Land Improvement Research Articles

Comprehensive assessment of land degradation in the arid and semiarid area based on the optimal land degradation index model

Paying attention to land degradation in drylands is of international significance because it plays a crucial role in global food production. This study developed the optimal land degradation index (OLDI) model for arid and semiarid areas. The model utilized a system that assessed soil condition, climate response, human disturbance, and vegetation growth. It was based on a constrained optimization algorithm. Based on the analysis of the distribution pattern of the OLDI in the Hexi Corridor, this study aims to explore the spatial and temporal characteristics of land degradation and the variations in land sensitivity to degradation across different seasons through trend analysis. Furthermore, the main variables that control the environment and are responsible for land degradation or improvement were revealed through the analysis of driving factors. It was found that the oasis areas in the southern part of the Hexi Corridor experienced land improvement due to the combined influence of human activities and climate change, while the northern region underwent continuous land degradation. However, overall, the majority of the study area's land remained stable. The reduction in precipitation and the increase in wind speed were identified as the primary driving forces behind land degradation. Different vegetation types exhibited distinct responses to environmental control factors, and these responses varied significantly with the changing seasons. Based on the regional variations in land degradation and the observed sensitivity characteristics during different seasons, this study proposes a land management strategy that combines natural recovery with artificial restoration to achieve effective prevention, control, and management of land degradation. This study provided an effective tool for monitoring land degradation in arid and semiarid areas, which is of significant importance for land resource management and the sustainable development of the green economy, not only in the northwest region of China but also in arid and semiarid areas worldwide.

Analysis of Land Engineering Strategies for Urban Land Ecological Renovation

With the acceleration of urban ecological civilization construction, the demand for ecological land in urban construction is increasing day by day. Currently, land improvement projects often aim to minimize project costs and maximize land use, neglecting the ecological carrying capacity of the site. In the construction of urban ecological space land improvement projects in China, there are phenomena such as excessive emphasis on aesthetics and visual effects, blind introduction of foreign species, unreasonable plant configuration, and large-scale use of lawns, which have also caused many problems in the construction of urban ecological civilization. Land is the foundation of urban construction and sustainable development, and making land clean, healthy, and safe is a prerequisite for the construction of ecological cities. Government departments need to use ecological concepts as work guidance to continuously improve the effectiveness of land resource remediation and maximize the efficiency of land use. Land engineering technology plays an important role in the ecological remediation of urban land. We need to keep up with the pace of development of the times, apply various advanced technologies, and effectively address various problems, in order to achieve better results. This article conducts research on land ecological remediation and proposes optimization strategies for land ecological remediation.

Effect of filling materials on reconstructed soil phosphorus adsorption and desorption in mining area

Utilization of alternative soil substrates for minesoil reconstruction can affect the nutrient status of reclaimed minesoil (RMS), particularly the availability of phosphorus. This study investigated the adsorption and desorption capacities of phosphorus in three typical reclamation lands using coal gangue (CGR), lake mud (LMR), and Yellow River sand (YSR) as filling materials. The results showed that (i) the phosphorus adsorption capacity of all RMS samples was lower than that of the normal cultivated soil (NCS), the YSR was lower than the CGR and LMR in phosphorus adsorption capacities, while the YSR had better phosphorus desorption capacity than the CGR and LMR. (ii) The specific surface area, pore size, soil texture, mineral composition, functional group composition, and iron/aluminum element content of RMS were varied after the filling of alternative soil substrates, and (iii) the surface characteristics played a vital role in driving the phosphorus adsorption-desorption, while soil texture, and organic matter drove the phosphorus desorption behavior via non-linear ways. This study reveals the difference of phosphorus adsorption-desorption in RMS, and provides a theoretical basis for the rational utilization of alternative soil substrates and the improvement of reclamation land in coal mining subsidence areas.

