Abstract
The effects of biochar and sewage sludge application on spinach (Spinacia oleracea L.) yield and soil NO3- content were investigated in typical soils of Botswana (Luvisol, Cambisol) under field conditions. Ten treatments with 3 levels of biochar (0, 2.5, 5 tons ha-1) and sewage sludge (0, 6, 12 ton ha-1) were applied in 2 subsequent seasons. Significant (p < 0.05) yield increase on the Luvisol occurred if sewage sludge was added at 12 Mg ha-1 with or without biochar. A combination of 6 Mg ha-1 sludge and 5 Mg ha-1 biochar application resulted in the highest crop yield over 2 seasons. On the Cambisol, only marginal yield increase occurred upon high rates of sole organic amendments and chemical fertilizer, while co-applications decreased yields. Decrease in soil NO3- content caused yield declines in the second season, while P uptake increased significantly (p < 0.05). Correlations between yields, soil NO3- and leaf N contents were insignificant (p > 0.05). On the Cambisol, a significant regression model for sludge and soil NO3- was determined. Therefore, one – time combined application of 6 Mg ha-1 sewage sludge and 5 Mg ha-1 on the Luvisol, and 12 Mg ha-1 sewage sludge are recommended for spinach production on the Luvisol and Cambisol, respectively. In subsequent seasons, crop productivity could be maintained by application of mineral N in order to mitigate over-application of P. Key words: Biochar, sewage sludge, soil NO3-, luvisol, cambisol.
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Claims 11
Claim · model-written summary
Sewage sludge at 12 Mg ha-1 significantly increased spinach yield on Luvisol, with or without biochar.
- Taxon
- spinach
Spinacia oleraceat0 - Treatment
- sewage sludge was added at 12 Mg ha-1e0
- Outcome
- yielde0
- Direction
- increasee0
- Value
- 12 Mg ha-1e0
- Setting
- Luvisole0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Significant (p < 0.05) yield increase on the Luvisol occurred if sewage sludge was added at 12 Mg ha-1 with or without biochar”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
The combined 6 Mg ha-1 sludge and 5 Mg ha-1 biochar application produced the highest yield across two seasons.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- 6 Mg ha-1 sludge and 5 Mg ha-1 biochar applicatione0
- Outcome
- crop yielde0
- Direction
- higheste0
- Qualifier
- over 2 seasonse0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“A combination of 6 Mg ha-1 sludge and 5 Mg ha-1 biochar application resulted in the highest crop yield over 2 seasons”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
Sole organic amendments at high rates and chemical fertilizer yielded only marginal increases on Cambisol.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- high rates of sole organic amendments and chemical fertilizere0
- Outcome
- yielde0
- Direction
- increasee0
- Qualifier
- only marginale0
- Setting
- Cambisole0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“On the Cambisol, only marginal yield increase occurred upon high rates of sole organic amendments and chemical fertilizer”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
Co-applications decreased spinach yield on Cambisol.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- co-applicationse0
- Outcome
- yieldse0
- Direction
- decreasede0
- Setting
- Cambisole0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“On the Cambisol, only marginal yield increase occurred upon high rates of sole organic amendments and chemical fertilizer, while co-applications decreased yields”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
Lower soil NO3- content was reported to cause yield decline in the second season.
- Taxon
- spinachSpinacia oleraceat0
- Compound
- NO3-e0
- Outcome
- yield declinese0
- Direction
- declinese0
- Qualifier
- second seasone0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Decrease in soil NO3- content caused yield declines in the second season”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
Spinach P uptake increased significantly.
- Taxon
- spinachSpinacia oleraceat0
- Outcome
- P uptakee0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“P uptake increased significantly (p < 0.05)”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
Yield, soil NO3- and leaf N contents showed insignificant correlations.
- Taxon
- spinachSpinacia oleraceat0
- Compound
- NO3-e0
- Outcome
- Correlations between yields, soil NO3- and leaf N contentse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Correlations between yields, soil NO3- and leaf N contents were insignificant (p > 0.05)”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
A significant regression relation between sludge and soil NO3- was found on Cambisol.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- sludgee0
- Outcome
- regression model for sludge and soil NO3-e0
- Setting
- Cambisole0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“On the Cambisol, a significant regression model for sludge and soil NO3- was determined”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
The authors recommend one-time combined sludge and biochar application for spinach on Luvisol.
- Taxon
- spinachSpinacia oleraceat0
- Outcome
- one – time combined application of 6 Mg ha-1 sewage sludge and 5 Mg ha-1 on the Luvisole0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“one – time combined application of 6 Mg ha-1 sewage sludge and 5 Mg ha-1 on the Luvisol”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
The authors recommend 12 Mg ha-1 sewage sludge for spinach on Cambisol.
- Taxon
- spinachSpinacia oleraceat0
- Outcome
- 12 Mg ha-1 sewage sludge are recommendede0
- Setting
- Cambisole0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“12 Mg ha-1 sewage sludge are recommended for spinach production on the Luvisol and Cambisol, respectively”
t0“spinach (Spinacia oleracea L.)”
Claim · model-written summary
The authors suggest mineral N in subsequent seasons to maintain productivity and avoid excess P.
- Taxon
- spinachSpinacia oleraceat0
- Outcome
- crop productivity could be maintained by application of mineral Ne0
- Qualifier
- subsequent seasonse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In subsequent seasons, crop productivity could be maintained by application of mineral N in order to mitigate over-application of P”
t0“spinach (Spinacia oleracea L.)”
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See all 9 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.