Effect of Cultivars, Harvesting Time and Level of Nitrogen Fertilizer on Nitrate and Nitrite Content, Yield in Romaine Lettuce
Naser Alemzadeh Ansari
Farideh Sedighie Dehcordie
In order to evaluate the effect of nitrogen fertilizer levels (0, 60, 120, 180), cultivars (Pich Ahwazi, Pich Varamini) and harvesting time (morning, evening) on yield, nitrate and nitrite accumulation in edible parts of lettuce, a research was conducted in Shahid Chamran University of Ahwaz, Iran. This study was arranged in spilt plot experiment on randomized complete block design base, in three replications. Results indicated that effects of nitrogen fertilizer amount on yield were significant at 1% levels. Highest yield was accomplished when the Pich Ahwazi cultivar received 120 kg N ha-1. There was appositive relation ship between amount of nitrogen fertilizer and level of nitrate and nitrite accumulation in edible parts of lettuce. In two cultivars nitrate and nitrite is stem and of outer leaves were higher than inner leaves. The effect of harvest time on nitrate and nitrite content was significant at 1% level and nitrate and nitrite amount were lower in evening in comparison to morning harvesting. There had significant different in the nitrate content between cultivar and nitrite accumulation in Pich Varamini was higher than Pich Ahwazi but significant different was not seen among cultivars in nitrite accumulation. Therefore, nitrogen fertilizer and harvesting time are major factors on nitrate and nitrite accumulation in lettuce.
Nitrogen is one of essential elements for growth and development plants and in the nutrition of plants plays a significant role. Plants absorb of nitrogen from the soil in the form of nitrates, which are then converted into proteins and other nitrogen-containing substances (Cash et al., 2002). Nitrate content in a plant represents a dynamic balance between rate of absorption, assimilation and translocation (Maynard et al., 1976). In certain conditions, this balance can be disrupted so that the roots will accumulate nitrate faster than the plant can convert the nitrate to protein (Cash et al., 2002). Nitrate accumulation in plant can be hazardous to human heath. Because, in the human body nitrate con be reduced to nitrite which may cause methemoglobinemia furthermore, the possible formation of N-nitroso-compounds from nitrite and secondary nitrogen compounds in the human stomach constitutes a risk (Breimer, 1982).
Vegetables are a major source of nitrate and nitrite in human diet (Amr and Hadidi, 2001). It is estimated that they contribute about 85% (Gaugolli et al., 1994) and 14-43% (Cassens, 1995) of the daily dietary intakes of nitrate and nitrite, respectively, in a number of societies.
Leafy vegetables such as spinach, lettuce and celery contain nitrate at significant levels (Maynard et al., 1976). A number of factors influence nitrate and nitrite accumulation in vegetables such as nitrate supply from the soil, genotype of plants (Blom-Zandstra and Eenink, 1986; Behr and Wiebe, 1989) and environment under which the plants are grown, such as light intensity and photoperiod (Blom-Zandstra and Lampe, 1985; Van der Boon et al., 1990) and temperature (Van der Boon et al., 1990).
Thus, the many investigations carried out for decreasing nitrate and nitrite accumulation in vegetables. Byrns et al. (2001) reported that increasing nitrogen rates of soil caused increases nitrate accumulation in lettuce and outer leaves accumulated higher nitrate than inner leaves. The investigations carried out by Tittonell et al. (2003) on lettuce showed that water content and nitrate accumulation in leaf tissues increased with nitrogen application. Amr and Hadidi (2000) in comparison vegetable types observed that effect of cultivar was not significant on nitrate and nitrite content in vegetables. The aim of this work was to determine effect of different nitrogen level, cultivar and time harvest an nitrate and nitrite accumulation in lettuce.
MATERIALS AND METHODS
This study was carried out in the experimental field of Agricultural faculty
in Shahid Chamran University of Ahwaz, Iran (from October 2005 to March 2006).
The experimental design was a spilt plot in randomized complete blocks with
||Some physical and chemical properties of experimental soil
|EC: Electrical conductivity, N: Nitrogen and P: Available
phosphate K: Available potassium
The main plots were included four nitrogen levels (0, 60, 120 and 180 kg ha-1)
and sub plots were considered two lettuce cultivar (Pich Ahwazi and Pich Varamini)
and two harvesting time (evening and morning harvest). Physical and chemical
properties of soil taken prom 0 to 60 cm depth in the experimental field are
given in Table 1. Before planting, phosphorous (P2O5)
and potassium (K2O5) were applied at a rate of 150 and
100 kg ha-1, respectively. Lettuce seeds were sown in chamber on
24 October 2005. Seven weeks after emergence, seedlings of lettuce were planted
in a field at the spacing of 40 cm between rows and 30 cm within plants. Nitrogen
fertilizer was applied in three different periods (2, 4 and 8 weeks after lettuce
transplanting). In different stages, all protections of farming such as irrigating,
weeding, were carried out similarly in all treatments. In harvesting time, sampling
of plants was carried out in morning and evening, nitrate and nitrite rate in
stem, outer leaves and inner leaves were determined by the similar method. Statistical
analysis of experimental data was accomplished using the MSTATC software package
and the means were separated by Duncans multiple range test.