Intercropping of Echinochloa frumentacea with Leguminous Forages Improves Hay Yields, Arbuscular Mycorrhizal Fungi Diversity, and Soil Enzyme Activities in Saline–Alkali Soil

Soil salinization is detrimental to crop growth, agricultural yields, and environmental protection. Echinochloa frumentacea (Roxb.) Link is a pioneer species for the alteration of saline–alkali lands. In this paper, we examined the effects of intercropping between E. frumentacea and leguminous forages on saline land improvement in the saline–alkali soil of the Hetao-Ningxia Plain, China. We found that intercropping increased the diversity and richness of the arbuscular mycorrhizal fungi (AMF) community in the rhizosphere soil of E. frumentacea. Glomus was the dominant genus in the saline–alkali soil of the Hetao-Ningxia Plain, where Glomeraceae, VTX00067, VTX000193, and VTX000165 were the dominant species. Intercropping improved the activities of soil urease, sucrase, alkaline phosphatase, and catalase. The hay yields of E. frumentacea were correlated positively with soil enzyme activities, Chao1 index, and ACE index, and negatively with total water-soluble salt content. Together, intercropping between E. frumentacea and leguminous forages enhances AMF diversity and soil enzyme activities, which provides an agricultural practice for improving sustainability of the agro-ecosystem in saline–alkali areas.

Physiological and transcriptomic analysis of salt tolerant Glaux maritima grown under high saline condition.

Land salinization considerably limits crop production. Biological improvement of saline and alkaline land is an important way to achieve efficient land use. It is crucial to study the salt tolerance of halophyte resources in order to explore and improve plant resources through biological improvement. Glaux maritima is a mesophyte halophyte with strong salt tolerance. In this study, we conducted research on the salt tolerance mechanism of G. maritima through phenotypic, physiological, and transcriptomic aspects. The results indicate that leaf cross-sections revealed that G. maritima has a salt gland tissue composed of stalk, collecting, and secretory cells, which are trapped in epidermal cells. At the physiological level, the maximum salt tolerance threshold of G. maritima leaves was 600 mM/L. At this concentration, proline content, relative conductivity, and superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) enzyme activities were maximum. At the transcriptional level, transcriptome data of three experimental groups (N0: 0 mM/L, N3: 600 mM/L, and N4: 800 mM/L) were analyzed, and six essential genes related to proline synthesis and five essential genes related to SOD and CAT enzyme activities were identified. Two genes involved in CAT enzyme activity were also found to play an important role in the MAPK signaling pathway. Trend analysis revealed that the MAPK signaling regulation (37 differentially expressed genes (DEGs)), phytohormone regulation (48 DEGs), glutathione metabolism (8 DEGs), flavonoid and flavonoid biosynthesis (2DEGs), and flavonoid biosynthesis (24 DEGs) pathways played important roles in regulating the salt tolerance of G. maritima. These findings provide valuable information for further studies on the functional characteristics of G. maritima in response to abiotic stress and may contribute to salt resistance breeding of fodder crops for cultivation in saline alkali land.

Vermicompost Combined with Soil Conditioner Improves the Ecosystem Multifunctionality in Saline-Alkali Land

Addressing the challenges posed by Saline-Alkali land holds significant promise for optimizing agricultural resources and fostering sustainable agricultural development in affected areas. This study explores the efficacy of coal-based solid waste soil conditioner and vermicompost as mixed-component soil amendments in varying proportions. Through comprehensive field experiments, we investigate the impact of these amendments on soil physicochemical properties, microbial diversity, and the growth of L. chinensis, a grass species native to saline areas. Our findings reveal that the application of vermicompost-based soil amendments effectively reduced soil conductivity and led to noteworthy improvements in the pH of Saline-Alkali soil. Moreover, these amendments demonstrated a marked capacity to enhance soil organic matter and available nutrients, most notably available phosphorus. Concurrently, the introduced soil amendments exhibited a positive influence on soil microbial diversity. A correlation analysis underscores the pivotal roles of soil pH and organic matter in shifting soil microbial communities. In response to amendments, L. chinensis exhibited varying degrees of growth enhancement, with biomass increments ranging from 6.37% to 19.91%. In summary, vermicompost and soil conditioner can improve Saline-Alkali land by supplementing organic matter and effective nutrients, improving pH and conductivity, and regulating microbial community, so as to realize the restoration and improvement of Saline-Alkali land; the greatest improvement was achieved with soil conditioner and vermicompost application rates of 30,000 kg·ha−1 and 15,000 kg·ha−1, respectively. Our results provide robust support for advocating for the integration of vermicompost-based soil amendments in Saline-Alkali land management strategies.

