Sayjro K. Nouwakpo, Christopher J. Williams, Osama Z. Al-Hamdan, Mark A. Weltz, Fred Pierson, Mark Nearing, A review of concentrated flow erosion processes on rangelands: Fundamental understanding and knowledge gaps, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 75-86, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.05.003.

(http://www.sciencedirect.com/science/article/pii/S2095633916300168)

Abstract: Abstract

Concentrated flow erosion processes are distinguished from splash and sheetflow processes in their enhanced ability to mobilize and transport large amounts of soil, water and dissolved elements. On rangelands, soil, nutrients and water are scarce and only narrow margins of resource losses are tolerable before crossing the sustainability threshold. In these ecosystems, concentrated flow processes are perceived as indicators of degradation and often warrant the implementation of mitigation strategies. Nevertheless, this negative perception of concentrated flow processes may conflict with the need to improve understanding of the role of these transport vessels in redistributing water, soil and nutrients along the rangeland hillslope. Vegetation influences the development and erosion of concentrated flowpaths and has been the primary factor used to control and mitigate erosion on rangelands. At the ecohydrologic level, vegetation and concentrated flow pathways are engaged in a feedback relationship, the understanding of which might help improve rangeland management and restoration strategies. In this paper, we review published literature on experimental and conceptual research pertaining to concentrated flow processes on rangelands to: (1) present the fundamental science underpinning concentrated flow erosion modeling in these landscapes, (2) discuss the influence of vegetation on these erosion processes, (3) evaluate the contribution of concentrated flow erosion to overall sediment budget and (4) identify knowledge gaps.

Keywords: Erosion; Rangeland; Concentrated flow; Rill; Gully

Xiaonan Shi, Tingwu Lei, Yan Yan, Fan Zhang, Determination and impact factor analysis of hydrodynamic dispersion coefficient within a gravel layer using an electrolyte tracer method, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 87-92, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.05.001.

(http://www.sciencedirect.com/science/article/pii/S2095633916300120)

Abstract: Abstract

Hydrodynamic dispersion is a measure for describing the process of solute transport in porous media. Characterizing the dispersion of water flow within gravel is essential for the prediction of solute transport especially nonpoint source pollutants migration in alpine watersheds where the land surface is typically covered with gravel. In this study, an integrated model and experimental method using an electrolyte tracer is proposed for determination of the hydrodynamic dispersion coefficient. Two experimental scenarios were designed to measure electrolyte tracer transport processes in both free water flow and gravel layer flow under different slope gradients and transport distances. Subsequently, the measured data were used to simultaneously calculate both the hydrodynamic dispersion coefficient and flow velocity by fitting the experimental data with the mathematical model. Dispersivity, as a critical feature of hydrodynamic dispersion, was determined as well under the two specified scenarios. Finally, the impact mechanisms of the gravel layer and factors related to the dispersion processes were comprehensively analyzed. The results indicate that the presence of a gravel layer significantly reduces flow velocity and the hydrodynamic dispersion coefficient, but increases solute dispersivity. For the flow within gravel layers, with much lower velocity, the positive effect of the gravel layer on dispersivity may be neutralized or even surpassed by the negative effect of flow velocity. The results should be helpful in characterizing the dispersion processes of water flow within gravel layer and hence in predicting solute transport, especially in nonpoint source pollutants migration in alpine watersheds where the land surface is richly covered with gravel.

Keywords: Hydrodynamic dispersion coefficient; Flow velocity; Gravel layer; Electrolyte tracer

Iraj Eskandari, Hosain Navid, Kazem Rangzan, Evaluating spectral indices for determining conservation and conventional tillage systems in a vetch-wheat rotation, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 93-98, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.04.002.

(http://www.sciencedirect.com/science/article/pii/S2095633915301209)

Abstract: Abstract

Conservation tillage (CT) systems, which consist of reduced and no-tillage systems, retain considerable quantities of crop residues on the soil surface. These crop residues perform as a barrier to wind and water to decrease soil erosion and evaporation. The use of remote sensing technology provides fast, objective and effective tool for estimating and measuring any agricultural event. The challenge is to differentiate the tillage systems by the crop residue cover on the soil surface. Spectrally derived normalized difference tillage index (NDTI), Shortwave infrared normalized difference residue index (SINDRI), cellulose absorption index (CAI) and Lignin-cellulose absorption index (LCA) were examined to distinguish their value as remote sensing methods for identifying crop residue cover in conventional and conservation tillage systems. Tillage treatments included conventional tillage (MD: Mouldboard plow+Disk harrow), reduced tillage (CD: Chisel plow+Disk harrow), minimum till (MT: Stubble cultivator), and no-tillage (NT1 and NT2: with standing stubble and standing stubble plus threshing residue, respectively).

