Tree Planting in Problem Soils - Hard Clayey Soils

Hard Clayey Soils


These are the soils in which clay particles constitute over 35% or more of the total weight.  These soils are extensively distributed in salt range foot hills of Punjab and western Kohistan of Sindh.  The plants that grow in these soils have to face the following problems.


  • Soil is compact. There is lack of aeration and drainage. Root penetration and respiration is restricted. Soil is usually shallow due to presence of Ca pan in the lower horizons. This leads to reduced water storage in the thin surface layer of the soil which is exhausted very soon.
  • Because of high adsorptive power of clay, even a slight but continuous addition of Na is enough to cause deflocculation which is very harmful phenomenon for plants.


Some kind of help will have to be provided during establishment of vegetation and initial growth stages. Once establishment and having gained complete control of site, the vegetation will by itself bring rapid improvements in soil conditions and will significantly ameliorate the microclimate. The presence of plant canopy and litter will prevent evaporation from soil surface and will, therefore minimize the development of crevices and fissures. The addition of humus and the activity of subterranean fauna such as insects, worms and rodents etc. will improve the soil structure that will result into easier root penetration, better aeration and better drainage. Such a soil will eventually become highly productive as a result of permanent woody vegetation.
The following points should be kept in view while undertaking any planting in such area:



  • Suitable species should be selected. Such a species for example should be hardy, drought resistant, fast growing and should have a high turnover rate. Species having deep root system should be preferred. A few examples are; prosopis, Syzygium, Albizzia etc.
  • Large sized plants with intact root system be used. Potted plants or the one with balls of earth be preferred. Necessary pruning of branches should be done just prior to or after planting in order to improve root shoot ratio in favour of roots.
  • A large pit of 1 meter diameter and 1.25 meter depth be dug. One should make sure that kankar (hard Calcium) pan, if present, is broken. This will increase the depth of available soil. An 8 cm thick layer of pure sand or fine gravel be provided at the surface of each pit. This will cut down evaporation loss of soil water. More water thus becomes available to plants.
  • The pit should be filled with a mixture of soil, coarse sand or gravel and organic manure. Sand is, however, most important component. This will improve aeration and drainage and will minimize crevices and fissures and breaking of roots.





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