1. TÓM TẮT NỘI DUNG CHÍNH LUẬN ÁN 1.1. Điều tra, đánh giá thực trạng sản xuất ngô Xuân trên đất ruộng bậc thang một vụ tại tỉnh Yên Bái. 1.2. Nghiên cứu xác định giống ngô phù hợp cho canh tác vụ Xuân trên đất ruộng bậc thang một vụ tại Yên Bái. 1.3. Nghiên cứu một số biện pháp kỹ thuật canh tác ngô Xuân trên đất ruộng bậc thang một vụ tại tỉnh Yên Bái. 1.4. Xây dựng mô hình sản xuất ngô Xuân lấy hạt trên đất ruộng bậc thang một vụ tại tỉnh Yên Bái. 2. NHỮNG KẾT LUẬN MỚI CỦA LUẬN ÁN 1. Diện tích đất ruộng bậc thang 1 vụ của toàn tỉnh Yên Bái hiện còn khoảng trên 2.500 ha. Các nguyên nhân chính dẫn đến bỏ hóa đất ruộng bậc thang ở vụ xuân và vụ đông: (1) Thiếu nước tưới do hệ thống kênh mương trên ruộng bậc thang không đầy đủ; (2) nhiệt độ thấp ở đầu vụ xuân, không đảm bảo cho các cây lương thực sinh trưởng phát triển nếu không can thiệp về mặt kỹ thuật; (3) tập quán thả rông trâu bò của người dân trong vùng; (4) tập quán canh tác truyền thống khó thay đổi của người dân; (5) thiếu vốn và kỹ thuật canh tác ở vụ xuân. 2. Đã xác định được 2 giống ngô là NK6101 và LVN17 phù hợp cho canh tác vụ Xuân trên đất ruộng bậc thang tỉnh Yên Bái và cho năng suất thực thu đạt cao nhất (60,51 - 71,19 tạ/ha) tại cả ba điểm nghiên cứu tỉnh Yên Bái. 3. Đã xác định được các biện pháp kỹ thuật để canh tác ngô xuân trên đất ruộng bậc thang một vụ tại tỉnh Yên Bái gồm: - Xác định được thời vụ gieo từ 10/2 đến 20/2 là khung thời vụ phù hợp ngô LVN17 sinh trưởng và phát triển trong điều kiện vụ xuân trên đất ruộng bậc thang tỉnh Yên Bái. Ngô sinh trưởng thuận lợi, tỷ lệ sâu bệnh hại thấp (< 10%) và cho năng suất thực thu cao (67,5 - 68,3 tạ/ha). - Phương pháp làm đất tối thiểu, kết hợp thời vụ gieo ngày 10/2 đến 20/2 thích hợp để giống ngô LVN17 sinh trưởng phát triển thuận lợi, năng suất thực thu đạt cao nhất (60,7 - 71,5 tạ/ha).
MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURAL SCIENCES … .*****…… NGUYEN VAN CHINH IDENTIFICATION OF TECHNICAL SOLUTIONS TO DEVELOP SPRING MAIZE PRODUCTION ON ONE CROP TERRACES IN YEN BAI PROVINCE Major: Crop Science Code: 62 01 10 SUMMARY OF THE THESIS Ha Noi - 2022 The thesis was completed at: VIETNAM ACADEMY OF AGRICULTURAL SCIENCES Major: Assoc Prof Le Quoc Thanh Dr Luu Ngoc quyen Critic 1: Critic 2: The thesis will be defended in the university-level dissertation committee Meeting at: VIETNAM ACADEMY OF AGRICULTURAL SCIENCES At hour minute, date month year 2022 The thesis can be found at: National Library of Vietnam Library of Vietnam Academy of Agricultural Sciences Library of Nomafsi INTRODUCTION The context Cultivation of terraces has long been considered a unique type of farming by the highland people in Yen Bai province, terraces not only are valuable in food security, but also as a basis for sedentary cultivation, settlement and ethnic traditions of the highland people of the province The current area of terraces in Yen Bai province was 5,787.78 hectares, accounting for 5.36% of the total agricultural production area and mainly concentrated in Van Chan, Van Yen, Mu Cang Chai and Tram Tau districts The terraces has low to medium fertility, the main crop structure is once summer rice crop However, the yield of summer rice season is low, the production efficiency is not high and especially the fallow period is long (7 months) Changing the crop structure, increasing the planting season on one crop terraces can increase one more crop in the winter or spring In the Spring season, from February to May, the average temperature is 20 - 250C, the average minimum temperature is 15.7 - 210C, the average rainfall is 450 - 550 mm, the seasonal frame is 125 days It is possible to grow one more crop in the Spring crop with crops such as corn, beans, To add spring maize crop on one-crop terraced fields in Yen Bai province, it is very necessary to choose short-term maize varieties suitable to the spring planting time frame, maize varieties with good drought tolerance, maize varieties have morphological characteristics suitable to the farming practices of the people of the region, Besides, the study of maize farming techniques is suitable for the conditions of spring crop cultivation on terraced fields with one crop in Yen Bai province is also a very important job to ensure the transformation of crop structure, increase the spring maize crop on once terraces of Yen Bai province develop sustainably From the above mentioned problems, we have done the topic: "Identifaiton of on technical solutions to develop spring maize production on one crop terraces in Yen Bai province" The purpose of the thesis - Assessed the current situation, including favorable and unfavorable factors in the production of Spring maize on once crop terraced fields in Yen Bai province - Identifyed the high yield maize varieties, suitable to ecological conditions and farming practices on terraced fields of Yen Bai province - Identifyed the maize farming techniques (planting season, planting method, fertilizer, ) suitable to spring crop conditions on terraced fields of the region - Built the model of producing Spring maize on one crop terraced fields in Yen Bai province New contributions of the thesis - The thesis has assessed the limitations of spring maize cultivation on terraces in Yen Bai province such as low temperature, drought, farming practices, - The thesis has identified maize varieties (LVN17, NK6101), reasonable maize cultivation techniques (planting season 10/2 - 20/2; fertilizer 150 kg N + 120 kg P2O5 + 90 K2O/ha on mulching base of tons of botanical material/ha for corn crop; planting density of 77 thousand plants and fertilizing 180 kg of N/ha with high biomass maize volume for animal feed) to develop Spring maize production on terraced fields in Yen Bai province The scientific and practical meanings of the thesis The scientific meanings - The thesis was a synchronous research on varietial identification and general technical measures for Spring maize season on one crop terraces Yen Bai province The research results of the thesis were valuable scientific datas not only for the planning of planting Spring maize on the single-crop terraces in Yen Bai province, but also as a basis data source for the development of maize in the northern mountainous region of Vietnam - The thesis could be used as a documentation in teaching and scientific research The practical meanings - The results had selected maize varieties, suitable farming techniques to develop and scaling out the structure of Spring maize - Summer rice on single-crop terraces in Yen Bai province, increasing the efficiency of land use, effectively exploiting and using redundant rural labor in the spring crop, promoting livestock development, contributing to socio-economic development for upland people - The results on increasing the Spring maize crop on once crop terraced fields can be applied to some other provinces in the Northern mountainous region with similar conditions Structure of thesis The thesis was presented in 142 pages of A4 size paper Chapter 1: Overview of the literature; Chapter 2: Research activities and methods; Chapter 3: Results and discussion with 46 tables and figures List of 113 references (79 documents in Vietnamese, 34 documents in English) The appendix contains detailed data from chapters and CHAPTER I OVERVIEW OF THE LITERATURE 1.1 Overview of terraces 1.1.1 Research on terraced fields in the world In the world, the terraces was considered popular type for mountainous areas of many countries such as Japan, China, Philippines, Indonesia, Nepal, Thailand Terraces appeared a long time ago, around the 14th to 16th centuries in Japan; In China, terraced fields appeared 1.300 years ago and on the Bali islands - Indonesia terraces existed more than 2.000 years ago; In the Philippines, terraced fields are mountains of land conquered with an altitude of 700m to 1.500m and there are terraced fields thousands of years old In Yuanyang, the area of terraced fields is over 11.000 hectares and over 3.000 steps Most of the terraced fields in China are used by people to make the edge of the field (Courtesy of Nguyen Truong Giang, 2015) The method of terrace farming reduced the slope to - 50, then the erosion will be reduced 1-3 times (Zheng, 2014) When studying the crop system on terraced fields, scientists have confirmed that increasing the dry crop especially legumes, both improves soil fertility and increases economic efficiency than monoculture with rice In fact, terraces were not only beauty of the landscape but also have many values that need to be preserved and promoted for future advantages 1.1.2 Research on terraced fields in the northern mountainous region of Vietnam The midland and Northern mountainous region has 187 thousand hectares of land for cultivation with only one crop