Effects of alternate moistube-irrigation on soil water infiltration

Alternate moistube-irrigation is a new type of water-saving irrigation,and research on water infiltration with alternate moistube-irrigation is important for the design of irrigation schemes and helpful to understand and apply this technology.The effects of the pressure head(1.0 m and 1.5 m)and tube spacing(10 cm,20 cm,and 30 cm between two moistubes respectively)on soil water infiltration in alternate moistube-irrigation were studied in laboratory experiments,and the cumulative infiltration,discharge of the moistube,and shape and water distribution of the cross-section of the wetting front were determined.The cumulative infiltration increased quickly and linearly with the infiltration time at 0-96 h(R^(2)>0.99),and changed smoothly at 96-192 h with a basically steady infiltration rate.The discharge of the moistube increased rapidly at the beginning of irrigation,then decreased before stabilizing.The cumulative infiltrations and discharges of moistube under the 1.5 m pressure head were more than those under the 1.0 m pressure head.The shape of the cross-section of the wetting front for a single moistube was similar to a concentric circle.With the increase of tube spacing,the interaction between water infiltrations of two moistubes decreased.The soil water distributions around two moistubes were similar to each other under the 1.0 m pressure head and large tube spacing.When the tube spacing was 20 cm,the soil water distribution was more uniform around two moistubes.

Effect of Pisha sandstone on water infiltration of different soils on the Chinese Loess Plateau

The infiltration of water into soil is one of the most important soil physical properties that affect soil erosion and the eco-environment, especially in the Pisha sandstone area on the Chinese Loess Plateau. We studied the one-dimensional vertical infiltration of water in three experimental soils, created by mixing Pisha sandstone with sandy soil, irrigation-silted soil, and loessial soil, at mass ratios of 1：1, 1：2, 1：3, 1：4, and 1：5. Our objective was to compare water infiltration in the experimental soils and to evaluate the effect of Pisha sandstone on water infiltration. We assessed the effect by measuring soil bulk density（BD）, porosity, cumulative infiltration, infiltration rate and saturated hydraulic conductivity（Ks）. The results showed that Pisha sandstone decreased the infiltration rate and saturated hydraulic conductivity in the three experimental soils. Cumulative infiltration over time was well described by the Philip equation. Sandy soil mixed with the Pisha sandstone at a ratio of 1：3 had the best water-holding capacity. The results provided experimental evidence for the movement of soil water and a technical support for the reconstruction and reclamation of mining soils in the Pisha sandstone area.

Simulated rainfall in Brazil:An alternative for assesment of soil surface processes and an opportunity for technological development

Rainfall simulators(RS)have been used,above all,to evaluate hydrological processes related to soil water infiltration,surface runoff and soil erosion.They allow repeatability of rain application with different precipitation intensities in field and/or laboratory conditions and should produce events with physical characteristics similar to natural rain.In this manuscript,we carried out a bibliometric and scientometric analysis of studies with simulated rainfall in Brazil to assess the temporal evolution of publications,the main topics addressed and the degree of technological development of the equipment.We searched for the terms“rainfall simulator”OR“simulated rainfall”AND“Brazil”in the Scopus,Web of Science,SciELO and Google Scholar databases.We found 143 articles published in the last 37 years(1985-2022).Our findings indicate that the main research areas covered in papers are soil erosion(57.34%),soil water infiltration(24.47%),nutrient losses(9.8%)and RS development and calibration/assessment(8.39%).In recent years,the number of published papers in international high-impact factor journals has increased.Most of the papers(49.65%)refer to studies carried out by institutions located in the south and southeast regions of Brazil.Moreover,there is a large gap of studies on simulated rainfall in other regions of Brazil,where important biomes such as the Cerrado,Amazon,Caatinga,and their transitions are located.This study informs research priorities on soil erosion under simulated rainfall and provides a bibliographic database that can assist in more detailed future analyses.

