Environmental Factors and Cultural Measures Affecting The Nitrate Content In Spinach

110 Pages·1982·5.49 MB·English

by  T. Breimer (auth.)

Environmental factors and cultural measures affecting the nitrate
content in spinach
iii
EN~RONMENTALFACTORSAND
CULTURAL MEASURES AFFECTING
THE NITRATE CONTENT IN
SPINACH
T.BREIMER
1982
MARTINUS NIJHOFF/DR W. JUNK PUBLISHERS
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for the United States and Canada
Kluwer Boston, Inc.
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Hingham, MA 02043
USA
for all other countries
Kluwer Academic Publishers Group
Distribution Center
P.D.Box 322
3300 AH Dordrecht
The Netherlands
Library of Congress Cataloging in Publication Data
Breimer, T.
Environmental factors and cultural measures affecting
the nitrate content in spinach.
Bibliography: p.
1. Spinach. 2. Spinach--Composition. 3. Nitrates.
I. Title.
SB351.S7B73 1982 635'.41 82-10580
ISBN-13: 978-90-247-3053-7 e-ISBN-13: 978-94-009-7687-0
001: 1O.lOO7/978-94-D09-7687-0
Reprinted from Fertilizer Research, vol. 3, no. 3 (1982)
Copyright © 1982 by Martinus Nijhoff / Dr W. Junk Publishers, The Hague.
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system,
or transmitted in any form or by any means, mechanical, photocopying, recording, or
otherwise, without the prior written permission of the publishers,
Martinus Nijhoff / Dr W. Junk Publishers, P.D.Box 566, 2501 CN The Hague, The Netherlands.
v
Preface
The present investigation was carried out in the period 1977-1981 at the
Department of Soil Science and Plant Nutrition of the Agricultural University
Wageningen, Netherlands. This university supplied the major financial sup
port through a research grant, with additional financial support rendered by
the Dutch Nitrogen Fertilizer Industry and Unilever Research, Netherlands.
This support is gratefully acknowledged. In the present form this report is
the author's doctoral dissertation submitted to the Faculty of the Agricul
tural University.
The author hereby wishes to thank prof.dr.ir. A. van Diest for his criti
cal reading and correction of the English text, and drjr. J.H.G. Slangen
for his valuable advices during the investigations and in the course of the
preparation of this report. The au thor also acknowledges the valuable support
received from several Agricultural Research Institutes and University Depart
ments which made facilities and manpower available to conduct the ex
periments and to transform the results obtained into the present report.
Contents
Preface / v
Abstract / 1
List of ab breviations / 2
Introduction / 3
2 Literature / 6
2.1 Nitrogen transformations in soil / 7
2.2 Nitrate uptake / 7
2.3 Nitrate reduction in plants / 7
2.4 Nitrate contents in plants / 8
2.5 Cultural measures / 9
2.5.1 Nitrogen dressing / 9
2.5.1.1 Nitrogen amount / 9
2.5 .1.2 Nitrogen form / 10
2.5.1.3 Time of application of nitrogen / 11
2.5.2 Other nutrients / 12
2.5 .3 Herbicides / 12
2.5.4 Spinach variety / 13
2.5.5 Harvesting procedure / 13
2.6 Environmental conditions / 14
2.6.1 Light / 14
2.6.2 Carbon dioxide / 15
2.6.3 Temperature / 15
2.6.4 Water / 15
2.6.5 Season / 15
2.6.6 Location / 16
3 Materials and methods / 17
3.1 Indoor experiments / 17
3.1.1 General / 17
3.1.2 Water-culture experiments / 17
3.1.3 Sand-culture experiments / 18
3.1.4 Soil-culture experiments / 18
3.2 Field experiments / 24
3.2.1 General / 24
3.2.2 Duiven experiments / 25
3.2.3 Lelystad experiments / 26
3.2.4 HeIden experiments / 27
3.3 Weather conditions / 28
3.4 Harvest / 28
3.5 Chemical analysis / 30
3.6 Soil analysis / 31
4 Nitrogen nutrition and the ionic balance in spinach; results of
indoor experiments / 33
4.1 General introduction / 33
4.2 Spinach grown in water-cultures / 34
4.3 Spinach grown in sand-cultures with nitrate-and ammonium
nitrogen / 35
4.4 The effects of nitrate-nitrogen on yield and chemical
