Geography Optional Answer Writing Day-17 Synopsis. As per the scheme of this
Q.3) Classify soils based on their zonal distribution and describe the characteristics of pedocals. (2015) (20 marks)
Answer
All terrestrial life owes its existence to over a dozen elements derived from soil through plants, hence soil has accurately been called the bridge between life and earth. In fact, it is the very heart of the life layer on the continents.
The genetic classification of soil by Marbut is the most suitable classification for Geographers. He recognized a strong relationship between climate, Vegetation and Soil throughout the world. The three main class of soil recognized are Zonal, Intrazonal and Azonal.
Pedocals
Pedocals are soils of arid and semi-arid condition. They are classified into Chernozem, Chestnut, Prairie, rendzina, Terra Rossa, lithosols and Regosols.
Chernozem Soils: Of the zonal soils of the semiarid and sub humid climates of the middle latitudes, the most distinctive and widely distributed of the great-soil groups are the Chernozem soils. A typical Chernozem profile appears to consist essentially of two layers. Immediately beneath the sod is a dark layer rich in humus, the A horizon, up to 1 m (3 ft) thick.
In this layer the soil structure is crumb or nut. Chernozem soils are rich in calcium, which appears in excess as calcium carbonate precipitated in the lower B horizon or just beneath the B horizon.
Prairie Soils: Between the Chernozem soils and the Gray-Brown soils lies the zone of Prairie soils; the are a transitional group. The Prairie soils are similar to the Chernozems in profile, but differ through the lack of excess calcium carbonate.
Prairie soils are extremely productive, combining the fertility of the Chernozems with a somewhat moister climate. The outstanding crop is corn.
Chestnut Soils and Brown Soils: To the arid side of the Chernozem soils in both North America and Eurasia lie the belts of chest nut soils and brown soils. The profile of the chestnut soils is generally similar to that of the Chernozem, but less humus and hence not dark in color. The Chestnut soils are fertile under the conditions of adequate rainfall or if irrigation is furnished. They lie in hazardous marginal zone in which sequences of drought and adequate rainfall are alternated.
Soils of the midlatitude and tropical deserts fall into two great soils groups on the basis of color: Gray desert soils and Red desert soils.
The Gray desert soils contain little humus because of the sparseness of vegetation. Colour ranges from light gray to grayish brown. Horizons are present but not conspicuous, Excessive amounts of calcium carbonate are present at depths of less than 30 cm and take the form of lime crust or caliche.
In the more arid, hotter tropical are found the Red deserts soils, these range from a pale reddish grey to a pronounced deep red. Horizons are poorly developed; texture is often coarse, with many fragments of parent rock throughout the soil. Deposits of calcium carbonate are present, as in the Gray desert soils.
Intrazonal Soils (Calcimorphic)
Terra Rossa Soils: Terra Rossa is a type produced by the weathering of limestone. when the soils are above the water table. iron oxide in the clay. This gives it a characteristic to orange color. Terra Rossa is typically found in regions with a Mediterranean climate.
Compared to most clay soils, terra Rossa has surprisingly good drainage characteristics. This makes it a popular soil type for wine production. Among other wine regions, it is found in La Mancha in Spain and Coonawarra in Australia.
Rendzina Soils: Rendzina is a dark, grayish-brown, It is one of the soils most closely bedrock type and an example of initial stages of soil development. It is usually formed by weathering of soft rock types: usually carbonate rocks (dolomite, limestone, marl, chalk) but occasionally sulfate racks (gypsum).
The soil of this type contains a significant amount gravel and stones, which, during plowing, produce various sound effects (clicking, screeching, etc.), i.e., “talk” to the ploughman. Hence the name Rendzina.
Q.4) Present a classification of the soils of the world and give their economic significance. (1992) (15 marks)
Answer
Soil is a 3-dimensional body with properties that reflect the impact of (1) climate, (2) vegetation, fauna, Man and (3) topography on the soil’s (4) parent material over a variable (5) time span. The nature and relative importance of each of these five `soil forming factors’ vary in time and in space. With few exceptions, soils are still in a process of change; they show in their `soil profile’ signs of differentiation or alteration of the soil material incurred in a process of soil formation or `pedogenesis’.
