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Soil Degradation of Raised-beds on Orchards in the Mekong Delta Field and Laboratory Methods
KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering. An Giang University.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soil degradation is a complex process which may occur anywhere and at any time. It directly affects the physical, chemical and biological processes within the soil profile. Soil degradation can either be as a result of natural hazards or due to manmade actions, such as mismanagement on cropping patterns, soil preparation and cultivation practices. Regardless of how it is caused, soil degradation has strong negative effects on plant and soil productivity. Soil degradation can accelerate a series of processes such as erosion, compaction, loss of organic matter, loss of whole soil biota, surface sealing and contamination. This thesis presents the assessment of soil properties to improve our understanding of soil degradation on raised-bed orchards in the Vietnamese Mekong delta (MD). Measurements were made on 10 citrus plantations which had been established during a range of years from 1970 to 1998 at Hau Giang province. Soil sampling was made in the dry season of 2010 at two soil depths for each raised-bed to determine soil chemical and physical properties. The soil penetration resistance (PR) was periodically measured once a week together with soil sampling for moisture measurements during a period of 5 months. Analysis indicated the pH value of the soil was tending to decrease, nutrient imbalance and deficiency was developing, and the soil structure was deteriorating during the age since the raised-beds were originally constructed. Preventive and restorative measures need to be considered for restoring and retaining the quality of the soil and the ground water. These measures should consist of (1) neutralizing of excess acidity, (2) balancing of nutrients, (3) maintaining of soil organic matter, and (4) application of appropriate irrigation schedules.

Abstract [vi]

Suy thoái đất là một tiến trình phức tạp xuất hiện ở mọi nơi, mọi lúc làm tác động trực tiếpđến các quá trình lý, hóa và sinh học trong phẫu diện đất. Nó có thể là kết quả của các hoạtđộng do tự nhiên hoặc do con người như sử dụng sai hoặc thực hành quản lý đất đai bất hợplý. Cho dù nguyên nhân thế nào chăng nữa, suy thoái đất cũng gây ra các ảnh hưởng bất lợinặng nề lên cây trồng và sức sản suất của đất. Suy thoái đất có thể thúc đẩy hàng loạt cácquá trình như là xói mòn, nén dẽ, mất vật liệu hữu cơ và sinh vật đất, đóng váng bề mặt vàô nhiễm. Luận văn này trình bày sự đánh giá về các đặc tính của đất để mở mang sự hiểubiết về suy thoái đất trên các vườn cây ăn trái ở đồng bằng sông Cửu Long. Thí nghiệmthực hiện trên 10 vườn cam quít với khoảng thời gian thành lập vườn từ 1970 đến 1998 tạitỉnh Hậu Giang. Mẫu đất được lấy vào mùa khô năm 2010 ở hai độ sâu cho mỗi vườn đểphân tích các chỉ tiêu lý hóa đất. Sức kháng xuyên của đất được đo định kỳ mỗi tuần kếthợp với lấy mẫu để xác định ẩm độ đất trong suốt khoảng thời gian 5 tháng. Kết quả phântích cho thấy pH đất có khuynh hướng giảm, sự thiếu và mất cân bằng dinh dưỡng đất ngàycàng lộ rõ, và cấu trúc đất đang xấu đi theo độ tuổi của vườn. Các biện pháp phòng ngừa vàphục hồi cần được quan tâm đối với việc phục hồi và duy trì chất lượng của đất và nướcngầm. Các biện pháp nên bao gồm (1) trung hòa độ chua đất, (2) cân bằng dinh dưỡng, (3)duy trì vật liệu hữu cơ trong đất, và (4) áp dụng chế độ tưới thích hợp.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2013. , xvi, 29 p.
Series
Trita-LWR. PHD, ISSN 1650-8602 ; 1073
Keyword [en]
citrus orchards; nutrient; soil fertility; soil strength; soil degradation; alluvial soil; Mekong delta
National Category
Soil Science
Identifiers
URN: urn:nbn:se:kth:diva-127802ISBN: 978-91-7501-857-7 (print)OAI: oai:DiVA.org:kth-127802DiVA: diva2:645889
Public defence
2013-09-26, Sal V3, Teknikringen 76, 2 tr, KTH, Stockholm, 13:00 (English)
Opponent
Supervisors
Note

