Abstract
Land-use change from perennial grasslands to cultivated croplands leads to reduced soil organic C (SOC) and total N. Among other factors, introduction of annual crops and soil disturbance by tillage may account for reduced amounts of SOC and total N. However, agricultural practices of no-till and N fertilizer application may maintain soil N in cropped soils. We measured soil N changes and N-use efficiency in a field experiment initiated in 1968, consisting of completely randomized tillage practices (conventional mechanical till [CT], and no-till [NT]), crop residue management (residue burned [RB], and residue retained [RR]), and N fertilization (0, 30, and 90 kg N ha−1) on a Vertisol (Ustic Pellusert) over 40 yr. Crops grown were mainly wheat (Triticum aestivum L.) except for five barley (Hordeum vulgare L.) crops early in the experiment. Significant effects of treatments on soil total N were primarily confined to the top 0.1-m depth. Soil total N exponentially declined in all treatments even though apparent fertilizer N recoveries during this period (1969–2008) were only 46 and 59% of N applied at 90 and 30 kg N ha−1, respectively. Mineral N in the soil profile (0–1.2 m) ranged from 68 to 496 kg N ha−1. Nitrogen-use efficiency was similar (P = 0.13) under CT and NT in this Vertisol. However, crop residue retention and a low rate of N application had greater N-use efficiency (35–40%) than RB and a high rate of N application (21–25%) under the annual cereal grain cropping system. If perennial grasslands are considered ecological benchmarks for agricultural sustainability, primarily through large root biomass that utilizes water and nutrients efficiently, then the challenge remains to develop cropping systems that successfully mimic grassland ecosystems.
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Claims 8
Claim · model-written summary
Treatment effects on soil total N were concentrated in the top 0.1 m.
- Taxon
- wheat
Triticum aestivume1 - Outcome
- soil total Ne0
- Qualifier
- top 0.1-m depthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant effects of treatments on soil total N were primarily confined to the top 0.1-m depth”
e1“Crops grown were mainly wheat (Triticum aestivum L.)”
Claim · model-written summary
Soil total N declined exponentially under all cereal management treatments.
- Taxon
- wheatTriticum aestivume1
- Outcome
- Soil total Ne0
- Direction
- declinede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soil total N exponentially declined in all treatments”
e1“Crops grown were mainly wheat (Triticum aestivum L.)”
Claim · model-written summary
Apparent fertilizer N recovery was 46% at 90 kg N ha−1.
- Taxon
- wheatTriticum aestivume1
- Treatment
- 90e0
- Outcome
- apparent fertilizer N recoveriese0
- Value
- 46e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“apparent fertilizer N recoveries during this period (1969–2008) were only 46 and 59% of N applied at 90 and 30 kg N ha−1, respectively”
e1“Crops grown were mainly wheat (Triticum aestivum L.)”
Claim · model-written summary
Apparent fertilizer N recovery was 59% at 30 kg N ha−1.
- Taxon
- wheatTriticum aestivume1
- Treatment
- 30 kg N ha−1e0
- Outcome
- apparent fertilizer N recoveriese0
- Value
- 59%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“apparent fertilizer N recoveries during this period (1969–2008) were only 46 and 59% of N applied at 90 and 30 kg N ha−1, respectively”
e1“Crops grown were mainly wheat (Triticum aestivum L.)”
Claim · model-written summary
Soil profile mineral N ranged from 68 to 496 kg N ha−1.
- Taxon
- wheatTriticum aestivume1
- Outcome
- Mineral N in the soil profilee0
- Value
- 68 to 496 kg N ha−1e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Mineral N in the soil profile (0–1.2 m) ranged from 68 to 496 kg N ha−1”
e1“Crops grown were mainly wheat (Triticum aestivum L.)”
Claim · model-written summary
Nitrogen-use efficiency was similar under conventional and no tillage.
- Taxon
- wheatTriticum aestivume1
- Treatment
- NTe0
- Outcome
- Nitrogen-use efficiencye0
- Direction
- similare0
- Comparator
- CTe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen-use efficiency was similar (P = 0.13) under CT and NT in this Vertisol”
e1“Crops grown were mainly wheat (Triticum aestivum L.)”
Claim · model-written summary
Residue retention had higher N-use efficiency than residue burning.
- Taxon
- wheatTriticum aestivume1
- Treatment
- crop residue retentione0
- Outcome
- N-use efficiencye0
- Direction
- greatere0
- Value
- 35–40%e0
- Qualifier
- 21–25%e0
- Comparator
- RBe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“crop residue retention and a low rate of N application had greater N-use efficiency (35–40%) than RB and a high rate of N application (21–25%) under the annual cereal grain cropping system”
e1“Crops grown were mainly wheat (Triticum aestivum L.)”
Claim · model-written summary
Low N application had higher N-use efficiency than high application.
- Taxon
- wheatTriticum aestivume1
- Treatment
- a low rate of N applicatione0
- Outcome
- N-use efficiencye0
- Direction
- greatere0
- Value
- 35–40%e0
- Qualifier
- 21–25%e0
- Comparator
- a high rate of N applicatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“crop residue retention and a low rate of N application had greater N-use efficiency (35–40%) than RB and a high rate of N application (21–25%) under the annual cereal grain cropping system”
e1“Crops grown were mainly wheat (Triticum aestivum L.)”
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