Is the fragility of a liquid embedded in the properties of its glass?

When a liquid is cooled below its melting temperature, it usually crystallizes. However, if the quenching rate is fast enough, the system may remain in a disordered state, progressively losing its fluidity upon further cooling. When the time needed for the rearrangement of the local atomic structure reaches approximately 100 seconds, the system becomes "solid" for any practical purpose, and this defines the glass transition temperature Tg. Approaching this transition from the liquid side, different systems show qualitatively different temperature dependencies of the viscosity, and accordingly they have been classified by introducing the concept of "fragility." We report experimental observations that relate the microscopic properties of the glassy phase to the fragility. We find that the vibrational properties of the glass well below Tg are correlated with the fragility value. Consequently, we extend the fragility concept to the glassy state and indicate how to determine the fragility uniquely from glass properties well below Tg.     

Depoliticizing land and water “grabs” in Colombia: the limits of Bonsucro certification for enhancing sustainable biofuel practices

As concerns heighten over links between biomass production and land grabs in the global south, attention is turning to understanding the role of governance of biofuels systems, whereby decision-making and conduct are not solely determined through government regulations but increasingly shaped by non-state actors, including multi-stakeholder initiatives (MSI). Launched in 2005, Bonsucro is the principal MSI that focuses on sustainability standards for sugar and sugarcane ethanol production. Bonsucro claims that because it is free from government interference and draws on scientific metrics, their standards transcend localized, political–economic contexts. In this paper, we illustrate how the local context shapes the prospects for Bonsucro sustainably certified biofuel production in relation to land and water grabs. To accomplish this, our case focuses on Colombia, which has used a range of national policy mandates to establish itself as one of the larger producers of agrofuels in Latin America. We draw on interviews with stakeholders in the sugar and ethanol industries, paired with an examination of Bonsucro principles on land rights and water use, to illustrate how the sugar industry is framing their participation in Bonsucro, and the effects of the increasing intensification of sugarcane for ethanol production on land and water access for communities. We find that within the context of Colombia, efforts such as Bonsucro provide a veil of legitimacy and authority to a system that is premised on deeply entrenched historical patterns of inequitable land ownership patterns and access to natural resources.     

Drip irrigation incorporating water conservation measures: Effects on soil water–nitrogen utilization,root traits and grain production of spring maize in semi-arid areas

The Northeast Plain is the largest maize production area in China, and drip irrigation has recently been proposed to cope with the effects of frequent droughts and to improve water use efficiency (WUE). In order to develop an efficient and environmentally friendly irrigation system, drip irrigation experiments were conducted in 2016–2018 incorporating different soil water conservation measures as follows: (1) drip irrigation under plastic film mulch (PI), (2) drip irrigation under biodegradable film mulch (BI), (3) drip irrigation incorporating straw returning (SI), and (4) drip irrigation with the tape buried at a shallow soil depth (OI); with furrow irrigation (FI) used as the control. The results showed that PI and BI gave the highest maize yield, as well as the highest WUE and nitrogen use efficiency (NUE) because of the higher root length density (RLD) and better heat conditions during the vegetative stage. But compared with BI, PI consumed more soil water in the 20–60 and 60–100 cm soil layers, and accelerated the progress of root and leaf senescence due to a larger root system in the top 0–20 cm soil layer and a higher soil temperature during the reproductive stage. SI was effective in improving soil water and nitrate contents, and promoted RLD in deeper soil layers, thereby maintaining higher physiological activity during the reproductive stage. FI resulted in higher nitrate levels in the deep 60–100 cm soil layer, which increased the risk of nitrogen losses by leaching compared with the drip irrigation treatments. RLD in the 0–20 cm soil layer was highly positively correlated with yield, WUE and NUE (P<0.001), but it was negatively correlated with root nitrogen use efficiency (NRE) (P<0.05), and the correlation was weaker in deeper soil layers. We concluded that BI had advantages in water–nitrogen utilization and yield stability response to drought stress, and thus is recommended for environmentally friendly and sustainable maize production in Northeast China.     

