Abstract
Helianthus cultivated in upland fields converted from rice paddy often suffers from excess moisture injury and is difficult to sow appropriately using sowing machines now possessed by farmers. We conducted sowing tests in the fields of farmers using a simplified ridging method to cope with excess moisture injury and a replaceable sowing roll for helianthus. Furthermore, we studied inter-tillage and topdressing techniques in order to increase the helianthus yield.
Helianthus seeds were sown at intervals of 80cm between ridges and 25cm between plants using the helianthus sowing roll in farm fields. The inter-tillage method with the ridger width reduced to about 20cm so as not to damage helianthus roots achieved a yield exceeding that where there was no weeding or where weeding was performed manually, and it was confirmed that a sufficient increase in yield could be expected if fertilization with nitrogen content of 2.1kg/10a and topdressing with 10kg/10a of nitrogen content are applied.
Furthermore, the plant separation was compared between those fields where the sowing rolls for helianthus supplied to the local farmers' union were used and that in fields where no such rolls were used. A significant difference was found : 59.6% of the plants were appropriately spaced when sowing rolls were used, but only 37.1% of the plants were appropriately spaced when the rolls were not used. Fifteen sowing rolls for helianthus were distributed to local farmers in 2009, the year after the tests.