Zonal System of Classification: This system links the distribution of various soil types to the distribution of climate and vegetation.
Economic significance of various soils is as explained below.
Latosols are quickly lose fertility under crop cultivation because of excessive leaching has removed the plant nutrients. But the evergreen broadleaf hardwood forest supplies the hardwood for commercial activities.
Podzols are the typical soils of coniferous or boreal forests. They are also the typical soils of eucalypt forests and heathlands in southern Australia. In Western Europe, Podzols develop on heathland, which is often a construct of human interference through grazing and burning.
Severe acidity, high Al-levels, low chemical fertility and unfavorable physical properties make most Podzols unattractive for arable cropping, unless improved, e.g. by deep-plowing and fertilization. Podzols have some potential for forestry and extensive grazing.
Russian soil scientists rank the deep, central Chernozems among the best soils in the world. With less than half of all Chernozems in Eurasia being used for arable cropping, these soils constitute a formidable resource for the future.
Wheat, barley and maize are the principal crops grown, alongside other food crops and vegetables. Part of the Chernozem area is used for livestock rearing.
In the northern temperate climatic belt, the possible growing period is short and the principal crops grown are wheat and barley, in places in rotation with vegetables. Maize is widely grown in the warm temperate belt. Maize production tends to stagnate in drier years unless the crop is adequately irrigated.
Solonchaks – Strongly salt-affected soils have little agricultural value: they are used for extensive grazing of sheep, goats, camels and cattle or lie idle. Only after the salts have been flushed from the soil (which then ceases to be a Solonchaks) may good yields be hoped for. Irrigation of crops in arid and semi-arid regions must be accompanied by drainage whereby drainage facilities should be designed to keep the groundwater table below the critical depth.
By and large, Solonetz are problem soils when used for arable agriculture. he majority of the world’s Solonetz was never reclaimed and is used for extensive grazing or lies idle.
Many Regosols are used for extensive grazing. Many Regosols on colluvial deposits in the loess belt of northern Europe and North America are cultivated; they are planted to small grains, sugar beet or fruit trees. Regosols in mountain regions are quite delicate and are best left under forest.
Alluvial soils are extensively used for agriculture. The plains of Ganga-Brahmaputra, Indus, etc are the worlds most cultivated lands.
Q.5) Healthy soil is the real key to feeding the world. Explain (15 marks)
The answer is informative on many dimensions and hence not adheres to word limit.
Answer
By 2050 we’ll need to feed two billion more people. How can we do that without overwhelming the planet?
There are many myths about the conventional method of industrial agriculture, which we think needed to end the hunger.
According to a recent U.N. Food and Agriculture Organization (FAO) report, family farms produce over three-quarters of the world’s food.
A 2016 Environmental Working Group report found that almost 90 percent of U.S. agricultural exports went to developed countries with few hungry people.
While mechanization can provide cost and labor efficiencies on large farms, bigger farms do not necessarily produce more food. According to a 1992 agricultural census report, small, diversified farms produce more than twice as much food per acre than large farms do.
A 1989 National Research Council study concluded that “well-managed alternative farming systems nearly always use less synthetic chemical pesticides, fertilizers, and antibiotics per unit of production than conventional farms.”
While large farms excel at producing a lot of a particular crop – like corn or wheat – small diversified farms produce more food and more kinds of food per hectare overall.
Effects of conventional method of industrial agriculture on soil.
Industrial agriculture based on a mechanistic paradigm and use of fossil fuels has created ignorance and blindness to the living processes that create a living soil.
External inputs and mechanisation are imperative for monocultures. By exposing the soil to wind, sun and rain, monocultures expose the soil to erosion by wind and water.
Soils with low organic matter are also most easily eroded, since organic matter creates, aggregates and binds the soil.
Chemical monocultures also make soils more vulnerable to drought and further contribute to food insecurity.
Further, eroded soils and soils without organic matter absorb 10 to 300 mm less water per ha per year from rainfall. This represents 7 to 44 per cent decrease in water availability for food production, contributing to a decline in biological productivity from 10-25 per cent.
