Final Infiltration Rate Research Articles

Efficacy of Natural Polymer Derivatives on Soil Physical Properties and Erosion on an Experimental Loess Hillslope.

Raindrops disperse large soil aggregates into smaller particles, which can clog soil pores, cause soil crusting, reduce rainfall infiltration and increase soil loss. It was found that natural polymer derivatives were effective in improving soil physical properties and decreasing soil erosion on an experimental loess hillslope. This study investigated the effect of new natural polymer derivatives (Jag S and Jag C162) on soil properties, rainfall infiltration and sediment yield at four rates of sprayed polymers (0, 1, 3 and 5 g/m2), three rainfall intensities (1, 1.5 and 2 mm/min) and a slope gradient of 15° with a silt loam soil through simulated rain. The results showed that both Jag S and Jag C162 significantly increased the shear strength and improved the aggregates composition of the soil surface. The water-stable soil aggregates >0.25 mm increased from 9% to 50% with increasing rates of Jag S and Jag C162. Jag S and Jag C162 also effectively increased rainfall infiltration and final infiltration rate, and reduced erosion compared to controls without natural polymer derivatives added. However, higher rates of Jag S produced lower infiltration rates. Although both Jag S and Jag C162 effectively influenced soil physical properties and erosion, the effect of Jag C162 was more significant than that of Jag S.

Infiltration into frozen soil: From core‐scale dynamics to hillslope‐scale connectivity

AbstractInfiltration into frozen soil is a key hydrological process in cold regions. Although the mechanisms behind point‐scale infiltration into frozen soil are relatively well understood, questions remain about upscaling point‐scale results to estimate hillslope‐scale run‐off generation. Here, we tackle this question by combining laboratory, field, and modelling experiments. Six large (0.30‐m diameter by 0.35‐m deep) soil cores were extracted from an experimental hillslope on the Canadian Prairies. In the laboratory, we measured run‐off and infiltration rates of the cores for two antecedent moisture conditions under snowmelt rates and diurnal freeze–thaw conditions observed on the same hillslope. We combined the infiltration data with spatially variable data from the hillslope, to parameterise a surface run‐off redistribution model. We used the model to determine how spatial patterns of soil water content, snowpack water equivalent (SWE), and snowmelt rates affect the spatial variability of infiltration and hydrological connectivity over frozen soil. Our experiments showed that antecedent moisture conditions of the frozen soil affected infiltration rates by limiting the initial soil storage capacity and infiltration front penetration depth. However, shallow depths of infiltration and refreezing created saturated conditions at the surface for dry and wet antecedent conditions, resulting in similar final infiltration rates (0.3 mm hr−1). On the hillslope‐scale, the spatial variability of snowmelt rates controlled the development of hydrological connectivity during the 2014 spring melt, whereas SWE and antecedent soil moisture were unimportant. Geostatistical analysis showed that this was because SWE variability and antecedent moisture variability occurred at distances shorter than that of topographic variability, whereas melt variability occurred at distances longer than that of topographic variability. The importance of spatial controls will shift for differing locations and winter conditions. Overall, our results suggest that run‐off connectivity is determined by (a) a pre‐fill phase, during which a thin surface soil layer wets up, refreezes, and saturates, before infiltration excess run‐off is generated and (b) a subsequent fill‐and‐spill phase on the surface that drives hillslope‐scale run‐off.

Grazing and Tillage Effects on Soil Properties, Rain Infiltration, and Sediment Transport during Fallow

Core Ideas Soil loss tended higher (>40%) with grazing, but tillage increased soil loss significantly. Infiltration increased with tillage and did not vary with grazing during either fallow phase. Combined grazing and NT management decreased infiltration without tillage to disrupt compaction. Depletion of the High Plains Aquifer that supplies irrigation water for the semiarid Southern Great Plains may necessitate dryland production of crops like wheat (Triticum aestivum L.) and grain sorghum [Sorghum bicolor (L.) Moench] using the wheat–sorghum–fallow (WSF) rotation. Reduced crop productivity without irrigation can be offset by intensifying the WSF rotation with cattle (Bos taurus) grazing. Biomass removal and soil trampling without tillage, however, may reduce rain infiltration and storage during fallow that increases with no‐tillage (NT) over stubble‐mulch (SM) tillage. Our objective was to quantify grazing and tillage effects on infiltration, sediment transport, and aggregate stability during fallow periods after sorghum and wheat. Using a split plot randomized complete block design, we compared wet aggregate size distribution of a Pullman clay loam (fine, mixed, superactive, thermic Torrertic Paleustoll; 0.0–0.05 m) and sediment yield in runoff of simulated rain during the fallow‐like idle period after wheat and the sorghum fallow. Sediment concentration and yield for both fallows were numerically larger (>40%) with grazing. Sediment concentration from SM tillage increased significantly over NT for either fallow, but soil loss differed only for wheat fallow. Mean final infiltration rate (IRf) and amount (IA60) did not differ significantly with grazing during either fallow, but IA60 was usually 20% lower for grazed than for ungrazed paddocks. Because SM tillage after grazed wheat significantly (P < 0.01) increased IRf and IA60 over NT, occasional SM tillage to disrupt compaction from trampling may increase water conservation for dryland cropping systems combining grazing with NT residue management.

