Abstract
Excessive nitrogen fertilizer application in greenhouse vegetable production (GVP) is of scientific and public concern because of its significance to international environmental sustainability. We conducted a meta-analysis using 1174 paired observations from 69 publications on the effects of nitrogen fertilizer application and reducing nitrogen fertilizer application on the nitrogen losses on a broad scale. We found that the increase in nitrogen loss is much higher than that in production gain caused by excessive application of nitrogen fertilizer: nitrate leaching (+187.5%), ammonium leaching (+28.1%), total nitrogen leaching (+217.0%), nitrous oxide emission (+202.0%), ammonia emission (+176.4%), nitric oxide emission (+543.3%), yield (+35.7%) and nitrogen uptake (+24.5%). Environmental variables respond nonlinearly to nitrogen fertilizer application, with severe nitrate leaching and nitrous oxide emission when the application rate exceeds 570 kg N/ha and 733 kg/N, respectively. The effect of nitrogen fertilizer on yield growth decreases when the application rate exceeds 302 kg N/ha. Appropriate reduction in nitrogen fertilizer application rate substantially mitigates the environmental cost, for example, decreasing nitrate leaching (−32.4%), ammonium leaching (−6.5%), total nitrogen leaching (−37.3%), ammonia emission (−28.4%), nitrous oxide emission (−38.6%) and nitric oxide emission (−8.0%), while it has no significant effect on the nitrogen uptake and yield.
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Claims 18
Claim · model-written summary
Excessive nitrogen fertilizer increased nitrate leaching by 187.5%.
- Treatment
- excessive application of nitrogen fertilizere0
- Outcome
- nitrate leachinge0
- Direction
- increasee0
- Value
- +187.5%e0
Not reportedTaxonComparator
Verbatim
e0“the increase in nitrogen loss is much higher than that in production gain caused by excessive application of nitrogen fertilizer: nitrate leaching (+187.5%)”
Claim · model-written summary
Excessive nitrogen fertilizer increased ammonium leaching by 28.1%.
- Treatment
- excessive application of nitrogen fertilizere0
- Outcome
- ammonium leachinge0
- Direction
- increaseinferrede0
- Value
- +28.1%e0
Not reportedTaxonComparator
Verbatim
e0“excessive application of nitrogen fertilizer: nitrate leaching (+187.5%), ammonium leaching (+28.1%)”
Claim · model-written summary
Excessive nitrogen fertilizer increased total nitrogen leaching by 217.0%.
- Treatment
- excessive application of nitrogen fertilizere0
- Outcome
- total nitrogen leachinge0
- Direction
- increaseinferrede0
- Value
- +217.0%e0
Not reportedTaxonComparator
Verbatim
e0“excessive application of nitrogen fertilizer: nitrate leaching (+187.5%), ammonium leaching (+28.1%), total nitrogen leaching (+217.0%)”
Claim · model-written summary
Excessive nitrogen fertilizer increased nitrous oxide emission by 202.0%.
- Treatment
- excessive application of nitrogen fertilizere1
- Outcome
- nitrous oxide emissione0
- Direction
- increaseinferrede0
- Value
- +202.0%e0
Not reportedTaxonComparator
Verbatim
e0“nitrous oxide emission (+202.0%)”
e1“excessive application of nitrogen fertilizer”
Claim · model-written summary
Excessive nitrogen fertilizer increased ammonia emission by 176.4%.
- Treatment
- excessive application of nitrogen fertilizere1
- Outcome
- ammonia emissione0
- Direction
- increaseinferrede0
- Value
- +176.4%e0
Not reportedTaxonComparator
Verbatim
e0“ammonia emission (+176.4%)”
e1“excessive application of nitrogen fertilizer”
Claim · model-written summary
Excessive nitrogen fertilizer increased nitric oxide emission by 543.3%.
- Treatment
- excessive application of nitrogen fertilizere1
- Outcome
- nitric oxide emissione0
- Direction
- increaseinferrede0
- Value
- +543.3%e0
Not reportedTaxonComparator
Verbatim
e0“nitric oxide emission (+543.3%)”
e1“excessive application of nitrogen fertilizer”
Claim · model-written summary
Excessive nitrogen fertilizer increased vegetable yield by 35.7%.
- Taxon
- vegetablee2
- Treatment
- excessive application of nitrogen fertilizere1
- Outcome
- yielde0
- Direction
- increaseinferrede0
- Value
- +35.7%e0
Not reportedComparator
Verbatim
e0“yield (+35.7%)”
e1“excessive application of nitrogen fertilizer”
e2“greenhouse vegetable production (GVP)”
Claim · model-written summary
Excessive nitrogen fertilizer increased vegetable nitrogen uptake by 24.5%.