QC 20130909

Available from: 2013-09-09 Created: 2013-09-05 Last updated: 2013-09-09Bibliographically approved
List of papers
1. Development and description of soil compaction on orchard soils in the Mekong Delta (Vietnam)
Open this publication in new window or tab >>Development and description of soil compaction on orchard soils in the Mekong Delta (Vietnam)
2008 (English)In: Scientific Research and Essays, ISSN 1992-2248, E-ISSN 1992-2248, Vol. 3, no 10, 500-504 p.Article in journal (Refereed) Published
Abstract [en]

The study conducted in the Vietnamese Mekong Delta (VMD) was to examine soil degradation and soil compaction in fruit tree plantations due to the impact of agricultural activities. The specific objective was to elucidate the impact of soil compaction on current and future production. Fruit trees are one of the most important components for the development of the delta. The plantation areas have increased rapidly over the recent years (from 117,000 ha in 1996 to 300,000 ha by the year 2006). Fruit trees in this region are usually grown on raised beds to avoid submergence due to annual flood. Most of the soils of raised beds are alluvial and perturbed from the natural soils. Studies on the raised beds have recognized trends of soil compaction during ageing of the raised beds. However, there are many uncertainties and consequently a need for further investigations exists, to improve the knowledge and understanding of soil processes in the region.

Keyword
Citrus orchards, soil compaction, soil degradation, Mekong delta
National Category
Environmental Sciences related to Agriculture and Land-use
Identifiers
urn:nbn:se:kth:diva-17928 (URN)000260502500007 ()2-s2.0-70350139688 (Scopus ID)
Note

QC 20100525

Available from: 2010-08-05 Created: 2010-08-05 Last updated: 2017-12-12Bibliographically approved
2. Chemical properties during different development stages of fruit orchards in the mekong delta (Vietnam)
Open this publication in new window or tab >>Chemical properties during different development stages of fruit orchards in the mekong delta (Vietnam)
2011 (English)In: Agricultural Sciences, ISSN 2156-8553, E-ISSN 2156-8561, Vol. 2, no 3, 375-381 p.Article in journal (Refereed) Published
Abstract [en]

This study to examine soil fertility status was conducted on 10 citrus plantations in Hau Giang province within the Vietnamese Mekong Delta, Vietnam. Fruit trees are mostly grown on the raised beds to avoid annual flood with alluvial soil type. Soil sampling was done in the dry season of 2010 at two soil depths, for each raised bed. Development ages of raised beds were represented by two groups, young age group (≤ 30 years) and old age group (> 30 years). For chemical analysis, pH, organic matter, CEC, total nitrogen, NH4+, NO3– and exchangeable Ca, Mg and K were determined. The results showed that the pH (water) was strongly acid. The CEC was in average 19.2 cmol+.kg–1 in topsoil (0 - 20 cm depth) and 18.7 cmol+.kg–1 in subsoil (20 - 50 cm depth) for young age group. Similarly, the CEC was 16.7 cmol+.kg–1 in topsoil and 15.8 cmol+.kg–1 in subsoil for old age group. Organic matter on young age group (7.38 and 5.47% on average for topsoil and subsoil respectively) was significantly higher than that of old age group (5.20 and 3.81% on average for topsoil and subsoil respectively). Total nitrogen was not significantly different between the sites for the age groups of raised as well as the soil layers. Ammonium-N levels were excessive, and NO3--N levels were high. Potassium and Mg2+ were significantly different between age groups of raised beds and the same pattern between soil layers, while Ca2+ did not vary significantly. Potassium and Ca2+ levels were moderate, Mg2+ was high and P levels were very high. Soil fertility in the raised beds subjected to an adverse on plant growth and an imbalance in soil nutrients under low pH conditions. Loss of soil quality was exhibited in reduced organic matter with the aging of raised beds.