RESULTS AND DISCUSSION
Yields: The effect of different levels of nitrogen on yield was significant at 1% level ( Table 2). The highest yield in lettuce was obtained as 7 kg m-2 in 120 kg ha-1 application; the lowest yield was obtained as 2.83 kg m-1 in the zero nitrogen application. Increasing the N levels of the fertilizers to 120 kg N ha-1 significantly increased yield of lettuce while yield decreased at the highest nitrogen dose. Decreasing yield might be due to toxicity of plant or non attraction of nitrogen by plant that resulted from the consumption of excesses nitrogen fertilizer (Tabatabaie and Malakoutie, 1997).
Shahbazie (2005) reported that by increasing nitrogen level from 0 to 120 kg
N ha-1 yield of lettuce increased but between 100, 150, 200 kg N
ha-1 were not observed significant difference. Also, Behtash et
al. (1995) during experimental on cabbage and celery resulted that application
of nitrogen fertilizer increased yield in comparison with control treatment
but economically yield and best quality obtained in 100 kg ha-1 application.
|| Mean effects of different nitrogen levels and cultivar on
the yield of lettuce
|*: Means followed by the same letter(s) did not differ significantly
at 5% levels of probability
The effects of cultivar, rate of fertilizer and interaction between cultivar
and fertilizer application were not significant.
Nitrate: The results of statistical analysis indicated that effect of
nitrogen level on nitrate accumulation was significant at 1% level ( Table
3). The rate of nitrate accumulation in lettuce increased when the nitrogen
rate was raised to 120 kg N ha-1, whereas application of 180 kg N
ha-1 was caused reduction of nitrate accumulation thereby decreasing
nitrate content might be due to non uptake of nitrogen or non convert ammonium
to nitrate as a result of bacteria toxicity are responsible nitrification in
soil (Tabatabaie and Malakoutie, 1997). In two cultivars of lettuce obtained
highest nitrate accumulations in stem, the lowest nitrate content obtained in
inner leaves. A such seem that stem in comparison with other plant organs had
activer vacuole or and cytoplast system, thus higher nitrate accumulated in
it (Zarei, 1995). There had significant difference in the nitrate content between
cultivars, nitrate accumulation in Pich Varamini was higher than Pich Ahwazi.
The investigations carried out by Parente et al. (2006) on lettuce showed
that tendency to nitrate accumulation is differed among lettuce cultivars. Therefore,
type of cultivar has important role on nitrate accumulation in vegetables and
the effect of cultivar on nitrate accumulation has determined in often studies
(Munzert, 1989; Rostamforoudy, 1999; Shahbazie, 2005). Interaction between nitrogen
fertilizer rate and cultivar on nitrate accumulation was significant, the lowest
nitrate rates in different organs was existed in the control treatment and Pich
Ahwazi cultivar, the highest NO3 content in inner and outer leaves
was existed in the nitrogen level of 120 kg N ha-1 and Pich Ahwazi
cultivar, in stem was in nitrogen level of 120 kg N ha-1 and Pich
Varamini cultivar. The effect of harvesting time on nitrate accumulation was
significant at 1% level and nitrate amount was lower in evening in comparison
to morning harvesting. Because, during day trough solar radiation increasing
nitrate reductase activity and nitrate assimilation and thereby decreasing nitrate
content of plants (Minnoti, 1977; Lorenz, 1978; Maynard and Barker, 1979).
|| Mean effects of different nitrogen levels, cultivar and harvest
time on nitrate and nitrite accumulation of lettuce
|*: Means followed by the same letter(s) did not differ significantly
at 5% levels of probability
In this case has been a reported similar result by Krohn et al. (2003),
Cardenas-Navarro et al. (1999). Interaction between nitrogen fertilizer
rate and harvesting time on nitrate amount was significant at 1% level, in different
parts was found the highest nitrate amount in three treatment (120 kg N ha-1),
morning harvest and the lowest nitrate content was obtained in the control treatment
and evening harvest. Also, Interaction cultivars and harvesting time on nitrate
accumulation was significant at 1% level. The lowest nitrate content in inner
and outer leaves was related to Pich Varamini cultivar and evening harvest,
in stem was related to Pich Ahwazi. Cultivar and evening harvest. The highest
nitrate content in different organs was Obtained Pich Varamini and morning harvest.
