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Article  |  2021-11-30

Preparation and Characterization of High-Strength Geopolymer Based on BH-1 Lunar Soil Simulant with Low Alkali Content

The construction of a lunar base and habitation on the Moon has always been on researchers’ minds. Building materials used in in situ lunar resources are of great significance for saving expensive space freight. In this study, a new type of lunar soil simulant named Beihang (BH)-1 was developed. The chemical mineral composition and microstructure of BH-1 closely resemble those of real lunar soil, as verified by X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and reflectance spectra. This research also synthesized a geopolymer based on BH-1 cured at simulated lunar atmospheric conditions. We also investigated the effect of supplementing aluminum (Al) sources on the enhancement of geopolymer strength based on BH-1. The rheological behavior of alkali-activated BH-1 pastes was determined for workability. XRF, XRD, Fourier transform infrared spectroscopy, SEM coupled with energy dispersive spectroscopy, and 27Al magic angle spinning-nuclear magnetic resonance were used to characterize resulting geopolymers. Rheological test findings showed that the rheology of BH-1 pastes fits the Herschel–Bulkley model, and they behaved like a shear-thinning fluid. The results showed that the 28-day compressive strength of the BH-1 geopolymer was improved by up to 100.8%. Meanwhile, the weight of additives required to produce per unit strength decreased, significantly reducing the mass of materials transported from the Earth for the construction of lunar infrastructure and saving space transportation costs. Microscopic analyses showed that the mechanism to improve the mechanical properties of the BH-1 geopolymer by adding an additional Al source enhances the replacement of silicon atoms by Al atoms in the silicon–oxygen group and generates a more complete and dense amorphous gel structure.

Siqi Zhou ,   Chenghong Lu   et al.

Article  |  2021-11-30

Mars Helicopter Exceeds Expectations

Mitch Leslie  

Article  |  2021-12-03

DESIGNING DIVERSIFIED CROPPING SYSTEMS IN CHINA: THEORY, APPROACHES AND IMPLEMENTATION

Intensive agriculture in China over recent decades has successfully realized food security but at the expense of negative environmental impacts. Achieving green transformation of agriculture in China requires fundamental restructuring of cropping systems. This paper presents a theoretical framework of theory, approaches and implementation of crop diversification schemes in China. Initially, crop diversification schemes require identifying multiple objectives by simultaneously considering natural resources, limiting factors/constraints, and social and economic demands of different stakeholders. Then, it is necessary to optimize existing and/or design novel cropping systems based upon farming practices and ecological principles, and to strengthen targeted ecosystem services to achieve the identified objectives. Next, the resulting diversified cropping systems need to be evaluated and examined by employing experimental and modeling approaches. Finally, a strategic plan, as presented in this paper, is needed for implementing an optimized crop diversification in China based upon regional characteristics with the concurrent objectives of safe, nutritious food production and environmental protection. The North China Plain is used as an example to illustrate the strategic plan to optimize and design diversified cropping systems. The implementation of crop diversification in China will set an example for other countries undergoing agricultural transition, and contribute to global sustainable development.

 

 

Article  |  2021-12-03

CROP DIVERSITY AND SUSTAINABLE AGRICULTURE: MECHANISMS, DESIGNS AND APPLICATIONS

Intensive monoculture agriculture has contributed greatly to global food supply over many decades, but the excessive use of agricultural chemicals (fertilizers, herbicides and pesticides) and intensive cultivation systems has resulted in negative side effects, such as soil erosion, soil degradation, and non-point source pollution[1]. To many observers, agriculture looms as a major global threat to nature conservation and biodiversity. As noted in the Global Biodiversity Outlook 4[2], the drivers associated with food systems and agriculture account for around 70% and 50% of the projected losses by 2050 of terrestrial and freshwater biodiversity, respectively[3].

In addition, agricultural development and modernization of agriculture has led to a decline in the total number of plant species upon which humans depend for food[4]. Currently, fewer than 200 of some 6000 plant species grown for food contribute substantially to global food output, and only nine species account for 67% of total crop production[3]. The global crop diversity has declined in past decades.

Crop species diversity at a national scale was identified as one of the most important factors that stabilize grain production at a national level[5]. A group of long-term field experiments demonstrated that crop diversity also stabilizes temporal grain productivity at field level[6]. Therefore, maintaining crop diversity at both national and field levels is of considerable importance for food security at national and global scales.

Crop diversity includes temporal (crop rotation) and spatial diversity (e.g., intercropping, agroforestry, cultivar mixtures and cover crops) at field scale. Compared to intensive monocultures, diversified cropping systems provide additional options to support multiple ecosystem functions. For instance, crop diversity may increase above- and belowground biodiversity, improve yield stability, reduce pest and disease damage, reduce uses of chemicals, increase the efficiency of the use land, light water and nutrient resources, and enhance stress resilience in agricultural systems.

