Soil Erosion

Introduction The prediction of soil erosion by water can be useful in understanding the risk of soil loss as well as the impact of potential climate change, and the Water Erosion Prediction Project (WEPP) model can be a useful tool. WEPP is new generation erosion prediction technology developed by the USDA-Agricultural Research Service in the United States, and is a process-based, distributed parameter, continuous simulation model (Flanagan and Nearing, 1995). It was developed to replace the mature Universal Soil Loss Equation (USLE) technology (Wischmeier and Smith, 1978) for estimating soil loss on hillslope profiles. WEPP also provides additional functionality over USLE by predicting sediment deposition, sediment delivery from fields and small watersheds, and spatial and temporal estimates of soil loss. WEPP was initially developed for widespread use in the United States, with databases created there for climate, soils and management practices. This work examined application of the WEPP model in a Mediterranean environment. Creation of model input files specific for the climate, soils and cropping/management in Sicily was necessary. WEPP was applied in two ways – in an uncalibrated mode using default model parameterization equations for erodibility and infiltration variables based on basic soil properties (Flanagan and Livingston, 1995); and calibration simulations adjusting effective hydraulic conductivity to affect runoff predictions and soil critical hydraulic shear to impact soil loss predictions.

So far, drying systems have not been classified systematically. However, drying methods can be broadly classified on the basis of either the mode of heat transfer to the wet solid or the handling characteristics and physical properties of the wet material. The first method of classification reveals differences in dryer design and operation, while the second method is most useful in the selection of a group of dryers for preliminary consideration in a given drying problem. According to the mode of heat transfer, drying methods can be divided into: (a) conduction drying, (b) convection drying, and (c) radiation drying. There are other methods of drying also, namely, dielectric drying, chemical or sorption drying, vacuum dryi ng, freeze drying, etc. Of them, convection drying is commonly used for drying of all types of grain and conduction drying can be employed for drying of parboiled grain. Conduction drying When the heat for drying is transferred to the wet solid mainly by conduction through a solid surface (usually metallic) the phenomenon is known as conduction or contact drying. In this method, conduction is the principal mode of heat transfer and the vaporised moisture is removed independently of the heating media. Conduction drying is characterised by: (a) Heat transfer to the wet solid takes place by conduction through a solid surface, usually metallic. The source of heat may be hot water, steam, flue gases, hot oil, etc.; (b) Surface temperatures may vary widely; (c) Contact dryers can be operated under low pressure and in inert atmosphere; (d) Dust and dusty materials can be removed very effectively; and (e) When agitation is done, more uniform dried product and increased drying rate are achieved by using conduction drying. Conduction drying can be carried out either continuously or batch-wise. Cylinder dryers, drum dryers, steam tube rotary dryers are some of the continuous conduction dryers. Vacuum tray dryers, freeze dryers, agitated pan dryers are the examples of batc h conduction dryers. Convection drying In convection drying, the drying agent (hot gases) in contact with the wet solid is used to supply heat and carry away the va porised moisture and the heat is transferred to the wet solid mainly by convection. The characteristics of convection drying are: (a) Drying is dependent upon the heat transfer from the drying agent to the wet material, the former being the carrier of vaporis ed moisture; (b) Steam heated air, direct flue gases of agricultural waste, etc., can be used as drying agents; (c) Drying temperature varies widely; (d) At gas temperatures below the boiling point, the vapour content of the gas affects the drying rate and the final moisture content of the solid; (e) If the atmospheric humidities are high, natural air drying needs dehumidification; and (f) Fuel consumption per kg of moisture evaporated is always higher than that of conduction drying. Convection drying is most popular in grain drying. It can be carried out either continuously or batch-wise. Continuous tray dryers, continuous sheeting dryers, pneumatic conveying dryers, rotary dryers, tunnel dryers come under the continuous system, wherea s tray and compartment dryers, batch through circulation dryers are the batch dryers. Convection drying can be further classified as follows: Pneumatic or fluidised bed drying: When the hot gas (drying agent) is supplied at a velocity higher than the terminal velocity of the wet solid, the drying of the wet solid occurs in a suspended or fluidised state. This phenomenon is known as fluidised bed drying. Drying may be carried out in a semi-suspended state or spouted bed condition also. Generally, the convection drying is conducted under ordinary state, i.e., drying agent is supplied at a velocity much lower than the terminal velocity of the wet m aterial. In natural air drying, the unheated air as supplied by the nature is utilized. In drying with supplemental heat just sufficient amount of heat (temperature rise within 5 to 10°C) only, is supplied to the drying air to reduce its relative humidity so that drying can ta ke place. In heated air drying, the drying air is heated to a considerable extent. The natural air drying and drying with supplemental heat methods which may require one to four weeks or even more to reduce the grain moisture content to safe levels, are generally used to dry grain for short-term storage in the farm. Heated air drying is most useful when large quantity of grain is to be dried within a short time and marketed at once. It is used for both short and long-term storage. Comparative advantages and disadvantages of the three convective drying methods are given as follows: NATURAL AIR DRYING: Advantages: (1) Lowest initial investment and maintenance cost. (2) No fuel cost. (3) No fire hazard. (4) Least supervision. (5) Least mould growth compared to supplemental heat. Disadvantages: (1) Very slow drying rate, drying period may be extended to several weeks. (2) Weather dependent. (3) More drying space necessary in comparison to heated air drying. (4) Useful particularly for short-term storage in the farm. (5) Not useful for humid tropics. SUPPLIMENTAL HEAT DRYING: Advantages: (1) Lower cost of equipment and maintenance. (2) Independent of weather. (3) Requires less supervision. (4) Most Convection drying Drying under Fluidised state Drying under Spouted bed condition Drying under ordinary state Natural / unheated air drying Heated air drying Air drying with supplemental heat

