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Research Article
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Effects of Fertilizers Containing Calcium and/or Magnesium on the Growth, Development of Plants and the Quality of Tomato Fruits in the Western Highlands of Cameroon
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Jean Aghofack- Nguemezi
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Valere Tatchago
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ABSTRACT
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The study was undertaken to determine the effects of calcium and magnesium nutrients on the development of plants and subsequent postharvest conservation of tomato fruits. Tomato plants were treated by applications of N/P/K (9.5/8/10) and fertilizers containing Ca2+ and/or Mg2+. Control plants received only N/P/K. Two fertilizer combinations (N/P/K + foliar spray of Manvert Magnesium and N/P/K + calcium nitrate at 800 kg ha-1 + foliar spray of Manvert Magnesium) induced a significant delay in the flowering of plants. Combinations of soil applications of N/P/K and calcium nitrate at 200 kg ha-1 with foliar sprays of Manvert Calcium and/or Manvert Magnesium led to significant increases in the content of Ca2+ in mature-green fruits and subsequently to the delay of their ripening and the prolongation of the conservation period. Combinations of N/P/K + calcium nitrate at 200 kg ha-1 + Manvert Magnesium and N/P/K + calcium nitrate at 400 kg ha-1 + Manvert Calcium + Manvert Magnesium led to significant increases in the Mg2+ content in fruits. Fruits produced by plants that received these fertilizer combinations also showed a prolongation of the duration of ripening period and that of the conservation. The longest shelf-life was obtained after simultaneous applications on soil of N/P/K and calcium nitrate at 200 kg ha-1 and foliar sprays of Manvert Calcium and Manvert Magnesium. These results indicated that calcium and magnesium could be considered as key elements of fertilizers with regard to the delay of ripening of mature-green tomato fruits and to the prolongation of the shelf-life of the red-ripe ones.
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How
to cite this article:
Jean Aghofack- Nguemezi and Valere Tatchago, 2010. Effects of Fertilizers Containing Calcium and/or Magnesium on the Growth, Development of Plants and the Quality of Tomato Fruits in the Western Highlands of Cameroon. International Journal of Agricultural Research, 5: 821-831. DOI: 10.3923/ijar.2010.821.831 URL: https://scialert.net/abstract/?doi=ijar.2010.821.831
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Received: March 25, 2010;
Accepted: June 08, 2010;
Published: June 26, 2010
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INTRODUCTION
In the course of the past decades, coffee was the main source of income for
most of farmers in the western highlands of Cameroon. But now, these farmers
have to face the problems of the drastic price reduction and the decrease in
the production of these cash crops due to the exhaustion of cultivated soils
(Kuete, 2008; Gillermou and Kamga,
2004). It therefore becomes urgent to search for alternative income generating
products. In this context, seasonal cultures such as vegetables and fruits are
gaining more and more interest.
Indeed, fruits like tomatoes can be cultivated as well during the raining season
on lands as during the dry season on marshes. Thus, farmers can harvest tomato
fruits twice a year (Uwizeyimana, 2009).
The tomato fruit is one of most widely grown fruits for consumption with more
than 122 million tons being produced worldwide in 2005 (FAOSTAT,
2005). It plays an important role in human nutrition due to its content
in flavonoids, carotenoids and vitamins (Abushita et
al., 2000; Scalbert and Williamson, 2000; Rodriguez-Amaya,
1999). β-Carotene found in tomatoes is the most potent dietary precursor
of vitamin A, the deficiency of which leads to blindness and premature death
(Mayne, 1996). Carotenoids and flavonoids, when taken
regularly and in considerable quantities, provide health benefit by decreasing
the risk of disorders (e.g., certain cancers and cardiovascular diseases) and
the incidence of age-related degeneration (Santagelo et
al., 2007; Giovannucci, 1999; Weisburger,
1998; Seddon et al., 1994).
Although, new cultivars are already known, most of the developing countries
are still facing enormous postharvest losses in quality (appearance, firmness,
flavor and nutritional value) and quantity of tomato fruits mainly due to the
inaccessibility of genetically ameliorated seeds and inadequate fruit conservation
methods (Kader, 1986, 2005).
