Abstract
Nitrogen fertilization is a simple and effective field management strategy for increasing plant productivity, but the regulatory mechanisms of nitrogen forms and proportions on soil nutrients and plant growth remain unclear. Therefore, we investigated soil enzyme activities and nutrient contents of alfalfa under different forms and proportions of exogenous nitrogen addition. Results showed that nitrogen input significantly increased the activity of three oxidoreductases (hydroxylamine reductase, nitrate reductase, and nitrite reductase) while having no significant effects on urease. A high proportion of ammonium nitrogen significantly increased neutral protease activity. The amylase activity markedly increased under mixed-nitrogen addition but decreased under single-nitrogen addition. Additionally, the contents of soil nutrients (soil organic matter, total nitrogen, nitrate nitrogen, ammonium nitrogen, available phosphorus, and available potassium) were significantly increased under different exogenous nitrogen inputs, which drove the changes in enzyme activities. Further, nitrogen addition also improved the biomass and nitrogen content of alfalfa. These findings indicated that applying different forms and proportions of exogenous nitrogen may stimulate soil enzyme activities, which will accelerate the transformation of nutrients and then promote alfalfa growth.
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Claims 8
Claim · model-written summary
Nitrogen input increased three soil oxidoreductase activities.
- Treatment
- nitrogen inpute0
- Outcome
- activity of three oxidoreductases (hydroxylamine reductase, nitrate reductase, and nitrite reductase)e0
- Direction
- increasede0
Not reportedTaxonComparator
Verbatim
e0“nitrogen input significantly increased the activity of three oxidoreductases (hydroxylamine reductase, nitrate reductase, and nitrite reductase)”
Claim · model-written summary
Nitrogen input had no significant effect on soil urease.
Not reportedTaxonComparator
Verbatim
e0“nitrogen input significantly increased the activity of three oxidoreductases (hydroxylamine reductase, nitrate reductase, and nitrite reductase) while having no significant effects on urease”
Claim · model-written summary
A high proportion of ammonium nitrogen increased neutral protease activity.
- Treatment
- A high proportion of ammonium nitrogene0
- Outcome
- neutral protease activitye0
- Direction
- increasede0
Not reportedTaxonComparator
Verbatim
e0“A high proportion of ammonium nitrogen significantly increased neutral protease activity”
Claim · model-written summary
Mixed nitrogen increased amylase activity.
Not reportedTaxonComparator
Verbatim
e0“The amylase activity markedly increased under mixed-nitrogen addition”
Claim · model-written summary
Single nitrogen decreased amylase activity.
Not reportedTaxonComparator
Verbatim
e0“The amylase activity markedly increased under mixed-nitrogen addition but decreased under single-nitrogen addition”
Claim · model-written summary
Different nitrogen inputs increased six soil nutrient contents.
- Treatment
- different exogenous nitrogen inputse0
- Outcome
- contents of soil nutrientse0
- Direction
- increasede0
Not reportedTaxonComparator
Verbatim
e0“contents of soil nutrients (soil organic matter, total nitrogen, nitrate nitrogen, ammonium nitrogen, available phosphorus, and available potassium) were significantly increased under different exogenous nitrogen inputs”
Claim · model-written summary
Nitrogen addition improved alfalfa biomass.
- Taxon
- alfalfa
Medicago sativae0 - Treatment
- nitrogen additione0
- Outcome
- biomasse0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nitrogen addition also improved the biomass and nitrogen content of alfalfa”
Claim · model-written summary
Nitrogen addition improved alfalfa nitrogen content.
- Taxon
- alfalfaMedicago sativae0
- Treatment
- nitrogen additione0
- Outcome
- nitrogen contente0
- Direction
- improvede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“nitrogen addition also improved the biomass and nitrogen content of alfalfa”
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