Soil Chemical Analysis

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

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Climate Change 2007: The Physical Science Basis.

Climate change is causing drylands to expand and this work shows that they will cover half of the land surface by 2100 under a moderate emissions scenario. Drylands are home to more than 38% of the total global population and are one of the most sensitive areas to climate change and human activities1,2. Projecting the areal change in drylands is essential for taking early action to prevent the aggravation of global desertification3,4. However, dryland expansion has been underestimated in the Fifth Coupled Model Intercomparison Project (CMIP5) simulations5 considering the past 58 years (1948–2005). Here, using historical data to bias-correct CMIP5 projections, we show an increase in dryland expansion rate resulting in the drylands covering half of the global land surface by the end of this century. Dryland area, projected under representative concentration pathways (RCPs) RCP8.5 and RCP4.5, will increase by 23% and 11%, respectively, relative to 1961–1990 baseline, equalling 56% and 50%, respectively, of total land surface. Such an expansion of drylands would lead to reduced carbon sequestration and enhanced regional warming6,7, resulting in warming trends over the present drylands that are double those over humid regions. The increasing aridity, enhanced warming and rapidly growing human population will exacerbate the risk of land degradation and desertification in the near future in the drylands of developing countries, where 78% of dryland expansion and 50% of the population growth will occur under RCP8.5.

Accelerated dryland expansion under climate change

Climate Change 1995 is a scientific assessment that was generated by more than 1 000 contributors from over 50 nations. It was jointly co-ordinated through two international agencies; the World Meteorological Organization and the United Nations Environment Programme. The assessment was completed by the Intergovernmental Panel on Climate Change (IPCC) with a primary aim of reviewing the current state of knowledge concerning the impacts of climate change on physical and ecological systems, human health, and socioeconomic factors. The second aim was to review the available information on the technical and economic feasibility of the potential mitigation and adaptation strategies.

Climate Change 1995

Plastic mulching in agriculture. Trading short-term agronomic benefits for long-term soil degradation?

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.

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

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Resource Management for Sustainable Agriculture

A Field experiment was conducted during 2005-06 and 2006-07 at Dryland Research Sub Station, Dhiansar to study the influence of tillage and mulching practices on crop productivity, economics and soil properties of maize -wheat system under rainfed situation.Four different tillage methods, viz conventional, minimum, no tillage and raised bed were used in the main plots and four different mulch materials, viz straw, polyethylene, soil mulch including no mulch were used in the sub-plots. Tillage practices significantly influenced the yield of maize and wheat. Grain yield of maize and wheat was statistically at par in conventional and minimum tillage system and significantly higher than no tillage system in both the years. Mulching also resulted in increased in yield. Significantly higher mean grain yield of maize (1.91tonnes/ha) and wheat (0.63 tonnes/ha) was recorded from polyethylene mulch, followed by straw mulch (1.77 tonnes/ha, 0.61tonnes/ha) respectively. Minimum tillage and polyethylene mulch or straw mulch conserve more moisture and infiltration rate than other tillage methods and mulch application. The highest mean net returns (Rs 10 078) and benefit:cost ratio (1.28) was obtained with minimum tillage and lowest with conventional tillage (Rs 8 631 0.90). Minimum tillage in conjunction with polyethylene mulch or straw mulch was economically profitable and improve, the crop production and soil quality for maize-wheat sequence in rainfed condition.

Influence of tillage practices and mulching options on productivity, economics and soil physical properties of maize (Zea mays)-wheat (Triticum aestivum) system.

Climate change is the biggest threat to humanity with implications for food production, natural ecosystems, health etc. The primary greenhouse gases are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O). Although carbon dioxide is the most prevalent greenhouse gas in the atmosphere, nitrous oxide and methane have longer durations in the atmosphere and absorb more long-wave radiations. Therefore, small quantities of methane and nitrous oxide can have significant effects on climate change. The mean global level of greenhouse gases in the atmosphere is increasing to a level that can generate serious climate changes in air temperature, aggressive weather cycles and greater frequency of storms (Osborn et al., 2000). The primary sources of greenhouse gases in agriculture are the production of nitrogen based fertilizers; the combustion of fossil fuels such as coal, gasoline, diesel fuel, natural gas; and waste management. Livestock enteric fermentation results in methane emissions. Increased levels of greenhouse gases enhance the naturally occurring greenhouse effect by trapping even more of the sun’s heat, resulting in a global warming effect. The average surface temperature of the earth is likely to increase by 2 to 11.5°F (1.16.4°C) by the end of the 21st century, relative to 1980-1990, with a best estimate of 3.2 to 7.2°F (1.8-4.0°C) (Fig. 1). The average rate of warming over each inhabited continent is very likely to be at least twice as large as that experienced during the 20th century.

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Vikas Abrol

Papers

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

Resource Management for Sustainable Agriculture

Influence of tillage practices and mulching options on productivity, economics and soil physical properties of maize (Zea mays)-wheat (Triticum aestivum) system.

Climate Change and Carbon Sequestration in Dryland Soils

Biochar - An Imperative Amendment for Soil and the Environment