a year, accounting for 36% of the field area Of which, the Northeast had about 148.6 thousand hectares and the Northwest has about 38.5 thousand hectares According to research results of Nguyen Truong Giang, (2015) terraced fields of the Northern mountainous region were mainly distributed in the provinces: Lai Chau, Son La, Lao Cai, Yen Bai, Ha Giang and Cao Bang In the whole region, the slope of land below 15o accounts for 27.78% of the natural area, the slope of 15 - 25o accounts for 17.10% and 55.10% of the land slopes above 25° In all three economic, social and environmental criteria, rice cultingvation is a long-standing and quite sustainable farming style that can both control erosion, wash out and keep soil fertility due to have waterretaining banks and can be cultivated for long time; In terms of cultural values: Terraced fields are achievements both in terms of culture and folk knowledge, which have brought into play their effects and created wet rice production in the highlands and are the heritage of each family in need to be protected and developed, to contribute to the national heritage; Regarding the farming system, terraced fields in the midland and northern mountainous provinces currently have two main cropping structures: monoculture of one season of rice (accounting for 92.4% of the area) and monoculture of one food crop (accounting for 7.6% area) The studies of Le Van Tiem (2005), Le Quoc Doanh et al (1994, 2008), Mai Quang Vinh (2002) on terraced fields in the Northern mountainous region had pointed out four main difficulties in production on rice production: (1) Lack of water in the spring crop; (2) Soil degradation through after many years cultivation; (3) The structure of rice varieties is not suitable, the yield is low; (4) Lack of knowledge and inefficient land use techniques 1.1.3 Research on terraced fields in Yen Bai province The area of one-crop terraced fields in Yen Bai province in 2010 was 6.256 hectares, to 2018 it decreased to 2.850 hectares (down 54.44%) due to the restructuring of crops, increasing the area for spring crop farming season The one-crop terraced field area of the province was concentrated in high districts such as Van Yen district (8.7%), Mu Cang Chai district (62.8%), Tram Tau district (8.4%) Van Chan district (9.9%), Luc Yen district (6.8%), and Yen Binh district (3.4%) Summary statistics of districts in Yen Bai province in 2019 In recent years, there have been many research projects on restructuring crops and increasing production value on one-crop terraced fields in Yen Bai province, such as: Adding the spring soybean crop season, spring upland rice or converting early summer season with upland rice and adding a bean crop in Autumn - Winter, has helped increase production efficiency per unit of arable land and reduce pressure on shifting cultivation Currently, a number of communes in four highland districts of Yen Bai province have experimented with planting the Spring maize on once terraced fields However, due to the lack of identification of suitable maize varieties, reasonable cultivation time, appropriate planting and care techniques, the production efficiency is not high 1.2 The role of maize Maize is an important crop for aller most countries in the world and Vietnam Maize together with wheat and wet rice are the three main food crops of mankind, maize ranks third in area (after wheat and wet rice), but has the highest yield and yield among cereal crops Maize is a typical plant that has applied many scientific achievements in the fields of genetics, breeding, biotechnology, mechanization, electrification and informatics, etc to research and production Huu Tinh, 1997) Corn is the most important ingredient in animal feed In addition, corn is used as a raw material for the food processing industry with about 670 kinds of cornbased products by the food, food, light industry and pharmaceutical industries In Vietnam, maize is both an important food crop and animal feed In addition, corn is also considered an energy for the 21st century, with the role of raw materials for the production of environmentally clean Ethanol-E5 biofuel In Yen Bai province, maize is an important food crop in the provincial agricultural restructuring scheme If successfully transforming the crop structure of spring maize - summer rice, maize will help Yen Bai solve problems of food security, hunger eradication and poverty alleviation, problem of redundant labor and economic development sustainably in high districts 1.3 Ecological requirements of maize 1.3.1 Temperature Maize is tropical crop, at the germination period the temperature requires about 18.30C; temperatures below 12.80C reduced yield The minimum temperature for maize plants to grow and develop is between 100C (Dinh The Loc et al., 1997) According to Wallace and Bressman (1937), at an average temperature between 15.5 - 18.30C, the time from sowing to sprouting is usually 8-10 days At a temperature of 10 - 12.80C, the germination process lasted from 18 to 20 days If the soil is moist and at a temperature of 21.10C, germination can occur in - days Cold and humid has more disease Several authors have shown that various diseases can cause damage to seeds and seedlings at low temperatures 1.3.2 Sunlight Maize is a tropical crop that belongs to the group of short-day crops Studying the response of maize plants to day length showed that maize plants formed different morphological patterns with different day lengths Daylength of maize were determined to occur at the stage of differentiation step to step of reproductive organogenesis In maize, the development of flower earlier than silk corn In addition, different light forms and different light spectrum compositions not only affect the growth of flagellum and cobs, but also the growth of stem, burning length as well as muscle leaf texture and size 1.3.3 Water Water is an important environmental factor for the life of maizes, belong to C4, it need from 350 - 500 liters of water to produce kg of grain (depending on climate and soil nutrient status) (David, 2002) A corn plant can release 2-4 liters of water/day, during the growth and development of of corn, about 1,800 tons of water are released, equivalent to about 175mm of rain According to Tran Duc Hanh, the coefficient of water consumption to form a dry matter unit of corn is 250 - 400 (Tran Duc Hanh et al., 1997) The water requirements and drought tolerance of maizes are different during each growing period In the early stage, corn grows slowly, accumulates less green matter so it does not need much water In the period of - 13 leaves, maize needs from 28-35 m3 of water/day/ha In the period of twisting the stem, growing the flowing, and spraying the beard, 65 - 70m3 of water/day/ha is required 1.4 Reasearh on technical measures to increase maize yield 1.4.1 Research on maize varieties in Vietnam The seed is a important key to promote maize production, increase yield and output The strong development of biotechnology has contributed to improving research efficiency and increasing excellent materials to serve to select high-yielding maize varieties, varieties with drought and salt tolerance, and good resistance to pests From there, it shows that the combination of traditional methods and biotechnology (gene transfer, anther culture, ) is a solid basis in research and breeding of new maize varieties today However, the variety can only promote its full potential in the right soil environment, suitable climate and reasonable cultivation methods At the same time, study farming techniques such as planting density, appropriate fertilizer dosage, for each maize variety Along with the needs of the livestock industry, a series of studies on maize biomass are being carried out by researchers in two directions: One is to select varieties from successful hybridization of varieties such as VN8960, LVN146, VN5885, LCH9 , CS71; CN18-7, VN172, CP511, NK7328, VN172, DH17-5… The second is importing varieties from other countries and assessing ecological regions such as varieties NK7328, NK4300, NK6253, CP111, P4311, Pioneer Brand P4554… Since then evaluate phenotypes, biomass yield, green matter quality, physiological and biochemical criteria to select and put into production 1.4.2 Research on planting time of maize In Viet Nam, there are agro-ecological regions where maize can be grown with high yield Depending on weather conditions, climate and local crop rotation system, agricultural scientists have shown the planting time of maize in general in ecological regions in Vietnam, in which the planting season In the Northern mountainous region, specifically as follows: The Northwest region is the main maize crop: Sowing from late April to early May, Autumn-Winter crop sowing late