Catchment scale spatial variability of soil salt content in agricultural oasis, Northwest China

Soil salinization is a serious environmental problem in the world, especially in arid and semi-arid regions. Therefore, estimating spatial variability of soil salinity plays an important role in environmental sciences. Aiming at the problem of soil salinization inside an oasis, a case study was carried out at the Sangong River catchment in Xinjiang province, northwest China. Methods of classical statistics, geostatistics, remote sensing (RS) and geographic information system (GIS) were applied to estimate the spatial variability of soil salt content in the topsoil (0-20 cm) and its relationship with landscape structure at catchment scale. The objective of this study was to provide a scientific basis to understand the heterogeneous of spatial distribution of soil salt content at a large scale. The results revealed that (1) elevation of landform was a key factor for soil salt content's spatial variability, and soil salt content had a strong spatial autocorrelation, which was mainly induced by structural factors. (2) Mapping of soil salt content by Kriging and comparing it with landscape maps showed that area of soil salinization in old oasis was smaller than that in new oasis, and degree of soil salinization in old oasis was also lower than that in the new one. Among all landscapes, cropland was mostly affected by salinity, with 38.8% of the cropland in new oasis moderately affected by soil salinity, and 8.54% in old oasis

Fewer, tastier tomatoes: Expanding the use of saltwater in agriculture

As the world experiences increasing freshwater crises, researchers turn to saline waters. Can the use of saltwater be expanded? The development of appropriate practices for the use of saline waters for irrigation requires an adequate understanding of how salts affect waters, soils and plants, as FAO states in their book The use of saline waters for crop production, 1992. Plants can grow in saline waters, if the salinity of the soil is controlled and monitored, and the soil salt content is not allowed to increase past a level that damages the plants. Irrigation of salt tolerant plants with slightly saline waters offers a substantial opportunity to increase the yearly crop production of the world

Nutrient recycling from bio-digestion waste as green fertilizers

In the transition from a fossil to a bio-based economy, it has become an important challenge to maximally recuperate valuable nutrients coming from waste streams. Nutrient resources are rapidly depleting, significant amounts of fossil energy are used for the production of chemical fertilizers, whereas costs for energy and fertilizers are increasing. In the meantime, biogas production through anaerobic digestion produces nutrient-rich digestates. In high-nutrient regions, these products cannot or only sparingly be returned to agricultural land in its crude unprocessed form. The consequent processing of this digestate requires a variety of technologies producing a lot of different derivatives, which could potentially be re-used as green fertilizers in agriculture. As such, a sustainable alternative for fossil-based mineral fertilizers could be provided. The aim of this study is to characterize the physicochemical properties of digestates and derivatives, in order to identify the fertilizer value and potential bottlenecks for agricultural re-use of these products, in line with European legislative constraints. In addition, the economic and ecological benefits of substituting conventional fertilizers by digestates and derivatives are quantified and evaluated. Waste water from acidic air scrubbers for ammonia removal shows potential as N-S-fertilizer, whereas concentrates resulting from membrane filtrated liquid fraction of digestate show promise as N-K-fertilizer. Substituting artificial fertilizers by air scrubber water or membrane filtration concentrates theoretically always results in significant economic and ecological benefits for the agriculturist. Field research is now on-going in order to evaluate the impact on soil and crop production by application of these new green fertilizers

The Ecological Restoration of Heavily Degraded Saline Wetland in the Yellow River Delta

