Surface sealing
- Surface sealing is the process of impediment of soil pores of various size with dispersed soil particles (the finer particles) resulting from the slacking action and their transport leading to the impeded air and water regulation in the soil surface.
Mechanism of surface sealing
The seal formation takes place due to
- Breakdown of soil aggregate by raindrop impact and slacking. This occurs due to the impact of falling raindrop on the surface of soil. The energy involved during raindrop activity is expressed in kinetic energy.
Thus, kinetic energy of falling rain drop =1/2 × mass × (velocity)2
The mass of raindrop depends upon its size. The terminal velocity of falling raindrop increases with their size. The falling raindrop breaks down the soil aggregate and detaches soil particles from each other. Splash erosion also seals the soil surface and increases the rate of runoff.
- Washing of dispersed fine particles into surface pores.
- Compaction of surface producing a thin layer of crust almost equal to o.1mm.
- Sometimes when ground water table is high, the salt present in water may come up to the surface and seal the pores.
Management practices to reduce surface sealing
Reduces the impact of kinetic energy of rainfall by mulching or keeping the soil under vegetation. Sod, mulch and cover crops can serve the function.
Improving the aggregate stability by
Þ Addition of organic matter
Þ Addition of lime in acid soil which increases the microbial activity in the soil and they will decompose the organic matter rapidly which help in binding of aggregates
Þ Growing grasses, legumes in rotation etc
Þ Work when soil moisture status is desirable or that does not destroy structure of soil If the land surface is rough i.e. covered with residues, grassland causes impediment to splash.