characteristics of spinach grown on various soils / 39
4.4.1 The amount of nitrate-nitrogen applied / 39
4.4.2 Distribution of plant nutrients in the aerial parts of
spinach / 42
4.4.3 Age of plants and season of growth / 44
4.4.4 Time of application of nitrate-nitrogen / 45
4.4.5 Soil-moisture content / 45
4.4.6 Soil pH / 45
4.4.7 Mo-spraying on two soil types / 45
4.5 The effects of variations in N-form in soil-cultures on yield
and chemical characteristics of spinach / 48
4.5.1 Ammonium-and nitrate-nitrogen dressings / 48
4.5.2 Light intensity-and temperature effects with different
amounts of nitrogen and varying N03 : NH4 -ratios / 49
4.6 Comparison of the performances of different N-carriers as
reflected in yields and N0 -contents of spinach / 51
3
4.7 The effects of N in manures on yield and chemical com
position spinach / 48
4.8 Effects of variations in P-dressing and in soil P-status on
yield and chemical composition of spinach / 54
4.9 Effects of variations in the size of K-dressings and in type of
K-carrier on yield and chemical composition of spinach / 54
4.1 0 Effect of varietal differences on yield and N0 -contents in
3
spinach / 55
5 Results of outdoor experiments / 56
5.1 The effects of variations in nitrate dressings / 56
5.1.1 Yields and dry-matter contents of spinach / 56
5.1.2 N0 -contents in spinach / 56
3
5.1.3 N-contents and total N in the aerial parts of spinach / 57
5.1.4 Available N in the soil profile / 57
5.1.5 Plant nutrients other than nitrogen / 61
5.2 The effects of variations in timing of nitrogen
applications / 66
5.2.1 Yields and dry-matter contents of spinach / 66
5.2.2 N0 -contents and N-contents and total N in the aerial parts
3
of spinach / 67
5.3 The effects of variations in N03 ; NH4 -ratio / 67
5.3.1 Yields and dry-matter contents of spinach / 67
5.3.2 N0 -contents in spinach / 68
3
5.3.3 N-contents and total N in the aerial parts of spinach / 69
5.3.4 The ratio (C-A) ; org N in the aerial parts of spinach / 69
5.4 Experiments on farmers' fields / 73
5.4.1 Yields and dry-matter contents of spinach / 73
5.4.2 N0 -contents in spinach / 73
3
6 Discussion / 75
6.1 Cultural measures, other than nitrogen dressings, aimed at
minimizing N0 -contents in spinach / 75
3
6.2 Cultural measures related to nitrogen, aimed at minimizing
N0 -contents in spinach / 78
3
Summary / 86
List of figures / 89
List of tables / 91
Appendix / 92
References / 93
Abstract
Environmental factors and cultural measures affecting the N0 -content in
3
spinach were studied indoors, in water-, sand- and soil-culture experiments.
In the field, the influences of variations in N-fertilizing practices and in spin
ach varieties were also tested.
High N03-contents in spinach were found with low light intensities, with
low soil-moisture contents, and with high temperatures. N0 -contents
3
increased with increasing K-dressing (less so with KCI than with K2S04), but
decreased with increasing soil pH. In pot experiments, positive results were
obtained with sulphur-coated urea, with farmyard manure and with pig
manure slurry.
Application of Mo as a spray onto spinach leaves, and variations in P-dres
sings and in soil P-status were found not to affect the N0 -content in spin
3
ach.
In pot experiments, N03- contents decreased with progressing plant age (in
autumn less so than in spring). Within spinach plants, N03-contents were
highest in petioles and older leaves. Varietal differences in N0 -contents
3
were observed in a pot-and a field experiment.
In pot- and field experiments, partial or complete replacement of N0 -N
3
by NH -N in general caused the N0 -content in spinach to decrease. How
4 3
ever, such a replacement was shown not always to result in lower N03-
contents. Additional factors involved are e.g. the use and effectiveness of
nitrification inhibitors, the soil type and the amount of available N.