July and early August Northeast region Spring crop (1 crop land) Spring) is sown from January 25 to February 15, the main corn crop is sown from the end of April to the beginning of May, the Autumn-Winter crop is sown from the beginning of August to the beginning of September 1.4.3 Research on Fertilizer 1.4.3.1 Research on nitrogen fertilizers In Vietnam, from 1985 to now, the use of nitrogen fertilizer in our country has increased by an average of 7.2%/year The rate of N : P2O5 : K2O in the past 10 years has been more balanced with the corresponding ratio in 1990, 1995 and 2000 being 1: 0.12: 0.05; 1: 0.46: 0.12 and 1: 0.44: 0.37 The amount of fertilizer/ha has also increased over the years 1990, 1995, 2000 with the total amount of N : P2O5 : K2O respectively 58.7; 117.7 and 170.8 kg/ha, this rate is still low compared to developed countries such as the US, Korea, France, and Japan with a total amount of N: P2O5 : K2O about 240-400 kg/ha (Bui Huy Hien) (2002) According to Nguyen Van Bo (2007) the amount of fertilizer recommended for maize must depend on the soil, maize variety and season.The general recommended dosage for maize is: For early ripening varieties, apply from 120 to 150 kg N, medium and late ripening varieties fertilize 150 - 180 kg N To produce once ton of biomass maize NK7328, the plants must absorb from the soil an easily digestible amount of nitrogen from 2.40 - 3.05 kg N; 0.98 - 1.06 kg P2O5 and 1.55 - 1.63 kg K2O (Vo Thi Hoa, 2018 This data is similar to the data of Ngo Ngoc Hung 2009), which announced that the nitrogen requirement to create a ton of biomass is about 2.3 - 3.5 kg N and depends on the season 1.4.3.2 Research on phosphate fertilizers Research on nutritional needs of maize shows that: To produce ton of corn, maize plants absorb an average of 8.5 kg from the soil, the amount of P consumed to produce ton of corn is 14.5 kg of P 2O5 equivalent to the demand rate N : P : K is : 0.35 : 0.45 In which stage 6-7 leaves 51.7% N : 8.3% P2O5 : 40.0% K2O, flowring stage 47.47% N : 9.8% P2O5 : 42.7% K2O and harvest stage 52.2% N : 19.1% P2O5 : 28.7% K2O The results of this study are consistent with foreign studies and clearly show that potassium absorption is completed early before beard spraying, while other nutrients such as nitrogen and phosphorus continue until the corn is ripe 1.4.3.3 Research on potasium fertilizers For maize, potassium is considered the second most important element after nitrogen Potassium helps promote protein synthesis, limit the accumulation of nitrate in leaves, and limit the harmful effects of excessive nitrogen fertilization Increasing K use increases leaf area while also increasing seed fullness The author also pointed out that, using potassium fertilizer in the condition of water shortage reduced the yield of corn kernels from 19.96 to 48.37% The study by Babak Peykarestan et al (2012) showed that the dose of 120 kg of potassium sulfate/ha had a positive effect on the weight of 1,000 grains, yield, and weight of maize and related to corn length, corn diameter and tree height The yield of kg K2O varies by crop: wet rice 6.7 - 18.1 kg; Corn kernels 3.9 - 107.5 kg; Soybean 6.7 - 10.8 kg (Baffour Badu- Apraku et al., 2012) 1.4.4 Research on mulching In using sloping land for sustainable development of agro-forestry production, mulching not only has the effect of limiting soil erosion, limiting weeds, reducing runoff on the ground, keeping nutrients and water from drifting along depth and pull nutrients from deep down into the arable soil layer In addition, mulching helps increase crop productivity, diversify incomes, increase economic efficiency per unit area, and help develop effective and sustainable agro-forestry production for sloping land 1.4.5 Research on density for maize Density is one of the important cultivation parts to determine grain yield (Sangoi, 2000) The study of corn densities in the world is not only about determining planting density, but also determining the distance between plants in rows and between rows The determination of planting density for maize depends on many factors: Varieties factor, hybrid maize varieties can withstand planting density 2-3 times higher than traditional maize varieties; Second is the row spacing, when planting at the same density, the narrow sowing spacing gives higher yield than the wide row; In addition, the planting density also depends on the level of cover, the amount of nitrogen fertilizer, the conditions with or without irrigation, The results of the study on the density and distance of maize planting on high land and sloping land in Vietnam show that: Depending on the characteristics of the variety, the amount of fertilizer, soil conditions, weather and climate of each region, the density varies, there is a significant difference in the appropriate planting distance The appropriate density of maize planting on sloping land tends to increase gradually from 50 to 70 thousand plants/ha and the row spacing ranges from 50 to 70 cm, the distance between plants from 20 to 30 cm gives maximum yield Research on density of biomass maize: It is recommended to plant biomass maize with a denser density than that of seed maize from to 10 thousand plants/ha, that is 65 – 80 thousand plants/ha should be achieved on most soil types Dairy (Australia, 2018) believes that the density of biomass maize grown under irrigated conditions should be at a density of 80 - 100 thousand plants/ha Studies in Vietnam show that: Depending on the variety and type of soil, the biomass maize planting density ranges from 71 to 95 thousand plants/ha with a spacing of 70 cm x 15-20 cm or 60 cm x 20 cm brings high economic efficiency 1.5 Conclusions from the overview The one-crop terraced field area of the northern mountainous provinces in general and Yen Bai province in particular accounts for a fairly large proportion of the agricultural land area, the cultivation time is only 4-5 months/year fallow period of 7-8 months/year, affecting the food security of the region, especially in difficult areas From the research results, it showed that maize varieties are a key step to promote maize production, increase yield and output Currently, in the world and in Vietnam, there have been many researches on selection of maize varieties, however, research on selection of varieties adapted to sloping soil conditions, terraced fields, and arid areas is not much and new stop at some basic research (selective research) Therefore, it is necessary to have studies to select promising hybrid maize varieties with high yield and good adaptability to Yen Bai province in particular and the Midlands and Northern mountainous provinces in general The terraces in Yen Bai province was cultivated only one rice season per year, from early May to the end of September, fallow 120 days of spring crop and 120 days of winter crop In addition, the average temperature from November to next February is usually low (15-180C), so when increasing the spring maize crop on terraced fields in districts of Yen Bai province, it is necessary to choose maize varieties with good drought tolerance and short duration, both benefit with local planting time frame and ensuring favorable growth and development without affecting Summer rice crop season Soil erosion and runing down on sloping in agricultural production are big problems for the world Therefore, farming techniques such as minimum tillage, mini-terraced model, mulch cover have been studied in some places in our country and abroad However, through the investigation and assessment of maize production on sloping land in Yen Bai province, farmer is still practicing slash-and-burn activities, traditional farming leading to the process of soil erosion and washing away occurring and has not shown a decreasing trend It is necessary to have researches on techniques of minimum tillage and mulch cover, increase soil fertility, protect the sustainable ecological environment In addition, mulching helps increase crop productivity, diversify incomes, increase economic efficiency per unit area and help develop effective and sustainable agroforestry production for sloping land CHAPTER II RESEARCH METHODS 2.1 Materials for research - Materials were hybrid maize varieties: LVN885, LVN092, LVN17, CP501, NK4300, NK6101, DK9955, B9698 LVN885 variety was popular in local, it was used as a control - Fertilizers: Locally produced organic fertilizers; nitrogen: Use urea (46%N); phosphorus: use single super phosphate (20% P205); potassium: use potassium chloride (60% K20 Lime: use locally produced - Mulching materials: Straw, rice straw, plant residues - Soil conditions: All research did on red - yellow ferranite terraced fields 2.2 Research activites 2.2.1 Investigated, evaluated the