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` MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURAL SCIENCES * TRINH DUC TOAN A STUDY ON SOME TECHNICAL SOLUTIONS TO INCREASE THE MAIZE P[.]
MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURAL SCIENCES -* - TRINH DUC TOAN A STUDY ON SOME TECHNICAL SOLUTIONS TO INCREASE THE MAIZE PRODUCTION EFFECTIVENESS ON SLOPING-LAND IN NORTHERN CENTRE REGION Field of study: Crop Science Code: 9.62.01.10 SUMMARY OF AGRICULTURAL DOCTORAL THESIS Hanoi - 2022 ` The study is published at: VIETNAM ACADEMY OF AGRICULTURAL SCIENCES Scientific supervisors: Dr Luong Van Vang Assoc Prof Dr Ho Quang Duc Judge 1: Judge 2: Judge 3: The thesis will be defended at the meeting of the reviewing committee at: Vietnam Academy of Agricultural Sciences Meeting at At , date month year 20 The thesis can be found at: National Library of Vietnam Library of Vietnam Academy of Agricultural Sciences INTRODUCTION In Vietnam, maize is the second cereal crop after rice The area, yield and quantity of maize increased year by year, from cultivated area of more than 200 thousand hectares and a yield of 10 quintals/ha in 1960, increased to 1,170.3 thousand and million tons, respectively, in 2019 However, compared to average maize yield globally, it of Vietnam is still low, reaching only 80.7% of the world average (57.6 quintals/ha) Although the increase in cultivated area of maize is quite fast, the maize yield is still not enough to meet human demand In recent years, the maize quanlity of Viet Nam has reached 4.5-5 million tons/year, we still need to import 10-12 million tons per year Northern Central is a region which has a complex topography, more than 70% of the area is mountainous Therefore, sloping land occupies an important position in agricultural production development According to statistics, the North Central Coast and the South Central Coast have the second largest corn area in the country, the total corn area in 2019 of the whole region reached 182,600 hectares, accounting for 15.5% of the whole country's maize area In which, the average maize yield is 47.1 quintals/ha The area is mainly located in Nghe An (47,700 ha) and Thanh Hoa (46,100 ha) provinces Practical production of maize in recent years has indicated that it faces with a lot of difficulties, such as, nutrient degradation, drought, floods, hot strong wind, etc, therefore, the maize production effectiveness has not really effective In agricultural prouction, a new cultivated practices must be formed and exist based on a natural conditions (soil, water, climate), production culture, locally knowledge, possible investment, and consumption target Cultivated practices will also determines the sustainable of production, environment, economic, and social Therefore, it is necessary to have further studies on new maize varieties and cultivated practices on sloping-land to improve the productivity and efficiency of maize production, protect and improve soil fertility, while limiting the erosion and protecting the ecology balance in the Northern Central region From such above issues, to contribute for a maize production more effective in Northern central region of Vietnam, we conducted "A study on some technical solutions to increase the maize production effectiveness on sloping-land in Northern Central region" OBJECTIVES 2.1 General objectives Study on technical solutions for improving the efficiency of maize production on sloping-land in the North Central region (Nghe An and Thanh Hoa provinces) 2.2 Specific objectives - To assess the current status of maize production on sloping land in the North Central region - To identify some technical solutions (varieties, cultivated practices) to improve the production and efficiency of hybrid maize varieties in North Central provinces - To set up an experimental model in which some appropriate technical solutions are used for new hybrid maize varieties in the North Central region SCIENTIFIC AND PRACTICAL MEANING 3.1 Scientific meaning - The obtained results of this study provide a scientific database on technical solutions (variety selection and cultivated practices) for