|
|||||
|
|
Efficiency of nitrogen uptake by potatoes |
|
| Authors: | K B Tyler F E Broadbent J C Bishop |
| Institution: | 1. Cooperative Extension, SJVAR&EC, Parlier 2. Dept. of Land, Air and Water Resources, Davis 3. Dept. of Vegetable Crops, Shafter, CA |
| Abstract: | White Rose potatoes were fertilized with isotopically labeled ammonium sulfate at rates of 67, 134, 202 and 270 kg N/ha to evaluate N uptake efficiency. All N application increased yields above the control, however the 3 higher N rates produced the same yields statistically. All N rates which maximized yields maintained petiole levels of total N above 600 ppm. Rapid changes in petiole inorganic N occurred during the growing season. Fertilizer derived inorganic N decreased at rates ranging from 67 to 518 ppm/day during the third month after planting. Total inorganic N in petioles during the same period dropped at rates ranging from 500 to 880 ppm/ day. Tubers grown in N-fertilized plots assimilated total N in a nearly linear pattern during the period 82 to 125 days after planting. Uptake of total N ranged from 142 to 233 kg/ha. In assessing N utilization by 3 methods, good agreement was achieved between the isotope and difference method in the first and third (last) samplings, however, agreement was poor between the two in the second sampling. With N rates to 202 kg/ha the uptake efficiency was about 57% but dropped to 39% with application of 270 kg N/ha. When uptake efficiency was measured by dry matter production in relation to units of N fertilizer, the 67 kg N rate was superior to other rates. Inorganic N levels in the surface meter of soil were higher before planting and fertilizer application than after harvest. Following harvest the control plots had more N below 1.5 m than did the N fertilized plots. In control plots, the total inorganic N between 1.5 and 2.5 m depths was equivalent to 170 kg N/ha. Virtually none of the accumulated N below 1 m was due to labeled N applied in the experiment. Using 134 kg N/ha as the optimum rate, tubers removed 178 kg N/ha of which 78 kg was derived from the applied fertilizer. With total N input of 191 kg/ha (57 kg N/ha from irrigation water) the N rate required for maximum yield would pose no risk of nitrate pollution since it represents only 13 kg more than crop removal (191 vs 178 kg N/ha). |
| Keywords: | |
| 本文献已被 SpringerLink 等数据库收录！ | |