Evaluation location: , United States
METHOD: Chemical Assay CONDITIONS: Field METHOD NARR: Seedlings were planted into rows and subjected to 2 Nitrogen treatments (0kg and 225kg N per ha). Nitrogen as ammonium nitrate was applied on three occaissions. Tubers, roots, shoots and fruits were collected seperately. After washing, the samples were oven-dried at 70C and the dry weight of the seperate parts recorded. Total tissue N was determined conductimetrically, following a salicylic Kjeldahl nitrogen digestion procedure. Nitrogen uptake and utilization efficiencies were calculated. Year 2 RESULTS NARR: Nitrogen uptake efficiency was calculated as follows: NUE = (PN/SN) x (TDW/PN) = (TDW/SN) where (PN/SN) is (total plant N content/fertilizer N) and (TDW/PN) is (total dry weight of all plant parts/total plant N content). More simply, NUE is (Uptake efficiency) x (Utilization efficiency) = (Yield efficiency). Efficiency of utilization (per Siddiqi & Glass) is calculated as follows: E = (TDW/PN) x TDW = TDWsquared/PN. AUTHOR EXPLANATION: An uncontrollable outbreak of CPB occured in 1994 severely affecting susceptible cultivars but not resistant wild species. Dry weight partitioning was closely associated with the level of domestication of the potato species. Poor tuber production by wild types is most likely due to the lack of short day conditions.