Generally, the productivity of plants and quality of fruits can be ameliorated
either through genetic engineering or cultivation practices. In this regard,
applications of fertilizers containing calcium and/or magnesium concomitantly
with standard N/P/K-fertilizers could positively influence the growth and development
of plants as well as the ripening and ageing of fruits produced. Calcium participate
in the regulation of many processes related to plant growth and development
including biomass partitioning and fruit yield (Hao and
Papadopoulos, 2004), signal transduction (Hepler, 2005;
Navarro-Avino and Bennett, 2005; Trewavas,
2000; Malho, 2000; Raz and Flur,
1992), induction of early auxin-responsive genes (Singha
et al., 2006), resistance to pathogens (Ho and
White, 2005; Ehret et al., 2002), stress-tolerance
(Jiang et al., 2005; Jiang
and Huang, 2001), chlorophyll biosynthesis (Jiang and
Huang, 2001), pollination (Dumas and Gaude, 2006),
senescence (Hepler and Wayne, 1985; Leshem,
1991) and fruit ripening (Aghofack-Nguemezi and Dassie,
2007; Park et al., 2005; Aghofack-Nguemezi
and Yambou, 2005). While intracellular Ca2+ concentration is
submicromolar, the concentration of closely related divalent cation Mg2+
is millimolar. Despite the concentration difference that would favor Mg2+,
cellular processes display enormous selectivity for Ca2+ (Hepler,
2005). It has recently been reported that although Mn2+ and Mg2+
enhanced the nitrate uptake and growth of barley seedlings under saline conditions,
none of them was as effective as Ca2+ (Ward et
al., 2005).
Notwithstanding the positive physiological roles of Ca2+ and Mg2+ in plant growth and development the use of conventional fertilizers such as N/P/K mixtures or urea is still, to the best of our knowledge, a common agricultural practice in the western highlands of Cameroon. The present study was thus undertaken to examine the influence of different fertilizers containing Ca2+ and Mg2+ applied either by spraying on aerial plant parts or by application on the soil on the growth, crop yield and some parameters related to the quality, ripening and senescence of tomatoes. MATERIALS AND METHODS
Description of the Experimental Site
The experiment was conducted at the research farm of the Institute of Agricultural
Research for Development in Dschang from September 2006 to March 2007. Dschang
is
Table 1: |
Means of the daily duration of sunshine, of monthly pluviometry
and daily temperature during the experimental period as recorded by the
meteorological station of the Institute of Agricultural Research for the
development in Dschang |
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Table 2: |
Compositions of different fertilizer combinations |
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located in the western highlands of Cameroon at 5.26°N latitude, 10.26°E longitude and 1400 m altitude. The experimental period coincided with least rainfall and highest sunniness in the locality (Table 1).
Experimental Design and Plant Materials
Seeds of Solanum lycopersicum Mill. var. Rio Grande were sowed in
a nursery on a soil enriched with urea and hen droppings at the doses of 300
and 26.1 g m-2, respectively. Seedlings in the nursery were treated
with the fungicides Banko PlusTM (chlorothalomil + carbendazime)
and BeauchampTM (metalaxyl + mancozebe). Forty eight days after sowing,
seedlings were pricked out in a soil previously enriched with 3 t ha-1
hen droppings according to a randomized complete bloc design with seventeen
treatments (Table 2) and four replications. Urea, super phosphate
and potassium chloride were applied on the soil respectively 11, 14 and 15 days
after planting out of seedlings at doses of 95, 80 and 100 kg ha-1,
respectively. Control tomato plants received only N/P/K (9.5/8/10) whereas other
plants received N/P/K, calcium nitrate and/or liquid fertilizers containing
Ca2+ or Mg2+. Liquid fertilizers were of the trademark
Manvert (BIOVERT, Spain). The ManvertTM solutions (3 mL L-1)
were sprayed weekly on the aerial parts of tomato plants from 24 days after
pricking out onwards till the harvest of the first mature fruits. Tomato plants
were in case of need watered; they were treated with the insecticide CalllidimTM
(dimethoate) and the fungicides BankoTM and BeauchampTM.
A manual weeding was done when necessary.
Determination of the Number Days after Pricking out Required for the Flowering
of 50% of Plants and of the Percentage of Abortion of Floral Buds and Flower
The time in days passed between the pricking out of seedlings and the flowering
of 50% of plants in each plot was recorded.
Floral buds were counted from 38 days after pricking out onwards. Seven days
before the harvest of the first mature fruits, the total numbers of floral buds,
flowers and fruits in each plot were recorded. The percentage of floral bud
and flower abortion was calculated according to Tarchoun and Dridi (Tarchoun
and Didri, 2005).
Determination of the Diameter and Height
The diameter and height of plants were measured at the sixth week after
pricking out. The height was measured from the first branching upwards. The
diameter of the stem was measured at the level of collar. At harvest, the diameter
of fruits was also measured both laterally and longitudinally. The measurement
of the diameter was done using a vernier caliper.
Determination of Water Content in Fruits and Estimation of Crop Yield
Fresh tomato fruits were weighed and dried in an oven successively at 65
and 105°C for 5 day and 24 h, respectively. They were then weighed for the
determination of dry matter weight according to Chapman (1976).
