Abstract
Abstract A yield decline and increase in soil pH under continuous cropping of aerobic rice have been reported in previous studies. However, the underlying mechanisms governing the poor growth and low yield of aerobic rice following an increase in soil pH are unknown. The objective of the present study was to determine the effect of soil acidification on the soil nutrient availability, plant nutrition and growth of aerobic rice grown in continuously cropped aerobic soil. Two pot experiments were conducted using soil from a field where aerobic rice had been grown for 13 consecutive seasons. Soil was acidified by adding 50–300 mL of 0.05 mol L–1 sulfuric acid to 3.0 kg of air-dried soil to achieve a range of soil pH levels. Rice was grown aerobically with N rates of 0–1.2 g per pot using urea or ammonium sulfate. Soil chemical properties were measured as were leaf nutrient concentrations, plant growth parameters, and the above-ground N uptake. A 5.5-fold and 1.5-fold increase in soil ammonium and nitrate were observed, respectively, after adding sulfuric acid. Plant growth and N uptake improved significantly with soil acidification, regardless of N rates or N sources, and were associated with an improvement in plant N nutrition. The application of N had greater positive effects on plant growth and N uptake than soil acidification. The growth response to soil acidification reduced as the rate of N application increased. These results suggest that the yield decline of continuous aerobic rice is probably associated with a reduction in soil N availability and plant N uptake as a result of a gradual increase in soil pH.
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Claims 8
Claim · model-written summary
Sulfuric acid increased soil ammonium by 5.5-fold.
- Taxon
- aerobic ricet0
- Treatment
- adding sulfuric acide0
- Outcome
- soil ammoniume0
- Direction
- increasee0
- Value
- 5.5-folde0
Not reportedComparator
Verbatim
e0“A 5.5-fold and 1.5-fold increase in soil ammonium and nitrate were observed, respectively, after adding sulfuric acid”
t0“aerobic rice”
Claim · model-written summary
Sulfuric acid increased nitrate by 1.5-fold.
- Taxon
- aerobic ricet0
- Treatment
- adding sulfuric acide0
- Outcome
- nitratee0
- Direction
- increasee0
- Value
- 1.5-folde0
Not reportedComparator
Verbatim
e0“A 5.5-fold and 1.5-fold increase in soil ammonium and nitrate were observed, respectively, after adding sulfuric acid”
t0“aerobic rice”
Claim · model-written summary
Soil acidification significantly improved rice plant growth regardless of N rate or source.
- Taxon
- aerobic ricet0
- Treatment
- soil acidificatione0
- Outcome
- Plant growthe0
- Direction
- improvede0
- Qualifier
- regardless of N rates or N sourcese0
Not reportedComparator
Verbatim
e0“Plant growth and N uptake improved significantly with soil acidification, regardless of N rates or N sources, and were associated with an improvement in plant N nutrition”
t0“aerobic rice”
Claim · model-written summary
Soil acidification significantly improved rice n uptake regardless of N rate or source.
- Taxon
- aerobic ricet0
- Treatment
- soil acidificatione0
- Outcome
- N uptakee0
- Direction
- improvede0
- Qualifier
- regardless of N rates or N sourcese0
Not reportedComparator
Verbatim
e0“Plant growth and N uptake improved significantly with soil acidification, regardless of N rates or N sources, and were associated with an improvement in plant N nutrition”
t0“aerobic rice”
Claim · model-written summary
N application improved plant growth more than acidification.
Verbatim
e0“The application of N had greater positive effects on plant growth and N uptake than soil acidification”
t0“aerobic rice”
Claim · model-written summary
N application improved N uptake more than acidification.
Verbatim
e0“The application of N had greater positive effects on plant growth and N uptake than soil acidification”
t0“aerobic rice”
Claim · model-written summary
Rice growth response to acidification declined as N application rose.
Verbatim
e0“The growth response to soil acidification reduced as the rate of N application increased”
t0“aerobic rice”
Claim · model-written summary
Continuous rice yield decline is probably associated with reduced soil N availability and plant N uptake as pH rises.
Verbatim
e0“the yield decline of continuous aerobic rice is probably associated with a reduction in soil N availability and plant N uptake as a result of a gradual increase in soil pH”
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