Abstract
SUMMARY Nitrogen (N) nutrition is a key factor for vegetable growth and yield. However, different rates of nitrogen fertilization may trigger different responses to vegetables. A survey was conducted to investigate the effect of soil fertility management practices on nitrate concentration in vegetables. The survey results were used to plan experiments on the effect of chicken and cattle manures on nitrate levels in Chinese cabbage ( Brassica rapa ) and amaranthus ( Amaranthus cruentus ) grown in Tanzania and the patterns of mineral nitrogen in soils under open field conditions. Chicken or cattle manure at 200, 300 kg N ha −1 and 170 250 kg N ha −1 for Chinese cabbage and amaranthus respectively, and control were compared in a randomized complete block design. We observed a higher nitrate content in fertilized Chinese cabbage at day 30 than at day 44 after sowing, ranging from 3243 to 4993 mg kg −1 fresh matter regardless of the N source and rates. Only application of manures at high levels (250 kg N ha −1 ) induced significantly ( p < 0.05) higher nitrate contents in amaranthus at day 28 after sowing, although there was a clear indication of nitrate accumulation even at 170 kg N ha −1 application. Soil NH 4 + -N + NO 3 − -N in both Chinese cabbage and amaranthus plots were increased with increasing N application rates and differences between control and amended soils were significant ( p < 0.01). There was a positive relationship between NO 3 − concentration in vegetables and NO 3 − -N in the rooted top soil layer (0–15 cm). However, higher NH 4 + concentrations depressed NO 3 − build up in crops and a significant negative relationship between soil (NH 4 + -N)/(NO 3 − -N) ratio and crop NO 3 − content was found. It is concluded that low manure application rates result in similar yields to high rates but reduces nitrate accumulation in vegetables and excess mineral nitrogen in soils.
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Claims 6
Claim · model-written summary
Fertilized Chinese cabbage had more nitrate at day 30 than day 44.
- Taxon
- Chinese cabbage
Brassica rapa subsp. pekinensise0 - Outcome
- nitrate contente0
- Direction
- highere0
- Value
- 3243 to 4993 mg kg −1 fresh mattere0
- Comparator
- day 44e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“higher nitrate content in fertilized Chinese cabbage at day 30 than at day 44 after sowing, ranging from 3243 to 4993 mg kg −1 fresh matter”
Claim · model-written summary
High manure rates significantly raised amaranthus nitrate content.
- Taxon
- amaranthus
_with_green_foliage%2C_photographed_in_Tamil_Nadu%2C_India.jpg?width=60)
Amaranthuse0 - Treatment
- manures at high levels (250 kg N ha −1 )e0
- Outcome
- nitrate contentse0
- Direction
- highere0
- Qualifier
- day 28 after sowinge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_with_green_foliage%2C_photographed_in_Tamil_Nadu%2C_India.jpg?width=500)
Verbatim
e0“Only application of manures at high levels (250 kg N ha −1 ) induced significantly ( p < 0.05) higher nitrate contents in amaranthus at day 28 after sowing”
Claim · model-written summary
Vegetable nitrate concentration was positively related to nitrate in rooted topsoil.
Verbatim
e0“positive relationship between NO 3 − concentration in vegetables and NO 3 − -N in the rooted top soil layer (0–15 cm)”
e1“Chinese cabbage ( Brassica rapa ) and amaranthus ( Amaranthus cruentus )”
Claim · model-written summary
Higher soil ammonium was associated with lower crop nitrate accumulation.
Verbatim
e0“higher NH 4 + concentrations depressed NO 3 − build up in crops and a significant negative relationship between soil (NH 4 + -N)/(NO 3 − -N) ratio and crop NO 3 − content was found”
Claim · model-written summary
Low manure rates gave similar yields to high rates.
Verbatim
e0“low manure application rates result in similar yields to high rates but reduces nitrate accumulation in vegetables”
Claim · model-written summary
Low manure rates reduced vegetable nitrate accumulation relative to high rates.
Verbatim
e0“low manure application rates result in similar yields to high rates but reduces nitrate accumulation in vegetables”
The same questions in other papers
nitrogen · nutrient: content · AmaranthusPositive and negative results
2 in the opposite direction
- positive
- positive
fertilization · nutrient: content · AmaranthusPositive and negative results
1 paper in the same direction as this paper · 7 in the opposite direction
- positive
- positive
- positive
5 papers more in this group
See all 9 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.