Assessment methods & techniques in cropland

Authors: Constantinos Kosmas, Katerina Kounalaki, Mina Karamesouti, Giovanni Quaranta, Rosanna Salvia, Honghu Liu, Artemio Cerda, Michiel Curfs, Anton Imeson

Editor's note 10Sept12. Source D711-7.2. To be reviewed in the context of the articles. Eleni - the text of this category introduction cannot be edited from the front end. You need to copy and paste into a word document, make the corrections using track changes and email it to Jane.

According to the definition adopted in LEDDRA, a response to LEDD includes any type of action taken in LEDD-affected regions with the purpose either of directly and explicitly tackling a LEDD problem or of addressing other socio-economic problems. LEDD and responses to LEDD are described in terms of their biophysical and associated socio-economic impacts. The assessment of impacts is based on the use of existing methods or on new methods and techniques (indicator-based, etc.) developed in this project.

The assessment involves first the identification of the most important LEDD issues and then the selection of the most appropriate assessment methods and techniques. The following are among the important LEDD issues in cropland: (a) decline in soil organic matter content, (b) decrease in soil water storage capacity, (c) soil erosion (including water erosion, tillage erosion, and wind erosion), (d) soil compaction, (e) land desertification, (f) soil crusting, (g) soil salinization, (i) water pollution, and (k) water stress.

Soil organic matter (SOM) influences many biological (micro-organism growth and population), chemical (availability of nutrients, nitrogen source, etc.), and physical (water retention, soil aggregate stability, etc.) soil functions and characteristics. The assessment of the change in SOM involves its monitoring in time intervals of 5 years. The amount of soil organic matter content at a certain time is determined by chemical analysis using the modified Walkey-Black wet oxidation procedure or by dry combustion (Nelson and Sommers, 2001).

Soil water storage capacity corresponds to the amount of water, which can be stored into the plant root zone. Decrease in soil water storage capacity is mainly caused by human actions causing soil erosion. A proposed method involves the measurement of certain soil physical characteristics related to soil moisture retention, such as field capacity and wilting point as well as soil depth (Gardner, 2001). The temporal scale for assessing change in soil water storage capacity is a period of 5 years, in areas experiencing soil erosion.

Soil erosion is one of the most important processes of land degradation in slopping areas distinguished into water, tillage, and wind erosion. Water erosion can be used by means of the PESERA (Pan - European Soil Erosion Risk Assessment) model (Kirkby, 2011). Tillage erosion caused by cultivation tilling implements is estimated by the method proposed by the EU research project TERON. The suggested temporal scale for assessing soil erosion is 3 or 5 years.

Soil compaction problems are especially important in cropland areas where heavy machineries are used. Soil compaction is assessed by examining the subsoil (soil layers or horizons below the ploughed layer, deeper than 20-35 cm). The assessment involves measurement of soil bulk density and saturate hydraulic conductivity (Blake and Hartge, 2001; Klute and Dirksen, 2001). Soil compaction can be changed with time, depending on the applied land management practices, therefore, a time interval of 5 years is proposed for measuring it.

Land desertification implies reduction of land productivity caused by various processes such as soil erosion, soil salinization, vegetation degradation etc. The Environmentally Sensitive Areas (ESAs) method, developed by MEDALUS III project, is proposed for assessing land desertification (Kosmas et al., 1999).

Soil crusting refers to formation processes resulting in a thin layer on the soil surface with low porosity and high penetration resistance. This layer is formed after repeated cultivation of the soils and continuously cropping and burning of plant residues. There are several techniques for assessing soil crusting. There is no unique index to characterise soil susceptibility to crusting since surface crusting processes are interrelated with the antecedent moisture conditions and the rainfall patterns. For the purpose of LEDDRA project, the proposed methodology for assessing crusting susceptibility is to use the soil characteristics: organic matter content, clay and silt content.

Soil salinization is an important process of land degradation mainly in the lowlands or om alluvial plains along the coastline. Soil salinization risk under various responses to LEDD in cropland is assessed using indicators combined in an algorithm developed by the DESIRE EU research project (2012). Soil salinization is a process greatly affected by climatic conditions and land management practices, therefore, a temporal scale of at least two years is proposed for assessing the stage of soil salinization.

Water pollution in cropland is mainly related to nitrates NO3 pollution in areas under intensive cultivation using high amounts of fertilizers. To assess the risk of groundwater pollution indicators related to water flow into the soil are used such as amount of rainfall, soil texture, soil depth, soil porosity, type of vegetation, etc. The proposed method is to use pedotransfer functions, which have been developed in the EC research projects: (a) Nitrates in soils (EV4V-0098-NL and EV4V-00107-C), and (b) WASTES [(STEP-CT90-0032-C (DSCN)].

Water stress in the growing plants is mainly related to soil and climate characteristics. Areas with soils with relatively shallow depth, under low annual rainfall, high aridity, high evapotranspiration rate, and long rainfall seasonality are vulnerable to land degradation and desertification risk due to water stress. The proposed method to assess water stress vulnerability is the use of indicators combined on an algorithm developed by the DESIRE EU research project (2012).

Methods and techniques for assessing socio-economic and other impacts of LEDD and of responses to LEDD in cropland have been identified. These are commonly applicable to the other two land themes too and they include: (1) cost-benefit analysis, (2) cost-effectiveness analysis, (3) multicriteria analysis. Furthermore, valuation techniques have been identified that can be used as tools to allow decision makers to evaluate tradeoffs between ecosystem management alternatives in order to meet economic, environmental and social goals. These include: (1) direct market valuation approach, (2) stated preference approach, and (3) revealed preference approach (see LEDDRA deliverable D121).

 

NB: Article titles marked ** are not available yet.

2014-11-28 10:49:11