The results shown that interaction between fertilizer level, cultivar and harvesting
time on nitrate accumulation in outer and inner leaves of lettuce was not statistically
significant, whereas interaction each three factors on nitrate content in stem
was significant and the highest nitrate level was found in three treatment (120
kg N ha-1), Pich Varamini cultivar and morning harvest, the lowest
nitrate level was obtained in control treatment, Pich Ahwazi cultivar and evening
Nitrite: The effect of fertilizer amount application on nitrite accumulation
was significant at 1% level ( Table 3). In different organs
was the lowest nitrite content related to the control treatment and the highest
nitrite accumulation related to the three treatments, however in outer leaves
and stem was not significant difference between Three (120 kg N ha-1)
and four (180 kg N ha-1) treatment. The similar results were obtained
by Gulser (2005) and Ceylan et al. (2002). The effect of cultivar and
also interaction cultivar and fertilizer level was not significant on nitrite
accumulation but in both cultivars, with increasing the nitrogen fertilizer
does increased nitrite accumulation in edible parts. A similar results obtained
in the investigations conducted by Amr and Hadidi (2001) and Lorenz (1987).
The effect of harvesting time on nitrite content was significant at 1% level
and nitrite accumulation was lower in evening in comparison to morning harvesting
the interaction of fertilizer amount and harvest time on nitrite accumulation
was statistically significant and the highest nitrite amount in stem and inner
leaves was existed in three treatment (120 kg N ha-1) and morning
harvest, in outer leaves was in control treatment and morning harvesting. In
different organs were the lowest nitrite amount in the control treatment and
evening harvest. Furthermore, the interaction of cultivar and harvesting time,
also levels of nitrogen fertilizer, cultivar and harvesting time were not significant
on nitrite accumulation.
The results indicated that the rate of nitrogen fertilizer was affected on
yield and also nitrate and nitrite accumulation in lettuce. Therefore, with
increasing the nitrogen application was increased yield, nitrate and nitrite
content in lettuce. Nitrate and nitrite concentration in edible parts of lettuce
were higher in morning in comparison to evening harvesting. In all treatments,
nitrate and nitrite rate were lower than toxic level. It might be due to that,
in the Khuzestan province is very low number of cloudy days (sunny hours were
263.1 on last growing month), thus very light intensity caused increasing nitrate
assimilation and thereby decreasing nitrate of plant in evaluating nitrate and
nitrite, the Joint FAO/WHO Expert Committee on Food Additives (JECFA) has established
Acceptable Daily Intakes (ADI) of nitrate and nitrate as 0-3.7 NO3
mg kg-1 body weight and 0-0.07 NO2 mg kg-1
body weight (JECFA, 1995). In 1997, the European Union established the maximum
levels for nitrate content in lettuce. Hence, it should be advised to protecting
quality and quantity lettuce use nitrogen fertilizer proportional with best
yield crop and for preventing undesirable nitrate and nitrite for human health
purpose in lettuce, plants harvesting should carry out in the evening. Also,
cultivars should use that nitrate and nitrite accumulation in they are low.
Amr, A. and N. Hadidi, 2001.
Effect of cultivar and harvest date on nitrate and nitrite content of selected vegetable grown under open field and greenhouse conditions in Jordan. J. Food Compos. Anal., 14: 59-67-67.Direct Link |
Behr, V. and H.J. Wiebe, 1989.
Nitrate content and osmotically active components in lettuce (Lactuca sativa
L.) cultivars. Acta Hortic., 244: 99-104.
Behtash, F., 1995.
Effects of nitrogen fertilizers on nitrate accumulation in the edible parts of cabbage and celery. University of Tarbiat Modares, Tahran, Iran.
Blom-Zandstra, M. and J.E.M. Lampe, 1985.
The role of nitrate in the osmoregulation of lettuce (Lactuca Sativa
L.) grown at different light intensities. J. Exp. Bot., 36: 1043-1052.
Blom-Zandstra, M. and A.H. Eenink, 1986.
Nitrate concentration and reduction in different of genotypes lettuce. J. Am. Soc. Hortic. Sci., 111: 908-911.
Breimer, T., 1982.