Sodicity effects on hydrological processes of sodic soil slopes under simulated rainfall

AbstractSoil salinization can occur in many regions of the world. Soil sodicity affects rainfall‐runoff relationships and related erosion processes considerably. We investigated sodicity effects on infiltration, runoff and erosion processes on sodic soil slopes for two soils from China under simulated rainfall. Five sodicity levels were established in a silt loam and a silty clay with clay contents of 8.5% and 46.0%, respectively. The soils, packed in 50 cm × 30 cm × 15 cm flumes at two slope gradients (22° and 35°), were exposed to 60 min of simulated rainfall (deionized water) at a constant intensity of 125 mm h−1. Results showed that, for both soils, increasing soil sodicity had some significant effects on hydrological processes, reducing the infiltration coefficient (pr = −0.69, P < 0.01) and the quasi‐steady final infiltration rate (pr = −0.80, P < 0.01), and increasing the mean sediment loss (pr = 0.39, P < 0.05); however, it did not significantly affect the cumulative rainfall to ponding (P > 0.05). Moreover, increasing sodicity significantly increased the Reynolds number and the stream power (pr = 0.78 and 0.66, P < 0.01, respectively) of the runoff, decreased Manning roughness and Darcy–Weisbach coefficient (pr = −0.52 and −0.52, P < 0.05, respectively), but did not significantly affect the mean flow velocity, mean flow depth, Froude number and hydraulic shear stress. Stream power was shown to be the most sensitive hydraulic variable affecting sediment loss for both soils. Furthermore, as sodicity increased, the values of critical stream power decreased for both the silt loam (R2 = 0.29, P < 0.05) and the silty clay (R2 = 0.49, P < 0.05). The findings of this study were applied to a real situation and identified some negative effects that can occur with increasing sodicity levels. This emphasized the importance of addressing the influences of soil sodicity in particularly high risk situations and when predicting soil and water losses.

Plot scale assessment of effect of watershed features on runoff and sediment generation in Uttarakhand, India

Daily runoff and sediment from twelve plots (22 m × 5 m) having various land uses (Sugracane, Blackgram, Maize and Fallow land) and slopes (5, 3 and 1%) recorded during the period of June 2014 to April 2015 in the Roorkee, Uttarakhand (India) were analysed together with daily rainfall to assess the effects of land use, soil type and antecedent soil moisture on runoff and sediment yield. The total annual surface runoff generated at 12 study plots was varied from 559.5 m3/ha to 1491.2 m3/ha with an average of 991.1 m3/ha. The total annual sediment yield varied between 0.673 t/ha to 2.63 t/ha. The higher value (= 2.63 t/ha) of sediment yield observed from the present study is lower than the soil erosion tolerance limit (2.5 to 12.5 t/ha/yr) for Indian subcontinent. The trend variability of runoff was higher than rainfall, indicating nonlinear relationship between both variables. Rainfall amount is significantly correlated to runoff amount and coefficient of determination (R2) ranged between values 0.435 to 0.82. Regression analyses revealed that sediment yield was more closely correlated to runoff than rainfall. The determination coefficient (R2) of the relationship between runoff and sediment yield for different land use was ranged 0.17 to 0.823. Land use type was an important explanatory factor for the variation in runoff and sediment, whereas slope was not. On average, the plots with sugarcane land use were found to produce higher amount of runoff as well as sediment followed by Maize, Blackgram and fallow land. In addition, both runoff coefficient and sediment yield were found to decreased with final infiltration rate of plots. The previous day soil moisture does not seem to play important role on hydrological response as event runoff coefficient (C) was found to correlate insignificantly with previous day soil moisture (θ).