Soils with organic matter are more resilient to drought and climate extremes. And increasing organic matter production through biodiversity intensive systems, which are in effect photosynthesis intensive systems is the most effective way to get the carbon dioxide out of the atmosphere, into the plants, and then into the soil through the Law of Return.
Benefits of organic farming
It aims to produce food while establishing an ecological balance to prevent soil fertility or pest problems. Organic agriculture takes a proactive approach as opposed to treating problems after they emerge.
Soil – Soil building practices such as crop rotations, inter-cropping, symbiotic associations, cover crops, organic fertilizers and minimum tillage are central to organic practices. These encourage soil fauna and flora, improving soil formation and structure and creating more stable systems.
In turn, nutrient and energy cycling is increased and the retentive abilities of the soil for nutrients and water are enhanced, compensating for the non-use of mineral fertilizers. Such management techniques also play an important role in soil erosion control.
The length of time that the soil is exposed to erosive forces is decreased, soil biodiversity is increased, and nutrient losses are reduced, helping to maintain and enhance soil productivity.
Crop export of nutrients is usually compensated by farm-derived renewable resources, but it is sometimes necessary to supplement organic soils with potassium, phosphate, calcium, magnesium and trace elements from external sources.
Water – In many agriculture areas, pollution of groundwater courses with synthetic fertilizers and pesticides is a major problem. As the use of these is prohibited in organic agriculture, they are replaced by organic fertilizers (e.g. compost, animal manure, green manure) and through the use of greater biodiversity (in terms of species cultivated and permanent vegetation), enhancing soil structure and water infiltration.
Well managed organic systems with better nutrient retentive abilities, greatly reduce the risk of groundwater pollution. In some areas where pollution is a real problem, conversion to organic agriculture is highly encouraged as a restorative measure (e.g. by the Governments of France and Germany).
Air and climate change – Organic agriculture reduces non-renewable energy use by decreasing agrochemical needs (these require high quantities of fossil fuel to be produced).
Organic agriculture contributes to mitigating the greenhouse effect and global warming through its ability to sequester carbon in the soil. Many management practices used by organic agriculture (e.g. minimum tillage, returning crop residues to the soil, the use of cover crops and rotations, and the greater integration of nitrogen-fixing legumes), increase the return of carbon to the soil, raising productivity and favouring carbon storage.
A number of studies revealed that soil organic carbon contents under organic farming are considerably higher. The more organic carbon is retained in the soil, the more the mitigation potential of agriculture against climate change is higher.
Biodiversity – Organic farmers are both custodians and users of biodiversity at all levels. At the gene level, traditional and adapted seeds and breeds are preferred for their greater resistance to diseases and their resilience to climatic stress.
At the species level, diverse combinations of plants and animals optimize nutrient and energy cycling for agricultural production. At the ecosystem level, the maintenance of natural areas within and around organic fields and absence of chemical inputs create suitable habitats for wildlife.
The frequent use of under-utilized species (often as rotation crops to build soil fertility) reduces erosion of agro-biodiversity, creating a healthier gene pool – the basis for future adaptation.
The provision of structures providing food and shelter, and the lack of pesticide use, attract new or re-colonizing species to the organic area (both permanent and migratory), including wild flora and fauna (e.g. birds) and organisms beneficial to the organic system such as pollinators and pest predators.
The number of studies on organic farming and biodiversity increased significantly within the last years. A Recent Study Reporting on A Meta-Analysis Of 766 Scientific Papers concluded that organic farming produces more biodiversity than other farming systems.
Ecological services – The impact of organic agriculture on natural resources favours interactions within the agro-ecosystem that are vital for both agricultural production and nature conservation.
Ecological services derived include soil forming and conditioning, soil stabilization, waste recycling, carbon sequestration, nutrients cycling, predation, pollination and habitats. By opting for organic products, the consumer through his/her purchasing power promotes a less polluting agricultural system.
The hidden costs of agriculture to the environment in terms of natural resource degradation are reduced.
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