Articles
Soil sampling depth for calculation of nitrogen base fertilization in field-grown spinach
Article number
1375_12
Pages
89 – 96
Language
English
Abstract
Spinach is a nitrogen (N)-demanding crop characterized by a shallow root architecture.
Especially in the first weeks after sowing, significant N uptake is limited to the uppermost few centimetres of the soil.
However, base fertilization is usually based on the soil mineral N (Nmin) concentration in the upper 30 cm.
Therefore, the objective of this study was to examine whether the soil sample depth for calculating the base N fertilization can be reduced to the 0-15 cm layer.
In seven field trials, conducted during spring, summer and autumn seasons, either a low or high base fertilization dose was applied at sowing.
Until top dressing, soil samples were frequently taken in the upper 0-15 and 15-30 cm layers to determine the average Nmin concentration in each layer.
Top dressing was applied when the first true leaves had unfurled.
With this fertilizer application, the total N supply was aligned between both treatments based on the Nmin concentration in the upper 30 cm of the soil.
Aboveground fresh and dry masses were determined after reaching a fresh mass yield of 15-20 t ha‑1 and related to the mean Nmin concentration in the first 3 to 4 weeks of cultivation between sowing and top dressing.
It was shown that the Nmin concentration in the upper 0-15 cm of the soil highly reflects the base fertilization rate.
By contrast, the Nmin concentration in the 15-30 cm layer remained unaffected.
However, the Nmin concentration of both top soil layers can affect fresh and dry mass yield at harvest.
Therefore, the entire 0-30 cm soil layer should be considered when calculating the base N fertilization rate in field-grown spinach.
Measurements revealed that spinach fresh and dry masses were increased until the N availability of between 54 and 59 kg ha‑1 (0-30 cm) was reached at the seedlings stage, respectively.
Especially in the first weeks after sowing, significant N uptake is limited to the uppermost few centimetres of the soil.
However, base fertilization is usually based on the soil mineral N (Nmin) concentration in the upper 30 cm.
Therefore, the objective of this study was to examine whether the soil sample depth for calculating the base N fertilization can be reduced to the 0-15 cm layer.
In seven field trials, conducted during spring, summer and autumn seasons, either a low or high base fertilization dose was applied at sowing.
Until top dressing, soil samples were frequently taken in the upper 0-15 and 15-30 cm layers to determine the average Nmin concentration in each layer.
Top dressing was applied when the first true leaves had unfurled.
With this fertilizer application, the total N supply was aligned between both treatments based on the Nmin concentration in the upper 30 cm of the soil.
Aboveground fresh and dry masses were determined after reaching a fresh mass yield of 15-20 t ha‑1 and related to the mean Nmin concentration in the first 3 to 4 weeks of cultivation between sowing and top dressing.
It was shown that the Nmin concentration in the upper 0-15 cm of the soil highly reflects the base fertilization rate.
By contrast, the Nmin concentration in the 15-30 cm layer remained unaffected.
However, the Nmin concentration of both top soil layers can affect fresh and dry mass yield at harvest.
Therefore, the entire 0-30 cm soil layer should be considered when calculating the base N fertilization rate in field-grown spinach.
Measurements revealed that spinach fresh and dry masses were increased until the N availability of between 54 and 59 kg ha‑1 (0-30 cm) was reached at the seedlings stage, respectively.
Authors
C. Frerichs, D. Daum
Keywords
Spinacia oleracea L., Nmin concentration, base fertilization, fresh mass yield, dry mass yield
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