To highlight advances in research and use of crop diversity, from developing and developed countries, we have prepared this special issue on “Crop Diversity and Sustainable Agriculture” for Frontiers of Agricultural Sciences and Engineering, mainly focusing on intercropping.

Intercropping, growing at least two crops at the same time as a mixture, for example, in alternate rows or strips, is one effective pathway for increasing crop diversity at the field scale. Over recent decades, there have been substantial advances in terms of understanding of processes between intercropped species and applications in practice. There are 10 articles in this special issue including letters, opinions, review and research articles with contributions from Belgium, China, Denmark, France, Germany, Greece, Italy, the Netherlands, Spain, Switzerlands, UK, and Mexico etc.

The contributors are internationally-active scientists and agronomists contributing to intercropping research and extension. For example, Antoine Messean is coordinator of the EU H2020 Research project DiverIMPACTS “Diversification through rotation, intercropping, multiple cropping, promoted with actors and value chains towards sustainability”. Eric Justes is coordinator of the EU H2020 Research project ReMIX “Redesigning European cropping systems based on species mixtures”. Maria Finckh has worked on crop cultivar mixture and organic agriculture over many years. Henrik Hauggaard-Nielsen has outstanding expertise in intercropping research and applications, moving from detailed studies on species interactions in intercropping to working with farmers and other stakeholders to make intercropping work in practical farming. In addition to these established scientists, young scientists who have taken an interest in intercropping also contribute to the special issue, including Wen-Feng Cong, Yixiang Liu, Qi Wang, Hao Yang and others.

The first contribution to this special issue addresses how to design cropping systems to reach crop diversification, with Wen-Feng Cong and coworkers ( https://doi.org/10.15302/J-FASE-2021392) considering that it is necessary to optimize existing and/or design novel cropping systems based on farming practices and ecological principles, and to strengthen targeted ecosystem services to achieve identified objectives. In addition, the design should consider regional characteristics with the concurrent objectives of safe, nutritious food production and environmental protection.

The benefits of crop diversification have been demonstrated in many studies. Wen-Feng Cong and coworkers describe the benefits of crop diversification at three scales: field, farm, and landscape. Hao Yang and coauthors reviewed the multiple functions of intercropping. Intercropping enhances crop productivity and its stability, it promotes efficient use of resources and saves mineral fertilizer, controls pests and diseases of crops and reduces the use of pesticides. It mitigates climate change by sequestering carbon in soil, reduces non-point source pollution, and increases above- and belowground biodiversity of other taxa at field scale ( https://doi.org/10.15302/J-FASE-2021398).

Eric Justes and coworkers proposed the “4C” framework to help understand the role of species interactions in intercropping ( https://doi.org/10.15302/J-FASE-2021414). The four components are competition, complementary, cooperation (facilitation) and compensation, which work often simultaneously in intercropping. Hao Yang and coworkers used the concept of diversity effect from ecology to understand the contribution of complementarity and selection effects to enhanced productivity in intercropping. The complementarity effect consists of interspecific facilitation and niche differentiation between crop species, whereas the selection effect is mainly derived from competitive processes between species such that one species dominates the other ( https://doi.org/10.15302/J-FASE-2021398). Also, Luis Garcia-Barrios and Yanus A. Dechnik-Vazquez dissected the ecological concept of the complementarity and selection effects to develop a relative multicrop resistance index to analyze the relation between higher multicrop yield and land use efficiency and the different ecological causes of overyielding under two contrasting water stress regimes ( https://doi.org/10.15302/J-FASE-2021412).

Odette Denise Weedon and Maria Renate Finckh found that composite cross populations, with different disease susceptibilities of three winter wheat cultivars, were moderately resistant to brown rust and even to the newly emerged stripe rust races prevalent in Europe since 2011, but performance varied between standard and organic management contexts ( https://doi.org/10.15302/J-FASE-2021394).

Comparing the performance of intercrops and sole crops is critical to make a sound evaluation of the benefits of intercropping and assess interactions between species choice, intercrop design, intercrop management and factors related to the production situation and pedoclimatic context. Wopke van der Werf and coworkers review some of the metrics that could be used in the quantitative synthesis of literature data on intercropping ( https://doi.org/10.15302/J-FASE-2021413).