Field Steady State Infiltration Rates of Soils in Kumba - Cameroon: Validation of Some Empirical Predictive Infiltration Models and GIS Applications

Kumba capital of Meme Division, one of the largest cocoa cash crop producing areas in Cameroon, is a typically agrarian town that needs a good understanding of the soil properties of the area. The evaluation of steady state infiltration rates of soils is important in agriculture, groundwater resources preservation and civil engineering to; increase the availability of data, determine regions of aquifer recharge and discharge, infer soil types, evaluate soil suitability for agriculture and provide another tool for generating water resources management parameters in the area. The double ring infiltrometer method was used to measure field infiltration rates from which steady state infiltration rates were determined. The steady state infiltration rates were compared to those determined using empirical predictive models to rate these models’ performance in Kumba. There is significant spatial variation in the steady state infiltration rates (vertical saturated hydraulic conductivities) in the vadose zone of the phreatic aquiferous formations in Kumba. The steady state infiltration rate values range from 0.01-0.96 m/d. Inferred soil types are 7.7% sandy soils, 26.9% sandy silty soils, 19.2% loam and 42.3% clays and 3.8% sodic clayey soils. Infiltration rate classes determined are; very slow to slow (46.1%), slow to moderately slow (19.2%), moderately-slow-to-moderatelyrapid (19.2%), moderately rapid to rapid (7.7%) and very rapid (7.7%). Soil’s suitability for surface irrigation is 38.5% optimum, 7.7% suitable, 34.6% marginally suitable and 7.7% unsuitable. 7.7% of soils are suitable and 34.6 % marginally suitable for rice cultivation. Recharge zones are located towards the south and southwestern parts of Kumba. Comparing measured and predictive model-estimated infiltration rates, the Kostiakov model gives the best prediction for the final infiltration rate in Kumba.

Effects of riverbed and lake bottom sediment thickness on infiltration and purification of reclaimed water

Municipal wastewater reuse has been an important way to enhance water pollution control and water conservation in China. However, many pollutants, such as N, P, chemical oxygen demand (CODCr), and 5-day biochemical oxygen demand (BOD5), are contained in the reclaimed water that can pollute the groundwater environment around rivers and lakes supplied with reclaimed water. Therefore, an environmentally friendly method to control infiltration and purification is quite necessary. Original sediment is one potential option. Therefore, in this study, the effects of sediment thickness at 5, 10, and 20 cm were studied for water infiltration and purification processes in riverbed media. The results indicate that the infiltration efficiency of the riverbed media was reduced when the sediment formed gradually and reached an appreciable level. The thickness was kept at 5–20 cm, and the ranges of the removal efficiencies for BOD5, CODCr, ammonium-nitrogen, nitrate-nitrogen, total nitrogen, and total phosphorus were 47.7–69.0, 49.9–62.7, 90.6–92.5, 30.5–45.8, 42.7–63.1, and 62.2–77.9%, respectively, by a sediment and soil pillar of riverbed media. The removal efficiencies increased by increasing the sediment thickness, and the final infiltration rates were over 10−4 cm/s. The riverbed infiltration remained steady even when thickness was beyond 20 cm, and the purification effect was obvious. The ammonium-nitrogen removal efficiency of the riverbed filtration system did not appear to have an unlimited increase with the increase in sediment thickness. Generally, the existence of a nitrification and denitrification interface was located in the sedimentary layer, and it remained anaerobic at the bottom over a 10-cm thickness. Because ammonium-nitrogen was involved in nitrification, the nitrate-nitrogen concentration of the percolate tended to increase at the beginning of experiments. As the adsorption and nitrification took place, over 90% of ammonium-nitrogen was removed in the riverbed infiltration system through attachment to sediments. The experimental results could be used as references in river regulation.