How do China's villages self‐organize collective land use under the background of rural revitalization? A multi‐case study in Zhejiang, Fujian and Guizhou provinces

AbstractAs land is one of the most important production factors in rural areas, it is becoming an important challenge for rural revitalization strategy to realize land value and promote the socioeconomic development of villages through the collective action of self‐organized collective land use. Various studies have discussed the relationships among land governance, rural revitalization and self‐organization, but few studies have focused on village cadres' roles and village rules. This paper aims to establish an analytical framework to explore these two operating mechanisms of self‐organization in collective land use. Two villages in eastern China and one village in western China are selected as typical cases to demonstrate how collective land use is self‐organized by village cadres' roles and village rules. The results indicate that village cadres play roles in the entrepreneurial spirit and resource access capacity to promote village economic and social development. In the utilization of collective land for farmers to live in peace and work happily, the configuration of rules at the village level to regulate the behaviour of villagers is a qualification on demand and “see who can take part”, cost sharing and benefit sharing, graduated sanction and supervision. The analysis in this article may provide an understanding of the mechanism driving the promotion and improvement of land self‐organization, which has important policy implications for China and other developing countries adopting this mode to promote regional economic development in rural areas.

Analysis and Evaluation of the Benefits of Rural Land Remediation Planning in China

Compared with land improvement performance evaluation and post evaluation, the essence of the former is to conduct predictive analysis and evaluation of events that have not occurred, while the latter can directly use indicator data that has occurred for analysis. This article conducts corresponding benefit analysis and evaluation of comprehensive land consolidation work through qualitative and quantitative evaluation, closely focusing on the goals and tasks of national land consolidation planning and provincial land use overall planning, and coordinating and arranging projects such as land consolidation, reclamation and development, and urban-rural construction land increase and decrease linkage. By utilizing urban land consolidation models such as old city renovation, we aim to improve the efficiency of urban land use and increase the effective area of urban construction land. In accordance with the requirements of the new rural construction, efforts will be made to strengthen land consolidation, concentrate on promoting land leveling and the construction of farmland water conservancy, field roads, and field protective forests, and effectively promote the scale and industrialization of agriculture; Efforts will be made to promote village renovation and form a new rural pattern with relatively concentrated housing and beautiful environment.

Assessing the intensity of reduction and restoration of irrigated lands’ state in the Republic of Bashkortostan

AbstractBackgroundIrrigation of lands over time leads to such negative processes as land salinization and waterlogging, reduction of soil fertility, changes in the chemical composition of groundwater, and the emergence of linear and irrigation erosion. The land improvement (ameliorative) categories adopted in Russia and several post‐Soviet countries determine their suitability for agricultural use and the focus of measures to preserve potential soil fertility.AimsThe study aims to build a mathematical model to assess the intensity of the reduction and restoration of irrigated lands’ state in the Republic of Bashkortostan.MethodsThe methods of the theory of random processes are proposed to estimate the intensity of reduction and restoration of irrigated lands’ state on the territory of the Republic.ResultsAs a result of the calculations, the values of intensities characterizing changes in the state of land in the region were obtained. The practical significance of the developed model consists of the possibility of short‐term forecasting and determination of the necessary intensity of land quality restoration taking into account planned values during the given period.ConclusionsThe offered indicator of intensity and the method of its definition can be used in research of similar processes proceeding on agricultural lands within the limits of large spatial units.