mid-duration hybrid maize varieties for the North Central provinces or similar ecological conditions region This study provides scientific envidents for improving the maize production effectiveness on sloping-land, contributing to the restructuring of the agricultural schedule and adaptation to climate change in the North Central provinces 3.2 Practical meaning - New technical practices for high yield, good quality, and good effectiveness are convincing evidence that can change people's awareness Since, they change the traditional farming to the new one, which applies new and/or mordern technologies, maintaining soil fertility, preventing soil from erosion, and protecting of the environment - New varieties together with new farming techniques contribute to increase productivity, quality and efficiency of maize production This is the basis for increasing farming value, improving life and income for people in the North Central region NEW CONTRIBUTIONS OF STUDY 4.1 The current status of maize production on sloping-land in the North Central region (Thanh Hoa and Nghe An) has been evaluated The main reason for limiting the efficiency of maize production on slopin- land is the lack of suitable varieties, farming techniques are not proper; 4.2 Identified CS71 has good growth and development ability, good resistance to hard conditions of sloping-land in Nghe An and Thanh Hoa The yield of CS71 in Nghe An and Thanh Hoa provinces is stable and in a range of 6.03-6.47 tons/ha in Srpring croppings; 4.3 Some appropriate farming techniques have been identified to improve yield and efficiency of CS71 on sloping-land, including: The planting duration is January - February 5; planting density is 6.5 - 7.5 thousand plants/ha; fertilizer regime: 180 kg Nitrogen + 80 kg Phosphorus + 100 kg Potassium; Application of mechanization in the following stages: plowing, harrowing, slitting and separating corn kernels; Using chemical compound: Acetochlor, Nicosulfuron to control weeds, compounds having active ingredients of Emamectin Benzoate to control stem borers or Difenoconazole and Propiconazole to prevent diseases from maize 4.4 A applied synchronous technical practices model has been built on sloping-land in Nghe An and Thanh Hoa provinces achieved a yield of over 65 quintals/ha, the economic efficiency increased by 22-30% compared to that of control CHAPTER LITERATURE REVIEW AND SCIENTIFIC BASE OF THE STUDY In summary, the synthesis of research results in Vietnam and abroad related to the main contents of this study indicated that: the selection of suitable maize varieties, planting density and balanced application of fertilizers based on the maize demand as well as some other technical impacts for an effective maize production In the current practical maize production in the North Central region, people often plant with wide spacing between maize rows and a low planting density This significantly reduces maize yield per unit area as well as per the region Besides, the unbalanced inorganic fertilizers utilization also negatively affects maize yield This are limitations in the current maize production in the North Central region On the other hand, author of this study found that there has not been any research on the above issues in the sloping land of the North Central provinces Especially, research on the selection of suitable maize varieties and planting time to avoid natural disasters, droughts, floods and pest control measures for maize on sloping land in the North Central region Therefore, it is necessary to have indepth studies in this field to solve the above issues and to contribute to increase productivity and economic efficiency of maize production, since to limit soil erosion, and ensure ecological balance in the North Central region CHAPTER MATERIAL AND METHODOLOGY 2.1 Material of study 2.1.1 Maize variety - The material source includes 12 hybrid maize varieties from Maize Research Institute and foreigner companies; variety PC999 is the variety being grown locally as a control The sources of materials for maize varieties used in the study are presented in Table 2.1 Table 2.1 Experimental maize