Biochar effects on soil water infiltration and erosion under seal formation conditions: rainfall simulation experiment

Soil amendment with biochar can result in decreased bulk density and soil penetration resistance, and increased water-holding capacity. We hypothesized that adding biochar could moderate the reductions in infiltration rates (IR) that occur during high-intensity rainstorms in seal-prone soils, and hence result in reduced runoff and erosion rates. The objectives were to (i) evaluate biochar potential to improve infiltration and control soil erosion, and (ii) investigate the mechanisms by which biochar influences infiltration rate and soil loss. Rainfall simulation experiments were conducted on two physicochemically contrasting, agriculturally significant, erosion-prone soils of Israel that are candidates for biochar amendment: (i) non-calcareous loamy sand, and (ii) calcareous loam. Biochar produced from mixed wood sievings from wood chip production at a highest treatment temperature of 620 °C was used as the amendment at concentrations from 0 to 2 wt%. In the non-calcareous loamy sand, 2 % biochar was found to significantly increase final IR (FIR) by 1.7 times, and significantly reduce soil loss by 3.6 times, compared with the 0 % biochar control. These effects persisted throughout a second rainfall simulation, and were attributed to an increase in soil solution Ca and decrease in Na, and a subsequently decreased sodium adsorption ratio (SAR). In the calcareous loam, biochar addition had no significant effect on FIR but did reduce soil loss by 1.3 times. There were no biochar-related chemical changes in the soil solution of the calcareous loam, which corresponds to the lack of biochar impact on FIR. Surface roughness of the calcareous loam increased as a result of accumulation of coarse biochar particles, which is consistent with decreased soil loss. These results confirm that biochar addition may be a tool for soil conservation in arid and semi-arid zone soils.

Evaluation of Infiltration Capacity and Water Retention Potential of Amended Soil Using Bamboo Charcoal and Humus for Urban Flood Prevention

In Japan, floods occur frequently in urban areas because non-infiltrating areas are seeing increased urbanization. To prevent floods, urban basins must improve the infiltration capacity and water retention of the whole basin. There are several basic technologies for river basin management, such as infiltration trenches or rainwater storage. However, a method of soil amendment that prevents flood disasters has not been established. This study aims to evaluate the infiltration capacity and water retention potential of soil amendments using bamboo charcoal and humus. A constant-head infiltration test and rainfall simulation were conducted to evaluate the properties of the soil amendments. The combination ratios of the improved soils used in the experiment were (1) 100% decomposed granite, (2) mixed with 10% bamboo charcoal, (3) mixed with 20% bamboo charcoal, (4) mixed with 30% bamboo charcoal, (5) mixed with 10% humus, (6) mixed with 20% humus, and (7) mixed with 30% humus. The constanthead infiltration test's results showed that soils mixed with 30% humus had the greatest potential for influencing initial and final infiltration rates, and the more the mixing rates of bamboo charcoal and humus were increased, the higher the water retention capacity. The results of the rainfall simulation showed that soils mixed with 30% humus had the highest final infiltration rates and lowest multiplication spillage. To reduce the runoff volume using soil amendment technology, it is important to delay overland flow, and the hydraulic properties of the soils mixed with bamboo charcoal and humus were as effective as those of granite soils.

Amending Soil with Sludge, Manure, Humic Acid, Orthophosphate and Phytic Acid: Effects on Infiltration, Runoff and Sediment Loss

AbstractApplication of organic wastes to cultivated lands can replace mineral fertilizers but may also alter soil physical properties and enhance pollution potential. The objective of this study was to investigate the effects of biosolids [composted manure (MC) and activated sludge (AS)] and specific biosolid component [orthophosphate (OP), phytic acid (PA) and humic acid (HA)] application on soils differing in texture [loamy‐sand (Ramat‐HaKovesh, RH), loam (Gilat, GL) and clay (Bet‐Dagan, BD)], infiltration rate, runoff volume and soil sediment loss. The soils were packed in erosion boxes (400 × 200 × 40 mm) and subjected to six consecutive simulated rainstorms, each of 186 mm deionized water. The results showed that runoff volume and sediment loss from untreated soils increased with increasing clay contents. In treated soils, the response to AS application differed from the response to other amendments; in the BD clay and GL loam, it was the only amendment that caused a decrease in sediment removed by runoff. In the RH loamy‐sand, all amendments reduced the final infiltration rate, but only AS and HA increased the measured runoff. It is proposed that the difference in the response of the soils to the amendments is associated with the soil's ability to attenuate changes in the negative charge on the clay edges following the increase in the specific adsorption of charged anions, thus controlling clay swelling and maintaining aggregate integrity. The effects of amending soils with a source of organic matter in order to control runoff and soil erosion are not straight forward and depend on soil and amendment properties. Copyright © 2015 John Wiley & Sons, Ltd.

