DETERMINING SOIL LIMITING FACTORS FOR CABBAGE IN THE MAIN VEGETABLE PRODUCTION AREA IN LAO CAI PROVINCE

MINISTRY OF EDUCATION AND TRAINING MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM ACADEMY OF AGRICULTURAL SCIENCES TRẦN THỊ MINH THU DETERMINING SOIL LIMITING FACTORS FOR CABBAGE

MINISTRY OF EDUCATION

AND TRAINING

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

VIETNAM ACADEMY OF AGRICULTURAL SCIENCES

TRẦN THỊ MINH THU

DETERMINING SOIL LIMITING FACTORS FOR CABBAGE IN THE MAIN VEGETABLE PRODUCTION AREA IN LAO CAI PROVINCE

Major: Soil science Code : 962 01 03

SUMMARY OF DOCTORAL THESIS IN AGRICULTURE

HA NOI, 2022

VIET NAM ACADEMY OF AGRICULTURAL SCIENCES

Scientific instructors: 1 Associated Prof Dr Nguyen Van Bo

2 Associated Prof. Dr Tran Minh Tien

Reviewer 1: Associated Prof Dr Le Van Thien

Reviewer 2: Associated Prof Dr Pham Quang Ha

Reviewer 3: Associated Prof Dr Ho Quang Duc

The thesis will be defended at the Institue’s Thesis Evaluation Council

at the Vietnam Academy of Agricutural Sciences:

Time : , date : / /2022

The thesis can be found at the:

Vietnam National Library

The Library of Vietnam Academy of Agricultural Sciences The Library of Soils and Fertilizer Research Institute

INTRODUCTION

1 Rationale of the research

Cabbage (Brassica oleracea var Capitata) plays a significant

role in vegetable production in cold winter of Northern Vietnam regions Advantages of cabbage are easy to grow, easy to store, easy

to transport Especially it brings high productivity and has a large consumption market

Lao Cai has the advantage of terrain, cool climate all year round, so it is considered an advantageous locality for vegetable production In particular, Sa Pa town and Bac Ha district, Lao Cai province are the areas with the most favorable conditions, which can grow many kinds of vegetables Due to the influence of altitude, this region has a climate that allows cabbage to be grown all year round with good yield and quality

However, cabbage productivity in Sa Pa and Bac Ha is not high compared to the potential, the annual output is still low compared to local consumption demand, not to mention export In addition to the causes due to the negative impacts of pests and diseases, natural disasters such as rain, frost, etc., the soil and nutrient management in the soil are extremely important factors directly related to the growth and development of crops in general and cabbage in particular Due to the change in fertilization and farming regimes, on the other hand, the cultivated land in Sa Pa and Bac Ha is mainly distributed on sloping terrain, with heavy rain with high intensity leading to erosion and washing away of the topsoil decrease in cation exchange capacity and base satiety, increase in acidity, increase in phosphorus fixation ability these are the causes leading to deficiency/excess, formation

of limiting factors in soil, reducing plant yield planting, and reducing production efficiency In order to make Lao Cai become one of the major producers of branded cabbage in the market, it is necessary to expand cabbage production in households However, to boost cabbage production, it is necessary to have appropriate technical solutions to improve production efficiency First, it is necessary to determine the limiting factors in the soil, from which to determine the appropriate farming techniques, to use fertilizers reasonably according to the requirements of the crop, in accordance with the cultivation conditions

of the locality method, not only increase crop productivity and,

production efficiency but also improving soil fertility towards building

an efficient and sustainable vegetable farming system Therefore, it is

urgent to conduct "Determination soil limiting factors for cabbage and vegetable crops in the main vegetable production area in Lao Cai province"

- Determining the limiting factors of soil and soil nutrients for cabbage productivity in the main vegetable production area of Lao Cai province

- Proposing solutions to overcome the limiting factors of soil and soil nutrients for cabbage, improving productivity and efficiency

of cabbage cultivation in Lao Cai province

- Build tests to verify the scientific conclusions that have been determined

3 Research scope and object

- Primary data: Collected during 2014-2015

- Secondary data: Collected during the period from 2014-2020

- Experiment and model: Implemented from 2016-2021

4 Scientific and practical significance of the research

4.1 Scientific significance

- Provide scientific data on limiting factors in soil, soil nutrients for cabbage productivity in Lao Cai and some remedial measures, as a

premise for further research

- Provide scientific data for further studies on cabbage in

Vietnam

4.2 Practical significance

- The results of the study are the scientific basis for building a reasonable fertilizer application process for cabbage plants in Sa Pa town and Bac Ha district, Lao Cai provinc,e and other localities with similar conditions, contributing to change production practices, shift towards commodity agriculture, improve profitability and sustainability in vegetable production of farmer households, farms and cooperatives producing vegetables and cabbage, contributing to hunger eradication, poverty reduction for ethnic minorities in the

province's highlands

- Contributing to improving soil fertility, protecting soil resources, protecting the environment and building a sustainable vegetable farming system

