Tài liệu 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 singlecrop-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 - 230C, 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% P2O5), Potassium chloride (56% K2O), 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-cropland 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 m2, 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 m2 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 P2O5, 100 K2O. Fertilizer applying: Base: 100% manure + 100% phosphate; First Sidedressing (4-5leaves): 60% N + 40% K2O, combined with weeding, digging, Apply 5-6 cm in depth, then filled with soil; Second Sidedressing (7-8 leaves): 40% N + 60% K2O, 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 m2, 10 m long and 2.2 m wide. The total area is 330 m2 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 m2, 10 m long, 2.2 m wide. The total area is 396 m2 in each plots (excluding the protected areas). - Experiments treatments: CT 1: 0 P2O5; CT 2: 30 P2O5 (control); CT 3: 60 P2O5; CT 4: 90 P2O5; CT 5: 120 P2O5; CT6: 150 P2O5. 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 m2, 10 m long, 2.2 m wide. The total area is 396 m2 each plots (excluding the protected areas). - Experiment treaments: CT 1: 0 K2O; CT 2: 30 K2O; CT 3: 60 K2O (Control); CT 4: 90 K2O; CT 5: 120 K2O; CT 6: 150 K2O. - 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 m2, 10 m long, 2.2 m wide. The total area is 396 m2 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 m2, 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 m2 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/m2 (rounded figures); M2: 3.3 plants/m2 (Control); M3: 2.8 plants/m2; M4: 2.4 plants/ m2. - 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: b x = 2a + The optimum amount of fertilizer for economic efficiency: y’ - b x’ = -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, P2O5, K2O, 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. Value of increased products (by applying fertilizer) VCR = 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-cropfarmland 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 Main tubes No. Variety 1 KMYB1(Control) 2 Sub-tubes Weight E.Y A.Y (Kg) (tons/ha) (tons/ha) 0.77 25.41 21.85 10.2 KMYB2 0.75 24.75 21.04 6.9 3 KMYB3 0.72 23.76 20.55 4 KMHG 0.78 25.74 5 KMBK 0.46 15.18 E.Y A.Y (tons/ha) (tons/ha) 8.46 35.17 30.31 5.48 31.13 26.52 7.48 6.44 31.24 26.99 0.031 7.57 6.46 33.31 28.08 0.032 12.88 11.25 28.06 24.10 Weight E.Y A.Y (kg) (tons/ha) (tons/ha) 0.029 9.76 0.028 6.38 8.1 0.028 21.62 7.4 12.86 12.2 Tubes/plant CV (%) 1.5 7.7 2.7 LSD0,05 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 Main tubes No. Variety 1 2 3 4 5 KMYB1 (Control) KMYB2 KMYB3 KMHG KMBK CV (%) LSD0,05 Sub-tubes E.Y Weight Tubes/ Tubes/ Tubes/ Tubes/pl (tons/ (Kg) plant plant plant ant ha) A.Y (tons/ ha) E.Y (tons/ ha) A.Y (tons/ ha) 0.76 25.08 21.95 8.5 0.029 8.13 7.09 33.21 29.04 0.73 0.71 0.79 0.48 24.09 23.43 26.07 15.84 20.72 20.07 22.08 13.80 2.4 0.88 5.6 6.3 5.8 11.7 0.028 0.028 0.031 0.032 5.17 5.82 5.93 12.36 4.47 4.99 4.93 10.81 6.4 0.78 29.26 29.25 32.00 28.20 25.19 25.06 27.01 24.61 2.7 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 = - 0,0001x2 + 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 = - 0,0001x2 + 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 P2O5 /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 P2O5/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 = -0,0001x2 + 0,0241x + 28,03. The optimal amount of nitrogen fertilizer (in techniques): 120.5 kg P2O5/ ha. The optimal amount of nitrogen fertilizer (in economic efficiency): 89.0 kg P2O5/ 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 = -0,0001x2 + 0,0270x + 27,62. The optimal amount of nitrogen fertilizer (in techniques): 135.0 kg P2O5/ ha. The optimal amount of nitrogen fertilizer (in economic efficiency): 104.0 kg P2O5/ ha. Phosphorous fertilizer use efficiency on farmland in Luc Yen district reached from 15.5 to 23.4 kg tubes/kg P2O5/ha (including main and sub tubes), highest performance at 30 kg P2O5/ha;