Effect of Inorganic Fertilizers and Farm Yard Manure on Physical Properties of Soil Under Rice-Wheat Cropping

In rice-wheat cropping, puddling of field in standing water damages soil structure and affects soil physical properties. Application of inorganic fertilizer and organic manure stimulates crop biomass and amount of residue returned into soil after crop harvest, and may improve soil physical properties. Therefore, a field experiment was conducted for 5 years at Regional station, Gurdaspur to assess the effect of inorganic fertilizers and farmyard manure (FYM) applied either alone or conjointly on physical properties of soil under rice-wheat cropping system. Soil fertility management treatments consisted of unfertilized control, NPK, FYM, N+FYM and NPK+FYM. Soil porosity increased significantly (p<0.05), while bulk density (Db) decreased with the application of NPK and FYM. The effect was however, more pronounced when applied conjointly. Final infiltration rate also increased significantly with the application of NPK and FYM either alone or conjointly, although the effect was greater when applied conjointly. Saturated hydraulic conductivity (Ks), on the other hand was significantly higher with FYM, compared with NPK alone application. Application of FYM either alone or conjointly with inorganic fertilizers (N+FYM/NPK+FYM) did not significantly influenced Ks. Soil moisture retention at field capacity (FC) and permanent wilting point (PWP) increased significantly with NPK+FYM application. Our results showed that conjoint application of inorganic fertilizers and organic manure improved physical properties of soil under ricewheat cropping system.

Slope length effects on processes of total nitrogen loss under simulated rainfall

Slope length effects on the processes of soil erosion have been the focus of research on hillslope hydrology and sediment transport. A field experiment was conducted to investigate the effects of slope lengths (1, 5, 10, 15 and 20m) and rainfall intensities (75, 50 and 25mmh−1) on runoff, soil and total nitrogen (TN) losses under simulated rainfall conditions. Kastanozem was selected in the experiment. Generally, runoff rates and runoff-associated TN loss rates decreased with slope length, whereas sediment and sediment-associated TN losses increased with slope length under three rainfall intensities. The relationship between runoff and time could be described by the Horton infiltration model, with a correlation coefficient R2>0.85. The function parameters of final infiltration rate (if) and coefficient (c) were closely related to slope length, suggesting that a model of runoff processes correlated to slope length was established. There was a significant positive power relationship between runoff and sediment yield rates (p<0.01). Runoff-associated TN losses were mainly controlled by runoff rates, whereas sediment-associated TN losses were mainly controlled by sediment yield rates, and positive linear correlations best represented their relationships. Because sediment-associated TN losses dominated the total TN losses, sediment yield rates were positively correlated with the total TN losses. Increasing rainfall intensity generally increased runoff, sediment yield and TN loss rates, but changes in rainfall intensity did not influence their relationships. This study demonstrated that a model could be established to simulate the processes of TN loss for different slope lengths.

Relationship between soil erodibility and modeled infiltration rate in different soils

The relationship between soil erodibility, which is hard to measure, and modeled infiltration rate were rarely researched. Here, the soil erodibility factors (K and Ke in the USLE, Ki and K1 in the WEPP) were calculated and the infiltration rates were modeled based on the designed laboratory simulation experiments and proposed infiltration model, in order to build their relationship. The impacts of compost amendment on the soil erosion characteristics and relationship were also studied. Two contrasting agricultural soils (bare and cultivated fluvo-aquic soils) were used, and different poultry compost contents (control, low and high) were applied to both soils. The results indicated that the runoff rate, sediment yield rate and soil erodibility of the bare soil treatments were generally higher than those of the corresponding cultivated soil treatments. The application of composts generally decreased sediment yield and soil erodibility but did not always decrease runoff. The comparison of measured and modeled infiltration rates indicated that the model represented the infiltration processes well with an N–S coefficient of 0.84 for overall treatments. Significant negative logarithmic correlations have been found between final infiltration rate (FIR) and the four soil erodibility factors, and the relationship between USLE-K and FIR demonstrated the best correlation. The application of poultry composts would not influence the logarithmic relationship between FIR and soil erodibility. Our study provided a useful tool to estimate soil erodibility.

