Calcium Stimulation of Ammonium Absorption In Radish
- L. B. Fenn * and
- R. M. Taylor
Nitrogen loss processes in soils have been widely studied and there have been many suggestions for improving N-use efficiency, such as using NH4-NO3 fertilizers, split fertilizer applications, application timing, and other techniques. The objective of this research was to examine the use of Ca as a means to increase the rate of NH4 absorption by radish (Raphanus sativus L.). Short-term 15NH4 absorption in the presence of variable Ca was measured in the greenhouse, long-term plant growth responses to NH4 in the presence of variable Ca were measured both in the greenhouse and in field production trials. Ammonium absorption (15NH4) increased in plants with increasing solution Ca to a Ca/NH4 ratio of 0.5:1 in the tops and to 2:1 in the roots. Vegetative growth increased in two greenhouse experiments as Ca concentrations increased, all at a constant NH4 concentration. As the Ca concentration increased, the total N concentration increased in foliar tissue and decreased in the roots. In the 2 yr of field testing, dry weight yield of roots increased 77 and 55%, respectively, in the urea + Ca treatment compared with the urea treatment alone. In the second year field data, total plant absorption of the added urea-N in the presence of added Ca increased by 109% compared with urea alone. Significant increases were found both in the root and foliar tissue N content, and growth in the 2 yr of field data. The addition of Ca with urea produced significantly improved plant N-use efficiency in the field as was suggested from the greenhouse data.
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