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Climate change and human activities lead to freshwater shortage, soil salinization, and food security crises in arable land. To explore the natural and irrigation factors on soil water and salt movement, this study quantitatively analyzed the dynamic characteristics of soil water and salt movement under precipitation, groundwater irrigation, and brackish water irrigation conditions for the next 30 years using Hydrus-1D model-based parameters obtained from the winter wheat–summer maize rotation experiments in the Yellow River Irrigation District. The results showed that precipitation was the key factor of climate change affecting soil water and salt migration, especially in the 0–20 cm soil layer. Under both SSP585 and SSP245 climate scenarios, rainfall in normal and wet years promoted salt leaching up to 1 m below the surface soil. But in dry years, salt washing treatment was required for the tillage layer to prevent salt accumulation. The higher the groundwater level was, the higher the soil water and salt content was in the 0–100 cm soil layer. In this soil layer, a 2 m groundwater level contributed 30% to wheat water needs, while a 3 m groundwater level contributed 18%, and no significant contribution was observed for a 4 m groundwater level. The salinity of the soil profile showed an overall increasing trend with irrigation using 1–3 g/L brackish water for 30 years. However, the salinity in the 0–100 cm soil layer was below the salt tolerance threshold of winter wheat and summer maize with salts accumulated in the 1–2 m soil layer. Considering the salinization of the root zone and crop water needs, it is recommended that the safe groundwater level for brackish water irrigation should be 3 m in the study region. This study provides scientific reference for groundwater–farmland ecosystems to utilize brackish water and treat saline–alkali lands. [ABSTRACT FROM AUTHOR]

The saline soils in the Yellow River Delta are primarily affected by seawater intrusion resulting from the intersection of land and sea, which exhibit variations in salinity. The quality of these soils is also influenced by anthropogenic reclamation, including fertilization and irrigation. This study quantitatively evaluated the distinct soil properties and soil quality characteristics of the Yellow River Delta during different reclamation years (i.e., 0a, 1a, 5a, 10a, and 20a) using principal component analysis (PCA) and the Soil Quality Index (SQI). The findings indicated that the soil salt content (SSC) significantly decreased (p < 0.05) from 6.60 g/kg in the initial reclamation year (0a) to 1.63 g/kg in the 10th year (10a) and then slightly increased to 2.85 g/kg in the 20th year (20a). Consequently, the soil salinity level shifted from saline soil to slight salinity and then increased to medium salinity. Ammonium nitrogen (NH4+-N) notably increased by 8.31 mg/kg during the first five years of reclamation (0a to 5a) and gradually decreased by 2.56 mg/kg in the 20th year (20a). On the other hand, nitrate nitrogen (NO3−-N) experienced a significant decrease of 2–5 times after reclamation but continued to increase by 8.96 mg/kg with subsequent reclamation years. The available nitrogen (AN), available phosphorus (AP), and soil organic carbon (SOC) exhibited a significant increase of 24.87 mg/kg, 10.11 mg/kg, and 6.76 g/kg, respectively, with increasing reclamation years. However, available potassium (AK) gradually decreased after reclamation and then increased in the 20th year (20a). The values of SQI for different reclamation years were 0.307 for 0a, 0.339 for 1a, 0.320 for 5a, 0.318 for 10a, and 0.327 for 20a, indicating an increasing trend with increasing reclamation years. It was discovered that long-term reclamation significantly reduced soil salinity and improved soil quality, leading to the sustainable development of reclaimed saline soils in the Yellow River Delta. [ABSTRACT FROM AUTHOR]

Saline soils are of great concern globally. Selecting the Yellow River Delta as a model site, the influence of reclamation on soil salinity and saline soil quality was investigated. Soil quality index (SQI) was applied to statistically analyze 210 soil profile samples collected at seven depth layers in 30 sampling sites among native saline soils and three croplands (peanut, cotton, and wheat) in May 2020. After reclamation, the soil salt content (SSC) reduced from 4.52 g/kg to 1.44 g/kg after reclamation, with the degree of soil salinity reducing from severe to slight. The nitrate nitrogen (NO3−-N) contents of peanut, cotton, and wheat croplands were 1.90, 2.02, and 4.29 times higher and the available phosphorus (AP) contents were 5.43, 3.57, and 8.77 mg/kg higher than that of the saline soils, respectively, while the soil ammonium nitrogen (NH4+-N) and available potassium (AK) contents were decreased. The NO3−-N, AN, and AP contents of the three croplands showed a significant surface aggregation at depth of 0–30 cm. SQI increased by 0.10, 0.09, and 0.02 after the reclamation with the enhancement effect of wheat and cotton was more pronounced. It was discovered that reclamation notably improved the soil quality as a result of crop growth and field management of fertilization and irrigation. [ABSTRACT FROM AUTHOR]

