INFLUENCE OF THE TILLING METHOD AND THE SOIL COMPACTION DUE TO MACHINE WEIGHT ON THE GROWTH AND YIELD OF RICE PLANTS

Working time required for tilling, changes in soil conditions, and growth and yield of rice plants influenced by the tilling methods and soil compaction due to machine weight were examined. Under normal paddy field conditions, rice plants, cv. Manryo, were grown in 1978 and 1979 in the following treatments; 1) 12 cm tilling depth, tilled by a small cultivator; 2) 12 cm depth, by a large tractor equipped with the rotary; 3) 18 cm depth, by a large tractor with the plow, and then harrowed; 4) 18 cm depth, by a large tractor with the rotary; 5) Soil compaction in dry condition just after harvest, and then tilled by a large tractor with the rotary, 12 cm depth; and 6) Soil compaction in wet condition, and then tilled by the same way as 5). The rotary tilling method was more profitable as compared with the plowing and harrowing method from the point of view to level off the field surface, and nutrition supply from soil lasted to the end of rice growth in 18 cm depth treatment because of enlargement of root zone. On the other hand, soil compaction attributed to machine weight did not change the hardness, the three phases and the consolidation of soil, but decreased the degree of water permearbility. The result was that the yield of rice plants in 18 cm tilling depth with the rotary method was best, followed by 18 cm depth with plowing method and soil compaction treatments against imagined negative effects. © 1990, CROP SCIENCE SOCIETY OF JAPAN. All rights reserved.