CAI had a linear relationship with crop residue cover, which the comparative intensity of cellulose and lignin absorption features near 2100 nm can be measure by it. Coefficients of determination (r2) for crop residue cover as a function of CAI and LCA were 0.89 and 0.79 respectively. Absorption specifications near 2.1 and 2.3 µm in the reflectance spectra of crop residues in minimum and no- tillage systems were related to cellulose and lignin. These specifications were not evident in the spectra of conventional tillage system. In this study the best index to use was CAI, which showed complete separation tillage systems, followed by LCA and NDTI. Four tillage intensity classes, corresponding to intensive (<6% residue cover), reduced (10–20% cover) minimum (25–40%) and no-tillage (>60% cover) tillage, were recognized in this study.

Keywords: Conservation tillage; Crop residue; Spectral response; Cellulose absorption index

Farnoosh Mahjoor, Ali Asghar Ghaemi, Mohammad Hossein Golabi, Interaction effects of water salinity and hydroponic growth medium on eggplant yield, water-use efficiency, and evapotranspiration, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 99-107, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.04.001.

(http://www.sciencedirect.com/science/article/pii/S2095633915301179)

Abstract: Abstract

Eggplant (Solanum melongena L.) is a plant native to tropical regions of Southeast Asia. The water crisis and drought on the one hand and eggplant greenhouse crop development as one of the most popular fruit vegetables for people on the other hand, led to the need for more research on the use of saline water and water stress to optimize salinity level and their impact on eggplant evapotranspiration and encounter better yield and crop quality. The objective of the present study was to investigate the interactions of water salinity and hydroponic growth medium on qualitative and quantitative properties of eggplant and its water-use efficiency. The study used the factorial experiment based on completely randomized design with three replications of four levels of water salinity (electrical conductivity of 0.8 (control), 2.5, 5, and 7 dS m−1) and three growth media (cocopeat, perlite, and a 50–50 mixture of the two by volume). Total yield, yield components, evapotranspiration, and water-use efficiency were determined during two growing periods, one each in 2012 and 2013. All of these indices decreased significantly as water salinity increased. Water with of 0.8 dS m−1 produced an average eggplant yield of 2510 g per plant in 2012 and 2600 g in 2013. The highest yield was observed in cocopeat. Water with 7 dS m−1 reduced yield to 906 g per plant in 2012 and to 960 g in 2013. Lowest yield was observed in perlite. The highest evapotranspiration values occurred in cocopeat at the lowest salinity in both years. Cocopeat and the cocopeat–perlite mixture were equally good substrates. The mixture significantly improved the quantitative and qualitative properties of eggplant yield.

Keywords: Cocopeat; Greenhouse; Penman–Montith; Qualitative; Water stress; Salinity

Adham Ammar, Michel Riksen, Mohamed Ouessar, Coen Ritsema, Identification of suitable sites for rainwater harvesting structures in arid and semi-arid regions: A review, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 108-120, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.03.001.

(http://www.sciencedirect.com/science/article/pii/S2095633915301118)

Abstract: Abstract

Harvested rainwater is an alternative source of water in arid and semi-arid regions (ASARs) around the world. Many researchers have developed and applied various methodologies and criteria to identify suitable sites and techniques for rainwater harvesting (RWH). Determining the best method or guidelines for site selection, however, is difficult. The main objective of this study was to define a general method for selecting suitable RWH sites in ASARs by assembling an inventory of the main methods and criteria developed during the last three decades. We categorised and compared four main methodologies of site selection from 48 studies published in scientific journals, reports of international organisations, or sources of information obtained from practitioners. We then identified three main sets of criteria for selecting RWH locations and the main characteristics of the most common RWH techniques used in ASARs. The methods were diverse, ranging from those based only on biophysical criteria to more integrated approaches including socio-economic criteria, especially after 2000. The most important criteria for the selection of suitable sites for RWH were slope, land use/cover, soil type, rainfall, distance to settlements/streams, and cost. The success rate of RWH projects tended to increase when these criteria were considered, but an objective evaluation of these selection methods is still lacking. Most studies now select RHW sites using geographic information systems in combination with hydrological models and multi-criteria analysis.

Keywords: Arid and semi-arid regions; RWH Suitability; Multi-criteria; GIS; Modelling

Pius Olufemi Olusegun Dada, Olusegun Rasheed Adeyanju, Olayemi Johnson Adeosun, Johnson Kayode Adewumi, Effects of soil physical properties on soil loss due to manual yam harvesting under a sandy loam environment, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 121-125, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.02.007.