current situation of Spring maize production on once crop terraced fields in Yen Bai province 2.2.2 Researched to identify maize varieties suitable for spring cultivation on once crop terraced fields in Yen Bai 2.2.3 Researched on some technical measures to cultivate Spring maize on once crop terraced fields in Yen Bai province 2.2.3.1 Determined a reasonable spring maize planting time frame on one-crop terraced fields in Yen Bai province 2.2.3.2 Determined the reasonable planting season of Spring maize on once crop terraced fields in Yen Bai province 2.2.3.3 Determined planting time combined with maize growing method 2.2.3.4 Determined the appropriate amount of phosphate fertilizer and mulching technique 2.2.3.5 Determined the appropriate amount of nitrogen fertilizer and planting density for biomass maize with high density as animal feed 2.2.4 Building the demonstration of Spring maize cultivtion on one crop terraces in Yen Bai province 2.3 Methods of research 2.3.1 The method of data collection Secondary datas were collected through Yen Bai Provincial Statistics Office and agricultural production reports of People's Committees of Mu Cang Chai, Van Yen and Van Chan districts, Yen Bai province Primary datas were collected by the rural rapid survey (PRA) method with the use of questionnaires Investigation period: February - June 2017 and from February - June 2018 interviewed with 90 questionnaires per district in districts of Mu Cang Chai, Van Yen and Van Chan, Yen Bai province Information collected from the questionnaires were statistically processed by descriptive statistics on a computer using EXCEL software 2.3.2 Experiment method - Field experiment methods were arranged during the period from February 2017 to June 2019 The variety comparison and seasonal experiments were arranged according to fully randomized block (CRBD), experiments on technical measures were arranged in large - small plots, the experimental treatments were repeated times, the area of each experimental plot were 14 m2; sowing distance 70 cm x 25 cm x plant/hole (equivalent to a density of about 57 thousand plants/ha For the density experiment, the density was arranged, the distance was the same as the experimental formula - Experimental location: + Experiments did at sites, Che Cu Nha commune - Mu Cang Chai district; Nam Lanh commune Van Chan district; Na Hau commune - Van Yen district + The experiment to determine the appropriate amount of nitrogen and planting density for biomass maize with high density as animal feed was carried out in Nam Lanh commune, Van Chan district and Na Hau commune, Van Yen district - Planting and care techniques: In addition to the planting seasons according to experimental formulas, other techniques are applied according to QCVN 01 - 56: 2011/MARD National Technical Regulation on Cultivation Value Trial and Use of maize varieties 2.3.3 Identified maize varieties suitable for spring cultivation on once crop terraced fields in Yen Bai - The experiment included hybrid maize varieties: LVN885, LVN092, LVN17, CP501, NK4300, NK6101, DK9955, B9698 LVN885 variety was popular in local, it was used as a control Conducted in the spring crop of 2017, at locations, Che Cu Nha commune, Mu Cang Chai district; Nam Lanh commune, Van Chan district; Na Hau commune, Van Yen district Sowing time February 1, 2017 2.3.4 Research on some technical measures to cultivate Spring maize on once crop terraced fields in Yen Bai province 2.3.4.1 Determined a reasonable spring maize planting time frame on one-crop terraced fields in Yen Bai province Simulation tools and scenarios: Determination of maize sowing season for districts (Mu Cang Chai, Van Chan and Van Yen) Corn planting scenarios were simulated by setting up a virtual experiment with elements: + Sowing date: From the 10th day (equivalent to January 10) to the 90th day of the year (equivalent to March 30) with days of sowing: 10, 20, 30, 40, 50, 60, 70, 80, 90 + Elevation with levels: 200, 400, 600, 800, 1.000 m The simulation of temperature effect by altitude is using Baker's conversion equation, for every 100 m altitude, the temperature decreases by 0.6oC (Baker, 1944) + Weather datas were used for the simulation included: Meteorological station data of Mu Cang Chai district for 15 years (from 2000 to 2015), Van Chan station for 15 years (from 2000 to 2015), at Van Yen due to There is no meteorological station, so the data of the meteorological station of Yen Bai city (the nearest place) should be used instead, 15 years from 2000 to 2015 Including data on a daily basis with the following criteria: Temperature (average, min, max), precipitation, light intensity, humidity (average, min, max), potential evaporation - Criteria for determining favorable sowing time The optimal planting time at a height is determined if the following three criteria are met: + P1: a growing rate of more than 80% + P2: Harvest before June 30 with a growing rate of more than 80%, to ensure land clearance, tillage and sowing the crop before July (the latest day for planting winter rice) + P3: For productivity > 70% of maximum productivity with a growing rate of over 80% The determination of this time period is applied the method "Favourable planting window" as shown in Figure 2.1 CHAPTER III RESEARCH RESULTS AND DISCUSSION 3.1 Investigation and assessment of the current situation of spring maize production on terraced fields in Yen Bai province 3.1.1 Natural conditions in Yen Bai province *) Geographical location: Yen Bai is a mountainous province located deep inland, is one of 14 northern mountainous provinces, located between the Northeast and Northwest regions It is bordered by Lao Cai province in the North, Phu Tho province in the South, Ha Giang and Tuyen Quang provinces in the East, and Son La province in the West Yen Bai has administrative units (1 city, town and districts) with a total of 173 communes, wards and townships (150 communes and 23 wards and townships); of which 70 highland communes and 62 extremely difficult communes are invested under the State's socio-economic development programs, there are highland districts of Tram Tau and Mu Cang Chai (the H'mong people account for nearly 80 %) are located in 61 poor and especially difficult districts of the country *) Climate: Yen Bai is located in a tropical climate, with high sunshine and rain volume, high temperature The average temperature has little variation, in the year the lowest is January: 14.4 oC, the highest is June: 26.0oC Rainfall is abundant but unevenly distributed, the average rainfall is 1,149 - 2,351 mm/year The lowest average rainfall in January: 9.7 mm/month; highest in July: 309.9 mm/month In some sub-climate regions, in the spring, there are often has longterm small rains Rainfall mode: Yen Bai belongs to an area with average rainfall, according to the data of the Provincial Hydrometeorological Center, the average rainfall at Yen Bai station is: 1,740.6 mm/year; Van Chan 1,368.7 mm/year; Mu Cang Chai 1,834.5 mm/year *) Land resources: Agricultural land accounts for over 85% of the natural land area of Yen Bai province, cultivation land accounts for more than 17%, forestry land accounts for more than 67.8% Soil resources are quite rich with 19 types of soil in main groups, of which 94.7% are concentrated in the group of red-yellow soil (feralit soil) and ferral humus Source: Yen Bai Provincial Statistical Yearbook 2019 3.1.2 Socio-economic characteristics of Yen Bai province *) Population and labor: In 2018 the total population of the province was 815,566 people The average population density was 118 people/km2, concentrated in some urban areas such as Yen Bai city, Nghia Lo town and towns and townships Yen Bai province has more than 30 ethnic groups living In which, Kinh people accounted for 49.6%, Tay people accounted for 18.58%, Dao people accounted for 10.31%, H'mong people accounted for 8.9% Thai people accounted for 6.7%, Cao Lan people accounted for 1% , the rest are other ethnic groups Regarding labor, in 2018, Yen Bai province's labor force was 526,656 people, accounting for 64.58% of the population In which, 90.18% of people of working age participate in the labor force and have jobs in economic sectors *) Economic structure: The current economic structure of the province is Agriculture - Industry Services (since 2005 until now, the production value of the crop industry has always accounted for an average proportion of about 50% - 70% production value of the whole province) In the period 2010 - 2015, the economic structure has changed, but in reality, industrial development has not been commensurate with the potential of the province; There are no high quality products available *) Infrastructure: Yen Bai's infrastructures developed at a low