Unit I
Soil quality and health,
Distribution of wasteland and problem soils in India.
Their categorization (based on properties)
Chapter 1
Soil Quality and Soil Health
Soil fertility- The ability of soil to supply essential nutrients available in the crop
Soil productivity- the ability of soil to produce a particular crop or sequence of crops under a specified management system. The crop producing capacity of the soil.
All productive soils are fertile but not vice-versa.
Crop production Factors
Nutrient availability
nutrient retention capacity
rooting cond
oxygen availability to roots
excess salts
toxicity
workability
Soil quality- The capacity of Soil to function within the boundaries of an ecosystem to sustain biological productivity. maintain environmental quality, and promote plant and animal health.
The soil quality concept was introduced by Warkentin and Fletcher (1977)
Tool for assessing soil quality specific soil properties that are indicative are measured. not possible to directly measure the rate of soil processes. the properties measured are termed indicators of soil quality.
Indicators- are physical, chemical and biological properties, processes and characteristics that can be measured to monitor changes in the soil
Physical Indicators related to the arrangement of solid particles and pores include topsoil depth, bulk density, porosity, aggregate stability, texture, crusting and compaction. primarily reflect limitations to root growth, seedling emergence, infiltration or movement of water within the soil profile.
Chemical Indicators- pH, salinity, organic matter, phosphorus conc., cation-exchange capacity, nutrient cycling, and concentration of elements that may be potential contaminants. Affects soil-plant relations, water quality, buffering capacity, availability of nutrients and water to plants, and mobility of contaminants.
Biological Indicators- micro and macro organisms, their activities and byproducts. preparation rate can be used to detect microbial activity, specifically microbial decomposition of organic matter in the soil.
Ergo sterol, a fungal byproduct- is used to measure the activity of organisms that play an important role in the formation and stability of soil aggregates.
Visual Indicators- Obtained from observation or photographic interpretation. Exposure of subsoil, colour change, ephemeral gullies, ponding, runoff etc.
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Often soil health is considered independently without referring to interlinked soil functions and also based on soil tests for a few parameters. The physical condition of the soil and biological fertility is overlooked in soil health management which needs revisiting by soil users. Recognizing the importance of soil health in all dimensions, 2015 has been declared the International Year of Soils by the 68th UN General Assembly. It is estimated that out of the 328.8 m ha of the total geographical area in India, 173.65 m ha are degraded, producing less than 20% of its potential yield (Govt. of India, 1990).
Healthy soils provide us with a range of ecosystem services such as resisting erosion, receiving and storing water, retaining nutrients and acting as an environmental buffer in the landscapes. Soils have undergone unabated degradation at an alarming rate by wind and water erosion, desertification and salinization resulting from misuse and improper farming practices.
Soil quality, an antonym for soil degradation, has deteriorated due to natural and anthropogenic activities, particularly with the advent of intensive management practices.
Soil Functions
Five soil functions as enunciated by Karlen et al. (1997) are:
Sustaining biological activity, diversity and productivity
Regulating and partitioning water and solute flow
Filtering, buffering, degrading, immobilizing and detoxifying organic and inorganic materials, including industrial and municipal by-products and atmospheric decomposition
Storing and cycling nutrients and other elements within the earth's biosphere
Providing support to socio-economic structures and protection for archaeological treasures associated with human habitation.
Thus, soil acts to supply nutrients and offer favourable Physico-chemical conditions to plant growth, promote and sustain crop production, provide habitat to soil organisms, ameliorate environmental pollution, resist degradation and maintain or improve human and animal health.
Distribution of Wasteland and problematic soil
In the Genreal term, Wastelands are any type of land irrespective of its ownership, which is producing less than 20% of its optimum biological productivity. The land which is degraded and is presently lying unutilised except a current fallow due to different constraints is known as wasteland.
Types of wasteland
1. Culturable wasteland
lands which are capable of or have the potential of development of vegetative cover. ex- sloppy land, shifting cultivation area, sand dunes, ravines land, salt-affected land, pasture and non-forest plantation land.
2. Uncultrable land
Land which cannot develop vegetative cover and include barren rocky areas and steep slopes and snow-covered areas.
The main cause of the formation of wasteland-
Indiscriminate and over utillllisation of forest
Overgrazing
The side effects of development projects
Mis-use and unscientific land management
Problematic soil
These are soils which are economical for Cultivation
The soils which possess characteristics that make them uneconomical for the cultivation of crops without adopting proper reclamation measures are known as problematic soil/problem soils.
Types of soil problems:-
1. Physical Problem Soil
2. Chemical Problem soil
3. Biological Problem soil
4. Nutritional Problem soil
1) Physical problem soil
Slow permeability or impermeability
soil surface crusting
subsoil hard pan
Shallow soils
high permeable soil
heavy clay soil
2) Chemical problem soil
Salt-affected soil- occurs in the air and semi-arid area
Evapotranspiration exceeds rainfall
Accumulation cause salinity or alkalinity
Ions mainly involved - Na, K, Mg and Calcium chlorides, carbonates
3) Biological Problem soil
Biological factors - Plants, animals, microorganisms, and humans affect soil formation. Animals and microorganisms mix soils and form burrows and pores. Plant roots open channels in the soils.