(http://www.sciencedirect.com/science/article/pii/S2095633915300939)

Abstract: Abstract

Soil degradation is a growing problem worldwide because it reduces the fertile top layer of the soil available for food production and one such degradative action is soil erosion due to the harvesting of crops. Soil loss due to crop harvesting with particular reference to yam tubers has not been quantified globally despite the fact that yam is a major staple food consumed worldwide and it is prevalent in many parts of Nigeria. Harvesting yams in our environment is usually done with the soil attached to the yams due to the fact that farmers do not want additional work of removing soil attached to the yams. This study investigates the soil physical properties that influence soil loss due to yam harvesting in Abeokuta, South-Western Nigeria and to assess the quantity of soil loss due to yam harvesting. Based on representative sampling area per location, yam tubers were harvested manually within the entire yam farmland from October to December 2012. Gross weight, net weight and the amount of soil adhering to the yams were measured. Effects of soil physical properties such as soil moisture content, heap bulk density, inter-heap bulk density and soil texture were investigated with respect to soil losses. The results showed that moisture content ranged from 4% to 15%, heap bulk density ranged from 0.93 to 1.29 g cm−3 and inter-heap bulk density ranged from 1.03 to 1.50 g cm−3. They all had a positive correlation with soil loss. Soil particle size analysis for Federal University of Agricultural, Abeokuta (FUNAAB) and Alabata revealed that sand content was (86.78% and 88.32%), clay content (10.69% and 7.6%) and silt content, (2.53% and 4.08%) respectively. Study also revealed that clay content of the soil positively influenced the total soil loss during the yam harvesting. The mean soil losses in Federal University of Agriculture, Abeokuta (FUNAAB) and Alabata village yam farms were 4303 and 2125 kg/ha/harvest respectively. The study also revealed that soil moisture content at harvesting time and clay content are the key factors affecting soil loss due to yam harvesting. Consequently, soil loss due to crop harvesting should be considered in soil erosion control strategies, sediment budget and for better post harvest procedures.

Keywords: Heap bulk density; Manual yam harvesting; Soil degradation; Soil loss; Soil physical properties

Habtamu Sewnet Gelagay, Amare Sewnet Minale, Soil loss estimation using GIS and Remote sensing techniques: A case of Koga watershed, Northwestern Ethiopia, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 126-136, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.01.002.

(http://www.sciencedirect.com/science/article/pii/S2095633915301076)

Abstract: Abstract

Soil loss by runoff is a severe and continuous ecological problem in Koga watershed. Deforestation, improper cultivation and uncontrolled grazing have resulted in accelerated soil erosion. Information on soil loss is essential to support agricultural productivity and natural resource management. Thus, this study was aimed to estimate and map the mean annual soil loss by using GIS and Remote sensing techniques. The soil loss was estimated by using Revised Universal Soil Equation (RUSLE) model. Topographic map of 1:50,000 scale, Aster Digital Elevation Model (DEM) of 20 m spatial resolution, digital soil map of 1:250,000 scale, thirteen years rainfall records of four stations, and land sat imagery (TM) with spatial resolution of 30 m was used to derive RUSLE's soil loss variables. The RUSLE parameters were analyzed and integrated using raster calculator in the geo-processing tools in ArcGIS 10.1 environment to estimate and map the annual soil loss of the study area. The result revealed that the annual soil loss of the watershed extends from none in the lower and middle part of the watershed to 265 t ha−1 year−1 in the steeper slope part of the watershed with a mean annual soil loss of 47 t ha−1 year−1. The total annual soil loss in the watershed was 255283 t, of these, 181801 (71%) tones cover about 6691 (24%) hectare of land. Most of these soil erosion affected areas are spatially situated in the upper steepest slope part (inlet) of the watershed. These are areas where Nitosols and Alisols with higher soil erodibility character (0.25) values are dominant. Hence, Slope gradient and length followed by soil erodibility factors were found to be the main factors of soil erosion. Thus, sustainable soil and water conservation practices should be adopted in steepest upper part of the study area by respecting and recognizing watershed logic, people and watershed potentials.

Keywords: Soil loss; GIS; Remote sensing; RUSLE; Land management; Koga watershed; Ethiopia

Carmelo Dazzi, Giuseppe Lo Papa, Taxonomic and environmental implication of pedotechnique in large scale farming, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 137-141, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.01.001.