level, still not meet the current and future socio-economic development requirements Due to the difficult terrain, difficult traffic, low education level and low investment, infrastructure such as electricity, roads, schools, medical stations, markets, clean water supply system, etc drainage and environmental landscape, both lack and poor quality; Most of the agro-processing industry establishments have not yet developed commensurate with their potential, old 11 technology, low efficiency, monotonous products in raw form, poor competitiveness, and unresponsiveness to market demand increasingly demanding both in terms of product quality and design 3.1.3 Producing one-crop terraces in Yen Bai province The one-crop terrace area in Yen Bai province was concentrated mainly in the highland districts of the province such as Van Yen district (8.7%), Mu Cang Chai district (62.8%), Tram Tau district (8) .4%), Van Chan district (9.9%), Luc Yen district (6.8%), and Yen Binh district (3.4%) In nearly 10 years, from 2010 to 2018, the area of once crop terraced fields in the whole province decreased sharply from 6,256 to 2,850 in 2018 (down 54.44%) due to the transformation of crop structure, increasing the cultivated area increasing spring crop From 2010 to 2018, in 3,406 hectares of one crop land area in Yen Bai province, which was successfully converted into two crops per year, the structure of spring rice - summer rice accounted for about 65% of the area (over 2,200 ha) due to the canal system ditches have been completed, water is sufficient for spring rice production, this crop structure is concentrated in terraced fields with low slope, in the valleys 3.1.4 Current status of Spring maize production on terraced fields in Yen Bai province 3.1.4.1 Spring maize production area on terraced fields in Yen Bai province Survey results in 2018 showed that the area of spring maize cultivation on terraced fields in Yen Bai province was about 790 hectares out of a total of 26,513 hectares of field paddy in the province (about 3%) of which mainly concentrated in highland districts of the province such as Van Yen district 179 ha, Mu Cang Chai district 119 ha, Tram Tau district 117 and Van Chan district 165 The land area for rice fields is 19,672 ha, accounting for 74.2% of the province's farmland The area of land for production of beans, potatoes, vegetables, etc in the spring-seasonal rice crop is 3,201 ha, accounting for 12.1% of the province's farmland The area of terraced fields for cultivation of only summer rice, leaving the spring and winter crops behind is 2,850 hectares, accounting for 10.7% of the province's total field area 3.1.4.2 Structure of spring maize varieties on terraced fields in Yen Bai province The results of the investigation on the use of maize varieties: 100% use hybrid maize varieties (accounting for 95.5% of the spring maize planting area on terraced fields), the area of sticky corn accounted for 4.5% 3.1.4.3 Planting season on terraced fields in Yen Bai province The crop structure of two rice crops per year accounts for 74.2% of terraced land in Yen Bai province, the spring planting season was started from January 20th to February 10th, the Summer season starting from January 10 to 30.6; In spring crop, hybrid rice varieties accounted for about 55%, pure rice about 45%; in the summer season, hybrid rice varieties accounted for about 35%, pure rice varieties accounted for 65%, commonly used rice varieties: San uu 63, N.u 69, N.u 89, Viet hybrid 20, Nhi uu 838; Huong Chiem, J02, Sheng Cu, The structure of grown crops in the spring crop - summer rice accounted for 15.1% of the terraced field area in the province, the spring planting time frame was from February to June 15; the time of summer season starting from June 10 to June 30; in the summer season, hybrid rice varieties accounted for about 35%, pure rice accounted for 65%, commonly used rice varieties: San uu 63, N.u 69, N.u 89, Viet hybrid 20, Nhi uu 838; Huong Chiem, J02, Sheng Cu, The one crop terrace area was accounted for over 10% of the total area of terraced fields in Yen Bai province, the planting time starts from May 15 to June 15, rice was harvested from the end of September to the beginning of october, the structure of rice varieties: Hybrid rice accounted for about 45%, pure rice accounted for 55%, commonly used rice varieties: San uu 63, N.u 69, N.u 89, Viet hybrid 20, Nhi uu 838 ; Huong Chiem, J02, Sheng Cu, HT1, Conclusionly: For the terraced land area where one season of rice was grown (one crop land), the cultivation time took only about 4-5 months/year, the fallow period is 7-8 months/year (after the Summer rice crop is harvested from November to the first month of May next year) If added more warm spring crops, the season was started from February and was harvested from June 10 to June 30 (the time to plant the summer 12 rice crop in the structure of crops/year), should arrange the crop with a growth period of less than 125 days to ensure the planting time frame 3.1.4.4 Some technical practices applied to Spring maize on terraces The survey results show that: The amount of maize seed sown per hectare is 22-25 kg (2.2 - 2.5 kg/1,000 m2) Maize planting time at the end of January accounted for 15% of households; maize planting time in early March accounted for 4.5%, maize planting time from February 10th to the end of February accounted for over 80% of maize growing households and 100% of the above households confirmed with maize planting time in spring season in February ensures the season for sowing summer rice Land preparation: 34.4% of households plowed and harrowed the fields before planting maize 65.6% of households dig holes and sowed seeds Mainly pure cultivation 89.5% of households; intercropping maize with beans and vegetables accounted for about 10% of households The results of the survey on the use of fertilizers for spring maize in Yen Bai, the amount of fertilizer for spring maize on terraced fields of households was very low and there is no balance between NPK compared to the maize growing process recommended by seed research unit 3.1.4.5 Main advantages and disadvantages of growing Spring maize on terraced land in Yen Bai province In nearly 10 years, Yen Bai province had successfully converted 3,406 hectares of one crop into two crops per year, in which the main structure was spring-season rice, accounted for about 65% of the area (over 2,200 hectares) The structure of spring maize - summer rice accounted for about 10% (nearly 350 ha) The conversion speed was quite quich However, in the transition process, there were also many advantages and disadvantages The main advantage was that the product is easy to consume, can take advantage of idle labor in the spring crop (85.8% of households), the terraced land area can be expanded to grow spring maize (65.6% of the households) ) Besides, the weather in the spring crop in recent years tends to warm up, corn can completely grow and develop well in the spring crop on terraced fields in the region The biggest difficulty was the lack of technical guidance on growing spring maize on terraced fields, no fixed seed structure, farmers did not have the habit of cultivating spring maize, the current corn price was very low and the production effeciency was very low Input of product maize was high and spring maize season affected to the yield of next crop, accounting for about 50% of the surveyed households 3.2 Researched to identify maize varieties suitable for spring cultivation on once crop terraced fields in Yen Bai The average crop duration in all study sites ranged from 115 - 121 days In which, the shortest crop duration variety was LVN885 - the control variety (115 days), 1-7 days shorter than that of other varieties, the longest crop duration variety was B9698 (121 days) For the same variety, at different study sites, the growth time varied considerably from to days The results of Spring season in 2017 show that: most varieties had mild reactions to the main pests and diseases The varieties with the lowest pest infestation rate in all study sites were NK6101 and LVN17 The number of seeds/row on the experimental maize varieties ranged from 28.4 to 39.7 seeds/row Only the NK6101 variety showed a higher number of seeds/row at Mu Cang Chai than the control variety, 7.1 seeds/row at 95% confidence level The weight of 1.000 seeds of the varieties varied from 262.4 - 312.3 grams Actual yield: The comparison experiment of maize varieties and the control variety LVN885 in the Spring crop at Van Chan, Van Yen and Mu Cang Chai showed that: The varieties NK6101, DK9955, NK4300 and LVN17 all gave higher yields compared to the control variety However, the two varieties NK6101 and LVN17 gave high and stable yields in all three