varieties No Variety Origin CS71 Maize research institute LVN146 Maize research institute LVN152 Maize research institute LVN102 Maize research institute LVN61 Maize research institute LVN66 Maize research institute P4199 Imported 30Y87 Imported DK9901 Imported 10 NK4300 Imported 11 NK7328 Imported 12 CP999 (ĐC) Imported A brief description on the main characteristics of maize varieties is presented in Appendix 2.1.2 Other materials - Fertilizers: River Gianh microbial organic fertilizers, Urea fertilizer (N: 46%); Superphosphate fertilizer (P2O5 content: 16%), Potassium chloride fertilizer (K2O content: 60%) were used in this experiment - Herbicides: MIZIN (with Atrazine active ingredient), Atamex 800WP (with Atrazine 800g/kg active ingredient), Luxdan 75WP (with Nicosulfuron active ingredient (min 94%): 750 g/kg), Dibstar 50EC (with Acetochlor active ingredient (min 93.3%) : 500g/l) - Pesticides: Proclaim 1.9 EC (with 19g/LEmamectin benzoate, Ofatox 400EC (with Fenitrothion 200gr/l; trichlorfon 200gr/l), Sutin 5EC (with Acetamiprid 30g/l + Imidacloprid 20g/l) Pesticides: Kasumin 2L (with Kasugamycin 2%), PRO-Thiram (with PRO-Thiram 800g/Kg), Vicarben 50SC with (Carbendazim… 500g/liter) These chemical components are used to control stem borers, maize borers and other main diseases of maize They are and in the list of permitted use of the Department of Plant Protection 2.1 Study conditions 2.2.1 Meteorology data In general, during the time of experiment in spring crop of 2013 - 2017, the weather conditions were quite favorable for the growth and development of maize However, in 2014 and 2015 there was less rainfall, thus affecting the growth and yield of maize 2.2.2 Experimental soil The experiments were arranged on a sloping land, the slope level ≤ 15⁰ , without active irrigation, sowing could only be done in the Spring crop: 2.3 Place and time of study 2.3.1 Study location Experiments and models are conducted on sloping land ≤ 15⁰ in Hoa Son commune, Anh Son district, Nghe An province and Hoa Quy commune, Nhu Xuan district, Thanh Hoa province 2.3.2 Study period - Experiments on new hybrid maize varieties were conducted in seasons: Spring 2013 and Spring 2014 - Experiments on planting density and fertilizer for new hybrid maize varieties were carried out in crops: Spring 2015 and Spring 2016 - The experiments on suitable planting time for maize variety CS71 on sloping land of Nghe An and Thanh Hoa were carried out in seasons: Spring 2015 and Spring 2016 - Research experiments on mechanization were carried out in crops: Spring 2015 and Spring 2016 - Research experiments on pesticides were carried out in crops: Spring 2015 and Spring 2016 - Building the maize models applying appropriate planting density and fertilizer dosage for new selected hybrid maize varieties on sloping land 2.4 Study content 2.4.1 Content 1: To survey and evaluate the current status of maize production in Nghe An and Thanh Hoa provinces; 2.4.2 Content2: Study on some technical solutions to improve the efficiency of maize production on sloping-land of Nghe An and Thanh Hoa provinces: a Experiment 1: Study on the suitable maize varieties for production on sloping-land in Nghe An and Thanh Hoa pr ovinces b Experiment 2: Study on the suitable planting time for selected maize varieties on sloping-land of Nghe An and Thanh Hoa provinces c Experiment 3: Study on the suitable planting density and fertilizer dosage for selected maize varieties on sloping-land of Nghe An and Thanh Hoa provinces d Experiment 4: Study on the mechanization for selected maize varieties on sloping-land of Nghe An and Thanh Hoa provinces e Experiment 5: Study on the treatment for pests and diseases of selected maize varieties on sloping-land of Nghe An and Thanh Hoa provinces f Proposing a technical process for maize cultivation with high efficiency on sloping land in Nghe An and Thanh Hoa provinces; 2.4.3 Content 3: Building-up a demonstration model which applied the integrated cutivated practies solutions on sloping-land of Nghe An and Thanh Hoa provinces 2.5 Methodology 2.5.1 Methodology of maize production survey Collecting information on