EFFECTS OF ROTATION LENGTH AND OXAMYL ON POTATO YIELD AND THE POTATO CYST-NEMATODE, GLOBODERA-ROSTOCHIENSIS, IN A SANDY LOAM SOIL

In sandy loam infested with golden potato cyst-nematode, Globodera rostochiensis, oxamyl at 5.6 kg a.i. ha-1 incorporated in the top 15 cm of the soil just before planting potatoes greatly reduced nematode population increase on susceptible cv. Desiree grown six, seven or eight years after the last susceptible potato crop, but did not significantly increase tuber yields. In four-course and two-course rotations, oxamyl also controlled increase of G. rostochiensis and greatly increased yields of both cv. Desiree and resistant cv. Maris Piper. Oxamyl maintained tuber yields in a four-course rotation at the same level as in a six to eight-course rotation. Decline of G. rostochiensis in the soil was much faster under barley in some two-course rotations than under barley in four-course rotations.