| Abstrakt: |
Corn (Zea maysL.) absorbs both ammonium and nitrate forms of N. Both are usually present in the soil and some control of their proportions can be obtained by controlling nitrification. Little is known about the relative rates of absorption of these ions or their effect on plant growth rate when both are present. We investigated the effects of NH4+and NO3−on corn by growing 13‐day‐old corn seedlings for an additional 5 days in 25 nutrient solutions consisting of 5 N concentrations (15.9, 67.1, 303, 1507, and 6015 μM) at each of 5 NH4+/NO3−ratios (8.40, 2.46, 1.05, 0.49, and 0.17). Solution NH4+, NO3−, and pH were monitored and variations kept to a minimum. Uptake rates of NH4+and NO3−were estimated separately from solution analysis. Maximum dry matter accumulated with an N concentration of 67 μM. Maximum N uptake occurred for the combination of 303 μMN and a NH4+/NO3−ratio of 2.46. Shoot/root ratio increased significantly with increased N concentration, but was unaffected by NH4+/NO3−ratio. Above 67 μM N, the NH4+/NO3−ratio of absorbed N tended toward 1.0 as compared with the ratio in solution. There was no significant difference between NH4+and NO3−in their relative rates of absorption. Increasing the concentration of NH4+reduced the NO3−uptake rate and increasing the NO3−concentration reduced the NH4+uptake rate. Each mutually influenced the absorption of the complementary nitrogen form to the same degree. |
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