Complete water accounting (WA) and crop water productivity (CWP) analysis is crucial for evaluating water use efficiency (WUE). This study aims to evaluate the contributions of hydro-meteorological factors to the changes of WA and CWP and subsequent WUE based on the data from 2009–2020 in the Nile River Basin (NRB), East Africa (EA). The Mann-Kendall (MK) statistical test and Sen's slope estimator were applied to detect the trends of climatic factors, and the AquaCrop model was used to simulate the crop yields in response to water balance and consumption based on crop physiological, soil water, and salt budget concepts. For the years 2012 and 2019, the mean of climatic water deficit P − ETa was 71.03 km3 and 37.03 km3, respectively, which was expected to rise to ~494.57 km3 by 2050. The results indicated that the basin water budget was unbalanced due to the coupled impact of year-to-year hot and dry conditions and increase in water abstraction, an indication of water deficit or stress. CWP and WUE increased during the study period with different changing patterns. CWP was also found to correlate to the yield of major crops (p-value > 0.05). It was concluded that climatic factors influenced the crop yield, CWP, and WUE in the study area. Thus, the improvement of CWP and WUE should rely on advanced water-saving innovations. The findings of this study could help water managers to improve water productivity by focusing on water account potentials and creating regional advantages by deploying water in combination with surplus flow from upstream to downstream consumption. [ABSTRACT FROM AUTHOR]

Soil water content (SWC) is a vital parameter for understanding crop growth and the soil nutrient water cycle. Monitoring SWC without inserting sensors into the soil, which can break the soil structure, has previously been a significant challenge for scientists. In this study, we developed a non-inserted portable frequency domain reflection (NIP-FDR) instrument to monitor SWC continuously and automatically. The working technique of this instrument was based on the improved adjustable high-frequency oscillation method originating from the frequency domain reflection principle. Compared to the control SWC measurement instrument, the difference in SWC at 0–10 cm, 10–20 cm, and 20–30 cm depth was within 1%, 3%, and 15%, respectively, and the mean variation of SWC was less than 5% in the indoor measurements. In the field verification experiment conducted in the summer of 2020, the mean error of SWC measurements at a depth of 0–20 cm was 5%, while we failed to compare SWC at a depth of 20–30 cm due to low variability in the SWC measurement at this depth during the summer measurement period. This pioneer NIP-FDR was able to effectively monitor surface SWC, especially at depths of 0–20 cm. [ABSTRACT FROM AUTHOR]

Soil water content (SWC) is an important factor restricting crop growth and yield in cropland ecosystems. The observation and simulation of soil moisture contribute greatly to improving water-use efficiency and crop yield. This study was conducted at the Shandong Yucheng Agro-ecosystem National Observation and Research Station in the North China Plain. The study period was across the winter wheat (Triticum aestivum L.) growth stages from 2017 to 2019. A cosmic-ray neutron probe was used to monitor the continuous daily SWC. Furthermore, the crop leaf area index (LAI), yield, and aboveground biomass of winter wheat were determined. The root zone quality model 2 (RZWQM2) was used to simulate and validate the SWC, crop LAI, yield, and aboveground biomass. The results showed that the simulation errors of SWC were minute across the wheat growth stages and mature stages in 2017–2019. The root mean square error (RMSE) and relative root mean square error (RRMSE) of the SWC simulation at the jointing stage of winter wheat were 0.0296 and 0.1605 in 2017–2018, and 0.0265 and 0.1480 in 2018–2019, respectively. During the rain-affected days, the RMSE (0.0253) and RRMSE (0.0980) for 2017–2018 were significantly lower than those of 2018–2019 (0.0301 and 0.1458, respectively), indicating that rain events decreased the model accuracy in the dry years compared to the wet years. The simulated LAIs were significantly higher than the measured values. The simulated yield value of winter wheat was 5.61% lower and 3.92% higher than the measured yield in 2017–2018 and in 2018–2019, respectively. The simulated value of aboveground biomass was significantly (45.48%) lower than the measured value in 2017–2018. This study showed that, compared with the dry and cold wheat growth period of 2018–2019, the higher precipitation and temperature in 2017–2018 led to a poorer simulation of SWC and crop-growth components. This study indicated that annual abnormal rainfall and temperature had a significant influence on the simulation of SWC and wheat growth, especially under intensive climate-change stress conditions. [ABSTRACT FROM AUTHOR]

