Investigations were made using onion cv Ringburger into the effects of mother nutrition on plant growth, bulb yield and chemical composition at the end of their first season. Yield and quality seed produced under greenhouse and field conditions in the second season were also investigated. Nitrogen application at the rate of 150 Kg/ha (medium level) was superior in increasing plant vigour, bulb size and yield and its effect was more pronounced when combined with P and/or K both at the rate of 250 Kg/ha. Mother bulb nutrient contents generally reflected the rates of the three nutrients applied. For seed production, N, P and K fertilizer treatments were given in a 3x3x3 factorial in the first experiment. In the second experiment selected bulbs of known nutrient contents were subjected to differential rates of N, P and K under glass. In the third experiment, which was conducted in the field, bulbs for seed production which had been raised under different N levels in their first season received different rates of N at different times. Results from the first and second experiments show that seed yield was significantly increased with increase in N up to medium levels, whereas P and K supply had no significant effects except when combined with N. This increase in seed yield was accompanied by a reduction in the quality of seed produced. In the third experiment neither the levels nor the time of N application had a significant effect on seed yield but the application of low N levels, especially at flowering time improved seed quality. Potassium reserved in the bulbs from first seasons application, supplied during plant growth or maintained from both sources proved beneficial in the quality of seed produced. Fertilizer rates for producing mother bulbs in the first season did not result in a significant increase in seed yield but their effects on seed quality were clearly observed. The high correlation between field emergence and seed germination after controlled deterioration suggested that this vigour test may be used as an indicator of potential onion seedling emergence in the field.
|Date of Award||1982|