Wednesday, November 15, 2006

Timing Vine Desiccation to Optimize Yield, Tuber Size Distribution, and Quality of Two Colorado Russet Potato.

Samuel Y.C. Essah*, David G. Holm, and Robert D. Davidson. Colorado State University, San Luis Valley Research Center, 0249 East Road 9 North, Center, CO 81125


            Time of vine desiccation is critical for tuber size and quality management to meet specific markets.  Timing of vine desiccation to optimize tuber size and quality varies among potato (Solanum tuberosum) cultivars.  A two years study was conducted at Colorado State University, to evaluate the effect of vine desiccation date on tuber yield, tuber size distribution, and quality of two russet potatoes, Russet Norkotah (selection 8) and CO93001-11RU.  Four vine desiccation dates, 90, 100, 110, and 120 days after planting (DAP) were compared.  For Russet Norkotah, optimum total yield (68 Mg ha-1) was attained when vines were desiccated at 120 DAP.  Optimum marketable size tubers [114 to 454 g (52 Mg ha-1)], large marketable size tubers [284 to 454 g (15 Mg ha-1)], and medium size tubers [114 to 284 g (38 Mg ha-1)] were harvested when vines were desiccated at 110 DAP, with high tuber specific gravity (1.082) and no tuber internal defects.  For CO93001-11RU, optimum total yield (57 Mg ha-1), marketable yield (47 Mg ha-1), large marketable tuber yield (9 Mg ha-1), and medium size tuber yield (38 Mg ha-1) were attained when vines were desiccated at 110 DAP, with no tuber internal defects, and tuber specific gravity of 1.079.   The two cultivars studied were comparable in marketable and medium size tuber yield, but Russet Norkotah yielded 61% more large marketable size tubers than CO93001-11RU.  In both cultivars tuber size distribution was skewed towards the 114 to 284 g size distribution range.  At the optimum time of vine desiccation (110 DAP), 73 and 80% of tubers from Russet Norkotah and CO93001-11RU, respectively, were in the 114 to 284 g tuber size range.  Results from this study indicate that for optimum tuber yield and quality, vines of Russet Norkotah and CO93001-11RU should be desiccated at 110 DAP.