Keyword
Citrus Orchards, Soil Properties, Alluvial Soil, Nutrient Balance, Soil Fertility, Mekong Delta, Vietnam
National Category
Environmental Sciences related to Agriculture and Land-use
Identifiers
urn:nbn:se:kth:diva-127817 (URN)10.4236/as.2011.23049 (DOI)
Note

QC 20130906

Available from: 2013-09-06 Created: 2013-09-06 Last updated: 2017-12-06Bibliographically approved
3. Soil physical properties during different development stage of fruit orchards
Open this publication in new window or tab >>Soil physical properties during different development stage of fruit orchards
2012 (English)In: Journal of Soil Science and Environmental Management, ISSN 2141-2391, Vol. 3, no 12, 308-319 p.Article in journal (Refereed) Published
Abstract [en]

In the Mekong Delta (MD), fruit trees are usually grown on raised-beds to avoid submergence due to annual flooding. The soils are mostly alluvial and disarranged from the natural soils. The soil may beadversely impacted temporally, particularly with its physical properties. The study was conducted on 10 citrus plantations in Hau Giang province, MD, to illustrate if the covariance between clay content andage can be separated from the impact of soil ageing on compaction; we further discuss the design of how to make an investigation where only age is the analyzed event that age has a covariance with the spatial scale. Soil sampling was done in the dry season 2010 at two soil depths for each raised-bed toanalyze soil physical properties. Soil texture can be classified as silty-clay soil. The bulk density of topsoils ranged from 0.76 to 1.18 g cm-3 and slightly lower than subsoils; 0.85 to 1.24 g cm-3. Saturated hydraulic conductivity spanned the range from 2.04 to 5.43 m day-1 for topsoils and significantly higher than in subsoils; 1.4 to 5.5 m day-1. Organic matter was in the range of 4.4 to 12.2% for topsoils and significantly higher than in subsoils; 3.0 to 9.6%. A significant tendency of soil degradation with aging was found. Clay content showed a covariance with age of raised-beds counteracting the compaction processes. The high clay content for the aged raised-bed may have been hiding some of the compaction process. The relation between age and soil degradation was seen for the larger pore sizes within the water retention curve.

Keyword
Soil physical properties, soil texture, soil compacti on, Mekong delta
National Category
Environmental Sciences related to Agriculture and Land-use
Identifiers
urn:nbn:se:kth:diva-127818 (URN)
Note

QC 20130906

Available from: 2013-09-06 Created: 2013-09-06 Last updated: 2017-04-28Bibliographically approved
4. Soil Penetration Resistance and Its Dependence on Soil Moisture and Age of the Raised-Beds in the Mekong Delta, Vietnam
Open this publication in new window or tab >>Soil Penetration Resistance and Its Dependence on Soil Moisture and Age of the Raised-Beds in the Mekong Delta, Vietnam
2012 (English)In: International Journal of Engineering Research and Development, ISSN 2278-067X, Vol. 4, no 8, 87-96 p.Article in journal (Refereed) Published
Abstract [en]

The research was conducted on 10 citrus plantations at Hau Giang province in the Mekong delta, Vietnam during one year with a portable electronic penetrometerto understand the impact of moisture on the soil compaction. Soil penetration resistance (PR) was measured in the depth of 0-80 cm depth and soil samples also taken at each 10 cm depth from the soil surface to the water level for soil moisture measurement. The results showed that PR increased as a function ofraised-bed’s age and it could be reached to a high degree by soil moisture variability during the season. The sensitivity of PR to soil moisture decreases with the age of raised-beds while the soil moisture represented an increasing tendency with the age of raised-beds. Relationship between PR and soil moisture are explained betterby the volumetric water content than the corresponding soil water potential expressed as pF values. The measurements of soil PR determined by the previous results, which are obtained from soil, core samples with the dry bulk density and water retention curves were calculated and analyzed. Using the PR data will be very useful; it is a complementary and important information for identification the soil structure and soil moisture content. Without such processing of PR measurements, the values of the PR measurements will be limited and not indicated for soil compaction. To minify soil compaction on the raised-beds, all the pressure and mechanical activities should not be done in the soil surface, specially in the wet condition. Organic fertilizers and Biocharcan be considered as soil conditioners and recommended to applied in orchard for improving soil properties.

Keyword
Citrus orchard, soil strength, soil compaction, Mekong delta
National Category
Environmental Sciences related to Agriculture and Land-use
Identifiers
urn:nbn:se:kth:diva-127829 (URN)
Note

QC 20130909

Available from: 2013-09-09 Created: 2013-09-09 Last updated: 2013-09-09Bibliographically approved

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