Given the impact of COVID-19 and the desert locust plague, the Ethiopian food security issue has once again received widespread attention. Its food crisis requires comprehensive and systematic research to achieve the United Nations Sustainable Development Goal of zero hunger. This review discusses the current situation and the causes of food security in Ethiopia. We focus on the challenges in the food security assessment field. The article lists seven typical causes of food insecurity and three roots of food security in Ethiopia. Long-term food security assessment and a comprehensive understanding and manageability for food security causes are considered as the main existing research challenges. Climate-resilient management, water management, and long-term ecosystem network monitoring and data mining are suggested as potential roadmap for future research. [ABSTRACT FROM AUTHOR]

Water is the key limiting factor in socioeconomic and ecological development, but it is adversely affected by climate change. The novel virtual water (VW) concept and water, energy, food, biodiversity, and human health (WEFBH) nexus approach are powerful tools to assess the sustainability of a region through the lens of climate change. Climate change-related challenges and water are complex and intertwined. This paper analyzed the significant WEFBH sectors using the multicriteria decision-making (MCDM) and analytic hierarchy process (AHP) model. The AHP model demonstrated quantitative relationships among WEFBH nexus sustainability indicators in the Greater Horn of Africa countries. Besides, the net VW imports and water footprints of major staple crops were assessed. The composite WEFBH nexus indices varied from 0.10 to 0.14. The water footprint of crops is increasing period by period. The results also revealed that most countries in the study area are facing WEFBH domains unsustainability due to weak planning or improper management strategies. The strong policy constancy among the WEFBH sector is vital for dissociating the high-water consumption from crop production, energy, environmental, and human health system. Thus, this study enhances insights into the interdependencies, interconnectedness, and interactions of sectors thereby strengthening the coordination, complementarities, and synergies among them. To attain sustainable development, we urgently call all public and private entities to value the amount of VW used in their daily activities and design better policies on the complex WEFBH nexus and future climate change. [ABSTRACT FROM AUTHOR]

Significant differences have been reported in root K+ uptake between high potassium efficiency (HKE) and low potassium efficiency (LKE) in vegetable soybean genotypes. The ideal morphological and physiological characteristics of HKE have been defined. However, the mechanism by which HKE vegetable soybean genotypes efficiently uptake K remains unclear. By using representative materials, this study investigated the responses of root development to low K (LK) stress, and identified and assessed the key genes affecting high-efficiency K uptake between HKE and LKE vegetable soybean roots. The root growth of LKE was significantly inhibited under the LK condition. Compared with LKE, HKE had more lateral roots in both LK and CK (control) conditions. Lateral root of HKE was more preferentially responsive to exogenous IAA, with a wider response threshold to IAA concentration (from 0.1 to 1 µM). Transcriptome analysis revealed that LK induced transport-related genes up-regulated in HKE compared with LKE. In HKE, homologous genes of a K channel encoding gene potassium channel AKT1 (AKT1) and a K transporter gene high-affinity K+ transporter 5 (HAK5) were both highly expressed under the LK stress. Additionally, genes related to plant hormones signal transductions were also identified differentially expressed between the two genotypes. Plant hormone signaling involved in root morphological regulation pathways may play significant roles in improving the efficiency of vegetable soybean K+ uptake. A diagram showing possible molecular mechanisms in regulating root high-efficiency uptake K+ in vegetable soybean is proposed. [ABSTRACT FROM AUTHOR]