Spatiotemporal evolution law and driving mechanism of production–living–ecological space from 2000 to 2020 in Xinjiang, China

Xinjiang is located in the northwest of China, with a vast territory and abundant resources, which holds an important strategic position for China. However, the climate in the region is arid and the ecological environment is fragile. In recent years, with the growth of population and the improvement of economic development level, construction and agricultural land in Xinjiang have gradually expanded, and ecological land has been extensively occupied. The competition between land resources is becoming increasingly fierce, leading to some ecological and environmental problems in the region. In this context, understanding the spatiotemporal changes and driving factors of Xinjiang's production space, living space and ecological space (PLES) is of great practical significance for promoting sustainable development in the region, and can also provide reference for the research of PLES in other arid areas at home and abroad. At present, most of the research on PLES is focused on small-scale areas such as urban agglomerations, rural areas, and watersheds, or non arid areas with relatively superior natural conditions, with less research on large-scale arid areas. In this study, the transfer matrix, the center of gravity movement trajectory, Moran's I and the spatial conflict measurement model were used to illustrate the spatial–temporal evolution of PLES in Xinjiang, and the correlation coefficient was used to determine the main factors affecting the change of PLES. Results show that (1) Xinjiang is dominated by ecological space, which accounts for more than 90% of the total area of Xinjiang and has significant continuity. They are mainly distributed in Tarim, Turpan, and the northern Junggar Basin. The production space area accounts for about 5% of the total area of Xinjiang and is distributed in the vicinity of the Tianshan and Kunlun Mountains. Living space accounts for about 1% of Xinjiang's total area and is scattered around cities. (2) From 2000 to 2020, the change degree of PLES in Xinjiang in the last decade is higher than that in the first decade, most of which is the transformation from ecological space to production space. The three types of spaces influence and restrict each other in the development process. (3) Population, crop sown area, natural conditions, policy and the development level of agricultural science and technology are the main factors affecting the spatial distribution of production. Environmental factors such as altitude, soil erosion and temperature have a great influence on ecological space. Population, the output value of various industries and total retail sales of consumer goods are the main factors affecting residential space. The evolution of Xinjiang PLES is the result of multiple factors. (4) The medium spatial conflict dominates, mainly distributed in Tarim Basin and Junggar Basin. The weak and strong space conflicts are concentrated in the oases in the north of the Tianshan and Kunlun Mountains, and the number is small. From 2000 to 2020, the increasing degree of spatial conflicts in Xinjiang is due to land desertification.

Application Effect of Straw Returning and Biochar in the Improvement of Saline-Alkali Land in Northeast China

Application Effect of Straw Returning and Biochar in the Improvement of Saline-Alkali Land in Northeast China

Effects of N and P addition on nutrient and stoichiometry of rhizosphere and non-rhizosphere soils of alfalfa in alkaline soil

Nitrogen (N) and phosphorus (P) are important nutrients for plant growth and development. Soil alkalization is one of the main obstacles limiting the sustainable development of agriculture. Northern Ningxia is located in the arid and semi-arid region, with serious soil alkalinization. Alfalfa has the advantages of strong saline-alkali tolerance, high yield, high quality, and wide adaptability. It is an important forage for the comprehensive improvement and rational utilization of saline-alkali land and has great significance for solving land resource shortages, improving the ecological environment, and ensuring food security. It is important to study soil organic carbon (SOC), total N (TN), total P (TP), and stoichiometry of the rhizosphere and non-rhizosphere of alfalfa in alkaline soils. Therefore, N and P were added to the alkaline alfalfa field in the Yinchuan Plain of Hetao Basin in our experiment. Six treatments were set up, i.e., N-free (WN), medium N (MN) for 90 kg/hm2, high N (HN) for 180 kg/hm2, P-free (WP), medium P (MP) for 135 kg/hm2, and high P (HP) for 270 kg/hm2. The results are as follows: The N addition promotes SOC and TN but inhibits TP, and P addition promotes SOC and TP but inhibits TN of three soil layers. The N addition decreases C/N but increases C/P and N/P, while the P addition increases C/N but decreases C/P and N/P of three soil layers. The SOC, TN, TP, C/N, C/P, and N/P under HN and HP treatment reach the significance level (P < 0.05). Appropriate additions of N and P can improve rhizosphere and non-rhizosphere nutrients and stoichiometric structure, facilitating absorption and utilization by alfalfa and improve the production potential of alfalfa in alkaline soil.