Water infiltration post-liquid dairy manure application in no-till Oxisol of Southern Brazil

Use of liquid dairy manure (LDM) is a common practice by livestock producers. However, soil, water and nutrient losses occur after intense rainfall. The objectives of this study were to: i) verify which infiltration model, i.e., Kostiakov–Lewis, Horton or Philip, is more appropriate to estimate final infiltration rate in a no-till soil after different amounts of LDM application (0, 30, 60 and 90m3ha−1); and ii) evaluate the effect of LDM application on the infiltration rate over time (1, 5, 10, 25 and 40 days). LDM application resulted in high infiltration variability. Among the infiltration models, the Horton model retained the best fit. The lowest final infiltration occurred at 90m3ha−1, 1 day post LDM application. Overall, infiltration did not differ for any LDM dosage for intervals longer than 5 days. Based on our analysis, we would recommend a maximum LDM dosage of 60m3ha−1 applied at least 5 days prior to high intensity rainfall. This procedure would minimize environmental problems with runoff associated pollutants.

Effect of 10-year continuous saffron cultivation on physical and chemical properties of soil

The effect of 10-year continuous saffron cultivation on physical and chemical properties of a silty clay loam soil was investigated in a research farm of College of Agriculture, Shiraz University, Shiraz (52 o 33ʹ E Longitude and 29o 36ʹ N latitude), Iran. This farm was irrigated with different regimes (100% of saffron's potential evapotranspiration (ETp), 75%ETp, 50%ETp) including rain fed treatment under two irrigation methods (basin and furrow irrigation). The results showed that the values of electrical conductivity, sodium adsorption ratio, Arsenic, Boron and soil bulk density of soil in the root zone increased significantly, but the final infiltration rate decreased significantly compared to the original soil. The value of pH in 100%ETp and 75%ETp treatments decreased and in 50%ETp and rain fed treatments increased compared to the original soil. Corms under high irrigation treatment had more weight up to a 6-year cultivation. However, after that, the corm weight declined to levels equal to or less than the low irrigation treatment cases. The number of total corms increased up to 6 years of cultivation and decreased after that. So, the continuous saffron cultivation causes some undesirable change in soil chemical and physical properties, which become pronounced after 6 years of cultivation.

Rainfall intensity and slope gradient effects on sediment losses and splash from a saline–sodic soil under coastal reclamation

Rainfall intensity and slope gradient play important roles in soil erosion processes. This study was conducted to investigate the effects of rainfall intensity and slope gradient, as well as of their interactions, on splash and overland flow transport on saline–sodic soil slopes. Rainfall intensities of 85, 95, 110 and 125mmh−1 were applied to slope gradients of 6°, 11°, 22° and 35°. Splash was partitioned into four directional components. Runoff, sediment and splash samples were collected throughout the rainstorms and infiltration was calculated. The final infiltrations under the lower rainfall intensities of 85mmh−1 were the largest for every slope gradient, but they decreased by 39.3% as the slope gradient increased from 6° to 35°. However, the final infiltration rates exhibited an increasing–decreasing trend for rainfall intensities higher than 85mmh−1 as the slope gradient increased. The critical slope gradient was about 11°. The influence of rainfall intensity on runoff was considerably reduced at the higher slope gradients due to increased infiltration. The influence of slope gradient on sediment loss was reduced as rainfall intensity increased, while the effect of rainfall intensity on sediment losses was greater on the gentler slopes than on the steeper slopes. The upslope splash (mean value) initially increased from 4.8 to 7.2gm−1h−1 before it decreased to 3gm−1h−1 as the slope gradient increased. The maximum measured value occurred when the slope gradient was 22°. Total splash increased to maximum levels as the slope gradient increased to 11°, but decreased with further increases in gradient. These results indicated that the effects of slope gradient and rainfall intensity on sediment losses, runoff and splash were interconnected.

Employment of Pedo-transfer functions for predicting initial and final infiltration rates using horton model and soil readily available characteristics

Field measurements of initial and final infiltration rates, two important soil characteristics in soil water management, are costly and time consuming. Research efforts are on for determining them by using the Horton model. Pedo-transfer functions (PTFs) were applied for predicting initial and final infiltration rates, and empirical coefficient k of the model using readily available characteristics (RACs) of the soil. Several RACs of the soil besides the soil infiltration curves were determined in 135 different points of East Azarbayjan Province, Iran. The infiltration rates of the model could be predicted reasonably well using the applied PTFs. Applied PTFs resulted in accurate prediction of initial and final infiltration rates of the model with adjusted R2 of 0.798 to 0.872 and 0.639 to 0.715, respectively. There was however, low accuracy for the empirical coefficient of the model.

