Abstract
Abstract Nitrogen fertilizer is applied to supplement soil nitrogen supply to maximize forage brassica crop dry‐matter production. However, nitrogen fertilizer applications in excess of that required to maximize growth result in potentially toxic nitrate–nitrogen ( NO 3 –N) concentrations in grazeable plant tissues. Three experiments, two for forage kale at L incoln ( C anterbury) and one for forage rape at H astings ( H awke's B ay) in N ew Z ealand were grown under different rates of nitrogen (0–500 kg N ha −1 ) to determine the effect of different rates of nitrogen on NO 3 –N content of different plant parts of the crops. One of the kale experiments was grown with either full irrigation or no rain and no irrigation over summer, hereafter referred to as summer drought. The NO 3 –N concentration on a whole plant (weighted average) basis increased from 0·1 mg g −1 dry matter for the control plots to 2·30 mg g −1 for the 500 kg N ha −1 plots for forage kale. It increased from 0·99 for the control plots to 3·37 mg g −1 for the 200 kg N ha −1 plots for forage rape crops. However, NO 3 –N concentration increased with N supply under the summer‐drought plots from an average of 0·33 mg g −1 when ≤120 kg N ha −1 was applied to 2·30 mg g −1 for the 240 kg N ha −1 treatments but was unaffected by N supply under irrigation. The NO 3 –N concentrations were higher in the stems and the petiole (which included the midrib of the leaf) than leaves in all three experiments. The NO 3 –N concentration was highest at the bottom of the kale stem and decreased towards the top. We recommend N application rates based on soil tests results, and for conditions similar to the current studies up to 300 kg N ha −1 under irrigation and adjusted lower N rates for regions prone to dry summers.
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Claims 7
Claim · model-written summary
Forage kale whole-plant nitrate concentration rose from 0·1 to 2·30 mg g −1 dry matter between control and 500 kg N ha −1 plots.
Verbatim
e0“The NO 3 –N concentration on a whole plant (weighted average) basis increased from 0·1 mg g −1 dry matter for the control plots to 2·30 mg g −1 for the 500 kg N ha −1 plots for forage kale”
Claim · model-written summary
Forage rape nitrate concentration rose from 0·99 in controls to 3·37 mg g −1 at 200 kg N ha −1.
Verbatim
e0“The NO 3 –N concentration on a whole plant (weighted average) basis increased from 0·1 mg g −1 dry matter for the control plots to 2·30 mg g −1 for the 500 kg N ha −1 plots for forage kale. It increased from 0·99 for the control plots to 3·37 mg g −1 for the 200 kg N ha −1 plots for forage rape crops”
Claim · model-written summary
Under summer drought, nitrate concentration rose with nitrogen supply from 0·33 to 2·30 mg g −1.
Verbatim
e0“NO 3 –N concentration increased with N supply under the summer‐drought plots from an average of 0·33 mg g −1 when ≤120 kg N ha −1 was applied to 2·30 mg g −1 for the 240 kg N ha −1 treatments”
t0“forage kale”
Claim · model-written summary
Under irrigation, nitrate concentration was unaffected by nitrogen supply.
- Taxon
- forage kalet0
- Treatment
- N supplye0
- Outcome
- NO 3 –N concentratione0
- Direction
- unaffectede0
- Qualifier
- under irrigatione0
Not reportedComparator
Verbatim
e0“NO 3 –N concentration increased with N supply under the summer‐drought plots from an average of 0·33 mg g −1 when ≤120 kg N ha −1 was applied to 2·30 mg g −1 for the 240 kg N ha −1 treatments but was unaffected by N supply under irrigation”
t0“forage kale”
Claim · model-written summary
Nitrate concentrations were higher in stems and petioles than leaves.
Verbatim
e0“The NO 3 –N concentrations were higher in the stems and the petiole (which included the midrib of the leaf) than leaves in all three experiments”
t0“forage kale and rape crops”
Claim · model-written summary
Nitrate concentration was highest at the bottom of the kale stem and decreased upward.
- Taxon
- kale
Brassica oleracea var. viridise0 - Organ / stage
- kale steme0
- Outcome
- NO 3 –N concentratione0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The NO 3 –N concentration was highest at the bottom of the kale stem and decreased towards the top”
Claim · model-written summary
The authors recommend soil-test-based nitrogen rates, up to 300 kg N ha −1 under similar irrigated conditions and lower rates in dry-summer regions.
Verbatim
e0“We recommend N application rates based on soil tests results, and for conditions similar to the current studies up to 300 kg N ha −1 under irrigation and adjusted lower N rates for regions prone to dry summers”
t0“forage kale and rape crops”
The same questions in other papers
nitrogen · molecular: metabolites · Brassica oleracea (wild cabbage)Positive and negative results
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See all 22 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.