Magnetic soils can seriously hamper the performance of electromagnetic sensors for the detection of buried land mines and unexploded ordnance (UXO). Soils formed on basaltic substrates commonly have large concentrations of ferrimagnetic iron oxide minerals, which are the main cause of soil magnetic behavior. Previous work has shown that viscous remanent magnetism (VRM) in particular, which is caused by the presence of ferrimagnetic minerals of different sizes and shapes, poses a large problem for electromagnetic surveys. The causes of the variability in magnetic soil properties in general and VRM in particular are not well understood. In this paper we present the results of laboratory studies of soil magnetic properties on three Hawaiian Islands: O"ahu, Kaho"olawe, and Hawaii. The data show a strong negative correlation between mean annual precipitation and induced magnetization, and a positive correlation between mean annual precipitation and the frequency dependent magnetic behavior. Soil erosion, which reduces the thickness of the soil cover, also influences the magnetic properties.

The environmental effects of the three strawberry (Fragaria ×ananassa) cold-climate production systems were compared: the traditional method of conventional matted row (CMR) and the two more recently developed practices of advanced matted row (AMR) and cold-climate plasticulture (CCP). Side-by-side field plots were instrumented with automated flow meters and samplers to measure and collect runoff, which was filtered and analyzed to determine soil, pesticide, and nitrogen losses. Although annual mean runoff volumes were similar for all three production systems, the soil losses from CMR plots were two to three times greater than the CCP plots throughout the study and two to three times greater than the AMR plots only in the first year of the 3-year study. In general, decreases in erosion and runoff volumes were observed in plots that were disturbed less by machine operations and had less foot traffic as a result of decreased need for hand weeding and in the plots that used straw mulch...