Comparing the Soil Conservation Service model with new machine learning algorithms for predicting cumulative infiltration in semi-arid regions

Water infiltration into soil is an important process in hydrologic cycle;however,its measurement is difficult,time-consuming and costly.Empirical and physical models have been developed to predict cumulative infiltration(CI),but are often inaccurate.In this study,several novel standalone machine learning algorithms(M5Prime(M5P),decision stump(DS),and sequential minimal optimization(SMO))and hybrid algorithms based on additive regression(AR)(i.e.,AR-M5P,AR-DS,and AR-SMO)and weighted instance handler wrapper(WIHW)(i.e.,WIHW-M5P,WIHW-DS,and WIHW-SMO)were developed for CI prediction.The Soil Conservation Service(SCS)model developed by the United States Department of Agriculture(USDA),one of the most popular empirical models to predict CI,was considered as a benchmark.Overall,154 measurements of CI(explanatory/input variables)were taken from 16 sites in a semi-arid region of Iran(Illam and Lorestan provinces).Six input variable combinations were considered based on Pearson correlations between candidate model inputs(time of measuring and soil bulk density,moisture content,and sand,clay,and silt percentages)and CI.The dataset was divided into two subgroups at random:70%of the data were used for model building(training dataset)and the remaining 30%were used for model validation(testing dataset).The various models were evaluated using different graphical approaches(bar charts,scatter plots,violin plots,and Taylor diagrams)and quantitative measures(root mean square error(RMSE),mean absolute error(MAE),Nash-Sutcliffe efficiency(NSE),and percent bias(PBIAS)).Time of measuring had the highest correlation with CI in the study area.The best input combinations were different for different algorithms.The results showed that all hybrid algorithms enhanced the CI prediction accuracy compared to the standalone models.The AR-M5P model provided the most accurate CI predictions(RMSE=0.75 cm,MAE=0.59 cm,NSE=0.98),while the SCS model had the lowest performance(RMSE=4.77 cm,MAE=2.64 cm,NSE=0.23).The differences in RMSE between the best model(AR-M5P)and the second-best(WIHW-M5P)and worst(SCS)were 40%and 84%,respectively.

Effects of alfalfa coverage on runoff,erosion and hydraulic characteristics of overland flow on loess slope plots

An evaluation of the interactions between vegetation,overland and soil erosion can provide valuable insight for the conservation of soil and water.An experiment was conducted to study water infiltration,runoff generation process,rate of sediment erosion,and hydrodynamic characteristics of overland flow from a sloping hillside with different draw-off discharges from alfalfa and control plots with 20°slope.The effect of alfalfa on runoff and sediment transport reduction was quantitatively analyzed.Alfalfa was discussed for its ability to reduce the overland flow scouring force or change the runoff movement.Compared to the bare-soil plots,alfalfa plots generated a 1.77 times increase in infiltration rate.Furthermore,the down-slope water infiltration rate for the bare soil plots was higher than in the up-slope,while the opposite was found in the alfalfa plots.In addition,alfalfa had a significant effect on runoff and sediment yield.In comparison to the control,the runoff coefficient and sediment transportation rate decreased by 28.3%and 78.4%in the grass slope,respectively.The runoff generated from the alfalfa and bare-soil plots had similar trends with an initial increase and subsequent leveling to a steady-state rate.The transport of sediment reduced with time as a consequence of the depletion of loose surface materials.The maximum sediment concentration was recorded within the first few minutes of each event.The alfalfa plots had subcritical flow while the baresoil plots had supercritical flow,which indicate that the capability of the alfalfa slope for resisting soil erosion and sediment movement was greater than for bare soil plots.Moreover,the flow resistance coefficient and roughness coefficient for the alfalfa plots were both higher than for the bare-soil plots,which indicate that overland flow in alfalfa plots had retarded and was blocked,and the flow energy along the runoff path had gradually dissipated.Finally,the ability to erode and transport sediment had decreased.