The problem soils are those which, owing to land or soil characteristics, cannot be economically used for the cultivation of crops without adopting proper reclamation measures. Highly eroded soils, ravine lands and soils on steeply sloping lands constitute another set of problem soils. The shallow soil depth, deep gullies and steep and complex slopes are some of the problems, which require to be tackled in such areas. Acid, saline and alkali soils constitute another set of problem soils, in the case of which acidity, soluble salts and exchangeable sodium limit the scope of cultivation.
Problem soils become based waste land if appropriate management practices of soil, plant and environment is not followed. The land is said to be waste land which has been previously used but which has been abandoned and for which no further use has been found. The adverse factors and ceaseless onslaughts leading to major degradation have turned more than half (175 m ha) of the country's area into wastelands in some or the other form, viz., water and wind eroded land (150 m ha), water logged land (6 m ha), saline and alkaline land (4 m ha) and land affected by rive action and other factors (7m ha). These degraded lands cover about 85 m ha of agricultural and 37 m ha of forest land. Forest cover is losing at the rate of 1.3 m ha a year and another 1.0 m ha of non-forest area is going out of productive use due to the factors cited earlier.
The wastelands are ecologically unstable. Over the years of human settlements, these lands have been subjected to different degrees of biotic or ecological interference, as a result, rendering them degraded, infertile and unculturable.
More than 70% of the population is still dependent on agriculture and about 60% of the rural population is living in poverty. Our natural resources, which are the base for generating income and employment are improperly utilised and mismanaged. Over half of the land area measuring 175 million hectares is either unproductive or in a state of neglect. Moreover 75 to 80% of livestock is unproductive of uneconomical. In spite of about 73% cropping area being dependent on rainfall, hardly about 15-20% of the rain water is effectively utilised and the rest is wasted. Nearly a half of the forestlands in the country has been denuded.
Systematic development practices can certainly help in sustainable use of natural resources. With the development of wastelands, there will be an improvement in the micro-climate and soil productivity and thus agricultural production can also be enhanced significantly. With the availability of fodder, the prodcuticvtivity of our livestock can be improved.
In arid and semi-arid areas during the periods of higher than average rainfall, the soluble salts are leached or washed out from the more permeable high lying areas to the low lying areas, where, if the drainage is restricted, salts accumulate on the surface as water evaporates. The excessive irrigation of the uplands containing salts results in the accumulation of slats in the valleys. In areas having a salt layer at lower depths in the profile; faulty water management or even seasonal irrigation may favour the upward movement of the salts.
A rise in the water table within 2 m of the surface due to irrigation the obstruction of natural drainage by roads or canals and the salutation of natural drainage may also cause soil salinity. In the coastal areas, the ingress of sea water induces salinity in the soil. When sodium ions predominate in the soil solution, and carbonates are present, alkali soils are formed.
Thus the salt affected soils differ a great deal in their physico-chemcial characteristics, as such, methods of their reclamation also differ. If the problem is only of salinity, the salts need to be leached below the root-zone and not allowed to come up. In practice, this might be difficult to accomplish, especially in deep and fine textured soils containing more salts in the lower layers. Under these conditions, a provision, of some kind of subsurface drains becomes important. If the soil contains a sandy layer at a lower depth, the leaching of the salts below this layer will check the rise of salts.
The number and frequency of leaching, the quantity of gypsum to be added and the techniques involved vary from region to region, depending upon the clay mineralogy of the soils, the intensity of the problem, the subsequent use of the soils, the availability and quantity of irrigation water and the economics of these operations.
In irrigated areas, special management practices become necessary to avoid salinity, alkalinity, waterlogging, leaching and the loss of plant nutrients.
The productive capacity of the soil should never be allowed to diminish, but rather should improved and maintained by providing adequate organic manures and plant nutrients. The fertility of land is dependent on the continued addition of organic matter. When and if the process of adding organic matters is abruptly stopped. The deterioration of the land starts.
There is a need for constantly adding about 7 tonnes of biomass every year so as to maintain the fertility of soil. Unfortunately this critical component is totally ignored by all and as such as feasibility of development of wastelands remains to be studies with reference to the methods and relative cost involved in them.
There is growing need for more and more attention on the part of the government towards the development of wastelands, so that some of the socio-economic problems could be done away with.
There are a few programmes at National and Regional levels for the development of wastelands. It requires community participation and the remaining intend to be led by government and non-government organizations. It is reported that neither the community nor the NGOs take active part in these programmes and follow up measure so that a collective and join attempt could not be ensured for development of wastelands. The level of public awareness of such progarmmes is lower than expected.
Wasteland development is not to be seen as an internal problem of the country. There must be international participation, as in the case of development and management of forests, for not only merely greening the wastelands but also for improving the ecology and environment around the world.
The reliability of data to be collected about problem soils depends on the supplying agency since the published data may differ from institution to institution between central and State Agencies. Also there is variation about primary data to be supplied by individual and institution.