Assessment of soil erosion risk, especially in hilly areas, is a challenging task mainly due to variability in topography and non-availability or insufficiency of relevant data. The Revised Universal Soil Loss Equation (RUSLE) model is applied worldwide for prediction of soil loss. Although it is an empirical model, it not only predicts erosion rates of ungauged watersheds but also presents the spatial heterogeneity of soil erosion that is too feasible with reasonable costs and better accuracy in larger areas. Remote sensing (RS) technology plays an important role in mapping of soil erosion risk in agriculture, forest and degraded land. Its application in the soil erosion risk mapping introduces new opportunities for conservation planning and management. With the incorporation of Geographical Information System (GIS), it is possible to analyze satellite data, which gives required information like land use and cover, slope, distribution of rainfall, flow direction etc. of study watershed. The capabilities of these technologies even increase when they are integrated with empirical erosion prediction models like RUSLE. RS and GIS integrated erosion prediction models do not only estimate soil loss but also provide the spatial distributions of the erosion. Generating accurate erosion risk maps in GIS environment is very important to locate the areas with high erosion risks for prioritization and to develop adequate conservation techniques. Micro-watershed prioritization within a large watershed is considered as one of the most important aspects of planning and development for natural resources for soil and water conservation measures. This review article highlights the application of RUSLE, RS and GIS technology in the study of soil erosion and gives an insight of their valuable application in soil erosion risk mapping

Climate models indicate that there will be an increase in both average annual temperature (+4.5 o C) and rainfall in the Midwestern U.S. by the year 2050 which may result in warmer, wetter conditions. Perhaps the most important factor will be less predictable weather patterns that will emerge, increasing the frequency of extreme weather events such as heavy downpours of precipitation, late season frosts and droughts. For example, July rainfall may increase 20% and might come in just two rainfall events. This study combines expertise from several disciplinary areas with modeling strategies to assess the impact of global climate change on midwestern agriculture. Predictions of warmer summers, wetter springs, and more extreme events indicate that the cropping system may need to be adjusted to effectively conserve soil, maintain timely planting, avoid early season frost damage, and respond to warmer growing conditions. Climate projections (HADCM2), crop growth models (DSSAT), the Water ...

Although USLE and RUSLE have been adjusted and validated for use in Uruguay, soil mass losses should be expressed in terms of soil productivity or land value losses, in order to guide management decision-making, and assess its impact in productive and economic terms. Procedures to this have been published (e.g. EPIC), but are not yet validated in Uruguay. Being extensive animal production, based on natural pastures grazing, the main agricultural activity in Uruguay (about 80% of the land), soil productivity loss due to soil erosion should be better expressed in these terms. Uruguay has a system of soil productivity assessment at individual farm level, that expresses soil potential animal production of beef and wool as a quantitative Productivity Index (PI), referred to the national average (PI=100). This system was developed 25 years ago overlapping soil maps at 1:20,000 scale, with the official records of production of 721 administrative divisions of the country, and the available ...

Status of organic carbon (C), total nitrogen (N), available potassium (K), calcium (Ca) and phosphorus (P) in three different depths (0−5 cm, 5−15 cm and 15−30 cm) on two hill slopes of 35% and 55% in orange orchard cultivated by the Mro tribe of Chittagong Hill Tracts (CHTs) were evaluated and compared with those in degraded bush forests, through digging three profiles in each land use. The content of all the five nutrients was found to be higher in the soil of orange orchard than in the soil of forest. But the variation was not consistent for both the slopes. The content varied depth wise also, having the highest value in surface soil in case of both the land uses on both the slopes. A mean available K content was significantly higher in orange orchard than in forest on 55% slope, while it was lower on 35% slope. Surface soil contained the nutrients of K and Ca with the amount of 0.2905-mg·g -1 soil and 3.025-mg·g -1 soil respectively in the orchard, while 0.1934-mg·g -1 soil and ...

The study was aimed at determining the effects of industrial effluents on the soil environment of Challawa industrial area, Kano State Nigeria. Profile pit soils were sampled in the areas affected by industrial effluents and the adjacent control area. Sampled soils were carried to the laboratories for physical (sand, silt and clay) and chemical (pH, OC, AP, Ca, Mg, K, Na, N, ECEC) properties determinations. The result of the analysis showed that different horizons of the affected pits had less sand than what was obtained at the unaffected pit (average 615.78 and 670 respectively), Apart from pH, nitrogen, available phosphorus content of the soils that were lower at the horizons from the affected area of the industrial site(on the average, pH 6.45; N-0.20 g/kg; AP-3.97 mg/kg), all other chemical properties (exchangeable bases like Ca (1.15 cmol/kg), Mg (0.4 cmol/kg) and Na (0.23 cmol/kg) were lower at the horizons of the unaffected profile pits. Other physical and chemical properties of the soils collected like the pH, organic carbon, total nitrogen and available phosphorus, Ca, Mg, K and Na were low in some pits and in some pits had higher concentration at the affected area. The revelation from the analysis showed that the top and upper horizons of the soil at the industrial site has been seriously tampered with by industrial effluents and inhabitants should be advised to plant mostly shallow rooted crops and cultivate on land farther away from the effluent sludge.

