This study was conducted to improve some pratical techniques for reducing both production costs and labor hours in crop rotation system based on the rice culture seeded on the dry field.
Soil packing after tillage was thought to be an important technique for the rice culture seeded on the dry field in Hokuriku district where has much rainfall in spring and winter. The experiment on rotation system consisting of 5 crops, (rice culture seeded on the dry field, rice culture seeded on the dry field, barley and soybean, and rice culture seeded on the dry field) was carried out in the 1.8 ha field for 4 years.
1) The soil after the rice culture seeded on the dry field showed high porosity, low plasticity index and no spreaded sign of grey horizon. This phenomenon meant to be the good conditinos for rotation crops such as barley and soybean. In the 4 year crop rotation based on the rice culture seeded on the dry field, the grey horizon decreased and the iron mottles increased in the soil structure.
2) The number of turns per unit area of large-lot field (210m×85m) were less than that of small one. So, the effective field capacity (ha/h) increased and the working efficiency was improved.
3) The total labor hours required for the rice culture seeded on the dry field was 13-14h/10 a, because of efficient work and management in the large-lot. This was about 1/3 as long as the hours required for the conventional transplanted rice culture.
4) The total labor hours required for the barley culture in the chop rotation system was 3.6h/10a (except drying and processing), and that for soybean culture was 6.9h/10a (except drying). These labor hours were about 1/3-1/2 as long as those for conventional culture.
5) In the rice culture seeded on the dry field, slow-release type fertilizer was incorporated as a basal dressing and irrigation water were supplied at 1.5-2.5 leaf-stage of rice seedling when was earlier than the usual. Therefore, rice plants showed higher rate of establishment (55-80%) and vigorous growth in later stage. The yields of Koshihikari and Kinuhikari were 512-577 and 523-630kg/10a, respectively. These yields were almost the same level as transplanted rice culture.
6) The well-drained field conditions made it possible to cultivate barley and soybean by the drill-seeded culture without additional drainage trenches. So, the yields of barley (Minorimugi) and soybean (Enrei) were 635 and 346kg/10a, respectively. These yields were about 2-3 times as much as those of conventional culture.