As a result of discontinuous water flow, agriculture, and increasing urban use of fresh water affecting the natural wetlands of the Yellow River Delta, these areas have experienced significant degradation in the past two decades, ultimately diminishing the overall natural wetland land area in the region. This study aimed to address the issue of decreasing fresh water in the Yellow River Delta by studying the effects of three different approaches to restoration on long-term wetland recovery. The results of the study demonstrated that soil salt and available Na contents significantly decreased in response to all three restoration treatments. Impacts of the restoration treatments were more significant in 2009 than in 2010, as shown by the high rate of activity in the reed debris group. The highest phosphatase activity of the experimental period was also observed in the reed debris group. Meanwhile, a marked variation in soil nutrient elements (total carbon (TC), total nitrogen (TN), available phosphorus, and available potassium) was observed in the restoration treatment plots throughout the experimental period. TC and TN contents were generally higher in the restoration treatment groups than in the control group. Moreover, urease and phosphatase activity levels were highly correlated with one another, as well as with soil nutrient elements. In 2009, the yield of the Suaeda salsa plant was highest in the reed debris treatment group and lowest in the ploughing treatment group. The S. salsa plant did show a positive response to all of the different restoration treatments. Taken together, these results suggest that restoration approaches that implement ploughing techniques aided in the restoration of degraded saline wetlands.As a result of discontinuous water flow, agriculture, and increasing urban use of fresh water affecting the natural wetlands of the Yellow River Delta, these areas have experienced significant degradation in the past two decades, ultimately diminishing the overall natural wetland land area in the region. This study aimed to address the issue of decreasing fresh water in the Yellow River Delta by studying the effects of three different approaches to restoration on long-term wetland recovery. The results of the study demonstrated that soil salt and available Na contents significantly decreased in response to all three restoration treatments. Impacts of the restoration treatments were more significant in 2009 than in 2010, as shown by the high rate of activity in the reed debris group. The highest phosphatase activity of the experimental period was also observed in the reed debris group. Meanwhile, a marked variation in soil nutrient elements (total carbon (TC), total nitrogen (TN), available phosphorus, and available potassium) was observed in the restoration treatment plots throughout the experimental period. TC and TN contents were generally higher in the restoration treatment groups than in the control group. Moreover, urease and phosphatase activity levels were highly correlated with one another, as well as with soil nutrient elements. In 2009, the yield of the Suaeda salsa plant was highest in the reed debris treatment group and lowest in the ploughing treatment group. The S. salsa plant did show a positive response to all of the different restoration treatments. Taken together, these results suggest that restoration approaches that implement ploughing techniques aided in the restoration of degraded saline wetlands

Incorporating new functions into the WAVES model, to better simulate cotton production under film mulching and severe salinity

Film mulching is widely used as an agronomic practice to counteract water scarcity in arid and semi-arid areas. Although crop models have emerged as powerful tools for system studies and scenarios analysis, they have been rarely used in areas with severe drought and salinization and where mulching is being used as a management practice. An earlier study shown great modelling potential under severe salinity in southern Xinjiang, China. The model is WAVES (the WAter Vegetation Energy and Solute), while evaporation was overestimated in the earlier study without considering the mulching effect. In this study, we used a modified WAVES model by incorporating three functions working on potential evaporation, underlying surface albedo, and soil resistance into it to represent the mulching effect. Calibration and validation were conducted using cotton field experiments from 2 different years. Of the 3 functions evaluated, the one representing potential evaporation reduction exerted the highest modification effect on soil water status. The modified model better simulated evaporation, soil-water content, soil-salt content, leaf area index (LAI), and yield than the original model, decreasing normalized root mean square error (NRMSE) by 173%, 15%, 14%, 9%, and 35%, respectively. The modification effects were most significant during the seedling stage. In addition, the modified model produced a higher realistic evaporation (E)/evapotranspiration (ET) under the film mulching environment. These findings suggest that the modified WAVES model can be applied for crop management under film mulching, particularly in areas with low rainfall and high salinization

Interactive Regimes of Reduced Irrigation and Salt Stress Depressed Tomato Water Use Efficiency at Leaf and Plant Scales by Affecting Leaf Physiology and Stem Sap Flow