5 New contributions of the thesis

- A comprehensive study on the limiting factor in soil and nutrient management for cabbage in Sa Pa town and Bac Ha district, Lao Cai province in particular and the northern mountainous region of

Vietnam in general

- Identified the trace element Bo (B) as an organic medicine for cabbage in the study area and determined the appropriate amount of

lime, nitrogen and phosphorus for cabbage in the study area

- Initially, using cabbage leaf analysis to determine the deficiency or excess of 12 nutritional elements N, P, K, Ca, Mg, S, B,

Mn, Fe, Cu, Zn and Mo for cabbage plants in Lao Cai, not only as a basis for the adjustment of suitable fertilizers, but also provide a data set to analyze the macronutrients, intermediate nutrients and micronutrients in cabbage leaves grown in the mountainous areas in northern Vietnam, as a basis for other studies on cabbage

to the thesis, 2 page; documents and references, 18 pages with 149 references in Vietnamese, English and online newspapers The thesis has 25 tables, 16 figures and charts

Chapter 1 LITERATURE REVIEW 1.1 Cabbage production

Asia leads the world in cabbage area and production, especially China In Vietnam, cabbage is also grown on a large scale for commodity production and is grown mainly in the northern midland and mountainous provinces, the Red River Delta and the Central Highlands

Sa Pa town and Bac Ha district in Lao Cai province have suitable climate and soil conditions for growing vegetables, especially cabbage Lao Cai cabbage has a reputation for quality such as tastier, crisper, stronger flavor than cabbage in other localities Although the quality is good, the productivity of Lao Cai cabbage is not high compared to the potential and the annual output has not yet met the consumption demand

1.2 Research results on the limited factors of soil properties and plant nutrients in soils for cabbage production

The causes of reducing cabbage yield due to farming techniques are lack of irrigation, excessive fertilization, imbalanced fertilization There are many methods to identify the limiting factor in soil and soil nutrients The most common way to identify the limiting factor is the FAO traditional land evaluation methods, Conduct field defect experiments; Diagnose nutrient deficiency/excess of crops through: (i) visible deficiency symptoms; (ii) crop analysis; (iii) soil analysis and (iv) determination of the nutrient balance of crops Although vegetable production in Vietnam in general and in Lao Cai province in particular plays an important role, there are few studies on the soil limiting factors for vegetable and cabbage

cultivation Therefore, it is necessary to study the limiting factors of soil and soil nutrients for cabbage in Vietnam

1.3 Research results on the solutions of mitigating limited factors

of soil properties and plant nutrients in soils for cabbage production

In addition to the study to determine the appropriate dosage and ratio of macronutrients (N, P, K), some solutions to overcome the limiting factors on soil and soil nutrients for cabbage plants have also been mentioned such as: Applying lime helps reduce acidity, limit diseases from soil and create favorable conditions for plants to absorb nutrients; Add trace elements such as molybdenum, spray 125 g of sodium- or ammonium molybdate in 500 liters of water per hectare when there are signs of deficiency; foliar spraying of iron sulfate (1%)

to overcome iron deficiency on alkaline and lime soils; foliar spray 5

kg of manganese sulfate or 2-3 kg of manganese oxide/ha when there are symptoms of plant deficiency; used at a dose of 3 kg Solubor/ha in areas with boron deficiency

Chapter 2 MATERIALS, CONTENTS AND METHODS 2.1 Materials

2.1.1 Experimental cabbage variety

Grand KK Cross and New Star Cross, this is a popular cabbage variety in the area during the study period

2.1.2 Fertilizers and soil amendments

Nitrogen urea (46% N), superphosphate (17% P2O5), potassium chloride (60% K2O); boric acid (H3BO3); copper(II) chloride dihydrate (CuCl2.2H2O); zinc sulfate heptahydrate (ZnSO4.7H2O) and ammonium heptamolybdate tetrahydrate ((NH4)6Mo7O24.4H2O); Lam Thao NPK 5:10:3, farmyard manure (with analysis of N, P, K); lime powder Ca(OH)2 or limestone powder CaCO3

