Abstract
Abstract A long‐term double cropping wheat (Triticum aestivum L.) and corn (Zea mays L.) experiment was conducted at Qiyang, Hunan, China, to study the effects of inorganic fertilizers on grain yields and soil properties and to identify the possible causes of yield trends. Six treatments of unfertilized control, N, NP, NK, PK, and NPK were included. The treatments (N, NP, NK, and NPK) where inorganic nitrogen (N) was added showed significant (P<0.05) yield declines of 76 to 114 kg ha−1 yr−1 for wheat and 94 to 260 kg ha−1 yr−1 for corn, respectively, except for corn yield in the NPK treatment in which the decline was not significant during a 15‐yr (1990–2005) period. Comparatively, the decline amounts in corn were much higher than in wheat. The yields of wheat and corn remained unchanged in the PK treatment. The total organic carbon (C), total N, phosphorus (P), and available P, potassium (K), copper (Cu), and zinc (Zn) contents of soil were either increased or decreased during the study period. Both the decreases of exchangeable calcium (Ca2+) and magnesium (Mg2+) and increases of exchangeable hydrogen (H+) and Al3+ contents of soil in the treatments where inorganic N was applied were significant (P<0.05). The same four treatments showed significant pH declines ranging from 0.07 to 0.12 yr−1. Several lines of evidence point to decline of soil pH due to inorganic N fertilizer added as leading to the overall yield decline of wheat and corn. However, the yields of both crops increased significantly after lime application. In the long term, the farmers should be encouraged to use adequate lime based on a balanced approach to ensure sustainable productivity.
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Claims 13
Claim · model-written summary
Nitrogen fertilizer treatments showed significant annual wheat yield declines of 76 to 114 kg ha−1 yr−1.
- Taxon
- wheat
Triticum aestivume1 - Treatment
- N, NP, NK, and NPKe0
- Outcome
- yield declinese0
- Direction
- declinese0
- Value
- 76 to 114 kg ha−1 yr−1e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The treatments (N, NP, NK, and NPK) where inorganic nitrogen (N) was added showed significant (P<0.05) yield declines of 76 to 114 kg ha−1 yr−1 for wheat and 94 to 260 kg ha−1 yr−1 for corn, respectively”
e1“wheat (Triticum aestivum L.)”
Claim · model-written summary
Nitrogen fertilizer treatments showed annual corn yield declines of 94 to 260 kg ha−1 yr−1, except for nonsignificant decline under NPK.
- Taxon
- corn
Zea mays subsp. mayse1 - Treatment
- N, NP, NK, and NPKe2
- Outcome
- corn yielde0
- Direction
- declinee0
- Value
- 94 to 260 kg ha−1 yr−1e0
- Qualifier
- except for corn yield in the NPK treatment in which the decline was not significante0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“94 to 260 kg ha−1 yr−1 for corn, respectively, except for corn yield in the NPK treatment in which the decline was not significant”
e1“corn (Zea mays L.)”
e2“N, NP, NK, and NPK”
Claim · model-written summary
Corn yield declines were greater than wheat yield declines.
- Taxon
- cornZea mays subsp. mayse0
- Outcome
- decline amounts in corne0
- Direction
- highere0
- Comparator
- wheate0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the decline amounts in corn were much higher than in wheat.”
Claim · model-written summary
Wheat yield remained unchanged under PK treatment.
- Taxon
- wheatTriticum aestivume0
- Treatment
- PK treatmente0
- Outcome
- yields of wheate0
- Direction
- remained unchangede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The yields of wheat and corn remained unchanged in the PK treatment.”
Claim · model-written summary
Corn yield remained unchanged under PK treatment.
- Taxon
- cornZea mays subsp. mayse0
- Treatment
- PK treatmente0
- Outcome
- corne0
- Direction
- remained unchangede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The yields of wheat and corn remained unchanged in the PK treatment.”
Claim · model-written summary
Soil nutrient and organic carbon contents changed during the study period.
- Taxon
- wheatTriticum aestivume1
- Outcome
- contents of soile0
- Qualifier
- either increased or decreasede0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The total organic carbon (C), total N, phosphorus (P), and available P, potassium (K), copper (Cu), and zinc (Zn) contents of soil were either increased or decreased during the study period.”
e1“wheat (Triticum aestivum L.)”
Claim · model-written summary
Exchangeable soil calcium and magnesium declined significantly under inorganic nitrogen.
- Taxon
- wheatTriticum aestivume1
- Treatment
- inorganic Ne0
- Outcome
- exchangeable calcium (Ca2+) and magnesium (Mg2+)e0
- Direction
- decreasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both the decreases of exchangeable calcium (Ca2+) and magnesium (Mg2+) and increases of exchangeable hydrogen (H+) and Al3+ contents of soil in the treatments where inorganic N was applied were significant (P<0.05).”
e1“wheat (Triticum aestivum L.)”
Claim · model-written summary
Exchangeable soil hydrogen and aluminum increased significantly under inorganic nitrogen.
- Taxon
- wheatTriticum aestivume1
- Treatment
- inorganic Ne0
- Outcome
- exchangeable hydrogen (H+) and Al3+ contents of soile0
- Direction
- increasese0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both the decreases of exchangeable calcium (Ca2+) and magnesium (Mg2+) and increases of exchangeable hydrogen (H+) and Al3+ contents of soil in the treatments where inorganic N was applied were significant (P<0.05).”
e1“wheat (Triticum aestivum L.)”
Claim · model-written summary
Soil pH declined significantly by 0.07 to 0.12 yr−1 under inorganic nitrogen treatments.
- Taxon
- wheatTriticum aestivume2
- Treatment
- inorganic Ne1
- Outcome
- pHe0
- Direction
- declinese0
- Value
- 0.07 to 0.12 yr−1e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The same four treatments showed significant pH declines ranging from 0.07 to 0.12 yr−1.”
e1“inorganic N was applied”
e2“wheat (Triticum aestivum L.)”
Claim · model-written summary
The authors attribute overall wheat and corn yield declines to soil acidification from inorganic nitrogen.
- Taxon
- wheat and cornTriticum aestivumZea mays subsp. mayse0
- Treatment
- inorganic N fertilizere0
- Outcome
- overall yield decline of wheat and corne0
- Qualifier
- decline of soil pHe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Several lines of evidence point to decline of soil pH due to inorganic N fertilizer added as leading to the overall yield decline of wheat and corn.”
Claim · model-written summary
Lime application significantly increased wheat yields.
- Taxon
- wheatTriticum aestivume1
- Treatment
- lime applicatione0
- Outcome
- yieldse0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the yields of both crops increased significantly after lime application.”
e1“wheat (Triticum aestivum L.)”
Claim · model-written summary
Lime application significantly increased corn yields.
- Taxon
- cornZea mays subsp. mayse1
- Treatment
- lime applicatione0
- Outcome
- yieldse0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the yields of both crops increased significantly after lime application.”
e1“corn (Zea mays L.)”
Claim · model-written summary
The authors recommend adequate lime for sustainable crop productivity.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- use adequate limee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the farmers should be encouraged to use adequate lime based on a balanced approach to ensure sustainable productivity.”
t0“Wheat–Corn”
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