Enviromental Factors and Cultural Measures Affecting the Nitrate Content In Spinach. Reprinted from Fertilizer Research. Martinus Martinus Nijoff/ Dr. Wr. Junk Publisher, Hague, Netherlands
Byrns, C., M.J. Maher and M.J. Hennerty, 2001.
Reducing the nitrogen content of protected lettuce crops. Irish J. Agric. Food Res., 39: 491-508.
Cardenas-Navarro, R., S. Adamowicz and A.P. Robin, 1999.
Nitrate accumulation in plants: A role for water. J. Exp. Bot., 50: 613-624.Direct Link |
Cash, D., R. Funston, M. King and D. Wichman, 2002.
Nitrate toxicity of montana forages. Montana State University, Bozeman, MT 59717. http:// animalrangeextension.montana.edu/Articles/Forage /General/Nitrate-tox.htm.
Cassens, R.G., 1995.
Use of sodium nitrite in cured meats today. Food Technol., 49: 72-80.Direct Link |
Ceylan, S., N. Mordogan, H. Cakici and F. Yoldas, 2002.
Effects of different nitrogen levels on the yield and nitrogen accumulation in the rocket. Asian J. Plant Sci., 1: 482-483.CrossRef | Direct Link |
Gaugolli, S., P. van den Brandt, V. Feron, C. Janz-Wsky and J. Koeman et al
Nitrate, nitrite and N
-nitroso compounds. Eur. J. Pharmacol.: Environ. Toxicol. Pharmacol., 292: 1-38.CrossRef | PubMed | Direct Link |
Gulser, F., 2005.
Effect of ammonium sulphate and urea on NO3
G and NO2
G accumulation nutrient contents and yield criteria in spinach. www. elsevier. com/locate/scihorti.
Evaluation of certain food additives and contaminants. 24th Joint FAO/WHO Expert Committee on Food Additives, World Health Organization,Geneva. http://whqlibdoc.who.int/trs/WHO_TRS_859.pdf.
Krohn, N.G., 2003.
Nitrate level on lettuce leaves in function of the harvest rearms and leaf type sampling. Braz. Hortic., 21: 216-224.
Lorenz, O.A., 1978.
Potential Nitrate Levels in Edible Plant Parts. In: Nitrogen in the Environment, Nielsen, D.R. and J.G. MacDonald (Eds.). Soil-Plant-Nitrogen Relationships, UK., pp: 201-219
Maynard, D.N., A.V. Barker, P.L. Minotti and N.H. Peck, 1976.
Nitrate accumulation in vegetables. Adv. Agron., 28: 71-118.
Maynard, D.N. and A.V. Barker, 1979.
Regulation of nitrate accumulation in vegetables. Acta Hortic., 93: 123-129.
Minnoti, P.L., 1977.
Critique of Potential Nitrite Levels in Edible Plant Parts. Cornell University, USA
Munzert, M., 1989.
Nitrate in der kartoffel-eine literator studied. Der Kartoffelbau, 40: 184-188.
Parente, A., M. Gonnella, P. Santamaria, P. Labbate, G. Conversa and A. Elia, 2006.
Nitrogen fertilization of new cultivars of lettuce. Acta Hort. (ISHS), 700: 137-140.Direct Link |
Rostamforoudy, B., A. Kashi, M. Babalaro and H. Zamani, 1999.
Effect of different urea levels on nitrate accumulation, modifications of phosphor and potassium in bulb and leaf of onion cultivars. Iran J. Agric. Sci., 3: 487-493.
Shahbazie, M., 2005.
Effects of different nitrogen levels on the yield and nitrate accumulation in the four of lettuce cultivars. M.Sc. Thesis, Islamic Azad University, Tehran, Iran.
Tabatabaie, S.J. and M.J. Malakoutie, 1997.
Studies on the effect of the N, P and K-fertilizers on the potato yield and nitrate accumulation in potato tuber. Iran. J. Soil Water Res., 11: 25-30.
Tittonell, P.A., J.D. Grazia and A. Chiesa, 2003.
Nitrate and dry water concentration in a leafy lettuce cultivar as affected by N fertilization population. Agric. Trop. Subtrop., 36: 82-87.
Van-Der-Boon, J., J.W. Steenhuizen and E.G. Steingr Over, 1990.
Growth and nitrate concentration of lettuce as affected by total nitrogen and chloride concentration, NH4
ration and temperature of the recirculating nutrient solution. J. Hortic. Sci., 65: 309-321.
Zarei, H., 1995.
Study of nitrate accumulation in vegetables of lettuce and spinach in related with optimum application of nitrogen fertilizers. M.Sc. Thesis, University of Tarbiat Modares, Tehran, Iran.