Interspecific interactions provide some of the advantages of intercropping, and can be divided into above- and belowground interactions. Aboveground interactions can include light and space competition, which is influenced by crop species traits. Root exudates are also important in interspecific interactions between intercropped or rotated species. Qi Wang and coworkers estimated the light interception of growth stage of maize-peanut intercropping and corresponding monocultures, and found that intercropping has higher light interception than monoculture, and increasing plant density did not further increase light interception of intercropping ( https://doi.org/10.15302/J-FASE-2021403). Yuxin Yang and coworkers reported that the root exudates of fennel (Foeniculum vulgare) can reduce infection of tobacco by Phytophthora nicotianae via inhibiting the motility and germination of the spores of the pathogen ( https://doi.org/10.15302/J-FASE-2021399).

Focusing on the application of intercropping, Wen-Feng Cong and coworkers formulated species recommendations for different regions of China for different crop diversity patterns and crop species combinations. These authors also suggested three steps for implementing crop diversification on the North China Plain. Although there are multiple benefits of crop diversification, its extension and application are hindered by various technical, organizational, and institutional barriers along value chains, especially in Europe. Based on the findings of the European Crop Diversification Cluster projects, Antoine Messéan and coworkers suggested that there needs to be more coordination and cooperation between agrifood system stakeholders, and establish multiactor networks, toward an agroecological transition of European agriculture ( https://doi.org/10.15302/J-FASE-2021406). In addition, Henrik Hauggaard-Nielsen and coworkers report the outcomes of a workshop for participatory research to overcome the barriers to enhanced coordination and networking between stakeholders ( https://doi.org/10.15302/J-FASE-2021416).

Intercropping, though highly effective in labor-intensive agriculture, may be difficult to implement in machine-intensive, large-scale modern agriculture because appropriate large equipment is not commercially available for planting and harvesting various crop mixtures grown with strip intercropping[6]. Thus, the appropriate machinery will need to be developed for further practical application in large-scale agriculture.

As the guest editors, we thank all the authors and reviewers for their great contributions to this special issue on “Crop Diversity and Sustainable Agriculture”. We also thank the FASE editorial team for their kind supports.

 

Article  |  2021-11-26

Development Strategy of the New-Generation Effectiveness-Oriented Earth-Observation System

China has established three series of remote sensing satellite systems for land, ocean, and atmosphere through the establishment of a high-resolution Earth observation system and the implementation of national civil space infrastructure planning. However, the current systems in China neglect data application and data services while emphasizing satellite engineering. Considering the future requirements of Earth observation for high quality, high benefit, and high efficiency, we adopt an effectiveness analysis method to study the Earth observation systems. We clarify the global development trends of Earth observation satellite systems and summarize the current status in China. Based on this, we analyze the demand and challenges for an effectiveness-oriented Earth-observation system and propose the development goals, components, and key tasks of the new-generation Earth-observation system that features system effectiveness. To improve the application service system and capabilities of China’s remote sensing satellites and to transform the orientation from business services to system effectiveness, it is necessary to build a space–ground integrated perception backbone network as well as management and data transmission tool networks based on top-level design with the High Resolution Earth Eye Program as the core, and implement major application demonstration projects. Moreover, national spectral data sources, quantitative application databases, and industrial ecology cloud platforms need to be strengthened, thereby transforming satellite engineering toward satellite application engineering and constructing a complete national civil space infrastructure.

Zhao Wenbo ,   Li Shuai   et al.

Article  |  2021-11-22

Strategic Planning of Global Innovation and Industry Highland in Guangdong–Hong Kong–Macao Greater Bay Area from a Medium- and Long-Term Perspective

As the construction of Guangdong–Hong Kong–Macao Greater Bay Area enters a new stage, it is necessary to further improve technological innovation and emerging industries of this area and promote its global influence to support the high-quality development of China’s industries. In this study, we analyze the role of this area in the national economic development and explore the development status of technological innovation and emerging industries in this area. Moreover, we propose strategic goals and key tasks for the medium- and long-term development under the unique institutional framework of “one country, two systems”. The Guangdong–Hong Kong–Macao Greater Bay Area can be built to be a global innovation and industry highland that is open, integrated, and sustainable via four steps by 2050, and a borderless Greater Bay Area can be constructed orderly through integrated technological innovation. The key tasks that we proposed include: (1) strengthening the construction of an international technological innovation center, (2) improving the ability of science and technology to support industrial development, (3) cultivating world-class clusters of emerging industries, (4) creating a gathering place for outstanding professionals in China and abroad, (5) deepening the integration of finance and technology, (6) establishing a diversified investment coordination mechanism for scientific innovation, and (7) exploring an innovation and industrial factor flow mechanism.

Wang Yingjun ,   Zeng Zhimin   et al.

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