Can food security and low carbon be achieved simultaneously? —An empirical analysis of the mechanisms influencing the carbon footprint of potato and corn cultivation in irrigation areas

Irrigated agriculture has tripled since 1950, accounting for 20% of the global arable land and 40% of food production.  Irrigated agriculture increases food security yet has controversial implications for global climate change.  Most previous studies have calculated carbon emissions and their composition in irrigated areas using the engineering approach to life-cycle assessment.  By combining life cycle assessment (LCA)-based carbon emissions accounting with econometric models such as multiple linear regression and structural equation modeling (SEM), we conducted an interdisciplinary study to identify the influencing factors and internal mechanisms of the carbon footprint (CFP) of smallholder crop cultivation on irrigation reform pilot areas.  To this end, we investigated corn and potato production data in the 2019–2020 crop years for 852 plots of 345 rural households in six villages (two irrigation agriculture pilot villages and four surrounding villages as controls) in Southwest China.  The crop CFP in the irrigation agriculture pilot areas was significantly lower than in non-reform areas.  Irrigation reforms mainly impacted the crop CFP through four intermediary effects: the project (implementation of field irrigation channels), technology (improving adoption of new irrigation technologies), management (proper irrigation operation and maintenance), and yield effects.  All effects inhibited the CFP, except for the project effect that promotes carbon emissions.  Among them, yield increase has the greatest impact on reducing CFP, followed by management and technology effects.  Furthermore, planting practices, individual characteristics, and plot quality significantly impacted the crop CFP.  This study has policy implications for understanding the food security–climate nexus in the food production industry.     

Effect of long-term fertilization on the nitrogen status of leached chernozem and the nitrogen balance in a grain–beet crop rotation

It has been revealed that the 70-year-long application of fertilizers to a sugar beet crop rotation in the forest-steppe of the Central Chernozemic Zone has significantly affected the nitrogen status of leached chernozem and increased the content of mineral nitrogen and the mobility of nitrogen compounds. High application rates of mineral fertilizers create a positive nitrogen balance in the crop rotation and could minimize the losses of total nitrogen in the future.     

Is food a motivation for urban gardeners? Multifunctionality and the relative importance of the food function in urban collective gardens of Paris and Montreal

In the cities of industrialized countries, the sudden keen interest in urban agriculture has resulted, inter alia, in the growth of the number and diversity of urban collective gardens. While the multifunctionality of collective gardens is well known, individual gardeners’ motivations have still not been thoroughly investigated. The aim of this article is to explore the role, for the gardeners, of the food function as one of the functions of gardens, and to establish whether and how this function is a motivating factor for them. We draw on a set of data from semi-structured interviews with 39 gardeners in 12 collective gardens in Paris and Montreal, as well as from a survey on 98 gardeners and from field observations of the gardeners’ practices. In the first part we present the nature and diversity of garden produce, and the gardeners’ assessment thereof. In the second part we describe the seven other functions mentioned by the gardeners, which enables us to situate the food function in relation to them. We conclude that the food function is the most significant function of the gardens, and discuss the implications for practitioners and policy makers.     

Estimating daily actual evapotranspiration of a rice–wheat rotation system in typical farmland in the Huai River Basin using a two-step model and two one-step models

The objective of this study is to evaluate the performance of three models for estimating daily evapotranspiration(ET) by employing flux observation data from three years(2007, 2008 and 2009) during the growing seasons of winter wheat and rice crops cultivated in a farmland ecosystem(Shouxian County) located in the Huai River Basin(HRB), China. The first model is a two-step model(PM-K_c); the other two are one-step models(e.g., Rana-Katerji(R-K) and advection-aridity(AA)). The results showed that the energy closure degrees of eddy covariance(EC) data during winter wheat and rice-growing seasons were reasonable in the HRB, with values ranging from 0.84 to 0.91 and R2 of approximately 0.80. Daily ET of winter wheat showed a slow decreasing trend followed by a rapid increase, while that of rice presented a decreasing trend after an increase. After calibrating the crop coefficient(K_c), the PM–K_c model performed better than the model using the K_c recommended by the Food and Agricultural Organization(FAO). The calibrated key parameters of the R-K model and AA model showed better universality. After calibration, the simulation performance of the PM-K_c model was satisfactory. Both the R-K model and AA model underestimated the daily ET of winter wheat and rice. Compared with that of the R-K model, the simulation result of the AA model was better, especially in the simulation of daily ET of rice. Overall, this research highlighted the consistency of the PM-K_c model to estimate the water demand for rice and wheat crops in the HRB and in similar climatic regions in the world.