Sub- theme - I KNOW YOUR LAND

Sub- theme:I

KNOW YOUR LAND

We know we belong to the land, and the land we belong to is grand!
-Oscar Hammerstein

Understanding land resources, its potential, utilization and management of any area reflect the levels of development and standard of living of the locality. Improper use of land due to anthropogenic pressure has created many problems like shrinkage of arable land due to encroachment, decline in fertility due to over use of inorganic fertilizers without soil test information and land degradation. In land resource management approach, spatial distribution of land use, intervention of local and scientific decision support system and control and conservation measures are of primary importance.

Land may be defined as a physical environment consisting of relief, soil, hydrology, climate and vegetation in so far as they are determined by the land use. Value of land depends on its size, location, distance from the market and nature of potential use besides productivity. The sum total of characteristics that distinguish a certain kind of area in the earth’s surface in contrast to other kind of areas to give it a distinguishing pattern is a landscape.

Soil is a dynamic natural body developed as a result of pedogenic processes during and after weathering of rocks, consisting of minerals and organic constituents, possessing definite chemical, physical, mineralogical and biological properties having a variable depth over the surface of earth and providing a medium for plant growth. Soils are formed by interaction of many factors, viz., climate, relief, organisms, parent materials and time etc. Soils are derived from their parent materials which are invariably derived from different rocks. There are three main kinds of rocks, viz. igneous rock, Sedimentary rock and metamorphic rock. Rocks are chemically composed of oxides of Si, Al, Fe, Ca, Mg, Mn, K, P etc. Chemical and physical disintegration and decomposition of rocks under different temperature, pressure and moisture condition results in the formation of parent material (C horizon or regolith) over which soil formation takes place. Afterwards both weathering and soil formation processes proceed simultaneously leading further development of soil.

Each soil is characterized by a given sequence of horizons. Combination of this sequence is known as soil profile i.e. a vertical section of the soil through its entire horizon. The layers or horizons in the soil profile which vary in thickness have different morphological characteristics. This includes colour texture, structure, etc. Horizons are generally designated as O (organic), A, E, B, C and R (regolith on which weathering processes act leading to soil formation). Therefore soil profile is taken as unit of study which helps the investigators not only to classify the soils but also to understand soil-moisture-plant-relationship. The soil profile in the field therefore furnishes a base which has to be supplemented by physical, chemical and biological properties of soils.

Soil mapping

The physical properties of soil are important since this determine the manner in which it can be used either for agriculture, forestry etc., and non agriculture purposes like habitat, recreation site etc. Properties viz: infiltration rate, water holding capacity, aeration, plasticity and nutrient supplying ability are influenced by the size, proportion, arrangement and mineral composition of the soil particles. Four major components of soil viz. inorganic or mineral particles, organic matter, water and air vary with different regions. Based on soil water plant relation, the soil water may be classified as gravitational water, capillary water, hygroscopic water etc. Water mostly available to plant growth held as capillary water within -15 bars.
Soil chemical properties are mainly due to most reactive part of the soil namely soil
colloids consisting of organic and inorganic phases. The organic phase consists of either fresh or decomposed residues of plants, animals, and microbes (fungi, bacteria, actinomycetes etc.) which may remain associated with inorganic phase or may be present in free form.

The life of mankind and almost all the flora and fauna on the earth is continuously influenced by an unending flux of water known as hydrologic cycle. In hydrologic cycle, soil act as a reservoir and water is always in transitory storage in soils. There are two interlocking cycles both starting with evaporation, from sea to atmosphere. The first shorter cycle is from rainfall into the soil and then as evaporation and transpiration back to atmosphere. This is sometimes called green water. The second cycle is blue water follows the longer part from rainfall through soil moisture, ground water and rivers to sea. It may be noted that hydrologic cycle is not always punctual and uniform in delivering precipitation to earth surface.

India is a vast country with a total area of 328.72 million hectare of which approximately 30 per cent is occupied by mountains and hills, 25 per cent by plateau and 45 per cent is occupies by plain valley. Out of the total geographical area forest covers an area of 69.02 m ha, area not available for cultivation 28.48 m ha, other uncultivated land including fallow land 53.38 m ha, cultivable wasteland 13.83 m ha, permanent pasture and grazing land 11.04 m ha, fallow land including current fallow 24.90 m ha, area not available for agriculture, forest etc. 50.19 m ha and net area under cultivation is 189.74 m ha. Out of the total geographical area, around 45 per cent of total geographical area is subjected to degradation problems. The area suffering due to water erosion, wind erosion, water logging, salinity/alkalinity, acidity and other complex problems are 93.6, 9.4, 14.3, 5.9, 16.0 and 7.4 million hectare, respectively.

Physiographically, the country can be put under seven regions, viz., northern mountains including the Himalayas and the mountain ranges in the north-east, Indo-Gangatic plain, Central Highlands, peninsular plateau, East coast, West coast and bordering seas and islands.

India has a diverse geology. Different regions of India contain rocks of various types belonging to different geologic periods. Some of the rocks are severely distorted and transmuted while others are lately deposited alluvium. Great variety of mineral deposits in huge quantity is found in the Indian Geological survey. India’s geographical land area can be categorized into Deccan Trap, Gondwana and Vindhyan. The Deccan Trap covering almost the entire state of Maharastra, a part of Gujrat, Karnataka, Madhya and Andhra Pradesh. Indian soils are normally divided into four broad groups. These comprise of alluvial soil, black soil, red soil and laterite soil. Allivial soils are derived from the deposition led by diffirent tributaries of Indus, Ganges and the Brahmaputra system. It includes soils in deltic alluvium, calcarious alluvium and coastal alluvium. It covers 40 per cent of land area. Black soils are dark in colour gently calcarious low in organic matter, high in clay content, high in cation exchange capacity. They are sticky and plastic. It covers about 22.2 per cent of total land area. Red soil of India covers almost all the states. The colour of red soil is due to wide diffusion of iron. These soils are poor in nitrogen, phosphorus and humus. Kaolinitic type of mineral is prevalent in red soil. Laterite soils are highly weathered materials rich in secondary oxides of iron, aluminum or both. It contains large amount of quartz and kaolinite.

The land system of our country is affected by influences of man interventions well as various natural processes. The removal of top soil, deforestation and banned agricultural practices would, many a time, force us to live in environmentally adverse conditions. The environmental degradation of land makes our country stressful situations, which has become concern for us to think over and act for sustainable development. Our future generation is in stake as a result of interference with natural processes causing many situations unfit for our well being and also for the well being of future generation. Therefore, the database on the past and present land use practices will lead us to predict the future pattern of change which will enrich us towards sustainable development.