productivity, area, output, variety structure by the rural rapid survey (PRA) method Each district surveyed communes Each commune randomly selected 20 households 2.5.2 Content2: Study on some technical solutions to improve the efficiency of maize production on sloping-land of Nghe An and Thanh Hoa provinces a) Experiment 1: Determining suitable maize varieties to grow on sloping-land of Nghe An and Thanh Hoa provinces from 12 maize varieties - There were 12 varieties in this experiment, each variety presented for each treatment The experiment was designed as Random Complete Block Dezign – RCBD, replications, the área for each plot was 14.0 m2, each plot contained maize rows with a length of 5m, the sowing space was 60 x 25 cm/plant b) Experiment 2: Determining the suitable planting time for CS71 variety on sloping-land in Nghe An and Thanh Hoa provinces Onefactor experiment in seasons, designed in a randomized complete block design (RCBD), with replicates c) Experiment 3: Determination of cultivated density and fertilizer dose for selected maize varieties (variety CS71) The experiment consisted of factors, designed as split plot design with replicates, the large plot is the density (4 levels: M1, M2, M3, M4), the small plot is fertilizer (5 levels: P1, P2, P3, P4, P5); Each large plot consists of 20 rows, each row is m length The monitoring and evaluation indicators are performed with plants of midle rows of the plot rainy season, often encountering flash floods, affecting seed formation and reducing yield Therefore, with the growing time in the middle-growth group (105 - 120 days), the experimental varieties are suitable for the Spring crop structure in Anh Son district, Nghe An province and Nhu Xuan district, Thanh Hoa province b) Plant height, cob height of maize varieties Plant height of all varieties ranged from 164.4 to 224.6 cm in Nghe An crop and from 190 to 217.1 cm in Thanh Hoa In which, the varieties with the highest height are P4199 and NK4300, respectively 217.1cm Varieties LVN61 and LVN66 have the lowest height, ranging from 164.4 to 190 cm These two varieties are lower than the control variety in height CP999 Through the experimental monitoring in the Spring 2013 and Spring 2014 crops in Nghe An and Thanh Hoa, it was found that: The experimental variety with the highest cob height was NK4300, P4199 with 21.5-39.9 cm higher than the control CP999 All other varieties have a cob height ranging from 54.5-103.6 cm In which, the variety with the lowest cob height is LVN61 (54.5 cm in Nghe An) c) Plant status and the coverness of corn Through monitoring and evaluation of experimental varieties in the Spring 2013 and Spring 2014 crops at experimental sites, it was found that all varieties had plant status ranging from points to (good and average) Varieties with better plant status than control (variety CP999) in crops at two locations are CS71, NK4300 and P4199 (point 2) Corn coverness: is an important parameter related to resistance to pests and diseases as well as adverse conditions, because the coverness play a role in protecting corn, and also play a part in photosynthesis to create a source of nutrients for corn, the coverness of corn depends on the genetic characteristics of the variety In general, the hybrid maize varieties with a good corn coverness (scores 1-2), better than the control variety CP999, there were varieties with similar corn coverness compared to the control LVN146, LVN152, LVN102 3.2.1.2 Situation of pests and diseases, resistance to falling and drought of hybrid maize varieties a) Situation of major pests and diseases of hybrid maize varieties The results of monitoring on tolerance to external conditions and some major pests and diseases of experiment in Nghe An and Thanh Hoa provinces show that: - Stem borers: All varieties participating in the experiment in two locations were damaged by stem borers, ranging from point to point - Corn borer: Most of the varieties tested at sites were affected by corn borer at a light level (points - 3), equivalent to the control variety CP999 Only varieties CS71 and P419 were infected with corn borer at very light levels (point 