Articles
15N FERTILIZER USE EFFICIENCY BY SPINACH GROWN UNDER PORTUGUESE FIELD CONDITIONS
Article number
563_7
Pages
67 – 72
Language
English
Abstract
Maximum nitrate (NO3–) levels in spinach leaves as proposed by the EU (1993) are 2500 mg kg-1 in fresh product for direct consumption, and 2000 mg kg-1 in fresh product for processing.
In Switzerland, the maximum NO3– level allowed in vegetables is 3500 mg kg-1 in fresh product.
Although not proven, it seems that excess NO3– in the leaves may cause methemoglobinaemia, particularly in pregnancy and babies.
The main objective of this study was to evaluate the N fertilizer use efficiency by two cultivars of Spinacea oleracea L. A split-plot randomized block experiment with four N levels (30, 60, 90 and 120 kg N ha-1) and four replicates was carried out in 1995 on an anthropogenic soil in west Portugal.
Microplots (1.2 m2) were fertilized with 30 kg N ha-1 of 15NH415NO3 with 4.8 atom % 15N excess, as basal dressing.
The remaining N was applied as topdressing, thirty days after sowing, in the form of 15NH415NO3 with 4.8 atom % 15N excess.
N treatment did not significantly affect yields and N uptake by the plants, except for total N in the petioles, which accumulated four times as much as in the blades, and exported N in the roots.
Nitrate content was lower than the EU (1993) recommended level for spinach.
Percent N in the blades derived from the fertilizer was significantly affected by the treatment, with higher values for 90 and 120 kg N ha-1. Most N in the crop (82.5%) came from the soil and irrigation water.
Recovered 15N in the crop did not vary significantly with the treatment and indicates very low fertilizer N use efficiency (17.5%). Cultivars differed significantly in yields and exported N, with Space (F1) giving a significantly higher yield (29 t ha-1), but 15N recovery in the crops did not vary significantly between cultivars.
In Switzerland, the maximum NO3– level allowed in vegetables is 3500 mg kg-1 in fresh product.
Although not proven, it seems that excess NO3– in the leaves may cause methemoglobinaemia, particularly in pregnancy and babies.
The main objective of this study was to evaluate the N fertilizer use efficiency by two cultivars of Spinacea oleracea L. A split-plot randomized block experiment with four N levels (30, 60, 90 and 120 kg N ha-1) and four replicates was carried out in 1995 on an anthropogenic soil in west Portugal.
Microplots (1.2 m2) were fertilized with 30 kg N ha-1 of 15NH415NO3 with 4.8 atom % 15N excess, as basal dressing.
The remaining N was applied as topdressing, thirty days after sowing, in the form of 15NH415NO3 with 4.8 atom % 15N excess.
N treatment did not significantly affect yields and N uptake by the plants, except for total N in the petioles, which accumulated four times as much as in the blades, and exported N in the roots.
Nitrate content was lower than the EU (1993) recommended level for spinach.
Percent N in the blades derived from the fertilizer was significantly affected by the treatment, with higher values for 90 and 120 kg N ha-1. Most N in the crop (82.5%) came from the soil and irrigation water.
Recovered 15N in the crop did not vary significantly with the treatment and indicates very low fertilizer N use efficiency (17.5%). Cultivars differed significantly in yields and exported N, with Space (F1) giving a significantly higher yield (29 t ha-1), but 15N recovery in the crops did not vary significantly between cultivars.
Authors
C. Carranca, A. Soares da Silva, M. Fernandes, J. Varela
Keywords
Blades, cultivars, Ndff, nitrate, N rates, 15N recovery, petioles, roots
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