Abstract
Although N fertilizers are not acidic, their inputs to soil are acid forming. As a result of the long-term use of N fertilizers, soils in the Great Plains are becoming more acidic and this acidity may become a yield-limiting factor. In 1970, long-term plots were initiated to compare sources (anhydrous NH3, NH4NO3, urea, and S-coated urea), application rates (34, 68, 136, and 272 kg N ha−1), and an untreated check (0 N) on wheat (Triticum aestivum L.) grain yield, soil pH, exchangeable base cations, and Al saturation. For the soil properties evaluated, significant differences among the different N sources did not exist after 30 annual applications of N fertilizer. The long-term N fertilization significantly reduced soil pH in the surface soil layer (0–15 cm), especially at the higher application levels. Soil pH decreased with time and was significantly related to the amount of total N applied for each N source. Nitrogen fertilization with each N source significantly increased exchangeable Al and Al saturation (Alsat) but decreased exchangeable base cations (Ca2+ and Mg2+). Both exchangeable Al and Alsat increased with increasing N rate and were inversely related to soil pH. Despite decreased soil pH levels to <5.0 as early as 1980 in the experiment, significant reductions of wheat yield did not occur until 1995. Reductions in yield occurring between 1995 and 2002 coincided with the greatest change in soil pH occurring during the same time period.
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Claims 8
Claim · model-written summary
Nitrogen sources did not differ significantly in the evaluated soil properties after 30 annual applications.
- Taxon
- wheat
Triticum aestivumt0 - Outcome
- soil propertiese0
- Comparator
- different N sourcese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For the soil properties evaluated, significant differences among the different N sources did not exist after 30 annual applications of N fertilizer”
t0“Winter Wheat”
t1“Winter Wheat”
Claim · model-written summary
Long-term nitrogen fertilization significantly lowered surface soil pH, especially at higher rates.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- long-term N fertilizatione0
- Outcome
- soil pHe0
- Direction
- reducede0
- Qualifier
- surface soil layer (0–15 cm)e0
Not reportedOrgan / stageComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The long-term N fertilization significantly reduced soil pH in the surface soil layer (0–15 cm), especially at the higher application levels”
t0“Winter Wheat”
t1“Winter Wheat”
Claim · model-written summary
Soil pH decreased with time and was significantly related to total nitrogen applied.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- total N appliede0
- Outcome
- Soil pHe0
- Direction
- decreasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soil pH decreased with time and was significantly related to the amount of total N applied for each N source”
t0“Winter Wheat”
t1“Winter Wheat”
Claim · model-written summary
Nitrogen fertilization increased exchangeable Al and Al saturation.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Nitrogen fertilizatione0
- Outcome
- exchangeable Al and Al saturation (Alsat)e0
- Direction
- increasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization with each N source significantly increased exchangeable Al and Al saturation (Alsat) but decreased exchangeable base cations (Ca2+ and Mg2+)”
t0“Winter Wheat”
t1“Winter Wheat”
Claim · model-written summary
Nitrogen fertilization decreased exchangeable base cations.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- Nitrogen fertilizatione0
- Outcome
- exchangeable base cations (Ca2+ and Mg2+)e0
- Direction
- decreasede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Nitrogen fertilization with each N source significantly increased exchangeable Al and Al saturation (Alsat) but decreased exchangeable base cations (Ca2+ and Mg2+)”
t0“Winter Wheat”
t1“Winter Wheat”
Claim · model-written summary
Exchangeable Al and Al saturation increased with nitrogen rate and were inversely related to soil pH.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- increasing N ratee0
- Outcome
- exchangeable Al and Alsate0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both exchangeable Al and Alsat increased with increasing N rate and were inversely related to soil pH”
t0“Winter Wheat”
t1“Winter Wheat”
Claim · model-written summary
Wheat yield was not significantly reduced until 1995 despite pH falling below 5.0 by 1980.
- Taxon
- wheatTriticum aestivume0
- Outcome
- wheat yielde0
- Direction
- reductionse0
- Qualifier
- until 1995e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Despite decreased soil pH levels to <5.0 as early as 1980 in the experiment, significant reductions of wheat yield did not occur until 1995”
Claim · model-written summary
Yield reductions during 1995–2002 coincided with the largest pH change.
- Taxon
- wheatTriticum aestivumt0
- Treatment
- soil pHe0
- Outcome
- yielde0
- Direction
- Reductionse0
- Qualifier
- between 1995 and 2002e0
Not reportedSetting
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Reductions in yield occurring between 1995 and 2002 coincided with the greatest change in soil pH occurring during the same time period”
t0“Winter Wheat”
t1“Winter Wheat”
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