PEMANFAATAN TEKNOLOGI PEMBUATAN POC GUNA MENAMBAH KETERAMPILAN DAN PENGHASILAN TAMBAHAN RUMAH TANGGA DI DESA UTEUNKOT LHOKSEUMAWE

Realizing a commitment to food security is closely related to social security, economic stability, political stability and national security or resilience. Continuous improvement of fertile land through the use of liquid organic fertilizers is expected to maintain the quality of soil nutrients which in turn will improve the quality of agriculture and the productivity of food crops. Based on observations in the field, the people of Uteunkot Village, Lhokseumawe City, had not managed waste properly, organic and inorganic waste had not been separated from one another, and waste was often thrown away without proper handling, causing foul odor that disturbs the environment. To overcome this problem, a solution was needed, namely utilizing organic waste as liquid organic fertilizer which is useful for the community in fertilizing plants in the yard of the house. This community service was held from July to September 2022 in Uteunkot Village, Lhokseumawe City. The purpose of this service activity was to find out the impact of counseling on the community regarding the manufacture and use of liquid organic fertilizer. The results of the community service activities showed the compatibility between the implementation and the guidelines for making liquid organic fertilizer from household organic waste, as well as increasing the knowledge of farmer groups in Uteunkot Village, Lhokseumawe City.

The soft rock can promote the improvement of aeolian sandy soil in Mu Us Sandy Land, China

This study focuses on the significance of improving the land degradation of Mu Us Sandy Land to increase cultivated land area and promote ecological green development. The research objects were four kinds of mixed soils, and rhizosphere soils were collected during the crop harvesting period. The volume ratio of soft rock to sand was 0:1 (control check, CK), 1:5 (composite soil one, PS1), 1:2 (composite soil two, PS2), and 1:1 (composite soil three, PS3). The results showed that the large aggregates were primarily mechanically stable aggregates, while the small aggregates were mainly water-stable aggregates. The soft rock promoted the increase of clay and silt content in sandy soil, and the soil texture changed from sand to loam. The contents of organic matter, available phosphorus, and available potassium increased significantly under PS2 and PS3 treatments, but there was no significant difference between them. Total nitrogen had no significant difference among treatments. Actinobaciota, Proteobateria, and Chloroflexi were the dominant bacteria in rhizosphere soil, accounting for about 75% of all microorganisms. At the Genus level, the soft rock contributes to richer species composition. The diversity index, evenness index, and richness index was higher in PS1, and the available phosphorus and available potassium content promoted the increase of diversity. Therefore, when the proportion of soft rock and sand compound soil is between 1: 5 and 1: 2, it can be used as an important basis and technical parameter for Mu Us Sandy Land improvement.

Development of a BIM-Enabled Automated Cost Segregation System

The cost segregation study is a tax planning strategy employed to optimize cash flow by redefining real estate assets as personal property and land improvement, enabling accelerated tax depreciation. However, conventional cost segregation practices suffer from limitations, such as time-consuming procedures and high associated costs, which hinder their effectiveness. To overcome these challenges, this paper presents an innovative strategy that integrates Building Information Modelling (BIM) to develop an automated cost segregation system. The research aims to optimize the workflow by developing a BIM model and using 5D BIM to perform a cost segregation study by categorizing building elements under a Modified Accelerated Cost Recovery System (MACRS). This workflow aims at minimizing the time and financial resources expended with traditional methodologies. The proposed workflow enables precise identification and separate depreciation of building components, resulting in significant tax deductions that would otherwise be unattainable. The results indicate that performing cost segregation with BIM leads to a significant increase in depreciation amounts, particularly during the initial six years, while also raising the net present value of depreciation by 45%. The integration of BIM technology facilitates effective management and sharing of cost segregation data among stakeholders, enhancing collaboration and decision-making throughout the project lifecycle. Owners can optimize cost management and financial planning, identifying tax-saving opportunities and improving cash flow. General Contractors (GCs) can leverage the system during the bidding process, enhancing their competitiveness and project acquisition potential. Future research can explore the integration of cost segregation modules from BIM with asset management tools, enabling improved facility and fiscal management of building components. Such integration holds promise for enhancing the construction and real estate industry’s overall efficiency and performance.

