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Single leg conventional subsoilers with curved and straight leg have been introduced in India to alleviate soil compaction problems in the lower soil profile, but require high draft. To overcome these problems a winged type subsoiler with and without leading tines have been designed and introduced. To compare the performance of different subsoilers namely, conventional curved leg, conventional straight leg, winged and winged with leading tines on the basis of draft, soil disturbance and specific draft at working depths of 250, 300, 350 and 400 mm, an experiment was carried out at G B Pant University of Agriculture and Technology, Pantnagar (India) in Randomized Block Design The soil of the experimental plot was silty clay loam (Sand 31 %, Silt 37 %, and Clay 32 %) having moisture content in the range of 15.4 to 16.75 % (d.b.). Results have shown that the critical depth of conventional curved leg subsoiler was 350 mm. However, the critical depth for other subsoilers was not observed even upto 400 mm depth. At 350 mm working depth, the draft force for winged subsoiler with leading tines increased by 39.75 % and 31.81 % over conventional curved and straight leg subsoilers, respectively while the soil disturbance increased by 3.03 times (203.25 %) and 2.35 times (135.42 %) times, but the specific draft reduced by 53.90 % and 44.00 %, respectively. Indiscriminate use of heavy machineries, particularly in wet soil conditions not only influences the cultivated layer but also causes gradual deterioration of subsoil structure with ultimate effect on soil workability, crop growth and yield (Wolkowski, 1990). The soil profile pit examination at a number of locations in Tarai region of Uttaranchal (India) has revealed the presence of hard pans/compacted layers at depths varying from 300 to 600 mm. This may be due to movement of heavy machineries like combine harvesters, tractors and other farm equipment as well as by natural processes. Moreover, these soils have not been cultivated deeply since the development of Tarai region for crop production. One of the reasons for stagnation in productivity of crops at certain location may be due to presence of compacted layers. This problem could be further aggravated due to introduction of high horse power tractors and related heavy machineries in recent years. Subsoil compaction is occurrence of densified layers at depths below Ap depth limit or the compaction below the depth of primary cultivation. These techniques improve soil structure by establishing a system of deep cracks and fissures in the subsoil which aid the downward movement of water, air and roots through a greater depth of soil profile (Carter et al., 1996). A comprehensive review on subsoiling and its effect on soil properties and yield response of various crops revealed substantial increase in their yields over a wide range of soil types (Thakur and Arun Kumar, 1999). A substantial amount of research work has been done in developed countries on compaction in tilled layers but the increasing weight of agricultural vehicles has attracted the attention of scientists towards occurrence of subsoil compaction. The existing subsoilers available in India are poorly designed and require heavy draft. However, in developed countries, winged subsoilers have found a suitable place in their crop production system for rootbed preparation. Keeping the above points in view, a winged subsoiler with leading tines was developed (Arun Kumar, 2003) and its performance was compared with different subsoilers on the basis of draft, soil disturbance and specific draft. |
