Abstract
Spinach is one of the most important green-leafy vegetables, consumed worldwide, and its intake is beneficial for human beings. In this crop, produce yield and quality are closely related to plant nitrogen (N) nutrition. A precise supply of N is also essential for high environmental and economic sustainability. Main aims of the work were: i) to establish relationships between produce yield or quality and mineral N availability in the root zone; and ii) to define an optimal mineral N level to be maintained in the root zone for spinach. Eight experiments were carried out during a four-year-long period under typical Mediterranean climate conditions. Different amounts of N fertilisers were supplied leading to twenty different levels of mineral N in the root zone. Experimental measurements included climate parameters, plant growth, tissue and soil analyses, produce yield and quality indicators. A segmented linear model significantly represented the relationship between crop yield (1.7 to 21.7 t ha–1) and soil mineral N concentration (7.6 to 41.0 mg kg–1). Basing on this model, an optimal mineral N threshold was fixed at 23.4 mg kg–1. Above this threshold, crop yield did not show any significant variations as well as tissue characteristics and produce quality. Plants grown under suboptimal N levels showed reduction in growth, tissue mineral (nutrients) content, and SPAD index. The proposed models could be implemented in fertilisation protocols for the optimization of N supply and the estimation of spinach growth and yield.
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Claims 8
Claim · model-written summary
A segmented linear model significantly represented crop yield against soil mineral nitrogen.
- Taxon
- spinach
Spinacia oleraceat0 - Outcome
- relationship between crop yield (1.7 to 21.7 t ha–1) and soil mineral N concentration (7.6 to 41.0 mg kg–1)e0
- Value
- 1.7 to 21.7 t ha–1e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“spinach (Spinacia oleracea L.)”
e0“A segmented linear model significantly represented the relationship between crop yield (1.7 to 21.7 t ha–1) and soil mineral N concentration (7.6 to 41.0 mg kg–1)”
Claim · model-written summary
The model set optimal mineral nitrogen at 23.4 mg kg–1.
- Taxon
- spinachSpinacia oleraceat0
- Outcome
- optimal mineral N thresholde0
- Value
- 23.4 mg kg–1e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“spinach (Spinacia oleracea L.)”
e0“Basing on this model, an optimal mineral N threshold was fixed at 23.4 mg kg–1”
Claim · model-written summary
Above the nitrogen threshold crop yield did not vary significantly.
- Taxon
- spinachSpinacia oleraceat0
- Outcome
- crop yielde0
- Direction
- did not show any significant variationse0
- Qualifier
- Above this thresholde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“spinach (Spinacia oleracea L.)”
e0“Above this threshold, crop yield did not show any significant variations as well as tissue characteristics and produce quality”
Claim · model-written summary
Above the threshold tissue characteristics and produce quality did not vary significantly.
- Taxon
- spinachSpinacia oleraceat0
- Outcome
- tissue characteristics and produce qualitye0
- Direction
- did not show any significant variationse0
- Qualifier
- Above this thresholde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“spinach (Spinacia oleracea L.)”
e0“Above this threshold, crop yield did not show any significant variations as well as tissue characteristics and produce quality”
Claim · model-written summary
Suboptimal nitrogen reduced plant growth.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- suboptimal N levelse0
- Outcome
- growthe0
- Direction
- reductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“spinach (Spinacia oleracea L.)”
e0“Plants grown under suboptimal N levels showed reduction in growth, tissue mineral (nutrients) content, and SPAD index”
Claim · model-written summary
Suboptimal nitrogen reduced tissue mineral content.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- suboptimal N levelse0
- Outcome
- tissue mineral (nutrients) contente0
- Direction
- reductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“spinach (Spinacia oleracea L.)”
e0“Plants grown under suboptimal N levels showed reduction in growth, tissue mineral (nutrients) content, and SPAD index”
Claim · model-written summary
Suboptimal nitrogen reduced SPAD index.
- Taxon
- spinachSpinacia oleraceat0
- Treatment
- suboptimal N levelse0
- Outcome
- SPAD indexe0
- Direction
- reductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“spinach (Spinacia oleracea L.)”
e0“Plants grown under suboptimal N levels showed reduction in growth, tissue mineral (nutrients) content, and SPAD index”
Claim · model-written summary
The authors propose their models for nitrogen supply and spinach growth and yield estimation.
- Taxon
- spinachSpinacia oleraceae0
- Outcome
- optimization of N supply and the estimation of spinach growth and yielde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The proposed models could be implemented in fertilisation protocols for the optimization of N supply and the estimation of spinach growth and yield”
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