POTATO PRODUCTION ON A CAT CLAY SOIL IN RELATION TO STABLE AND UNCONTROLLED WATER TABLES

To study potato (Solanum tuberosum) response to drainage in a poorly drained high-S de l'Anse clay loam (sulfaquept), five or six cultivars were grown for 3 consecutive years on separate plots where the water table fluctuated naturally or was maintained at 0.46-, 0.76-, or 1.22-m depth during the growing season. As the fixed water table was maintained at progressively lower levels, marketable tuber ( > 45 mm) yields declined linearly from 0.46 to 1.22 m in a year with normal July rainfall. Marketable yield plateaued at 0.76 m then decreased in years with wet or dry July periods. Specific gravity of the potatoes declined each year. The reduction was greater from 0.46 to 0.76 than from 0.76 to 1.22 m in the dry and wet years. In the wet year, there was a slight increase in specific gravity from 0.76 to 1.22 m. Soil temperature and soil pH showed no effect of water table reduction. Generally, the values for variables measured on the controls where the water table fluctuated naturally occurred somewhere between the two extremes of those measured between 0.46 and 1.22 m. Therefore, there was no advantage in lowering the water table for crop growth on a high-water-table soil and doing so resulted in negative effects due to less water being available. These negative effects were not due to increased acidity on this cat clay. Since water table had no effect on soil pH, it may be that the sulfur compounds in this soil were not significantly labile.