Abstract
Crop nitrogen (N) and phosphorus (P) stoichiometry can influence food nutritive quality and many ecosystem processes. However, how and why N and P stoichiometry respond to long-term agricultural management practices (e.g. N fertilization and film mulching) are not clearly understood. We collected maize tissues (leaf, stem, root and seed) and soil samples from a temperate cropland under 30-year continuous N fertilization and plastic film mulching treatments, measured their C, N and P concentrations (the proportion (%) relative to the sample mass), and used structural equation models to uncover the responding mechanisms for crop N and P contents (the total amount (g/m2) in crop biomass). Long-term N fertilization increased N concentrations in all crop tissues but sharply decreased P concentrations in vegetative tissues (leaf, stem and root), thereby reducing their C/N ratio and increasing C/P and N/P ratios. The drop in P concentration in vegetative tissues was due to the dilution effect by biomass increment and the priority of P supply for seed production. In contrast, film mulching decreased N concentration but increased P concentrations in most crop tissues, thereby increasing C/N ratio and reducing C/P and N/P ratios. Film mulching increased crop P content by increasing soil temperature and moisture; whereas, mulching showed little effect on crop N content, because a positive effects of soil temperature may have canceled out a negative effect by soil moisture. This indicated a decoupling of P and N uptake by crops under film mulching. In conclusion, N fertilization and plastic film mulching showed opposite effects of on crop N and P stoichiometry.
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Claims 13
Claim · model-written summary
Long-term N fertilization increased N concentration in all maize tissues.
- Treatment
- Long-term N fertilizatione0
- Outcome
- N concentrations in all crop tissuese0
- Direction
- increasede0
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Long-term N fertilization increased N concentrations in all crop tissues”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
Claim · model-written summary
Long-term N fertilization decreased P in vegetative tissues.
- Organ / stage
- leaf, stem and roote0
- Treatment
- N fertilizatione2
- Outcome
- P concentrations in vegetative tissuese0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“sharply decreased P concentrations in vegetative tissues (leaf, stem and root)”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
e2“Long-term N fertilization increased N concentrations in all crop tissues”
Claim · model-written summary
N fertilization reduced crop tissue C/N ratio.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“thereby reducing their C/N ratio and increasing C/P and N/P ratios”
t0“nitrogen fertilization”
e1“maize tissues (leaf, stem, root and seed)”
e2“Long-term N fertilization increased N concentrations in all crop tissues”
Claim · model-written summary
N fertilization increased C/P and N/P ratios.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“thereby reducing their C/N ratio and increasing C/P and N/P ratios”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
e2“Long-term N fertilization increased N concentrations in all crop tissues”
Claim · model-written summary
The authors attribute lower vegetative P to biomass dilution and priority for seed P.
- Outcome
- drop in P concentration in vegetative tissuese0
- Qualifier
- dilution effect by biomass increment and the priority of P supply for seed productione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The drop in P concentration in vegetative tissues was due to the dilution effect by biomass increment and the priority of P supply for seed production”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
Claim · model-written summary
Film mulching decreased N concentration in most crop tissues.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“film mulching decreased N concentration but increased P concentrations in most crop tissues”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
Claim · model-written summary
Film mulching increased P concentration in most crop tissues.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“film mulching decreased N concentration but increased P concentrations in most crop tissues”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
Claim · model-written summary
Film mulching increased crop C/N ratio.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“thereby increasing C/N ratio and reducing C/P and N/P ratios”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
e2“film mulching decreased N concentration but increased P concentrations in most crop tissues”
Claim · model-written summary
Film mulching reduced crop C/P and N/P ratios.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“thereby increasing C/N ratio and reducing C/P and N/P ratios”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
e2“film mulching decreased N concentration but increased P concentrations in most crop tissues”
Claim · model-written summary
Film mulching increased crop P content via warmer and moister soil.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Film mulching increased crop P content by increasing soil temperature and moisture”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
Claim · model-written summary
Film mulching had little effect on crop N content.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mulching showed little effect on crop N content”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
Claim · model-written summary
The authors propose opposing soil temperature and moisture effects canceled for crop N.
- Outcome
- positive effects of soil temperaturee0
- Qualifier
- canceled out a negative effect by soil moisturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“because a positive effects of soil temperature may have canceled out a negative effect by soil moisture”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
Claim · model-written summary
The authors infer decoupling of P and N uptake under film mulching.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a decoupling of P and N uptake by crops under film mulching”
t0“crop”
e1“maize tissues (leaf, stem, root and seed)”
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