The reclamation of the surface layer of mining landscapes of Kryvyi Rih landscape technical system

Purpose. To investigate the reclamation of the surface layer of mining landscapes of Kryvyi Rih landscape technical system on the example of Shymaniv and Hanniv dumps. Methods. Historical analysis, comparative, cartographic, method of anthropogenic landscape forecasting. Results. It has been determined that Shymaniv dump was created by the Southern Mining and Processing Plant in 1960–1967, belongs to mixed dumps, was formed by automobile tailings resulted into tiers with a leveled and plateau-like surface. The dump in the geological structure has a lower accumulative microstrip, which consists of crystalline rocks that are not involved into development, limestones, loess-like loams; the middle accumulative – denudation microstrip, which is characterized by crushed stone, sand, stone blocks and the upper denudation microstrip, which is represented by blocks and granites. The dump reclaimed and has favorable conditions for the germination of vegetation. By example of the Hanniv dump the possibility of rational use of the surface layer of mining landscapes was considered. The Hanniv dump is a mixed dump with its height of 90 m, partially reclaimed. A gradual biological reclamation technology is proposed for the rapid adaptation of plants to unusual terrain and the improvement of disturbed lands. Maps and technology of biological reclamation have been developed, which reflect the surface layer of mining landscapes of Kryvyi Rih landscape technical system. Conclusions. The reclamation of the surface layer of mining landscapes of Kryvyi Rih landscape technical system exists and needs a detailed study in order to prevent the degradation of disturbed lands due to the action of the mining industry. On the example of Shymaniv and Hanniv dumps the reclamation of the surface layer of mining landscapes has been investigated, the history of the dumps has been determined, the geological - geomorphological, hydrological, climatic, soil - biotic processes that influenced the favorable formation of the reclamation of the surface layer of the dumps have been substantiated, and a gradual biological reclamation technology has been proposed on the example of Hanniv dump.

Comprehensive insights into the application strategy of kitchen waste derived hydrochar: Random forest-based modelling

Due to the complex and variable composition of kitchen waste (KW), it is difficult to master the product properties after hydrothermal carbonization treatment. In this study, random forest method was adopted to firstly predict the application performance of hydrochar from the perspectives of fuel, soil amendment and adsorbent. A total of 9 correlation models were established, with organic components and reaction parameters taken as input variables. The training set was supported by 132 literature data and 153 experimental data, with 18 experimental data as testing set. Results showed that the correlation coefficients of 9 models were up to 0.89–0.99. The relative significance of input variables was also acquired by mean decrease impurity method. It was found that the effects of reaction temperature/time on hydrochar properties were relatively negligible. Thus, hydrochar properties can be generally predicted based on the composition of KW feedstocks. The high heating value of hydrochar was mainly in the range of 20–30 MJ/kg, which was comparable to that of coal. To obtain hydrochar with good fuel performance, KW with high lipid (>50%) and low carbohydrate (<25%) is suitable. The pH value and cation exchange capacity of hydrochar was 3.23–5.69 and 1.08–42.37 cmol+/kg, respectively, which can be used for the improvement of saline-alkali land. KW of high protein (>35%), high lipid (>25%) and low carbohydrate (<35%) was potential to be converted into excellent adsorbents with specific surface area over 2000 m2/g.

Current situation of "non-grain production" of cultivated land in China and the research progress of re-tillage and fertilization technology.

In recent years, the influx of business capital to rural areas, land transfer and adjustment in planting structure have led to the widespread of "non-grain production" of cultivated land in China, which threatens the "1.8 billion mu of arable land protection red line" as well as national food security. Both tillage layer stripped and unstripped are examples of "non-grain production" of cultivated land, which are detrimental to long-term food security because they might reduce soil fertility to varied degrees. In the former case, the original topsoil has been destroyed and the tillage layer is gone. In the latter, there may be impediments such as acidification and salinization. Domestic and international scholars have conducted extensive research on the improvement of degraded soils, including measures with guest soil and soil replacement, the reduction of soil barrier factors, biological fertilization and other measures. There are no systematic research results on the remediation of "non-grain production" of cultivated land. Using data from the National Statistical Yearbook data and literature analysis, we systematically summarized current status of "non-grain production" of cultivated land and key technologies for land improvement, recultivation and fertilization in China, and put forward future directions in this area.