experimental sites, besides that these two varieties had good growth and development ability, short crop duration on average 116 - 118 day, plant height, low corning height, low level of pest and disease infection, plant state, good corn condition In particular, the two varieties LVN17 13 and NK6101 had good ball tightness (point 1), suitable for local farming practices and have the highest net yield (60.51 - 71.19 quintals/ha) in three study sites Table 14 Yield and yield components of the experimental maize varieties in the Spring crop of 2017, in Yen Bai number of seeds/row (seed) weight of 1.000 seeds (g) VC VY MCC VC VY MCC VC VY MCC LVN885 (Control) 37,5 38,2 32,5 265,3 265,6 262,4 55,97b 57,89b 47,64c LVN092 34,8 36,8 28,4 304,6 304,8 295,3 53,71b 62,66ab 40,15d LVN17 38,5 38,6 36,3 310,2 309,5 294,2 67,66a 68,16a 60,51b CP501 35,7 37,3 32,7 274,4 272,7 268,7 48,86b 51,14c 42,07d NK4300 37,6 38,4 35,2 307,5 306,6 298,6 64,59a 65,77a 58,72b NK6101 38,6 39,7 39,6 312,3 312,1 307,4 70,22a 71,19a 69,45a DK9955 38,4 36,8 34,6 295,1 296,3 303,8 64,66a 67,88a 59,14b B9698 35,4 34,8 30,6 294,1 294,6 287,6 51,51b 51,13c 42,14d LSD0,05 4,14 3,92 4,98 21,3 19,8 17,9 8,32 5,68 4,78 CV% 6,4 6,0 8,4 7,1 9,8 11,5 8,0 5,2 5,2 Varieties Actual yield (quintals/ha) (Note: VC: Van Chan, VY: Van Yen, MCC: Mu Cang Chai Similar words in the same column indicate nonsignificant difference, different words in the same column indicate error other meaningful) 3.3 Researched on some technical measures to cultivate Spring maize on once crop terraced fields in Yen Bai province 3.3.1 Determined a reasonable spring maize planting time frame on one-crop terraced fields in Yen Bai province 3.3.1.1 The ability to avoid freezing to death (P1) To avoid cold death for spring maize reaching > 80%, simulation results showed that it can be sown in the following areas: + In Van Chan: Lowland areas < 400 m can be sown from January 10, areas of 400 - 600 m must be sown after the 20th day of the year (January 20), highland areas > 800 m must be sown after the 40th day (February 10) + In Van Yen: Lowland areas < 400 m can be sown from January 10, areas of 400 - 600 m must be sown after the 20th day of the year (January 20), highland areas > 800 m must be sown after the 50th day (February 20) + In Mu Cang Chai: Lowlands < 400 m can be sown from January 10, areas of 400 - 600 m must be sown after the 30th day of the year (January 30), highland areas > 800 m must be sown after the 40th day (February 10) 14 3.3.1.2 Results of determining sowing time for harvest before June 30 (P2) In order for spring maize to be harvested before June 30 with a success probability of > 80%, simulation results show that the sowing time in the regions is as follows: + In Van Chan: The lowland area < 400 m must be sown before the 60th day of the year (March 1), the 400 - 600 m area must be sown before the 50th day of the year (February 20), the highland area > 800 m must be sown before the 30th day of the year (January 30) + In Van Yen: The lowland area < 400 m must be sown before the 60th day of the year (March 1), the 400-600 m area must be sown before the 50th day of the year (February 20), the highland area > 800 m must be finished sowing before the 20th day of the year (January 20) + In Mu Cang Chai: Lowland areas < 400 m must be sown before the 70th day of the year (March 10), areas of 400-600 m must be sown before the 60th day of the year (March 1), highland areas > 800 m must be finished sowing before the 50th day of the year (February 20) 3.3.1.3 Sowing time to get over 70% of maximum yield (P3) In order to get high yield > 70% of maximum yield with success > 80%, according to simulation results (Figure 3), the sowing date in the regions is as follows: + In Van Chan: Lowland areas < 400 m must be sown after the 30th day of the year (January 30), areas of 400 - 600 m must sow after the 40th day of the year (February 10), highland areas > 800 m must be sown sow after the 60th day of the year (March 1) + In Van Yen: Lowland areas < 400 m should be sown after the 30th day of the year (January 30), areas of 400 - 600 m must be sown after the 30th day of the year (January 30), highland areas > 800 m must be sow after the 40th day of the year (February 10) + In Mu Cang Chai: Lowland areas < 400 m should be sown after the 30th day of the year (January 30), areas 400 - 600 m should be sown after the 40th day of the year (February 10), highlands > 800 m must be sown after the 40th day (February 10) 3.3.1.4 Suitable planting time frame in districts Table Optimal sowing time for spring maize in districts districts Van Chan Van Yen Mu Cang Chai Sowing time to get criteria High level (m) Sowing time to get all criteria (day) Sowing time to get P1&P2 (day) P1 P2 P3 < 400 After 10/1 Before 1/3 After 30/1 30/1-1/3 10/1-1/3 400 - 600 After 20/1 Before 20/2 After 10/2 10/2-20/2 20/1-20/2 > 800 After 10/2 Before 30/1 After 1/3 Unknown Unknown < 400 After 10/1 Before 1/3 After 30/1 30/1-1/3 10/1-1/3 400 - 600 After 20/1 Before 20/2 After 30/1 30/1-20/2 20/1-20/2 > 800 After 20/2 Before 20/1 After 10/2 Unknown Unknown < 400 After 10/1 Before 10/3 After 30/1 30/1-10/3 10/1-10/3 400 - 600 After 30/1 Before 1/3 After 10/2 10/2-1/3 30/1-1/3 > 800 After 10/2 Before 20/2 After 10/2 10/2-20/2 10/2-20/2 15 Simulation results: In order to achieve all criteria for maize in the first time to avoid cold death, timely harvest to ensure the summer rice crop and ensure productivity, the sowing time frame is reasonable with areas with high humidity less than 400m above sea level, is from January 30 to 1/3 With an altitude of 400 - 600 m to achieve all criteria, Mu Cang Chai district needs to sow from February 10 to 1/3; Van Chan district must be sow from February 10 to February 20; Van Yen district needs to sow January 30 - February 20 With an altitude of over 800 m to achieve all criteria, Mu Cang Chai district needs to sow maize in a very short time frame from February 10 to February 20; Van Chan and Van Yen districts did not determine a reasonable time to achieve both and criteria 3.3.2 Determined the reasonable planting season of Spring maize on once crop terraced fields in Yen Bai province The longest crop duartion of LVN17 maize variety was 120 days when sown in season (sowing on January 20) and the shortest crop duration when sown in season (sowing on February 10), 114 days in Spring 2017 and 117 days in Spring 2018, shorter than that of other seasons from to days The later the sowing time, the shorter the growing time of maize Pests and diseases rate : In the Spring crop of 2017 and 2018 in districts of Yen Bai province, the variety LVN17, when sown in the 3rd and 4th seasons (sowing from February 10 to February 20), the maize plant grew and developed well, had the lowest rate of pests and diseases Table 20 Average yield components and net yield of LVN17 variety when sown at different seasons in Spring crop 2017 and 2018, in Yen Bai (In Mu Cang Chai, Van Yen and Van Chan district, spring crop in 2017 and 2018) Number of Number of seed/row weight of 1.000 seeds row/corn (row) (seed) (g) Actual yield (quintals/ha) Seasons Spring 2017 Spring 2018 Spring 2017 Spring 2018 Spring 2017 Spring 2018 Spring 2017 Spring 2018 TV1 12,9 12,9 38,5 35,1 261,8 266,9 51,0b 51,5b TV2 (Control) 12,9 13,1 38,8 36,2 265,8 273,1 54,0b 54,6b TV3 12,4 12,9 39,1 36,5 289,7 283,6 68,3a 67,7a TV4 12,9 12,9 34,7 35,1 286,1 287,4 67,5a 68,3a TV5 13,1 12,7 35,0 38,2 276,4 285,4 55,2ab 56,9ab LSD0,05 1,88 1,96 6,76 6,99 15,14 18,99 11,18 11,00 CV% 8,7 9,0 10,8 11,5 3,3 4,0 11,2 10,9 (Note: TV1: Sowing 20/1, TV2 (Control): Sowing 01/02, TV3: Sowing 10/2, TV4: Sowing 20/2, TV5: Sowing 01/03, Same letters in the same letter one column indicates no significant difference, different letters in the same column indicate significant difference) The results in the Spring crop of 2017 and 2018 in districts of Yen Bai province, the LVN17 variety when sown in the 3rd and 4th seasons (sowing from February 10 to February 20), the maize plant grew and developed well, with a high rate of growth The rate of pests and diseases is low and the actual yield is high, with an average of 67.5 - 68.3 quintals/ha The results of modeling to determine the seasonal frame for three districts of Van Chan, Van Yen and Mu Cang Chai at an altitude of 400 - 600m have concluded that the 16 appropriate season is from February 10 to February 20 This is completely consistent with the experimental results, both to ensure that the first time after planting the maize plants to avoid cold death, the harvest is timely to ensure the summer rice crop and the maize yield is > 80% potential yield of the variety 3.3.3 Determined the planting season combined with the maize growing method Crop duration