Abstract
Bolting causes significant economic losses in sweet onion ( Allium cepa L.) production. Although temperature and photoperiod are considered to be the main factors that initiate bolting in onions, preliminary results suggested that low N fertilization rates increased bolting. The objective of our study was to determine the relationships of bolting, yield and bulb decay with N fertilization rates. The N fertilization rates applied ranged from the infraoptimal to the supraoptimal (from 102 to 302 kg·ha -1 N). Shoot and bulb N content increased with increasing N rates, but there were no differences in the respective shoot and bulb N contents among cultivars. Bolting incidence declined steadily with increasing N fertilization rates up to 197 kg·ha -1 N. Bolting incidence was among the highest in the cultivar Pegasus. The percent of decayed bulbs also increased at a steady rate with the rate of N applied. Total (14.7 t·ha -1 ) and marketable (0.8 t·ha -1 ) yields at the lowest N rate (102 kg·ha -1 N) were lower ( P ≤ 0.01) than those at higher N rates. Rates of N ≥145 kg·ha -1 had no significant effect on either total (mean = 33.6 t·ha -1 ) or marketable (mean = 21.6 t·ha -1 ) yields. Losses in marketable yield were primarily a combination of bolting and bulb decay and were minimized at 162 kg·ha -1 N. Yield losses at low N rates were mostly due to bolting while yield losses at high N rates were mostly due to decay. Thus, excess applications of N fertilizer should be avoided since they have little effect on yields or bolting but they increase bulb decay.
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Claims 15
Claim · model-written summary
Shoot nitrogen content rose with nitrogen rate.
- Taxon
- sweet oniont0
- Treatment
- increasing N ratese0
- Outcome
- Shoot and bulb N contente0
- Direction
- increasede0
Not reportedComparator
Verbatim
e0“Shoot and bulb N content increased with increasing N rates”
t0“Sweet Onion”
Claim · model-written summary
Bulb nitrogen content rose with nitrogen rate.
Not reportedComparator
Verbatim
e0“Shoot and bulb N content increased with increasing N rates”
t0“Sweet Onion”
Claim · model-written summary
Shoot and bulb nitrogen contents did not differ among cultivars.
Verbatim
e0“there were no differences in the respective shoot and bulb N contents among cultivars”
t0“Sweet Onion”
Claim · model-written summary
Bolting incidence declined as nitrogen rate rose to 197 kg per hectare.
- Taxon
- sweet oniont0
- Treatment
- increasing N fertilization rates up to 197 kg·ha -1 Ne0
- Outcome
- Bolting incidencee0
- Direction
- declinede0
- Value
- 197 kg·ha -1 Ne0
Not reportedComparator
Verbatim
e0“Bolting incidence declined steadily with increasing N fertilization rates up to 197 kg·ha -1 N”
t0“Sweet Onion”
Claim · model-written summary
Pegasus had among the highest bolting incidence.
Verbatim
e0“Bolting incidence was among the highest in the cultivar Pegasus”
t0“Sweet Onion”
Claim · model-written summary
The percentage of decayed bulbs rose with nitrogen rate.
Not reportedComparator
Verbatim
e0“The percent of decayed bulbs also increased at a steady rate with the rate of N applied”
t0“Sweet Onion”
Claim · model-written summary
Total yield at the lowest nitrogen rate was lower than at higher rates.
Verbatim
e0“Total (14.7 t·ha -1 ) and marketable (0.8 t·ha -1 ) yields at the lowest N rate (102 kg·ha -1 N) were lower ( P ≤ 0.01) than those at higher N rates”
t0“Sweet Onion”
Claim · model-written summary
Marketable yield at the lowest nitrogen rate was lower than at higher rates.
Verbatim
e0“Total (14.7 t·ha -1 ) and marketable (0.8 t·ha -1 ) yields at the lowest N rate (102 kg·ha -1 N) were lower ( P ≤ 0.01) than those at higher N rates”
t0“Sweet Onion”
Claim · model-written summary
At rates at least 145 kg per hectare, total yield had no significant rate response.
- Taxon
- sweet oniont0
- Treatment
- Rates of N ≥145 kg·ha -1e0
- Outcome
- yieldse0
- Direction
- no significant effecte0
- Value
- 33.6 t·ha -1e0
Not reportedComparator
Verbatim
e0“Rates of N ≥145 kg·ha -1 had no significant effect on either total (mean = 33.6 t·ha -1 ) or marketable (mean = 21.6 t·ha -1 ) yields”
t0“Sweet Onion”
Claim · model-written summary
At rates at least 145 kg per hectare, marketable yield had no significant rate response.
- Taxon
- sweet oniont0
- Treatment
- Rates of N ≥145 kg·ha -1e0
- Outcome
- yieldse0
- Direction
- no significant effecte0
- Value
- 21.6 t·ha -1e0
Not reportedComparator
Verbatim
e0“Rates of N ≥145 kg·ha -1 had no significant effect on either total (mean = 33.6 t·ha -1 ) or marketable (mean = 21.6 t·ha -1 ) yields”
t0“Sweet Onion”
Claim · model-written summary
Bolting and decay were the main combined sources of marketable yield loss.
Verbatim
e0“Losses in marketable yield were primarily a combination of bolting and bulb decay”
t0“Sweet Onion”
Claim · model-written summary
Marketable yield losses were minimized at 162 kg per hectare nitrogen.
Verbatim
e0“Losses in marketable yield were primarily a combination of bolting and bulb decay and were minimized at 162 kg·ha -1 N”
t0“Sweet Onion”
Claim · model-written summary
Low nitrogen yield losses were mostly due to bolting.
Verbatim
e0“Yield losses at low N rates were mostly due to bolting”
t0“Sweet Onion”
Claim · model-written summary
High nitrogen yield losses were mostly due to decay.
Verbatim
e0“yield losses at high N rates were mostly due to decay”
t0“Sweet Onion”
Claim · model-written summary
Excess nitrogen fertilizer should be avoided because it increases decay with little yield or bolting benefit.
Verbatim
e0“excess applications of N fertilizer should be avoided since they have little effect on yields or bolting but they increase bulb decay”
t0“Sweet Onion”
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See all 184 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.