1) - Powdery mildew: This is the most common disease on maize in the tropics, reducing yield and quality of maize The disease mainly appears and thrives from blooms, sprayed pollen, until harvest Through experimental monitoring, all experimental varieties in the spring crops of 2013 and 2014 in Nghe An and Thanh Hoa were infected with blight, leaf spot, at very mild to moderate levels - Large leaf spot disease: Through experimental monitoring at two sites, most varieties were infected with large leaf spot disease (from point to point 2) b) Resistance to shedding and drought of maize varieties In general, in the Spring 2013 and Spring 2014 crops, the weather in Anh Son district, Nghe An province and Nhu Xuan district, Thanh Hoa province sometimes encountered heavy rains in the waxy ripening stage, causing root loss in the experimental varieties The falling roots ability of the varieties ranged from 3.1 to 7.95% Among them, varieties CS71, P4199 have relatively good resistance (5%) Experimental varieties often break stems after thunderstorms However, most of the experimental varieties had broken stems at points and In which, varieties P4199, 30Y87 and VS71 had good resistance to stem breakage (point 1) The level of stem breakage of the remaining variety was similar to that of the control variety CP999 In the Spring 2013 and Spring 2014 crops, maize faced with drought in the germination period to the 7-9 leaf stage The results are as follows: The drought tolerance level of all tested varieties is from point to point LVN61 is the variety with the worst drought tolerance (point 3) The varieties CS71, 30Y87 and P4199 have good drought tolerance (point 1) The drought tolerance of the remaining varieties was equivalent to that of control CP999 (point 2) 3.2.1.3 Some factors constituting yield and yield of experimental maize varieties a) Number of corn/plant, number of rows of seeds/corn, number of seeds/row The results of grain parameters evaluation of maize for years at locations showed that, the number of rows/corn did not have a large difference among varieties, almost stable over years The variety with the highest number of rows/corn is P4199 (Nghe An 14.6 rows/cob; Thanh Hoa: 14.5 rows/corn) and VS71 (Nghe An: 14.6 rows/cob; Thanh Hoa: 14.3 rows/cob) goods/corn) The variety with the least number of rows/corn was the control CP999 (12.2-12.3 rows/cob) The remaining varieties had a higher number of rows/ corn in the two crops than the control CP999 and ranged from 13.4 to 14.4 rows/corn Number of seeds/ row: In Nghe An, the variety with the highest number of seeds per row was P4199 (30.6 seeds/row), higher than the control CP999 (1.6 seeds/row) In Thanh Hoa, varieties with lower number of seeds/ row than control CP999 such as: 30Y87, DK9901, LVN146, LVN152 , b) Weight of corn/plot, grain moisture, percentage of grain/corn - During the years of experiment, the weight of corn/plot ranging from 19.19 to 32.35 kg/plot The variety with the highest corn weight/plot was CS71 (31.28-32.35 kg/plot) The variety with the lowest corn weight/plot was the variety NK6326 with only 19.19 - 24.89 kg/plot - Seed moisture: The moisture content of the seeds ranged from 26.98% to 33.35% In which, the variety with the highest seed moisture content is NK4300 and the lowest is LVN152 - Ratio of grain/corn: The percentage of grain/corn of the experiment ranged from 67.65% - 83.50% The group of varieties with a high percentage of grain/corn are: NK4300 (83.50%), CS71 (80.25%), respectively The varieties with the lowest percentage of grain/corn were LVN66, LVN152, LVN61 (67.65 - 76.67%) c) Actual yield of maize varieties at the experimental sites The results of experiment in the two crops were obtained in Table 3.16 The yield of maize in Nghe An in 2013 and 2014 ranged from 38.32 to 64.69 quintals/ha In which, the varieties had significantly higher yield compared to control CP999 (53.13 quintals/ha) (significant level 0.05) were CS71 (64.69 quintal/ha), P4199 (62) ,68 quintals/ha) The varieties with significantly lower yield compared to the control CP999 were LVN66 and LVN46, respectively (40.96 - 42.63 quintals/ha) The