Abstract
Despite the importance of fertilizing practices in the crop yield improvement, nitrogen (N) utilization, and N status, their management by farmers is still rather empirical, especially when new organic materials are applied. Therefore, the aim of this research was to study the possible bio-products (anaerobic digestates and on-farm compost) applications and to evaluate their effects on lettuce performance, N efficiency and soil properties. The plant and soil N indicators were also investigated to reduce the N supply in lettuce production. To accomplish these objectives a three-year field experiment was carried out comparing the following N fertilization strategies: organic, with anaerobic digestates, based on stabilized wine distillery wastewater (SAD) and not stabilized wine distillery wastewater (NSAD) and on-farm compost, based on olive pomace compost (OPC); mineral (MIN), with ammonium sulfate and ammonium nitrate; mineral-organic, with a slow N release commercial fertilizer (CORG). All treatments received 140 kg N ha−1 and they were compared with an unfertilized control (CONTR). The organic material application increased the marketable yield of 25.6, 20.3 and 10.1% for SAD, NSAD, and OPC treatments, respectively, in comparison with the CONTR. No significant reduction was found for both anaerobic digestates in respect to conventional fertilizers, while the OPC application significantly decreased the crop yield compared to MIN and CORG treatments. Moreover, the marketable head weight showed no significant difference among MIN, CORG, and SAD treatments, while a significant reduction of the weight was observed for NSAD and OPC. These findings highlighted the importance of organic fertilizer choice to sustain lettuce yield. The anaerobic digestates also enhanced head weight of 18.9 and 11.9% for SAD and NSAD, respectively, compared to CONTR, pointing out that the by-products application could be a valid agricultural practice to provide nutrients. Besides, no significant difference in N utilization parameters was found between SAD, MIN and CORG, indicating the effectiveness of the stabilized wine wastewater. Among the plant and soil N indicators tested, our results suggested that the leaves green index and nitrate contents in the leafstalks not only were the most reliable methods for evaluating N status, but they also offered potential advantages of both an easier sampling and a higher positive correlation with lettuce performance. Finally, since the agro-industrial residues did not significantly increase the soil potentially toxic elements level, the findings of this research pointed out that the organic materials can be usefully applied, at least in the short-term period.
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Claims 14
Claim · model-written summary
SAD increased marketable lettuce yield by 25.6% over unfertilized control.
- Taxon
- lettuce
Lactuca sativae1 - Treatment
- SADe0
- Outcome
- marketable yielde0
- Direction
- increasede0
- Value
- 25.6e0
- Comparator
- CONTRe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The organic material application increased the marketable yield of 25.6, 20.3 and 10.1% for SAD, NSAD, and OPC treatments, respectively, in comparison with the CONTR.”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
NSAD increased marketable lettuce yield by 20.3% over unfertilized control.
- Taxon
- lettuceLactuca sativae1
- Treatment
- NSADe0
- Outcome
- marketable yielde0
- Direction
- increasede0
- Value
- 20.3e0
- Comparator
- CONTRe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The organic material application increased the marketable yield of 25.6, 20.3 and 10.1% for SAD, NSAD, and OPC treatments, respectively, in comparison with the CONTR.”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
OPC increased marketable lettuce yield by 10.1% over unfertilized control.
- Taxon
- lettuceLactuca sativae1
- Treatment
- OPCe0
- Outcome
- marketable yielde0
- Direction
- increasede0
- Value
- 10.1%e0
- Comparator
- CONTRe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The organic material application increased the marketable yield of 25.6, 20.3 and 10.1% for SAD, NSAD, and OPC treatments, respectively, in comparison with the CONTR.”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
Neither anaerobic digestate significantly reduced yield relative to conventional fertilizers.
- Taxon
- lettuceLactuca sativae1
- Treatment
- anaerobic digestatese0
- Direction
- No significant reductione0
- Comparator
- conventional fertilizerse0
Not reportedOutcome
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“No significant reduction was found for both anaerobic digestates in respect to conventional fertilizers”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
OPC significantly decreased crop yield compared with MIN and CORG.
- Taxon
- lettuceLactuca sativae1
- Treatment
- OPCe0
- Outcome
- crop yielde0
- Direction
- decreasede0
- Comparator
- MIN and CORGe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the OPC application significantly decreased the crop yield compared to MIN and CORG treatments”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
Marketable head weight did not differ significantly among MIN, CORG, and SAD.
- Taxon
- lettuceLactuca sativae1
- Treatment
- MIN, CORG, and SADe0
- Outcome
- marketable head weighte0
- Direction
- no significant differencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the marketable head weight showed no significant difference among MIN, CORG, and SAD treatments”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
NSAD and OPC significantly reduced marketable head weight.
- Taxon
- lettuceLactuca sativae2
- Treatment
- NSAD and OPCe0
- Outcome
- marketable head weighte1
- Direction
- reductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a significant reduction of the weight was observed for NSAD and OPC”
e1“the marketable head weight”
e2“to evaluate their effects on lettuce performance”
Claim · model-written summary
SAD increased lettuce head weight by 18.9% over control.
- Taxon
- lettuceLactuca sativae1
- Treatment
- SADe0
- Outcome
- head weighte0
- Direction
- enhancede0
- Value
- 18.9e0
- Comparator
- CONTRe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The anaerobic digestates also enhanced head weight of 18.9 and 11.9% for SAD and NSAD, respectively, compared to CONTR”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
NSAD increased lettuce head weight by 11.9% over control.
- Taxon
- lettuceLactuca sativae1
- Treatment
- NSADe0
- Outcome
- head weighte0
- Direction
- enhancede0
- Value
- 11.9%e0
- Comparator
- CONTRe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The anaerobic digestates also enhanced head weight of 18.9 and 11.9% for SAD and NSAD, respectively, compared to CONTR”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
Nitrogen utilization parameters did not differ significantly among SAD, MIN, and CORG.
- Taxon
- lettuceLactuca sativae1
- Treatment
- SAD, MIN and CORGe0
- Outcome
- N utilization parameterse0
- Direction
- no significant differencee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“no significant difference in N utilization parameters was found between SAD, MIN and CORG”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
Leaf green index and leafstalk nitrate content were the most reliable indicators of nitrogen status.
- Taxon
- lettuceLactuca sativae1
- Organ / stage
- leafstalkse0
- Outcome
- evaluating N statuse0
- Comparator
- most reliable methodse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the leaves green index and nitrate contents in the leafstalks not only were the most reliable methods for evaluating N status”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
Leaf green index and leafstalk nitrate content correlated more positively with lettuce performance and permitted easier sampling.
- Taxon
- lettuceLactuca sativae0
- Outcome
- an easier sampling and a higher positive correlation with lettuce performancee0
- Comparator
- highere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“they also offered potential advantages of both an easier sampling and a higher positive correlation with lettuce performance”
e1“the leaves green index and nitrate contents in the leafstalks”
Claim · model-written summary
Agro-industrial residues did not significantly increase soil potentially toxic element levels.
- Taxon
- lettuceLactuca sativae1
- Treatment
- agro-industrial residuese0
- Outcome
- soil potentially toxic elements levele0
- Direction
- did not significantly increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the agro-industrial residues did not significantly increase the soil potentially toxic elements level”
e1“to evaluate their effects on lettuce performance”
Claim · model-written summary
The authors recommend short-term use of organic materials in lettuce production.
- Taxon
- lettuceLactuca sativae1
- Outcome
- organic materials can be usefully appliede0
- Qualifier
- at least in the short-term periode0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“organic materials can be usefully applied, at least in the short-term period”
e1“lettuce production”
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