Soil Study

Waterlogged Soils These are the soils where water-table rises high and reaches within 3 feet of ground surface most of the time and thus affects crop roots. In extreme cases, the water-table rises even higher than ground surface. Waterlogging is very extensive problem in irrigated areas. It is caused by addition of huge amount of percolation and seepage water from canals, distributaries and water channels as well as inefficient irrigation practices and absence of any effective drainage system. The intensity of water logging is variable and depends on season, general land slope and soil porosity etc. Presence of gravitational water in the root zone for a long period of time excludes the soil air. Plant roots are therefore, unable to respire properly. Oxygen dissolved in soil water gets exhausted very soon because there is no new addition of oxygen to the standing water. In some cases, the ground water may pick up excessive amount of carbon dioxide and salts and intensif...

Wind Eroded Soils In arid sandy areas such as deserts and sea coast, strong wind bellow frequently and cause soil erosion as well as flagging of tree crowns. This is very acute problem in Thal, Cholistan, Tharparker and deserts of Balochistan. The plants that grow in such situation have to face some or all of the following problems. Since the soil is unstable, therefore; the plants are continuously faced with either exposure of their root system due to blowing away of sand or burial of their shoots due to deposition of new sand. Moving sand particles cause mechanical damage to tender shoots and foliage. The transpiratory load is extremely high. Light intensity tends to be very high due to its reflection from shining sandy surface. Water holding capacity of sandy soil is very low which leads to water deficiency for most of the time. The problem of soil erosion by wind can be successfully tackled by considering the following points: A species shou...

Salt affected Soils These soils are those in which either the salt contents of lower horizons concentrate in or on the soil surface or normal proportion of various cations and anions present in soil is disturbed in a big way by excess or shortage of certain ions. This redistribution of salts of salts in soil profile is generally caused by the rising of water table accompanied by intensive evaporation from the surface. The saline water moves up through capillaries and evaporates into the atmosphere while leaving the salts on the soil surface. These salts are frequently seen in the form of thin white crust in the saline area. This crust is quite conspicuous during winter. It has been estimated that about 1/4 to 1/3 of our irrigated area has gone out of production because of salinity. Product vising these areas by tree planting is a major breakthrough. Salinity of soils is rightly considered as enemy number one of World’s Agriculture. In Pakistan about 16.75 million acres area ...

Side Grafting In side grafting vigorous stock shoots are selected. Fresh and mature scion sticks about 12-13 cm long are collected from a desired variety and their leaves are clipped off. A 2-3 year old stock tree planted in orchard rows is selected. At the base of the scion on one side a longitudinal cut of 5-8 cm is made, cutting away half of the girth at the base and thus making a wedge. An oblique cut is made in the stock at an angle of 20-30 degree and about 2.5 cm deep, and the scion is inserted in the cut portion and gently pushed down until it is fixed in the bark. The union is tied with waxed cotton tape and wrapped with polythene. After the graft sprouts, the polythene is removed. This method can be performed in both spring and autumn, but the maximum rate of 90% is achieved during spring.  

Bridge Grafting and T-Grafting Bridge Grafting It is practiced to save valuable trees with diseased or damaged trunks. To prepare the tree trunk for bridge grafting, the damaged part is trimmed back to healthy tissue by removing dead or torn bark from the affected parts.  Bridge grafting is best performed during early spring when the bark can be lifted easily. Scions of sufficient length to bridge over the damaged area are taken. One long slanting cut is made at each end of the scion, both cuts on the same side. A second cut is made on back side. The bark on both upper and lower sides of the wounded area is loosened as in bark grafting, and the scions are then inserted between the bark and wood of the stock and are nailed down. All cut surfaces are carefully coated with wax, and any sprouting on scion surface should be removed. Complete healing takes place in a few years. T-Grafting               ...

Tongue Grafting and Bark Grafting Tongue Grafting                                 The scion and rootstock are cut exactly in the same way as in splice grafting. To provide strength and exposure of greater cambial area for union, tongue shaped slits are then made in both scion and stock. The secondary slits are half the length of the original slanting cuts. The scion and stocks are brought together, firmly interlocking. The graft wounds are waxed over, with or without typing. Bark Grafting                                 Unlike in the cleft graft, the stub of the stock is not cut horizontally. Instead, several scions with their basal ends trimmed as wedges are inserted betwe...

Splice Grafting A slanting cut about 10 cm long is made at the basal end of the scion, which is placed on a corresponding cut made on the rootstock seedling at a height of 30-40 cm from ground level, and then tied together. The cambial areas of scion and stock should be in close contact; to achieve these both should be of the same thickness. The top of the plant down to the graft union is covered with a polythene bag, loosely tied at the basal end to prevent excessive transpiration. The union takes place within three weeks to three months, depending upon the plant species involved and the age and condition of scion and rootstock. Splice grafting has been employed in grafting mango in the Philippines and Brazil, and for some varieties of Apple.