Abstract
• Over the past 3 years, we have had 6 experiments with isotope-labelled (15N) urea fertiliser in northern NSW and a further 11 in southern Qld, all focussed on measuring the fate of applied N fertilizer in summer sorghum. Normal fertiliser contains 14N so the use of 15N allows us to trace the fate of urea-N applied to the soil from sowing through to harvest. • Between 56 and 93% of the applied N was found in the soil and plant at harvest, with in-season rainfall (both timing and amount) and soil C and N status having a major impact on the seasonal loss potential. • Avoiding unnecessarily high N rates, delaying or splitting N fertiliser so that peak N availability coincides with peak crop N demand and relying on residual N from legume rotations all significantly reduced gaseous N losses from dryland sorghum, although the effectiveness of any management strategy varied with seasonal conditions. • Nitrification inhibitor-coated urea significantly reduced nitrous oxide emissions in all studies, but did not improve grain yields enough to justify the additional cost on an agronomic basis. • Depending on the season, delaying/splitting N applications gave either no yield benefit (dry season) or a significantly greater yield (good in-crop rainfall). Much of the unused N after a dry season remained in the soil and, provided loss events were not experienced during the fallow, significantly benefited the following crop. As reliance on N fertilizer increases, getting good crop recovery of applied N is essential Crop N recovery is most efficient when N is distributed through the root volume Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum. Ensuring fertilizer N is in the crop or deeper in the soil profile is the best defence against loss Controlled release fertilizers can reduce denitrification but are rarely economic; legume N is effective
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Claims 17
Claim · model-written summary
At harvest, 56–93% of applied nitrogen was recovered in soil and plant.
SorghumOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Between 56 and 93% of the applied N was found in the soil and plant at harvest, with in-season rainfall (both timing and amount) and soil C and N status having a major impact on the seasonal loss potential.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Seasonal rainfall and soil carbon and nitrogen status strongly affected nitrogen loss potential.
- Outcome
- seasonal loss potentiale0
- Qualifier
- in-season rainfall (both timing and amount) and soil C and N statuse0
- Setting
- soile0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Between 56 and 93% of the applied N was found in the soil and plant at harvest, with in-season rainfall (both timing and amount) and soil C and N status having a major impact on the seasonal loss potential.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Avoiding unnecessarily high nitrogen rates significantly reduced gaseous nitrogen loss from dryland sorghum.
- Taxon
- dryland sorghume0
- Treatment
- Avoiding unnecessarily high N ratese0
- Outcome
- gaseous N lossese0
- Direction
- reducede0
- Qualifier
- effectiveness of any management strategy varied with seasonal conditionse0
Not reportedComparator
Verbatim
e0“Avoiding unnecessarily high N rates, delaying or splitting N fertiliser so that peak N availability coincides with peak crop N demand and relying on residual N from legume rotations all significantly reduced gaseous N losses from dryland sorghum, although the effectiveness of any management strategy varied with seasonal conditions.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Delaying or splitting nitrogen fertilizer significantly reduced gaseous nitrogen loss from dryland sorghum.
- Taxon
- dryland sorghume0
- Treatment
- delaying or splitting N fertilisere0
- Outcome
- gaseous N lossese0
- Direction
- reducede0
- Qualifier
- effectiveness of any management strategy varied with seasonal conditionse0
Not reportedComparator
Verbatim
e0“Avoiding unnecessarily high N rates, delaying or splitting N fertiliser so that peak N availability coincides with peak crop N demand and relying on residual N from legume rotations all significantly reduced gaseous N losses from dryland sorghum, although the effectiveness of any management strategy varied with seasonal conditions.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Using residual nitrogen from legume rotations significantly reduced gaseous nitrogen loss from dryland sorghum.
- Taxon
- dryland sorghume0
- Treatment
- relying on residual N from legume rotationse0
- Outcome
- gaseous N lossese0
- Direction
- reducede0
- Qualifier
- effectiveness of any management strategy varied with seasonal conditionse0
Not reportedComparator
Verbatim
e0“Avoiding unnecessarily high N rates, delaying or splitting N fertiliser so that peak N availability coincides with peak crop N demand and relying on residual N from legume rotations all significantly reduced gaseous N losses from dryland sorghum, although the effectiveness of any management strategy varied with seasonal conditions.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Nitrification inhibitor-coated urea significantly reduced nitrous oxide emissions in all studies.