A practice study of land and water comprehensive remediation in urban-rural fringe-with Sichuan River Shaanxi Province, Northwest China, as an example.

Urban-rural fringe area (URFa) is an active and expansive region, and its environment is complex and frangible. Previous studies have focused on the landscape spatial pattern changes, the spatial-temporal variability of soil pollutants and the land management and policy issues, etc., but it is lack of the practice study of land and water comprehensive remediation in URFa. This article is taking the Sichuan River, a typical URFa, as an example. Based on field investigation and lab tests, the main characteristic form of the URFa and land and water comprehensive remediation measures are summarized in this paper. The results show that it is feasible to turn wasteland, low-efficiency land, and old deserted beach into farm land, residential land, and ecological land by comprehensive land improvement. For the farm land reconstruction, the texture is an important indicator. The content of soil organic matter (SOM), carbon, nitrogen, and phosphorus has increased after remediation. For the SOM, 58.3% are more than 10.0g·kg-1, and 79.2% are more than 8.0g·kg-1. For the frequent dry-off and polluted low flow river channels in URFa, the river bottom consolidation and water purification is the important measures. The water quality meets IV standard of the "Environmental Quality Standards for Surface Water" (GB3838-2002) (State EPA of China, 2002) by pollution treatment after remediation, and water volume keeps balance. The findings of this study are expected to provide support for better construction practices in arid and semiarid area in China and for the improvement of the ecological environment in URFa.

Comparison of yield prediction models and estimation of the relative importance of main agronomic traits affecting rice yield formation in saline-sodic paddy fields

Saline-sodic soils are widely distributed in the western Songnen Plain of Northeast China, and soil salinization has increasingly become an obstacle to local economic development and ecological security. The practice has proved that rice (Oryza sativa L.) cultivation is one of the most effective methods for the biological improvement and utilization of such land. However, the key limiting factors of rice yield are unclear because of lacking an effective method to quantitatively assess the relative importance of rice agronomic traits to yield formation, resulting in low rice yield in saline-sodic soils. In this study, the random forest model (RF) and the structural equation model (SEM) were conducted to quantitatively assess the relative importance of the rice agronomic traits to yield and the interrelationships and influence modes of rice yield components to yield, respectively. We also compared the prediction performance of different models using two-year data based on important agronomic traits and predicted yield-increasing potential in saline-sodic paddy fields. The results showed that the aboveground biomass and the straw weight were the most important explanatory variable for rice yield per hill, with the explained variation of 32.4 % and 19.4 %, respectively. The plant numbers per m2 and plant height were the most important explanatory variable for rice yield per m2, with the explained variation of 32.5 % and 20.6 %, respectively. Rice yield was directly affected by panicle numbers and panicle weight (decided by the spikelet number per panicle), and the yield-increasing potential of panicle numbers was greater than panicle weight. The random forest model (RF) performed much better than the traditional model (TR) and the multiple linear regression model (MLR) based on agronomic traits to predict yield in saline-sodic paddy fields, which showed a higher R2 and lower error indices (MAE and RMSE). The RF also predicted that rice yield can increase by 9.4 % if plant numbers per m2 increase by 18.4 % (when seedling number per hill reached the level of no salt-affected paddy fields) in saline-sodic paddy fields, and tillering capacity per hill plays a vital role in this process. Therefore, RF may be the preferred method for predicting rice yield based on agronomic traits in saline-sodic paddy fields. Rice cultivation in saline-sodic soils should pay attention to the regulation of dry matter accumulation and tillering capacity of rice during vegetative growth for ensuring sufficient panicle number in reproductive growth period to achieve the purpose of increasing yield.