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.Index terms: soil texture, stratification, soil erodibility, dam construction, soil conservation.

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Among the essential micronutrients, zinc (Zn) affects vital functions in crop plants. The influences of foliar nourishing with certain Zn-containing forms on the growth, productivity, and physiology of carrot plants (cv. Fire wedge F1) and their nutritional contents when grown in Zn-deficient soil were examined in both 2019/2020 and 2020/2021 field trials. Two doses of zinc oxide nanoparticles (ZnO-NPs(1) = 20 and ZnO-NPs(2) = 40 mg L−1), zinc–EDTA (Zn–EDTA(1) = 1 and Zn–EDTA(2) = 2 g L−1), or bulk zinc oxide (ZnO-B(1) = 200 and ZnO-B(2) = 400 mg L−1) were applied three times. The data outputted indicated, in general, that ZnO-NPs(2) were the best treatment that conferred more acceptable plant growth (measured as shoot length and fresh and dry weights), physiology (measured as cell membrane stability index, SPAD readings, and nutrient uptake), and nutritional homeostasis (e.g., P, Ca, Fe, Mn, Zn, and Cu contents). All these positive attributes were reflected in the highest yield, which was measured as fresh weight, dry matter, length, diameter, volume, and total yield of carrot roots. However, there were some exceptions, including the highest membrane stability index in both seasons, the highest Cu uptake and Mn content in the first season, and root fresh weight in both seasons obtained with ZnO-NPs(1). Moreover, the maximum P uptake and root dry matter were obtained with ZnO-B(1) and the highest content of root P was obtained by ZnO-B(2). Based on the above data, foliar nourishing with ZnO-NPs(2) can be recommended for the sustainability of carrot cultivation in Zn-deficient soils.

Deficit irrigation technique was introduced to find the best means to conserve irrigation water in arid lands. The most common model describing deficit irrigation is water yield response model. The main advantage of such model is that it can predict relative yield drop, which arises from relative water deficit, in order to maximize the economic return. The disadvantage of the model is that it uses evapotranspiration (ET), estimated by using meteorological data, which affects the applicability of the model when there is no weather station near the field. Furthermore, the sudden changes of weather parameters and the differences of the areas covered with green plant at different growth stages might also, affect the model applicability. Therefore, the research objectives were suggesting a modified version of FAO model, using soil moisture data instead of meteorological data to provide greater accuracy and applicability and validating the proposed model. Pot experiment was conducted to achieve these objectives. Four levels of soil available water were chosen to irrigate five cultivars of Medicago sativa (as one of the most important grazing crops) cultivated in two different soils (un-reclaimed). The results showed positive linear correlation between available soil water and crop yield at all the experimental treatments. Regression equations were developed to predict crop yield resulting from water deficit. The study indicated that the maximum yield is not necessarily the optimal one to maximize the profit in arid lands. The study recommended the modified model to predict yield drop and water saving and also, presented guidelines for water management of other similar plants grown in arid lands.