 2.2 - 3.8.
3.3.4. Effect of manure on yield of KMYB 1 taro variety on 2
types of soil
On single-crop farmland in Luc Yen: the Actual yield ranged from
25.88 - 30.25 tons/ha, highest was treatment 6 (30.4 tons/ha), lowest
was the control.
On lowland in Tran Yen: the Actual yield ranged from 24.88 -
29.61 tons/ha, highest was treatment 6 (30.4 tons/ha), lowest was the
control at 95% confidence level.
The regression equation showing the relationship between yield of
KMYB1 with the level of manure on farmland was the corresponding
parabolic function: Y = -0,0048x
2

+ 0,2946x + 25,88. The maximum
amount of manure (technique) : 30.7 tons / ha. Economic one was
18.8 tons / ha.
The regression equation showing the relationship between yield of
KMYB1 with the level of manure on farmland was the corresponding
parabolic function: Y = -0,006x
2
+ 0,3395x + 24,88. The maximum
amount of manure (technique) : 28.3 tons / ha. Economic one was
18.8 tons / ha.
Performance of manure on farmland ranged from 174.8 to 272.0 kg
tubes/ 1 ton of manure, highest at level of 5 tons of manure (134.0 kg
main tubes and 138.0 kg sub-tube). Profit factor was from 1.2 to 1.9.
21


Performance of manure on lowland ranged from 189.2 to 312.0 kg
tubes/ 1 ton of manure, highest at level of 5 tons of manure (312.0 kg
main tubes and 138.0 kg sub-tube). Profit factor was 1.2 when
applying 25 tons of manure.
3.3.5. Effect of density and season time to yield components and
yield of KMYB 1 on 2 types of soil
On a single-crop farmland, the density, season and the interaction
between density and season affected the productivity of the KMYB
1, the most suitable plant density of 3.3 plants / m2 had best results,
crop was planted with 4 time points from 15/12 - 30/1 whereas the
plating time of 30/12 - 15/1 had the best results. The highest real
yield was M2T3 that had 30.23 tons/ ha, the lowest was M4T4
treatment reached 22.02 tons / ha.
Density, season and the interaction between density and season

affected the yield components, and yield of KMYB 1 on lowland in
Tran Yen district. The most appropriate density, had highest yield
was density of 3.3 plants / m2 (M3), the most suitable season was
T2, T3 (30/12 - 15/1 planting date). The highest yield was treatment
M2T3 29.87 tons/ ha, the lowest was M4T4 reached 21.94 tons / ha.
3.4. Research results and technical measures to preserve seed
tubers KMYB 1
After 4 months of storage, the rate of diseases from 8.8 to 17.4%,
the most effective method was using wet sand.
In Tran Yen, the disease rate from 9.6 to 18.8%, the lowest was
still preserved by methods of wet sand. At two locations of
preservation, study results showed that the storage in moist sand and
cement ground had the lowest loss ratio, the number of kg of taro
tubes remaining after preservation was 79.7% in Luc Yen and 78.6%
in Tran Yen.
22


3.5. The results of building cultivation model of KMYB1 taro
variety on 2 types of land
Yield of KMYB1 taro variety on single-crop-farmland in Luc
Yen, Yen Bai was 29.87 tons/ha, on lowland was 29.16 tons/ha with
the benefit was 54.165.000 vnd/ha on farmland and 51.792.500
vnd/ha on lowland.
3.6. Proposed plan for complete the taro cultivation procedure
for KMYB1 on 2 types of soil
Proposed, finishing processes of planting KMYB1 on 2 types of
soil in Yen Bai province based on the results of research and
reference on plants taro.

CONCLUSIONS AND RECOMMENDATIONS
1. Conclusion
1.1. Natural conditions affecting to the development taro plants in
Yen Bai province
Conditions of climate and land in Yen Bai (7/9 districts) is quite
suitable for the development of taro plants, thus it can be grown and
expanded the cultivated taro plant areas in such single-crop-land and
lowland where have the similar natural conditions to Luc Yen and
Tran Yen district, Yen Bai province.
1.2. The growth and development of taro varieties on single-crop-
farmland in Luc Yen district and lowland in Tran Yen district, Yen
Bai province
- Taro varieties which were grown on single-crop-farmland in Luc
Yen district and lowland in Tran Yen district, Yen Bai province
grewth and developed well, suited to conditions of the local ecology.
- Actual yield of Yen Bai 1 taro variety was the highest, 30.31
tons/ha on farmland and 29.04 tons/ha in lowland. The lowest yield
was Bac Kan taro variety (24.10 tons/ha on farmland and 24.61
tons/ha in lowland)
23


- Seclecting the Yen Bai taro variety is the potential variety in
Yen Bai , which will be study te cultivation techniques in the next
year, 2012.
1.3. The results of the cultivation measures for the potential variety
(KMYB 1) on single-crop-farmland in Luc Yen district and lowland
in Tran Yen district, Yen Bai province
1.3.1. On single-crop-farmland in Luc Yen district, Yen Bai province
- The optimum amount of nitrogen fertilizer for cultivation was:

167.0 kg N/ha; for economic efficiency was 137.5 kg N/ha. For
phosphate, potassium and manure were 120.5 kg P
2
O
5
/ ha - 89.0 kg
P
2
O
5
/ha and 151.0 kg K
2
O/ha - 121.0 kg K
2
O/ha and 30.7 tons/ha -
18.8 ton/ha, respectively.
- Density and season: The most appropriate density and season for
taro plants was 3.3 plants / m2, planted on 15/1 (the highest yield of
30.23 tons / ha).
1.3.2. On lowland in Tran Yen district, Yen Bai province
- The optimum amount of nitrogen fertilizer for cultivation was:
178.0 kg N/ha; for economic efficiency was 148.5 kg N/ha. For
phosphate, potassium and manure were 135.5 kg P
2
O
5
/ ha - 104.0 kg
P
2
O

5
/ha and 154.0 kg K
2
O/ha - 124.0 kg K
2
O/ha and 28.3 tons/ha -
18.8 ton/ha, respectively.
- Density and season: The most appropriate density and season for
taro plants was 3.3 plants / m
2
, planted on 15/1 (the highest yield of
29.87 tons / ha).
1.4. The results of taro tuber preservation methods
In 4 taro tuber preservation methods, preserving by wet sand on
the cement ground (CT1) had the highest efficiency and the lowest
rate of diseases.
1.5. The results of building cultivation model of KMYB1 taro
variety on 2 types of land
Yield of KMYB1 taro variety on single-crop-farmland in Luc
Yen, Yen Bai was 29.87 tons/ha, on lowland was 29.16 tons/ha with