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Rice transplanting in Isfahan is done by manual labor, which is a tedious and laborious job. Mechanized rice transplanting required a seedling bed of special conditions. Information about pre-planting tillage aspects for mechanized rice transplanting in Isfahan is lacking. For this reason, suitability of some seedling-bed preparation methods for transplanting with a self-propelled walking-type transplanter was studied. A field experiment was conducted in 1998 at Kabootarabad Agricultural Research Station located 40 km southeast of Isfahan, on a silty clay soil. The effects of pre-planting tillage methods, namely soil puddling and compaction, followed by manual transplanting on soil physical properties, fuel requirement, machine capacity and rice yield, using a randomized complete block design with three replications, were evaluated. Soil puddling treatments included one and two rotary tillings (with L- and
knife-shaped blade rotary tillers) and six harrowings with a locally made rigid-shank field cultivator named Khishchee. Compaction treatment involved two passes of an ITM-750 tractor over the plots. In puddling operations, in addition to a four-wheel tractor (MF-285), cage wheels in conjunction with the rear pneumatic wheels of the tractor (dual wheels) were used in some treatments. A tiller (two-wheel walking-type tractor equipped with rotary tiller) was utilized in one puddling treatment as well. The field observations showed that the puddling implements worked satisfactorily, however, the tiller was bogged down due to lug blocking of its cage wheels. This was attributed to high wheel slippage and soil adhesion. The cage wheels reduced the fuel consumption of the tractor whenever more draft was required. The field tests on the transplanter showed that, when transplanting was done into very soft soil prepared with puddling, the transplanted seedlings were buried in mud. On the other hand, when the soil was left to become firmer, the transplanter was bogged down because of its cage wheels blocking. Although the transplanter performed well in compacted plots, most of the transplanted seedlings floated on the surface of water. This was due to not having enough soft surface soil for seedling establishment. Although the bulk density in the 0 to 0.15-m layer just before transplanting was not affected by pre-planting tillage methods, the methods significantly influenced the soil density measured after harvest. Puddling with two rotary tillings (with knife-shaped blades) and compaction method had the highest and lowest soil bulk density values, respectively. Clod size produced after plowing of puddled plots was significantly higher than that of compacted plots. Cumulative infiltration was lower on puddled (with rotary tillers) plots than on control (no treated soil) and was similar to the control on compacted plots for tests conducted on the base of the plowed layer after rice harvesting. In comparison with puddling with L-shaped rotary tiller, paddy yield of puddled plots with six harrowings with rigid-shank field cultivator (conventional method), was 3% less, however, its fuel requirement and operational time were 45 and 200% more, respectively. The results indicated,
transplanting with the transplanter in the seedling bed prepared with puddling in the fine-textured and sticky-soil field, which is used as a paddy field for the first time and has not undergone chemical changes to reduce its adhesion, is not recommended. Based on the results of this experiment, it is possible to produce at least similar grain yield with lower energy consumption and higher efficiency from puddling with a rotary tiller, as with conventional puddling under conditions similar to this experiment.