- Taxon
- summer cropst0
- Treatment
- Nitrification inhibitor-coated ureae0
- Outcome
- nitrous oxide emissionse0
- Direction
- reducede0
- Qualifier
- in all studiese0
Not reportedComparator
Verbatim
e0“Nitrification inhibitor-coated urea significantly reduced nitrous oxide emissions in all studies, but did not improve grain yields enough to justify the additional cost on an agronomic basis.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Nitrification inhibitor-coated urea did not improve grain yield enough to justify its added cost.
- Taxon
- summer cropst0
- Treatment
- Nitrification inhibitor-coated ureae0
- Outcome
- grain yieldse0
- Direction
- did not improvee0
- Qualifier
- enough to justify the additional cost on an agronomic basise0
Not reportedComparator
Verbatim
e0“Nitrification inhibitor-coated urea significantly reduced nitrous oxide emissions in all studies, but did not improve grain yields enough to justify the additional cost on an agronomic basis.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Delaying or splitting nitrogen applications gave no yield benefit in a dry season.
- Taxon
- summer cropst0
- Treatment
- delaying/splitting N applicationse0
- Outcome
- yield benefite0
- Direction
- no yield benefite0
- Qualifier
- dry seasone0
Not reportedComparator
Verbatim
e0“Depending on the season, delaying/splitting N applications gave either no yield benefit (dry season) or a significantly greater yield (good in-crop rainfall).”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Delaying or splitting nitrogen applications gave significantly greater yield with good in-crop rainfall.
- Taxon
- summer cropst0
- Treatment
- delaying/splitting N applicationse0
- Outcome
- yielde0
- Direction
- greatere0
- Qualifier
- good in-crop rainfalle0
Not reportedComparator
Verbatim
e0“Depending on the season, delaying/splitting N applications gave either no yield benefit (dry season) or a significantly greater yield (good in-crop rainfall).”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Much unused nitrogen remained in soil after a dry season.
Verbatim
e0“Much of the unused N after a dry season remained in the soil and, provided loss events were not experienced during the fallow, significantly benefited the following crop.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Unused soil nitrogen significantly benefited the following crop when no loss event occurred during fallow.
Verbatim
e0“Much of the unused N after a dry season remained in the soil and, provided loss events were not experienced during the fallow, significantly benefited the following crop.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Crop nitrogen recovery was most efficient when nitrogen was distributed through the root volume.
Verbatim
e0“Crop N recovery is most efficient when N is distributed through the root volume”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Gaseous fertilizer nitrogen losses can be substantial, especially through denitrification.
- Outcome
- Gaseous losses of fertilizer Ne0
- Direction
- substantiale0
- Qualifier
- denitrification of greatest concerne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Keeping fertilizer nitrogen in the crop or deeper soil is recommended to defend against loss.
Verbatim
e0“Ensuring fertilizer N is in the crop or deeper in the soil profile is the best defence against loss Controlled release fertilizers can reduce denitrification but are rarely economic; legume N is effective”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Controlled release fertilizers can reduce denitrification.
- Taxon
- summer cropst0
- Treatment
- Controlled release fertilizerse0
- Outcome
- denitrificatione0
- Direction
- reducee0
- Qualifier
- rarely economice0
Not reportedComparator
Verbatim
e0“Ensuring fertilizer N is in the crop or deeper in the soil profile is the best defence against loss Controlled release fertilizers can reduce denitrification but are rarely economic; legume N is effective”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Controlled release fertilizers are rarely economic.
Verbatim
e0“Ensuring fertilizer N is in the crop or deeper in the soil profile is the best defence against loss Controlled release fertilizers can reduce denitrification but are rarely economic; legume N is effective”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
Claim · model-written summary
Legume nitrogen was described as effective.
Verbatim
e0“Ensuring fertilizer N is in the crop or deeper in the soil profile is the best defence against loss Controlled release fertilizers can reduce denitrification but are rarely economic; legume N is effective”
e1“Gaseous losses of fertilizer N can be substantial, with denitrification of greatest concern for summer sorghum.”
t0“summer crops”
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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.