Particle size distribution (PSD) in the soil profile is strongly related to erosion, deposition, and physical and chemical processes. Water cycling and plant growth are also affected by PSD. Material sedimented upstream of the dam constructions formed large areas of deposited farmland (DF) soils on the Chinese Loess Plateau (CLP), which has been the site of the most severe soil erosion in the world. Two DFs without tillage on the CLP were chosen to study the combined effect of erosion and check dams on PSD. Eighty-eight layers (each 10 cm thick) of filled deposited farmland (FDF) soils and 22 layers of silting deposited farmland (SDF) soils of each studied soil profile were collected and 932 soil samples were investigated using laser granulometry. The particle sizes were stratified in both DFs based on soil properties and erosion resistance. The obtained results of clay and silt fractions showed similar horizontal distribution, indicating parallel characteristics of erosion and deposition processes. Fine sand represented the largest fraction, suggesting the preferential detachment of this fraction. The most erodible range of particle sizes was 0.25-0.5 mm, followed by 0.2-0.25 mm in the studied soil profiles. The correlation between particle size and soil water contents tended to increase with increasing water contents in FDF. Due to the abundant shallow groundwater, the relationship between particle size and soil water content in SDF was lost. Further studies on PSD in the DF area are needed to enhance the conservation management of soil and water resources in this region.

Climate change presents a significant challenge to water resource management in Egypt, particularly concerning agricultural irrigation. Egypt's principal water source is the Nile River under escalating strain from elevated temperatures, erratic precipitation, and severe weather phenomena. This study analyzes maize (Zea mays L.), an essential crop in Egypt, and its irrigation requirements over four decades (1982–2021) concerning climatic changes. The FAO-Penman-Monteith equation was utilized to compute reference evapotranspiration (ET0) and evaluate maize water needs using Cropwat program. The computation was conducted based on meteorological data for the Al-Gharbiya, Assiut, and Aswan governorates, sourced from both the Climwat program and NASA’s POWER. The results indicate that ET0 increased in all regions, with Aswan exhibiting the most significant increase, rising from 7.77 mm/day between 1982 and 1991 to 8.09 mm/day from 2012 to 2021. The water requirements for maize reached their zenith during the mid-growth stages, attaining a maximum of 136 mm in Al-Gharbiya and 194 mm in Assiut from 2002 to 2011. During the study period, net irrigation for maize escalated across all governorates, with Aswan's net irrigation requirement increasing from 1,316 mm in 1982-1991 to 1,342 mm in 2012-2021. The findings verify water demand increases, especially in areas such as Aswan, where elevated temperatures intensify water loss. The research highlights the significance of effective irrigation methods and sophisticated technologies to address increasing water demands and guarantee sustainable maize cultivation in Egypt's water-scarce context. These insights are essential for formulating climate-resilient agricultural strategies and alleviating the effects of water scarcity.