Modified CN Method for Small Watershed Infiltration Simulation

AbstractInfiltration is an essential process in watershed hydrology. The curve number (CN) method has been widely used to calculate watershed infiltration for a given rainfall input but does not consider steady infiltration. This study develops a modified CN (MCN) method that included a term for the steady infiltration amount (Fc). Observed rainfall–runoff data for 14 rainfall events from a typical small watershed on the Loess Plateau of China were used to derive the watershed final infiltration rate (fc). Watershed infiltration after runoff initiation was then calculated by both the MCN and CN methods using initial abstraction values that were either observed (Ia−obs) or calculated (Ia−0.2 S) based on the calibrated fc. Three criteria [relative error (Er), model efficiency coefficient (E), and root mean square error (RMSE)] and visual assessments of graphed results were used to evaluate the methods’ simulation performances. The MCN method generally outperformed the CN method when using either of the ini...

Soil Physical Characteristics and Crop Productivity as Affected by Tillage in Rice-Wheat System

Tillage practices significantly influences soil physical characteristics and crop productivity. The infiltration characteristics, bulk density, porosity, penetration resistance, grain yield of rice and wheat were measured under no-till without residue (NT), roto-tillage (RT), and no-till with residue i.e. happy seeder (HS) in rice-wheat cropping system in sandy loam (SL) and loamy sand (LS) soils. For surface soil layer (0-15 cm) highest soil bulk density (Mg m-3) was recorded in HS (1.58) followed by RT (1.56) and NT (1.55) in LS soil. Soil porosity ranged from 40.6 % to 41.2 % under HS and RT, respectively for 0-15 cm depth in SL soil. The PR (K Pa) varied from 2412 (NT) to 2539 (HS) in SL. In LS soil PR (K Pa) varied from 2433 (NT) to 2603 (RT). Final infiltration rate (FIR) varied from 0.1 to 0.3 cm hr-1 under RT and NT in SL soil, while, in LS soil FIR varied from 0.5 to 0.8 cm hr-1 in RT and HS, respectively. Maximum rice grain yield (t ha-1) was recorded in RT (8.0) followed by NT (7.5) and HS (7.0) in SL soil. The corresponding rice yield (t ha-1) in LS was 6.5, 5.8 and 5.5 in RT, NT and HS, respectively. Wheat straw yield (t ha-1) ranged from 4.9 (NT) to 5.9 (HS) in SL soil. The wheat grain yield (t ha-1) was observed to be maximum in HS (4.5), followed by RT (4.0) and NT (3.9) in SL soil, while in LS soil the wheat grain yield (t ha-1) values were observed to be 2.7, 3.0 and 3.6 in NT, RT and HS, respectively. No significant effect of tillage and residue management practices was observed on grain yield of rice and wheat, however, significant changes were observed on water transmission characteristics and straw yields.

Impacto hidrológico del cambio de uso del suelo de un pastizal nativo a praderas de zacate buffel (Pennisetum ciliare L.)

El objetivo de este trabajo es documentar el impacto del establecimiento de praderas de zacate buffel (Pennisetum ciliare L.) en terrenos de pastizal, sobre la tasa de infiltración del suelo. El estudio se estableció en el área de San Luis del Cordero, Dgo. Para determinar el impacto se realizaron pruebas de infiltración con un simulador de lluvia en praderas de zacate buffel y en terrenos de pastizal nativo. Las simulaciones se realizaron en condiciones secas y húmedas (24 horas después de las simulaciones en seco) para tres repeticiones en cada uso del suelo y condición de humedad. La base de datos hidrológica, lámina precipitada (mm) y volumen escurrido (l) fueron medidos cada 5 minutos durante la prueba, la cual tuvo una duración de 50 minutos. Los resultados indican que para las dos condiciones de uso del suelo la tasa de infiltración final se puede clasificar como moderada (entre 2.0 a 6.6 cm·h-1). Para las tasas de infiltración, la evaluación del cambio en el uso del suelo de un pastizal nativo al establecimiento de una pradera de zacate buffel en la región de estudio no representó diferencias estadísticamente significativas (P ≤ 0.05) entre usos de suelo. Para el sitio experimental, en la condición de la pradera con zacate buffel y la de pastizal nativo, en promedio la tasa de infiltración final fue de 5.04 y 3.88 cm·h-1, respectivamente.