remaining varieties had no difference from the control CP999 In Thanh Hoa, the experimental varieties achieved actual yield ranging from 44.04 to 63.06 quintals/ha In which, the variety with significantly higher yield compared to the control CP999 (52.29 quintal/ha) were CS71 (62.57 quintal/ha), P4199 (61.61 quintal/ha), 30Y87 (61 26 quintals/ha) and NK4300 (58.07 quintals) The results of the analysis of variance according to the multi-year, multi-point showed that the actual yield of the two maize varieties CS71 and P4199 at both Thanh Hoa and Nghe An sites in the two different Spring crops was not significant, but they had the highest yield among tested he maize varieties This proves that their productivity is stable in crops and at experimental sites To confirm the stability of the selected maize varieties within the framework of the study, the stability of the maize varieties was evaluated according to the model Eberhart and Russell (1966) Table 3.15 Practical yield of experimental maize varieties Practical yield (quintals/ha) Variety Nghe An 2013 2014 a 64,69 Thanh Hoa Average a a 2013 2014 a Average 64,08 62,07 a 62,57a CS71 63,46 LVN146 46,93 f 38,32 g 42,63f 55,47 f 49,97 de 52,72c LVN152 56,87 d 45,01 è 50,94de 47,36 i 46,38 f 46,87e LVN102 52,68 e 43,22 f 47,95ef 45,17 k 44,04 f 44,61e LVN61 58,02 cd 52,83 d 55,43bcde 49,34 h 46,65 è 48,00de LVN66 43,53 g 38,38 g 40,96f 46,32 j 49,77 de 48,05de P4199 64,45 a 60,90 ab 62,68ab 61,36 a 61,86 a 61,61a 30Y87 58,67 c 61,20 ab 59,94abc 61,39 b 61,13 ab 61,26a DK9901 57,71 cd 54,21 cd 55,96bcd 56,41 e 52,83 d 54,62bc NK4300 60,18 b 48,27 e 54,23cde 57,38 d 58,77 bc 58,07ab NK7328 57,07 d 57,45 bc 57,26abcd 52,65 g 57,51 c 55,08bc CP999 (control) 53,83 e 52,42 d LSD0,05 2,8 CV (%) 3,2 63,06 53,13cde 52,50 g 52,07 d 7,6 2,3 2,6 52,29cd 4,2 3.2.1.4 Evaluation of adaptability and yield stability of experimental maize varieties The analysis of genotype and environment interaction is a particularly important part of breeding and identification of varieties for different ecological regions and sub-regions The analysis of the interaction between the variety and the environment has been recognized by many authors and focuses mainly on the analysis of adaptability and the evaluation of the stability of the variety through a series of different models and concepts In order to select maize varieties with stability and wide adaptability to maize-producing hills in Nghe An and Thanh Hoa provinces, this study evaluated the growth and development characteristics, the resistance to major pests and diseases, and the yield and yield components of the experimental maize varieties Author also focused on analyzing the stability of the maize varieties in terms of yield through the model of Eberhart and Russell (1966), using the software ondinh.com of Nguyen Dinh Hien (1999) to analyze the data (Nguyen Huy Hoang et al., 2014) The results of stability analysis of the corn varieties tested in the Spring crop are presented in Table 3.16, Table 3.17 and Table 3.18 The average values of varieties across locations are presented in Table 3.16 Table 3.16 Medium value of varieties at different locations Nghe An Thanh Hoa Variety Variety mark name 2013 2014 2013 2014 V1 V2 V3 V4 V5 V6 V7 V8 V9 V10 V11 V12 CS71 LVN146 LVN152 LVN102 LVN61 LVN66 P4199 30Y87 DK9901 NK4300 NK7328 CP999 (Control) 63,46 46,93 56,87 52,68 58,02 43,53 64,45 58,67 57,71 60,18 57,07 64,69 38,32 45,01 43,22 52,83 38,38 60,90 61,20 54,21 48,27 57,45 62,07 55,47 47,36 45,17 49,34 46,32 61,36 61,39 56,41 57,38 52,65 63,06 49,97 46,38 44,04 46,65 49,77 61,86 61,13 52,83 58,77 57,51 53,83 52,42 52,50 52,07 The data in Table 3.16 shows that maize varieties have different responses to growing conditions in crops and at locations Nghe An and Thanh Hoa There are varieties with high yield in Nghe An, lower yield than in Thanh Hoa, for example CS71, Spring 2014 has a higher yield than Spring 2013 But there are also higher yielding varieties in Thanh Hoa, such as LVN66 This analysis result is consistent with the results of the analysis of experimental data according to the multi-point, multi-year anova analysis model