(http://www.sciencedirect.com/science/article/pii/S2095633915301222)

Abstract: Abstract

Human activities that involve deep modifications of the soils and a substantial deterioration of their features are numerous and very diverse. Such activities are considered as pedotechniques and, in large-scale farming, are used only under the boost of significant economic returns. In these last decades, the pedotechniques used to tailor soils suitable for table vine cultivation in the Acate valley (Sicily, Italy), not only led to objective difficulties in the classification of these deeply transformed soils but also, to several environmental hazards. In this work after considering the pedotechniques used in tailoring suitable soil for table vine cultivation, we propose to introduce Anthrosols as a new taxonomic soil Order in Soil Taxonomy stressing that a correct soil classification of these deeply modified soils allow for a correct understanding of their features and of the environmental hazards that their management could originate.

Keywords: Pedotechniques; Soil classification; Quality of the environment

Yunyun Ban, Tingwu Lei, Chao Chen, Zhiqiang Liu, Study on the facilities and procedures for meltwater erosion of thawed soil, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 142-147, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.04.003.

(http://www.sciencedirect.com/science/article/pii/S2095633915301106)

Abstract: Abstract

High erosion rate of seasonal thawed soils by snow- and ice-melting runoff in the high altitude and latitude cold regions has great impacts on ecological systems, industries, agriculture and various manmade infrastructures as well as people's lives. The facilities and procedures are of great importance for the studies on simulating erosion processes of melt-frozen soil. This study focuses on the method and facility for simulating the thawing process of frozen soil. The facility includes soil freezing system, melt-water supply system and experimental flume system for thawed soil erosion. The soil freezing system provides enough space to freeze soil columns in flumes. The water supply system deliveries snow- or ice-melting water flow of constant-rate at 0 °C. The soil flumes of 200 or 300 cm long, 10 cm wide and 12 cm high are designed to be assemble and convenient for soil freezing before they are thawed in one-dimensional manner from top to bottom. The one-dimensional thawing process is realized as follows. The frozen soil flume is put on ice boxes and thermally insulated with heat-insulating materials all around to prevent frozen soil from being thawed from sidewalls and bottom. The soil thaws with this system shows that it can meet the requirements of simulating the process of soil thawing from top to bottom. The thawed soil flumes are connected from end to end to form rills of 6–8 m long to run the erosion experiments under different designed hydraulic condition. The equipment provides facility, method and operation process for simulating one-dimensional soil thawing to serve research on the effect of thawed soil depth on erosion process.

Keywords: Melt-frozen; Soil erosion; Method; Facilities; Procedures

Jorge A. Delgado, Rui Li, The Nanchang Communication about the potential for implementation of conservation practices for climate change mitigation and adaptation to achieve food security in the 21st century, International Soil and Water Conservation Research, Volume 4, Issue 2, June 2016, Pages 148-150, ISSN 2095-6339, http://dx.doi.org/10.1016/j.iswcr.2016.05.002.

(http://www.sciencedirect.com/science/article/pii/S2095633916300557)

Abstract: Abstract

There is a large number of peer-reviewed publications reporting that a changing climate is one of the biggest challenges humanity will have during the 21st century. With population growth and the need to significantly increase agricultural production per unit of area during the 21st century, a changing climate will put additional stress on soil resources. Soil and water conservation will be key for the future of humanity. Professional societies in the area of agriculture and soil and water conservation have recognized the importance that soil resources will have for humanity during this century and have made calls for implementation of worldwide soil and water conservation. For example, in 2010 the Soil and Water Conservation Society (SWCS) invited a group of scientists to review the literature about the potential to use conservation practices for climate change adaptation and mitigation. The Delgado et al. (2011) paper was used by the SWCS to develop and adopt a position statement about the importance of using soil and water conservation practices to mitigate and adapt to climate change. The International Soil Conservation Organization (ISCO) invited the lead author to present the paper as a keynote presentation at the ISCO 2013 conference. The European Society of Soil Conservation (ESSC) published a short communication about this paper in one of their newsletters in 2014. The World Association of Soil and Water Conservation (WASWAC) also invited the lead author to present a keynote presentation on this topic at the 2015 WASWAC annual meeting in Nanchang. This paper (the Nanchang Communication) is a summary of the Delgado et al. (2011) paper that was used by the SWCS to develop the SWCS position statement related to soil and water conservation and climate change. The Nanchang Communication (this paper) was used by WASWAC to develop a position statement about the immediate need for implementation of conservation practices for mitigation of and adaptation to climate change to achieve food security in the 21st century. These papers (Delgado et al., 2011, Nanchang Communication), and the SWCS and WASWAC position statements, support the conclusions from the worldwide literature that without implementation of soil and water conservation practices for climate change mitigation and adaptation, the survival of life, including our own species, will be in jeopardy, since soils will be key to meeting the higher demands for food during the 21st century.

Keywords: Food security; Conservation practice; Climate change; WASWAC; SWCS