Interactive effects of reduced irrigation and salt stress on leaf physiological parameters, biomass accumulation, and water use efficiency (WUE) of tomato plants at leaf and whole plant scales were investigated in a field experiment during 2016 and a greenhouse experiment during 2017. Experiment utilized two irrigation regimes (full, 2/3 of full irrigation) and four soil salt regimes (0, 0.3, 0.6, 0.9% in 2016 season; and 0, 0.2, 0.3, 0.4% in 2017 season). Three salts, sodium chloride, magnesium sulfate, and calcium sulfate (mass ratio of 2:2:1), were homogeneously mixed with soil prior to packing into containers (0.024 m3). Li-COR 6400 was used to measure tomato leaf physiological parameters. Instantaneous water use efficiency (WUEins, μmol mmol−1) and intrinsic water use efficiency (WUEint, μmol mol−1) were determined at leaf scale, yield water use efficiency (WUEY, g L−1), and dry biomass water use efficiency (WUEDM, g L−1) were determined at whole plant scale. Plants irrigated with 2/3 of full irrigation with zero soil-salt treatment had higher dry biomass and yield per plant, resulting in the highest WUEDM and WUEY at whole plant scale. Increasing soil salinity decreased dry biomass and yield, leading to greater decreases in whole plant WUEDM and WUEY under both irrigation treatments. At full irrigation, no decreases in stomatal conductance (gs, mol m−2 s−1) and slight increase in photosynthetic rate (Pn, μmol m−2 s−1) led to higher WUEint at leaf scale during both years. Under full and reduced irrigation, increasing soil salt content decreased Pn and transpiration rate (Tr, mmol m−2 s−1) and led to reductions in WUEins at the leaf scale. However, compared to full irrigation, reduced irrigation improved WUEins with a significant decline in Tr in no salt and 0.3% soil-salt treatments during both years. For soil salt content of 0.6%, stomatal limitation due to salt stress resulted in higher WUEint, but soil salt content of 0.9% decreased WUEint due to non-stomatal limitation. Soil salt content significantly decreased sap flow, with the maximum variation of daily sap flow per plant of 7.96–31.37 g/h in 2016 and 12.52–36.02 g h−1 in 2017. Sap flow rate was linearly related to air temperature (Ta, °C), solar radiation (Rs, W m−2), and vapor pressure deficit (VPD, kPa). These results advance knowledge on tomato response to abiotic stresses and could improve management of tomato production in water- and salt-stressed areas

A hitchhiker from the beach: the spread of the maritime halophyte Cochlearia danica along salted continental roads

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Emergence of a new salt-tolerant alien grass along roadsides? Occurrence of Diplachne fusca subsp. fascicularis (Poaceae) in Hungary

This paper reports the occurrence of a North American salt-tolerant taxon, Diplachne fusca subsp. fascicularis (Lam.) P.M.Peterson et N.Snow in Hungary (Central-Europe). Two earlier Hungarian observations of D. fusca were known from 1915, near Győr (West Transdanubia), later the taxon was collected by Pénzes in 1958, in downtown Budatétény (central Hungary. Both observations seem to be occasional. Recently, the taxon has started spreading in Europe, mainly on rice paddy fields, with a serious invasion potential. In North America its appearance on ruderal habitats, as well as along roads and other linear infrastructures is a well known phenomenon. The Hungarian population was found near Cegléd (Central Hungary) on the roadside of the E40 primary main road in September 2018. In July 2019 more than one thousand (mostly vegetative) individuals were detected. The salt content of the habitat shows remarkable temporal and spatial variability. At one meter distance from the edge of the paved road soil salt content was higher in spring (after the winter de-icing regime), than in autumn. Salt concentration was highest in the vicinity of the road, and decreased with increasing distance from it. Germination tests revealed a significant negative effect of NaCl concentration on germination rates, but germination occurred even on extremely saline substrates with 1.5% NaCl concentration. Considering its biology and reproduction strategy, the further spread of Diplachne fusca is highly presumable

Developing and sustainably utilize the coastal mudflat areas in China

Coastalmudflat areas are regarded as the important reserve land resource in China. Rational exploitation and development of the mudflat areas can relieve the stress of inadequate land resources. Probing into the developing models of resource exploitation of coastal tidal mudflats is one of the important components of achieving the sustainable development in the coastal areas. Therefore, the development history of coastal mudflats after 1950s in China is briefly introduced in this paper. Then, the status in quo of the modes of development and utilization of coastal mudflat in China the paper is reviewed with a special attention payed to the agricultural use of coastal resource, especially halophytes and improved salt-tolerant varieties planting, agricultural dyke pond and coastal saline-alkali soil remediation. Based on related research frontier, sustainable developmental prospects of these coastal areas are presented as well. (C) 2016 Published by Elsevier B.V