presented in Table 3.15 Data on yield estimation of experimental maize varieties by regression with environmental index are presented in Table 3.17 Table 3.17 Estimation of yield of experimental maize varieties by regression with environmental index in spring crop at experimental sites (ton/ha) I index value of each point Regression Nghe An Thanh Hoa Variety Medium coefficient 2013 2014 2013 2014 (bi) 2,35 -2,36 0,10 -0,10 CS71 63,32 1,27 62,68 63,96 63,29 63,35 LVN146 47,67 1,88 52,09 43,24 47,86 47,49 LVN152 48,90 2,52 54,83 42,96 49,16 48,66 LVN102 46,28 2,01 51,01 41,53 46,48 46,08 LVN61 51,71 1,12 54,34 49,07 51,82 51,60 LVN66 44,50 1,06 47,00 41,99 44,61 44,40 P4199 61,89 0,74 63,63 61,15 61,97 61,82 30Y87 60,60 -0,53 59,34 61,86 60,54 60,65 DK9901 55,29 0,77 57,11 53,47 55,37 55,21 NK4300 56,,15 2,51 62,06 50,22 56,41 55,91 NK7328 56,17 0,12 56,46 56,16 56,18 55,87 CP999 52,71 0,30 53,42 51,99 52,74 52,68 (control) The analysis data of environmental index (I) at sites: Nghe An and Thanh Hoa in spring crop of 2013 and 2014 and yield estimate by regression with environmental index of the experimental varieties presented in Table 3.17 shows that: Nghe An has index I of 2,351 and -2.357; Thanh Hoa has I equal to 0.103 and -0.096, respectively Among the all varieties, there were varieties with the highest average yield: CS71 (63.32 quintals/ha), followed by P4199 (61.89 quintals/ha) and finally 30Y87 (60.59 quintals/ha) Table 3.18 presents values of regression coefficient (bi) and deviation from regression line (S2di) They are summary parameters for selecting stable varieties in spring crop on sloping land in Thanh Hoa and Nghe An in two spring crops of 2013 and 2014 Table 3.18 Summary of parameters for selecting maize varieties with stable yield for spring crop at experimental sites Average Regression No Variety yield coefficient Ttn P S2di Ftn P (ton/ha) (bi) CS71 63,32 1,27 0,13 0,767 -2,761 0,33 0,275 LVN146 47,67 0,88 0,39 0,635 53,304 13,943 1,000 * LVN152 48,90 1,52 1,75 0,888 4,284 2,040 0,872 LVN102 46,28 1,01 1,41 0,852 1,651 1,401 0,755 LVN61 51,71 0,12 0,07 0,527 25,059 7,085 0,999 * LVN66 44,50 0,06 0,04 0,515 24,326 6,907 0,999 * P4199 61,89 -0,26 0,63 0,704 -2,207 0,464 0,365 30Y87 60,60 -1,53 5,35 0,985 * -3,205 0,222 0,196 DK9901 55,29 -0,23 0,38 0,634 -0,274 0,933 0,604 10 NK4300 56,15 1,51 1,76 0,889 4,119 2,000 0,867 11 NK7328 56,17 -1,12 1,31 0,839 4,107 1,997 0,867 12 CP999 52,71 -0,70 3,72 0,968 * -3,728 0,095 0,091 (control) Note: * Significant difference with P≤0.05 The data in table 3.18 shows that: within 12 experimental varieties, varieties 2, 5, 6, and 12 (LVN46, LVN61, LVN66, 30Y87 and CP999) are unstable The regression coefficient bi were 0.534 and 0.303 for and 12, respectively (same as the asterisk in the table in column P to test the regression coefficient) is significantly different from with P≤0.05, which are unstable varieties, with the index of deviation compared with the large regression line (significantly different from 0, marked with an asterisk in column P corresponding to the S2di value of varieties 2, 5, 6) Among the tested varieties, there were varieties with the highest yield in locations, Thanh Hoa and Nghe An in the Spring crops of 2013 and 2014, namely No (CS71, NS: 63.32 quintals/ha), followed by No (P4199, NS: 61.89 quintals/ha) and No (30Y87, NS: 60.59 quintal/ha); In which, CS71 had the highest and stable yield on sloping land of Thanh Hoa and Nghe An in spring crops, so this variety was selected as a variety to develop further intensive ... improve yield and efficiency of CS71 on sloping-land, including: The planting duration is January - February 5; planting density is 6.5 - 7.5 thousand plants/ha; fertilizer regime: 180 kg Nitrogen... synthesis of research results in Vietnam and abroad related to the main contents of this study indicated that: the selection of suitable maize varieties, planting density and balanced application of... The experiments on suitable planting time for maize variety CS71 on sloping land of Nghe An and Thanh Hoa were carried out in seasons: Spring 2015 and Spring 2016 - Research experiments on mechanization