2.2 Content research

- Evaluation of the current situation of vegetable production and soil characteristics of cabbage and vegetables in the main vegetable production area of Lao Cai province

- Determination of limiting factors on soil and soil nutrients for cabbage in the main vegetable production area of Lao Cai province

- Researching solutions to overcome some limiting factors and improve the efficiency of cabbage cultivation in the main vegetable

production areas of Lao Cai province

- Build tests to verify the scientific conclusions that have been determined

2.3 Methods

- Data collection: Participatory rural appraisal (PRA)

- Soil samples were taken according to TCVN 7538-2:2005 Soil samples were analyzed according to Vietnamese standards (TCVN) The organic health hazards in soil with cabbage were determined according to the guidelines of FAO (1976)

- Cabbage leaves were taken at the end of vegetative growth period, leaf samples were analyzed for parameters by plasma mass spectrometry method, N and S criteria were analyzed by combustible gas analyzer The threshold for nutrient deficiency/excess in leaves was compared with published data in cabbage leaves (Reuter & Robinson, 1997; Bryson & Mills, 2014)

- Nutrient balance at household scale is determined based on the partial nutrient balance calculation method (Achim Dobermann, 2007)

- The experiment on lime in pots and jars included 7 treatments (0; 0.25; 0.5; 1.0; 2.0; 3.0 and 4.0 tons of lime/ha) and 3 replicates

- Field experiments were arranged in a completely randomized block design Lime experiment has 6 treatments (0; 0.25; 0.5; 1.0; 2.0 and 4.0 tons of lime/ha) with 3 replicates on the background with and without micronutrients The nitrogen experiment had 5 treatments (30; 90; 150; 210 and 270 kg N/ha) with 4 replicates The experiment on phosphorus had 6 treatments (0; 30; 60; 90, 120 and 150 kg P2O5/ha) with 4 reminders on fertilized and unlimed substrates The microbiological experiment consisted of 6 formulas: Control (no fertilization); Zn (0.2%); B (0.2%); Mo (0.1%); Cu (0.2%) and fully applied Zn + B + Mo + Cu with 4 replicates

- The experimental model was arranged according to the farm Research" method on the fields of farmers, including 02 formulas: Farmer (farmer-based farming) and Experimental (lime supplement, N-P-K balance and micronutrient supplements)

"On-Chapter 3 RESULTS AND DISCUSSIONS

3.1 The situation of cabbage production in the study area

3.1.1 Characteristics of the study area

Sa Pa and Bac Ha have a temperate climate, favorable for the development of many crops, suitable for building concentrated vegetable production areas, especially temperate vegetables such as cabbage, kohlrabi, and cauliflower

3.1.2 Status of vegetable production and methods of cultivating cabbage in the study area

Some limitations for vegetable production in the study area:

- High mountainous terrain, strongly dissected, affecting farming, transportation and production expansion

- Soil is sloping, easily eroded, washed away, arable land is often poor in nutrients, acidic and not porous

- Low production level of farmers greatly affects the efficiency

- Lime is rarely used for soil improvement

- Many plant diseases, especially cabbage root swelling disease

- Most of the area for growing vegetables and producing vegetables is still spontaneous by the people

- Cabbage yield is much lower than potential

3.2 Soil limiting factors and soil nutrients for cabbage

3.2.1 Determination of organic health of soil through assessment of suitability of soil characteristics for cabbage

The results of analysis of 96 soil samples in cabbage gardens of

96 surveyed households (57 samples in Sa Pa and 39 samples in Bac Ha) are shown in Table 3.6

Table 3.6 Statistical analysis results of soil samples for cabbage

cultivation

pHH2O 4,00 7,48 5,41 0,07 0,65 4,76 - 6,06 pHKCl 3,50 7,05 4,48 0,07 0,72 3,76 - 5,20

OM, % 1,06 7,37 3,32 0,12 1,19 2,12 - 4,51 Nts, % 0,06 0,36 0,16 0,01 0,05 0,11 - 0,21

P2O5ts, % 0,09 0,67 0,22 0,01 0,12 0,11 - 0,34

K2Ots, % 0,13 2,89 1,27 0,06 0,62 0,65 - 1,89

P2O5dt, 0,86 96,13 15,00 1,77 17,38 2,38 - 32,38

K2Odt, 4,32 67,00 19,47 1,21 11,89 7,57 - 31,36 CECmeq/

100g soil, 5,08 20,64 11,17 0,31 3,02 8,15 - 14,19 TBCmeq/

100g soil, 0,85 6,23 3,05 0,11 1,12 1,93 - 4,18 BS% 8,57 66,53 28,26 1,10 10,80 17,47 - 39,06 Compared with the requirements for soil properties of cabbage (FAO, 1976), the land for cabbage cultivation in Sa Pa and Bac Ha towns is evaluated as follows:

- Non-restrictive factors: Soil organic content (OC), phosphorus content (P2O5) in soil

- Factors at medium limit: nitrogen content (N%) in soil, potassium content (K2O) in soil, total alkaline cation exchange in soil (TBC), cation exchange capacity in soil (CEC) soil) and basic saturation (BS) in the soil

- Factors that are severely limiting: Soil acidity (pH)

3.2.2 Determination of limiting factors on soil and soil nutrients through analysis of cabbage leaves

The content of macro- and intermediate nutrients in leaves (N,

P, K, S and Ca) varied greatly (Table 3.8), possibly caused by the difference in the amount of fertilizer used by each household

For the remaining elements, the difference in nutrient content in leaves was relatively small, except for Fe in Sa Pa (110–420 mg/kg)

Table 3.8 Nutritional content of cabbage leaves

Compare with appropriate threshold nutrient content in dry matter of cabbage leaves The number and proportion of samples that are deficient (below the appropriate threshold), sufficient (within the appropriate threshold) and excess (outside the appropriate threshold) are shown in table 3.9:

- Excess nitrogen was identified as one of the limiting factors for cabbage production in Sa Pa and Bac Ha The amount of N applied

by farmers is greater than the demand for cabbage (investigation results) while the N content in cabbage leaves is in excess

- Excess sulfur in cabbage leaves has also been identified as one

of the public health concerns about the imbalanced use of nutrients by people, however, this limitation can be overcome when farmers change their fertilizer use habits , should not continuously use fertilizers containing S, especially fertilizers containing high levels of

S

- B and Cu deficiencies can be identified as limiting factors for cabbage However, the deficiency of these two elements in cabbage leaves can also be due to a deficiency in the soil or because the B and

Cu elements in the soil are not deficient but are difficult for plants to absorb

Range

Bac Ha Range

Table 3.9 Quantity and proportion of samples missing (below the

appropriate threshold), sufficient (within the appropriate threshold)

and redundant (outside the appropriate threshold)

Micronutrient supplementation experiment and leaf analysis data to conclude whether B and Cu are limiting factors for cabbage soil (Table 3.10):

- In the treatment supplemented with B (CT2 and CT6), the B content in cabbage leaves increased significantly Thus, the B supplement formulation increased the B content in leaves from very low levels to levels that were quite consistent with the appropriate threshold for cabbage

- For the elements Cu and Zn, there is no significant difference

in Cu/Zn content between the formulas adding Cu or the treatment adding Zn That means, when supplemented (sprayed directly on the leaves or under the base with large plants), cabbage also does not absorb Cu and Zn

- Thus, it can be confirmed that cabbage soil in Sa Pa and Bac

Ha is deficient in B and this has been identified as one of the TYHCs

for cabbage while Cu deficiency has not yet been clearly demonstrated

Table 3.10 Effect of micro-spray treatments on nutritional content of

cabbage leaves in Sa Pa and Bac Ha

CT5 Zn 4,3 2,8 23 0,6 2,9 3,7 27 0,12 CT6 Zn+B+Mo+Cu 23 2,3 18 7,2 21 3,2 25 3,9

3.2.3 Determination of limiting factors on soil and soil nutrients for cabbage vegetables through determination of nutrient balance at household scale

There is a significant difference in fertilizer use by households

in Sa Pa and Bac Ha (Figures 3.3 and 3.4) The average amount of fertilizer applied by households in Sa Pa tend to be higher than in Bac

Ha, especially phosphate fertilizer Yield and N, P2O5 and K2O contents of cabbage grown in Sa Pa were higher than in Bac Ha Despite the high productivity, households in Sa Pa have low fertilizer efficiency, due to the significant excess of fertilizer over demand and the loss of crops For farmers in Bac Ha, household number 07 has the lowest amount of fertilizer, however, the total yield of fresh biomass

is quite high and the efficiency of fertilizer use is the highest In contrast, for household number 02 in Sa Pa, although the number of nutrients applied to the plants was the highest, the fresh yield and the efficiency of fertilizer use were the lowest (table 3.12) Among the three types of macronutrients, the use of K2O fertilizers is the most effective, especially in Bac Ha, all three households have a K2O utilization coefficient in the range of 74.59-78.63%