- Taxon
- vegetablee2
- Treatment
- excessive application of nitrogen fertilizere1
- Outcome
- nitrogen uptakee0
- Direction
- increaseinferrede0
- Value
- +24.5%e0
Not reportedComparator
Verbatim
e0“nitrogen uptake (+24.5%)”
e1“excessive application of nitrogen fertilizer”
e2“greenhouse vegetable production (GVP)”
Claim · model-written summary
Nitrate leaching was severe above 570 kg N/ha fertilizer application.
Not reportedTaxonDirection
Verbatim
e0“Environmental variables respond nonlinearly to nitrogen fertilizer application, with severe nitrate leaching and nitrous oxide emission when the application rate exceeds 570 kg N/ha and 733 kg/N, respectively.”
Claim · model-written summary
Nitrous oxide emission was severe above the reported threshold of 733 kg/N.
- Treatment
- nitrogen fertilizer applicatione0
- Outcome
- nitrous oxide emissione0
- Value
- 733 kg/Ne0
- Qualifier
- respond nonlinearlye0
Not reportedTaxonDirection
Verbatim
e0“Environmental variables respond nonlinearly to nitrogen fertilizer application, with severe nitrate leaching and nitrous oxide emission when the application rate exceeds 570 kg N/ha and 733 kg/N, respectively.”
Claim · model-written summary
Fertilizer effects on yield growth decreased above 302 kg N/ha.
Verbatim
e0“The effect of nitrogen fertilizer on yield growth decreases when the application rate exceeds 302 kg N/ha.”
e1“greenhouse vegetable production (GVP)”
Claim · model-written summary
Reducing nitrogen fertilizer decreased nitrate leaching by 32.4%.
- Treatment
- reduction in nitrogen fertilizer application ratee0
- Outcome
- nitrate leachinge0
- Direction
- decreasinge0
- Value
- −32.4%e0
Not reportedTaxonComparator
Verbatim
e0“Appropriate reduction in nitrogen fertilizer application rate substantially mitigates the environmental cost, for example, decreasing nitrate leaching (−32.4%)”
Claim · model-written summary
Reducing nitrogen fertilizer decreased ammonium leaching by 6.5%.
- Treatment
- reduction in nitrogen fertilizer application ratee1
- Outcome
- ammonium leachinge0
- Direction
- decreaseinferrede0
- Value
- −6.5%e0
Not reportedTaxonComparator
Verbatim
e0“ammonium leaching (−6.5%)”
e1“Appropriate reduction in nitrogen fertilizer application rate”
Claim · model-written summary
Reducing nitrogen fertilizer decreased total nitrogen leaching by 37.3%.
- Treatment
- reduction in nitrogen fertilizer application ratee1
- Outcome
- total nitrogen leachinge0
- Direction
- decreaseinferrede0
- Value
- −37.3%e0
Not reportedTaxonComparator
Verbatim
e0“total nitrogen leaching (−37.3%)”
e1“Appropriate reduction in nitrogen fertilizer application rate”
Claim · model-written summary
Reducing nitrogen fertilizer decreased ammonia emission by 28.4%.
- Treatment
- reduction in nitrogen fertilizer application ratee1
- Outcome
- ammonia emissione0
- Direction
- decreaseinferrede0
- Value
- −28.4%e0
Not reportedTaxonComparator
Verbatim
e0“ammonia emission (−28.4%)”
e1“Appropriate reduction in nitrogen fertilizer application rate”
Claim · model-written summary
Reducing nitrogen fertilizer decreased nitrous oxide emission by 38.6%.
- Treatment
- reduction in nitrogen fertilizer application ratee1
- Outcome
- nitrous oxide emissione0
- Direction
- decreaseinferrede0
- Value
- −38.6%e0
Not reportedTaxonComparator
Verbatim
e0“nitrous oxide emission (−38.6%)”
e1“Appropriate reduction in nitrogen fertilizer application rate”
Claim · model-written summary
Reducing nitrogen fertilizer decreased nitric oxide emission by 8.0%.
- Treatment
- reduction in nitrogen fertilizer application ratee1
- Outcome
- nitric oxide emissione0
- Direction
- decreaseinferrede0
- Value
- −8.0%e0
Not reportedTaxonComparator
Verbatim
e0“nitric oxide emission (−8.0%)”
e1“Appropriate reduction in nitrogen fertilizer application rate”
Claim · model-written summary
Reducing nitrogen fertilizer had no significant effect on vegetable nitrogen uptake and yield.
- Taxon
- vegetablee2
- Treatment
- reduction in nitrogen fertilizer application ratee0
- Outcome
- nitrogen uptake and yielde1
Not reportedComparatorDirection
Verbatim
e0“Appropriate reduction in nitrogen fertilizer application rate”
e1“while it has no significant effect on the nitrogen uptake and yield.”
e2“greenhouse vegetable production (GVP)”