Rajasthan is the state with highest area under desertification ( land degradation) with respect to country’s total geographical area (TGA). The state has 62.90% of the TGA under desertification/ land degradation for the period of 2011-13. The desertification/ land degradation area in Rajasthan has decreased about 0.29% since 2003-05.
Definitions & Differences:
- Soil degradation is the decline in soil quality caused by its improper use, usually for agricultural, pastoral, industrial or urban purposes.
- Soil degradation is a serious global environmental problem and may be exacerbated by climate change. It encompasses physical (soil erosion), chemical (salinity and alkalinity, pollution) and biological deterioration (pollution and deterioration of vegetal cover).
- Soil erosion is the removal of top soil by agents like wind and water.
- Top soil has most of the nutrients necessary for a plant’s growth. With depth, the fertility of the soil decreases. Thus, erosion results in reduction of fertility of the soil by washing away the fertile top layer.
- UNCCD defines desertification as ‘land-degradation in arid, semi-arid and sub-humid areas resulting from various factors including climatic variations and human activities’.
- Loss of soil cover, mainly due to rainfall and surface runoff, is one of the biggest reasons for desertification.
Problems of Soils in Rajasthan
The degree of degradation and its severity are influenced by special variability and its niche with the surrounding. The terrain factors like slope, aspect, topographic position are found to be dominant factor while intensity and distribution of rainfall are climatic factors, determining the extent and severity of degradation.
Wind Erosion & Shifting Sand Dunes:
- Wind Erosion is the most significant cause of land degradation/desertification in Rajasthan.
- The wind erosion is playing a prominent role, in the western flank of the state and is found active with full force in the core of desert, causing sand blasting, sand drifting, which results active dunes and interduneal plains.
- Severity of water erosion is found at the peak in central highland, including Aravalli landscape and Bundelkhand upland.
- This causes loss of top soils through sheet and rill erosion.
- It also causes terrain deformation through gully and ravine land. Example: Ravine Lands along the Chambal River & its tributaries.
- With the introduction of canal irrigation system water table of the area is rising at an average rate of about 0.8 m per year.
- As a result of this large area has become water-logged and this area is increasing every year, it is a serious problem particularly in deep black soils.
Sodicity of Soil:
- Sodality of the soil and high residual sodium carbonate content of irrigation water are the main problems.
Salinity & Alkalinity:
- The Salinity & Alkalinity is found maximum in the Aravalli and Bundelkhand alluvial plains where the quality of ground water and poor management practices about the secondary salinization.
- Salinity is due to high permanent water table.
Steps for Soil Conservation in Rajasthan
- The solution for salinity & Alkalinity of soil is to provide of soil is to provide adequate drainage.
Use of Gypsum:
- Use of gypsum which is abundantly and cheaply available in Rajasthan, is economical and long term solution to the problem of Alkalinity.
- Large scale planting of saplings which act as wind breaks & also prevents soil erosion through water.
- In dry regions rows of trees are planted to check wind movement to protect soil cover.
- Stone, gross, soils are used to build barrier along contours. Trenches are made in front of the boomers to collect water.
- Plantation of trees & grasses on marginal and sub marginal land.
Wind strip cropping:
- Grass and crop strip at right angle to wind direction.
- Crop stubbles are left in the field and next crop planted with minimum tillage.
- Ravine land can be made cultivable by leveling followed by contour bonding
- The medium and deep gullies can also be converted into productive wood lands.
Proper Drainage System in canal Project Area:
- The problem of water logging can be checked and overcome by introducing proper drainage system in the canal project area.
- Dry Farming is a method of conserving soil moisture preventing soil erosion.
- Rock Dam is built to slow down its flow of water.
- A layer of organic matter is made on soil. It helps to retain soil moisture.
- Different crops are grown in alternative rows to protect the soil form rain wash
- Broad flat steps or terraces are made on the steep slopes so that flat surfaces are available to grow crops.
- They reduce surface run off & soil erosion.
- Plugging parallel to the contours of a hill slope to form a natural barrier for water to flow down the slope