of the experimental treatments ranged from 115 - 125 days When planting at the same season, the treatment applying the method of making potted corn had a shorter crop duration than that of the minimum tillage method on average from to days, when applying the same method of sowing, the late sowing ripen earlier than those with early sowing time When applying the potting method and sowing time on February 10 (B2 TV3), the LVN17 variety gave the shortest growing time, 115 days in Van Chan and Mu Cang Chai, 117 days in Van Yen Evaluation of pests and diseases: All treatments were infected with powdery mildew, but the degree of infection was mild from 1.2 to 5.6% (< 10%) Leaf spot disease has a more severe infection rate than blight with 1.5-9.5% of the affected leaf area, equivalent to points - 5, the minimum tillage formulas combined with sowing in the early season tend to be more susceptible to disease than the methods of sowing seeds by potting and sowing at late season Table 3.24 Effect of season and seeding method on yield components and net yield of maize variety LVN17 in the Spring crop 2018, in Yen Bai Formula /status Number of seed/row (seed) VC VY MCC TB weight of 1.000 seeds (g) VC VY MCC Actual yield (quintals/ha) TB VC VY MCC TB TV1 34 34 35 34 285,4 279,9 280,5 281,9 52,1b 50,6b 52,3b 51,6 TV2 36 35 36 35 292,3 286,4 285,7 288,1 54,5b 53,7b 55,1b 54,4 B1 TV3 36 35 36 36 312,5 307,8 304,6 308,3 71,5a 69,8a 71,0a 70,8 TV4 37 37 34 36 308,4 301,0 295,4 301,6 61,6ab 60,7ab 62,9ab 61,8 TV5 36 36 37 37 297,8 293,2 290,7 293,9 58,2b 57,2b 58,3b 57,9 TV1 34 34 34 34 278,6 282,4 290,4 283,8 52,0b 51,5b 52,5b 52,0 TV2 36 38 36 37 280,3 256,8 281,7 272,9 52,9b 51,4b 53,4b 52,6 B2 TV3 37 32 32 34 275,8 260,6 279,5 272,0 54,7b 53,5b 56,2b 54,8 TV4 35 36 35 35 286,5 268,9 274,2 276,5 52,4b 51,8b 52,3b 52,2 TV5 38 38 38 38 282,7 275,3 269,4 275,8 57,7b 57,5b 58,1b 57,8 9,96 10,76 10,61 10,1 11,1 LSDBxTV 8,42 8,15 8,21 CV% 13,6 13,3 13,5 19,38 23,38 20,55 3,9 4,8 4,2 10,7 (Note: B1 = Minimum tillage; B2 = potting soil; TV1 = 20/1; TV2 = 01/2; TV3 = 10/2; TV4 = 20/2; TV5 = 1/3; VC: Van Chan, VY: Van Yen, MCC: Mu Cang Chai ) 17 The average number of seeds/row of different treatments ranged from 34 - 38 seeds/row Weight of 1,000 seeds of LVN17 variety ranged from 272.0 to 308.3 grams In which, the lowest treatment was B2TV3 (272.0 grams) and the highest was treatment B1TV3 (308.3 grams) When planted in the same season, maize grown with the minimum tillage yielded a higher mass of 1,000 seeds than when grown with potting soil medium of 15.2 - 32.5 grams Early crops (TV1, TV2) tend to have lower 1,000 grain weights than later crops (TV3 and TV4) Maize variety LVN17, when applying the minimal tillage method, combines the sowing season from February 10 to February 20 (B1 TV3 and B1 TV4) had a short growing time (120 - 122 days), structural factors into a good yield and gave the highest net yield (60.7 - 71.5 quintals/ha) in all three ecological sub-regions where the experiment was conducted 3.3.4 Results of researching determine the appropriate amount of phosphate fertilizer and mulching technique Crop duration of maize: Mulching treatment CP3L3 and CP3L4 (5 tons organic mulching cover + 100 - 120 kg P2O5) for the shortest crop duration114 - 115 days, treatment CP1L1 (3 tons organic multing cover + 80 kg P2O5/ha) for the longest time 121 - 122 days Table 3.29 Effect of multing cover and phosphate level on yield and yield components of LVN17 variety in Spring 2017 and 2018 in Yen Bai (In Mu Cang Chai, Van Yen and Van Chan, in spring crop 2017 and 2018) average of three experimental sites Formula CP1 CP2 CP3 CP4 Number of row/corn (row) Number of seed/row weight of 1.000 (seed) seeds (g) X17 X18 X17 X18 Actual yield (quintals/ha) X17 X18 X17 X18 L1 14,0 14,0 30,7 29,7 311,0 311,3 50,2e 50,4g L2 14,0 14,0 32,3 31,8 318,2 320,1 53,8de 54,2efg L3 14,0 14,0 34,4 34,2 323,5 324,5 57,8cd 58,1def L4 14,0 14,0 36,1 35,6 328,2 329,4 60,6c 62.1cd L1 14,0 14,0 32,6 32,8 316,1 317,2 54,2de 54.2efg L2 14,0 14,0 38,8 38,4 343,8 343,5 66,3b 66,2b L3 14,0 14,0 39,5 40,0 343,0 347,0 69,8a 69,7a L4 14,0 14,0 36,9 35,9 339,1 340,6 63,6bc 64,5bc L1 14,0 14,0 33,4 34,7 320,2 320,6 57,9cd 57,0ef L2 14,0 14,0 35,5 36,9 329,4 331,0 61,1c 61,3cde L3 14,0 14,0 34,3 35,9 323,2 324,4 58.1cd 58.8de L4 14,0 14,0 35,2 35,0 328,7 330,2 62,2c 63,0cd L1 14,0 14,0 32,3 32,5 327,2 328,1 55,0d 55,2ef L2 14,0 14,0 31,9 32,3 328,3 329,2 57,1d 58,0ef L3 14,0 14,0 32,2 33,1 331,1 331,7 59,5cd 61,1de L4 14,0 14,0 35,8 35,9 333,4 335,0 60,8c 60,8de 2,79 2,8 8,59 8,45 3,25 3,28 LSDMxP CV% 8,7 8,7 2,8 2,7 5,9 5,9 (Note: CP1= tons organic multing cover ; CP2 = tons organic multing cover; CP3 = tons organic multing cover; CP4 = Nilong cover L1 = 80 P2O5 ; L2 = 100 P2O5; L3 = 120 P2O5, L4 = 140 P2O5, X17: Spring crop 2017, X18: Spring crop 2018) 18 Corn diameter of LVN17 variety fluctuated on average from 3.7 - 4.0 cm when applying phosphorus levels increased from 80 - 140 kg P2O5/ha in both 2017 and 2018 When applying phosphorus levels L3 and L4 (120 - 140kg P2O5/ha) LVN17 variety with the highest corn diameter of 4.0 cm The LVN17 variety was grown in Yen Bai, when mulching with tons of organic material combined with the level of phosphate fertilizer 100 - 120 kg P2O5/ha (CP2L2, CP2L3), the LVN17 variety has a short growing time (115 days), the components of good yield, the average high yield was 66.2 - 69.8 quintals/ha and the degree of pest infestation was mild in both Spring 2017 and 2018 crops, in three ecological sub-regions 3.3.5 Determined the appropriate amount of nitrogen fertilizer and planting density for biomass maize with high density as animal feed 3.3.5.1 Effect of density and nitrogen fertilizer on biomass maize growth Experimental results showed that: Overall, at both study sites, the treatment M2N2 and M2N3 showed that the biomass yield and dry matter yield were similar and reached the highest (65.0 - 68.2 tons/ha biomass yield and from 21.0 to 22.6 tons/ha dry matter yield) Table 3.34 Effect of density and nitrogen fertilizer on yield of LVN17 variety in districts of Van Chan and Van Yen, Yen Bai province, in the spring crop of 2019 Formula Fresh weight/plant (g) Biomass yield (ton/ha) Grain yield (ton/ha) VC VY VC VY VC VY M1N1 761,8 761,0 49,0b 52,0b 16,8ab 17,8ab M1N2 809,0 784,6 53,3ab 55,5b 17,7ab 18,4ab M1N3 818,7 792,3 59,4ab 55,0b 19,1a 18,9ab M2N1 774,2 822,6 53,6ab 55,3b 18,6a 18,5ab M2N2 972,7 961,5 68,2a 65,0a 22,6a 21,2a M2N3 992,2 993,0 67,8a 66,5a 21,9a 21,0a M3N1 786,9 747,8 57,3ab 55,4b 18,9a 18,3ab M3N2 790,8 755,0 60,4a 57,6ab 19,9a 19,6ab M3N3 855,0 818,2 65,3a 64,3a 20,8a 19,0ab 191,76 214,38 7,97 8,1 4,19 2,19 12,8 14,6 7,5 7,8 12 6,4 LSDMĐ x Đ CV% (Note: M1: 61.000 plant/ha, M2: 77.000 plant/ha, M3: 100.000 plant/ha; N1: 160 N, N2: 180 N, N3: 200 N; VC: Van Chan, VY: Van Yen) 3.3.5.2 Effect of density and nitrogen fertilizer on quality characteristics of biomass maize in Yen Bai The results showed that, with LVN17 variety, when planted at different densities and nitrogen levels, the pest infection rate was mild from point to Different treatments did not make any difference in Crude 19 Protein, Starch, Ash, Crude Fiber and Neutral Fiber (NDF) indexes of the LVN17 variety, only yield different Ether and ME Specifically, the treatment M1N3, M2N2, M2N3 gave the highest Ether and ME index (Ether: 2.84 - 3.14%, ME: 4,502 - 4,816 Kcal/kg) Table 36 Effect of nitrogen dose and density on the quality of biomass maize in the Spring crop of 2019, in Yen Bai VCK Ether ME Crude Starch Ash Fiber NDF Formula (%) (%) (Kcal/kg) Protein (%) (%) (%) (%) (%) Van Chan M1N1 30,8 2,3 4325 7,6 30,1 3,2 23,5 40,2 M1N2 30,8 2,6 4662 8,0 27,2 3,3 18,3 39,3 M1N3 35,5 3,1 4816 8,5 31,4 3,6 20,2 42,4 M2N1 31,3 3,1 4473 8,1 30,3 3,3 18,4 37,6 M2N2 38,7 3,0 4623 8,2 34,2 3,4 20,1 43,5 M2N3 39,4 2,8 4502 8,3 37,5 3,1 19,5 41,7 M3N1 33,7 3,0 4454 8,5 33,4 3,5 18,3 42,6 M3N2 34,6 2,7 4212 8,5 27,6 3,6 21,6 45,4 M3N3 36,3 2,6 4435 7,6 29,2 3,3 21,8 42,1 LSDMĐ+Đ 4,29 0,39 337,59 0,75 8,28 0,56 4,37 8,93 CV% 7,0 7,8 4,2 5,2 14,9 9,5 12,2 12,1 Van Yen M1N1 29,8 2,18 4581 7,52 29,2 2,85 22,70 39,3 M1N2 30,6 2,49 4613 7,90 26,0 2,78 17,80 38,9 M1N3 31,7 3,07 4455 8,34 30,8 3,40 19,60 41,0 M2N1 31,4 2,87 4306 7,95 29,9 3,18 17,60 36,8 M2N2 36,3 2,86 4774 8,07 33,0 3,32 19,50 42,9 M2N3 35,1 2,72 4481 8,21 36,2 2,92 18,20 40,6 M3N1 30,6 2,84 4427 8,32 32,2 3,30 17,90 41,3 M3N2 33,6 2,62 4169 8,43 26,5 3,45 20,40 44,7 M3N3 33,2 2,45 4412 7,49 28,9 3,20 20,30 41,5 LSDMĐ+Đ 5,51 0,32 404,92 0,72 8,23 0,68 4,04 9,34 CV% 9,5 6,6 5,1 5,1 15,3 12,1 11,7 12,9 (Note: M1: 61.000 plant/ha, M2: 77.000 plant/ha, M3: 100.000 plant/ha; N1: 160 N, N2: 180 N, N3: 200 N; Agricultural product quality analysis department - Nomafsi) Conclusionly, when planting LVN17 variety for biomass maize in Van Chan and Van Yen, planting at a density of 77 thousand plants and applying 180 kg N/ha (M2N2) will give optimum biomass yield and quality best 3.4 Building the demonstration of Spring maize on one crop terraced fields in Yen Bai province Selection of techniques from experimental results in 2017, 2018 applied to the model include: Sowing time on February 10 + minimal tillage method + mulching tons of organic matter + 150 kg N + 120 kg P2O5 + 90 K2O/ha The results of monitoring growth, development, and yield of LVN17 variety inside and outside the model are summarized as follows: 20 3.4.1 Evaluation of the influence of technical measures on the LVN17 maize model in the Spring crop of 2019 With the application of farming techniques, the maize plant grew and developed better than that of the control Specifically: The crop duration was shortened by - days, the plant height was higher by 8.4 - 11.8 cm, the rooting rate was reduced by 0.65 - 1.41% and the yield increased by 9.0 - 11.4 quintals/ha compared to the control model LVN17 model applied optimal technical measures had short crop duration (120 - 122 days), well growth and development, high yield components (seed row 14.0 - 14.3) row, seed/row 30.2 - 32.8 seeds, weight of 1000 seeds is 309.5 - 316.5 grams and high yield (51.6 - 55.5 quintals/ha), higher than that of the control model by 20, - 27.7% Table 41 Effect of technical measures on yield and yield components of LVN17 maize in the Spring crop of 2019, in Yen Bai Model/criteria Number of row/corn (row) Number of seed/row (seed) weight of 1.000 seeds (g) Actual yield (quintals /ha) Van Chan Model 14,0 30,2 306,5 55,5 Control 12,0 28,5 281,1 45,9 Compare with control (ta/ha) 9,6 Compare with control (%) 20,9 Van Yen Model 14,3 32,8 302,4 52,6 Control 12,5 28,9 292,3 41,2 Compare with control (ta/ha) 11,4 Compare with control (%) 27,7 Mu Cang Chai Model 14,6 31,5 309,5 51,6 Control 12,3 28,5 287,7 42,6 Compare with control (ta/ha) 9,0 Compare with control (%) 21,1 3.4.2 Evaluate the economic efficiency of the demonstration Evaluation of the economic efficiency of the demonstration (LVN17 variety, sowing time on February 10 + minimum tillage method + mulching tons of organic + 150 kg N + 120 kg P2O5 + 90 K2O/ha ) gave a 21 higher net profit of 23.68 - 30.75% compared to the control model (used LVN885 variety and applying farming techniques of the people and especially the marginal profit margin at a suitable threshold 1.64 - 1.77) Table 3.42 Evaluate the economic efficiency of the demonstration Unit: Thousand VND/ha Model Total expenditure Total revenue Net profit Profit margin Van Chan Model 21.935 36.075 Control 18.402 29.835 Compare with control (thousand VND/ha) 14.140 1,77 11.433 2.707 Compare with control (%) 23,68 Van Yen Model 21.935 34.190 Control 17.407 26.780 Compare with control (thousand VND/ha) 12.255 1,64 9.373 2.882 Compare with control (%) 30,75 Mu Cang Chai Model 21.935 33.540 Control 18.402 27.690 Compare with control (thousand VND/ha) 11.605 1,66 9.288 2.317 Compare with control (%) 24,95 3.5 Proposed technical solutions to develop Spring maize production on once crop terraced fields in Yen Bai province Based on the results of the studied and assessmented of the current situation of Spring maize production on single-crop terraced fields in Yen Bai province and the results of research on technical measures for Spring maize production, we propose the following methods: Technical measures to develop Spring maize in onecrop terraced fields for Yen Bai province are as follows: - About maize varieties: + Varieties should be used for corn production: Focusly short-day maize varieties, with good drought and cold tolerance, high yield, and good resistance to pests and diseases such as LVN17, NK6101, 22 + Varieties used for biomass production: Use varieties with high yield, big stems and leaves, good stem and leaf quality, good tolerance, medium to short crop duration such as NK4300, NK6101, LVN17 …and biomass maize varieties - Fertilizers: Training to guide the people on how to use fertilizers effectively and apply fertilizer in a balanced way for maize It is recommended to use a combination of fertilizers for the highest yield and economic efficiency of 150 kg N + 120 kg P2O5 + 90 K2O/ha on a multing cover of tons of organic material/ha - Cultivation techniques: + Sowing time: The most suitable time for spring maize on terraces field in Yen Bai is from February 10 to February 20 every year, provided the temperature is not lower than 140C - Land preparation method: Minimum tillage - Planting density: 57.000 plants/ha with a spacing of 70 x 25 cm - For biomass maize: Sow with a density of 77 thousand plants/ha; fertilizer 180N/ha - Pest control and other farming techniques: As recommended by each variety 23 CONCLUSIONS AND RECOMMENDATIONS 4.1 Conclusions The area of one crop terraced fields in Yen Bai province was currently over 2.500 hectares The main causes leading to fallow in spring season and winter season: (1) Lack of water due to inadequate canal system on terraced fields; (2) low temperature at the beginning of spring season; (3) the custom of free grazing cattle in the area; (4) the people's traditional farming practices that are difficult to change; (5) lack of capital and cultivation techniques in spring crop Identified two maize varieties, NK6101 and LVN17, that were suitable for spring cultivation on terraced fields in Yen Bai province and give the highest net yield (60.51 - 71.19 quintals/ha) in all three Yen Bai province research sites Identified the technical measures to cultivate spring maize on once crop terraced fields in Yen Bai province, including: - Identified the sowing time from 10th – 20th February is suitable time for LVN17 maize to grow and develop in spring season conditions on terraced fields in Yen Bai province Maize grows favorably, low rate of pests and diseases (< 10%) and has a high net yield (67.5 - 68.3 quintals/ha) - The minimum tillage method, combined the sowing time from 10th – 20th February, is suitable for LVN17 maize variety favorably growth and development, the highest net yield (60.7 - 71.5 quintals/ha) - Identified the mulching tons of botanical residues combined with phosphate fertilizer level of 120 kg P2O5/ha, the LVN17 variety had short crop duration (115 days), low pest and disease infection rate, high structural factors into a fairly yield, the high yield of 66.2 - 69.7 quintals/ha - Detemined the planting maize at a density of 77 thousand trees/ha and combination with the amount of nitrogen fertilizer 180 kg N/ha, the LVN17 variety haved the highest yield and quality of biomass maize The results of the demonstration model have confirmed that the synchronous application of the studied farming techniques to production (including: Sowing time from 10 - 20 February + minimum tillage method + mulching tons of organic + 150 kg N + 120 kg P2O5 + 90 K2O/ha) for LVN17 variety is suitable, the yield is 51.6 - 55.5 quintals/ha, net profit is higher than control model from 14.68 to 18.16%./ 4.2 Recommendations Continuing to study economic - technical - social solutions for the structure of biomass maize in the Spring - ricre in Summer for once crop terraced fields in Yen Bai province, helping to promote the livestock sustainable development in region It is proposed to apply the crop structure of Spring Maize - Summer rice with technical guidance (sowing season February 10 - February 20 + minimum tillage method + tons of organic mulch + 150 kg N + 120 kg P2O5 + 90 K2O/ha) proposed for once crop terrace fields in Yen Bai province 24 LIST OF PUBLISHED SCIENTIFIC WORKS RELATED TO THE THESIS Nguyen Van Chinh, Luu Ngoc Quyen (2021), “Evaluation of the growth and development of maize varieties in spring crop season on one-crop terraces in Yen Bai province” Vietnam Journal of Science and Technology, 02, – 12 Nguyen Van Chinh, Luu Ngoc Quyen (2021), “Determination of optimum sowing time in spring season for hybrid maize variety LVN17 in one - crop terrace lands in Yen Bai province” Vietnam Journal of Science and Technology, 03, 36 – 40 ... seasonal experiments were arranged according to fully randomized block (CRBD), experiments on technical measures were arranged in large - small plots, the experimental treatments were repeated... Research activities and methods; Chapter 3: Results and discussion with 46 tables and figures List of 113 references (79 documents in Vietnamese, 34 documents in English) The appendix contains detailed... The main research area of the thesis were highland districts of Yen Bai (Mu Cang Chai, Van Chan and Van Yen districts) which are districts have a lot of one crop terraces The weather and climate