Soil erosion research is a popular topic in soil science that appears in conjunction with several other topics like soil and/or water conservation, soil physics, - chemistry and - biology and others. A request for the term "soil erosion" on CAB abstract CD, dated from January 1992 to January 2001, resulted in 15.531 articles. According to the publication year on

This paper examines biocementation via the microbial-induced carbonate precipitation (MICP) process as an appropriate and promising new technology for stabilisation of loose sand and silty sand deposits as a method to mitigate wind erosion. The technique involves spray treating the sand surface layer with a mixture of cementation and bacterial-cell solutions, the ensuing reactions causing calcite precipitation to occur between the sand grains, thereby lightly cementing them together over time. The bench-scale experimental programme presented investigates the proposed technique's effectiveness for stabilisation of silica and carbonate sands with different gradations, determination of the optimal reagent concentrations, the time-dependent shear strength development for the crustal sand layer following single-and double-MICP spray treatments, as well as wind tunnel experiments. Of particular novelty were investigations of the effect of dew formation on crustal shear strength development with curing period and the efficiency of the MICP treatment for the outdoor environment compared to laboratory-controlled test conditions. The wind tunnel experiments demonstrated that 28-day cured singly MICP-spray-treated crustal sand layers were stable to simulated 20 m·s−1 winds measured at 20 cm above the layer surface.

Tbe potential for using coal-derived humic substances to improve the available water holding capacity (AWC) and awegate stability of typical Mediterranean soils was evaluated in the laboratory using an agricultural surface (0-20 cm) soil from each of three regions of Ital}, (Sicil}, Tuscany and Venetia) and five rates of humic acids (HA), 0, 0.05, 0.10, 0.50 and 1.00 g/kg.There were significant (P < 0.05) differences between the field capacity (FC), permanent wilting point (PWP), and availablewatercapacity(AWC) values of the controls and those treated with 0.05 glkg of the HA. Beyond this rate, differences in these pr[)perties were not significant. At the 1.00 g/kg HA rate, the relati,'e improvements in AWe over the three controls were 30%, 10% and 26%. Low rates (0.05 to 0.10 g/kg) of HA were also needed to obtain a 40 to 120% improvement in aggregate stability of these soils relative to the controls. These results indicate that the addition of highly humified organic matter such as coal-derived humic substances can improve the structural and water retention properties of degraded arable soils. However, since there is not yet any direct evidence that these humic materials can ameliorate soils under field conditions, field studies will be needed to validate these results.

In tropical acid soils, acidity is an important constraint for availability and uptake of nutrients by annual crops, and this leads to lower crop yields. Factors that contribute to low nutrient uptake efficiencies in these soils are low natural levels of most essential plant nutrients and unfavorable soil and plant environments. High P fixation capacity, Al, Mn and H toxicity,

In planning of a sound land and water management system for an area, assessment of rainfall erosivity and potential soil erosion is a prerequisite. A study was carried out using rainfall data and land characteristics to estimate the erosion risk in the central dry zone of Sri Lanka. Six locations were selected to represent the study region. Detailed analysis of rainfall data at Maha Illuppallama was carried out and results were examined with respect to other locations too. Results indicated that 70% of yala rainfall and 50-55% of maha rainfall are erosive. However, 55 65% of annul erosive rains occur during the maha monsoon. Erosion risk is high in low elevated areas. However, spatial variation of potential erosion is not only due to erosivity but also due to slope changes. The months, March and September would be vulnerable for high erosion risk as arable lands are bare because of clearing for seasonal cultivation in these two months.

KEY WORDS: Rainfall erosivity, Rhodustalf, Soil erosion