The amount of N added and, in the field, the amount of N available in the
soil before sowing, strongly affected the N03 -content in spinach. Under field
conditions, nitrogen appeared to be taken up from the top 60 cm of the soil
proflle.
The effects of variations in timing of nitrogen applications were absent in a
pot experiment and not consistent in field experiments.
[1]
List of abbreviations
A sum of inorganic anions (CI + H2P04 + S04 + N03) in meq
per kg DM (H2P04 stands for total P)
AD! acceptable daily intake
C = sum of inorganic cations (Ca + Mg + Na + K) in meq per kg DM
C-A = excess of inorganic cations over inorganic anions in plants,
meq per kg DM; NH4 -ions are not included
CEC = cation exchange capacity
DCD
DM = dry matter
FW fresh weight
FYM farmyard manure
JECFA Joint FAO/WHO Expert Committee on Food Additives
N-serve nitrification inhibitor, containing 2-chloro-6-(trichloromethyl)
pyridine (C6H3NCI4), known asnitrapyrin, as active compound
org N = organic nitrogen (= total N -N03-N)
PMS pig-manure slurry
SCU = sulphur-coated urea
WHC water-holding capacity
WHO = World Health Organization
In the text ionic species are represented by their chemical symbols, charge
signs being omitted, e.g. N03 instead of N03-.
[2]
1 Introduction
Nitrate is present in many foodstuffs either as a natural component or
as an additive. The main sources of dietary nitrate are vegetables and drinking
water [Loggers, 1979; Tremp, 1981; Walker, 1975; White, 1975]. In the
Netherlands, the mean daily intake of nitrate, estimated from 'total diet' stu
dies, is about 160 mg N0 per 11000 kJ, 75% of which comes from vege
3
tables and less than 10% from beverages and drinking water. There is a con
siderable variation in daily intake depending on amount and composition of
the vegetables ingested [Loggers, 1979].
Although the toxicity of nitrate is relatively low, its occurrence in
food must be considered hazardous because of the possible reduction of
nitrate to nitrite that can occur before ingestion, in the gastro-intestinal tract
or in saliva. Direct ingestion of nitrite can originate from additives of nitrate
or nitrite to meat, fish and cheese or from bacterial or enzymatic reduction of
nitrate in e.g. vegetables due to improper handling or storage [Tannenbaum,
1979]. In the Netherlands the estimated mean direct daily intake of nitrite is
about 6 mg N0 [Loggers, 1979].
2
After ingestion of a given dose of dietary nitrate this passes to and
through the stomach to be absorbed from the small intestine. Most of the ab
sorbed nitrate is rapidly excreted in urine, but a part of it is secreted in
the saliva, where in the presence of bacteria it is partly reduced to nitrite
[Harada et al., 1975; Ishiwata et aI., 1975; Spiegelhalder et aI., 1976;
Stephany & Schuller, 1978]. The extent of nitrite formation in saliva is re
lated to the quantity of nitrate, to the concentration of the nitrate source
and to the oral microflora [Tannenbaum et al., 1976]. On an average about
6% of the nitrate ingested is reduced to nitrite, which means that per 160 mg
nitrate (N03) about 10 mg will be reduced in saliva to produce about 7 mg
nitrite (N02) [Stephany & Schuller, 1980]. Another possible environment for
nitrate reduction is the human stomach. Nitrite concentrations in a normal
human stomach are generally lower than 1 mg per litre [Tannenbaum, 1979].
There are, however, conditions under which the human stomach can acquire
nitrite concentrations of tens or even hundreds of mg per litre [Ruddell et
aI., 1976; Tannenbaum et aI., 1979]. This occurs when the pH of the stom
ach, which is normally quite low, rises to a level high enough to allow the
growth of bacteria which can reduce nitrate to nitrite. Under these condi
tions, sometimes occurring in infants under three months of age and in
patients with specific gastric disorders, the stomach pH becomes similar to
that of the mouth and the stomach may even contain bacteria similar to those
found in the mouth. It was recently suggested that also under normal con
ditions nitrate and nitrite may be formed endogenously in the human intestine,
[3]