Abstract
Cost-effective methods for improving soil fertility and mitigating the negative impact of heavy metal contamination in agricultural soils are currently under investigation. This study aimed to evaluate the impact of soil lead (Pb) contamination and the application of secondary pulp and paper mill sludge on the relative growth rate (RGR) and its determinants, as well as the specific absorption rate (SAR) of nutrients of Lactuca sativa L. For the 46-day pot experiment, which was carried out in 2022 under controlled conditions at the Karelian Research Centre of RAS, sandy loam soil was used, to which Pb was added at rates of 0, 50, and 250 mg Pb(NO3)2 kg−1. Secondary sludge was applied with each watering at concentrations of 0%, 20%, and 40%. RGR values varied significantly, primarily due to changes in net assimilation rate (NAR) rather than specific leaf area. Positive relationships were found between RGR and NAR, and RGR and SAR of nitrogen and phosphorus, but not potassium. Sludge applications can stimulate NAR at early stages of plant growth. For plants grown on soil with the highest Pb concentration studied, secondary sludge reduced root lead content by an average of 35%. Soil contamination with lead increased nutrient SAR by 79 and 39% when applied as 20 and 40% sludge, respectively, while 40% sludge increased nitrogen SAR by 51% but did not change phosphorus and potassium SAR. A sludge-mediated reduction in root Pb content and an increase in NAR suggest that secondary paper sludge may contribute to the remediation of Pb-contaminated soils and reduce the toxicity of heavy metals to plants. The results may help in finding new ways to manage soil fertility, especially for contaminated soils.
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Claims 10
Claim · model-written summary
RGR varied significantly, primarily through NAR changes rather than specific leaf area.
- Taxon
- Lactuca sativa L.
Lactuca sativat0 - Outcome
- RGRe0
- Qualifier
- primarily due to changes in net assimilation rate (NAR) rather than specific leaf areae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“RGR values varied significantly, primarily due to changes in net assimilation rate (NAR) rather than specific leaf area.”
t0“Lactuca sativa L.”
Claim · model-written summary
RGR was positively related to NAR.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Outcome
- RGRe0
- Direction
- Positivee0
- Comparator
- NARe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Positive relationships were found between RGR and NAR, and RGR and SAR of nitrogen and phosphorus, but not potassium.”
t0“Lactuca sativa L.”
Claim · model-written summary
RGR was positively related to nitrogen and phosphorus SAR, but not potassium SAR.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Outcome
- RGRe0
- Direction
- Positivee0
- Qualifier
- but not potassiume0
- Comparator
- SAR of nitrogen and phosphoruse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Positive relationships were found between RGR and NAR, and RGR and SAR of nitrogen and phosphorus, but not potassium.”
t0“Lactuca sativa L.”
Claim · model-written summary
Sludge can stimulate early-growth NAR.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Organ / stage
- early stages of plant growthe0
- Treatment
- Sludge applicationse0
- Outcome
- NARe0
- Direction
- stimulatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Sludge applications can stimulate NAR at early stages of plant growth.”
t0“Lactuca sativa L.”
Claim · model-written summary
Secondary sludge reduced root lead content by an average 35% at the highest soil Pb concentration.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- secondary sludgee0
- Outcome
- root lead contente0
- Direction
- reducede0
- Value
- 35%e0
- Qualifier
- soil with the highest Pb concentration studiede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“For plants grown on soil with the highest Pb concentration studied, secondary sludge reduced root lead content by an average of 35%.”
t0“Lactuca sativa L.”
Claim · model-written summary
Lead contamination increased nutrient SAR by 79% with 20% sludge.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- Soil contamination with leade0
- Outcome
- nutrient SARe0
- Direction
- increasede0
- Value
- 79e0
- Qualifier
- 20e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soil contamination with lead increased nutrient SAR by 79 and 39% when applied as 20 and 40% sludge, respectively”
t0“Lactuca sativa L.”
Claim · model-written summary
Lead contamination increased nutrient SAR by 39% with 40% sludge.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- Soil contamination with leade0
- Outcome
- nutrient SARe0
- Direction
- increasede0
- Value
- 39%e0
- Qualifier
- 40% sludgee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soil contamination with lead increased nutrient SAR by 79 and 39% when applied as 20 and 40% sludge, respectively”
t0“Lactuca sativa L.”
Claim · model-written summary
40% sludge increased nitrogen SAR by 51%.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- 40% sludgee0
- Outcome
- nitrogen SARe0
- Direction
- increasede0
- Value
- 51%e0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“40% sludge increased nitrogen SAR by 51% but did not change phosphorus and potassium SAR.”
t0“Lactuca sativa L.”
Claim · model-written summary
40% sludge did not change phosphorus or potassium SAR.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Treatment
- 40% sludgee0
- Outcome
- phosphorus and potassium SARe0
- Direction
- did not changee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“40% sludge increased nitrogen SAR by 51% but did not change phosphorus and potassium SAR.”
t0“Lactuca sativa L.”
Claim · model-written summary
The authors suggest sludge may remediate Pb-contaminated soils and reduce plant heavy-metal toxicity.
- Taxon
- Lactuca sativa L.Lactuca sativat0
- Outcome
- secondary paper sludge may contribute to the remediation of Pb-contaminated soils and reduce the toxicity of heavy metals to plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A sludge-mediated reduction in root Pb content and an increase in NAR suggest that secondary paper sludge may contribute to the remediation of Pb-contaminated soils and reduce the toxicity of heavy metals to plants.”
t0“Lactuca sativa L.”
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See all 21 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.