The crop yield was obtained by calculating the total fresh weight of tomato
fruits harvested in all the plots that received the same treatment.
Determination of Carotenoid Content
The 0.5 g of the peel of mature green tomato fruits was ground and extracted
with a mixture of benzene/acetone/water (15/75/10, v/v). The extract was centrifugated
at 400 rpm for 30 min. The absorbance of the extract was then measured at 477
nm. The carotenoid content in peel extract of tomato fruits was calculated according
to Armenta et al. (2006).
Determination of Calcium and Magnesium Contents
Fresh tomato fruits were dried in an oven at 105°C for 24 h. One gram
of the dried samples was then calcined at 405°C for 24 h. Ten milliliter
of 1 N nitric acid solution were added to the ash and the mixture was heated
till the evaporation of half of the volume. The residue was completed to 50
mL with distilled water. This solution was further threefold diluted before
use. Ca2+ and Mg2+ contents were determined by the complexometric
method as described by Pauwels et al. (1992).
Determination of the Duration of the Ripening Period and of the Shelf-Life
Tomato fruits at mature green stage were harvested and stored at 25°C.
The number of days elapsed between the mature green stage and the red-ripe stage
for 100% of tomato fruits in each lot was recorded. The shelf-life was considered
as the length of time between the red-ripe stage and the trickling of 100% of
fruits.
Statistical Analysis
This analysis was done with the GraphPad InStat software. Group comparisons
were made using One-way Analysis of Variance (ANOVA) to see if variations among
the means were significantly greater than expected by chance. The Student-Newman-Keuls
Test was used to compare means differences, whereby a p value of <0.05 was
considered as statistically significant. The Linear Regression Test was used
to determine the correlation coefficients between some relevant parameters.
RESULTS AND DISCUSSION
Growth and Development
No significant effect of fertilizers containing calcium and/or magnesium
on stem diameter and height of tomato plants, on the percentage of abortion
of floral buds and the percentage of abortion of flowers could be observed (Table
3). Treatments of tomato plants with T6 (N/P/K application on
the soil and spray of Manvert Magnesium solution on aerial plant parts (SMMS))
or T15 (simultaneous application of N/P/K and 800 kg ha-1
calcium nitrate on the soil and SMMS) induced significant increases in the number
of days after planting out required by 50% of tomato plants to flower (Table
3). Obviously, calcium and magnesium ions could regulate the flowering duration
in tomato plants. This finding corroborated with previous results obtained from
Pharbitis nil. It has thus been reported that Ca2+ was involved
in the photoperiodic flower induction process of this species and that its endogenous
level may be a limiting factor (Friedman et al.,
1989). Furthermore, based on results of the analysis of ion distribution
in shoot apex of Pharbitis nil, Kobayashi et al.
(2006) suggested for the first time that Mg2+ plays an important
role in flower induction.
Fruit Quality and Yield
There was no significant alteration in water and total carotenoid contents
in tomato fruits produced by plants that received fertilizers containing Ca2+
and/or Mg2+ in comparison to fruits from control plants (Table
4). The calcium content in tomato fruits from plants that received fertilizers
containing Ca2+ and/or Mg2+ were generally higher than
that found in fruits produced by control plants. However, this increase trend
was not overall statistically confirmed. Thus, calcium contents in tomato fruits
produced by plants that received T12 (N/P/K + calcium nitrate at
400 kg ha-1 + SMMS), T13 (N/P/K + calcium nitrate at 400
kg ha-1 + spray of Manvert Magnesium solution on aerial plant parts
(SMCS) + SMMS) and T15 did not change significantly when compared
to fruits produced by control plants. No synergistic effect of soil application
of Ca(NO3)2 and foliar spray of Manvert Calcium on Ca2+
content in fruits could be observed. A slight negative correlation (r = -0.21)
between the dose of Ca(NO3)2 applied on the soil and the
Ca2+ content in fruits was found (Table 4). These
results demonstrated that applications of fertilizers containing Ca2+
either on the soil at doses = 400 kg ha-1 or on aerial plant parts
led to increases in the Ca2+ concentration in fruits.
Table 3: |
Effects of fertilizers containing calcium and/or magnesium
on stem diameter and height of tomato plants, on the number of days after
planting out required for the flowering of 50% of plants (D50F), the percentage
of abortion of floral buds (PAFB) and the percentage of abortion of flowers
(PAF) |
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Values are Mean±SD (n = 4). d.a.p.:days after pricking
out, *Values are statistically different from T0 at p<0.05 |
Table 4: |
Effects of fertilizers containing calcium and/or magnesium
on contents of water, carotenoids, calcium and magnesium ions in tomato
fruits, and the correlation between the dose of Ca(NO3)2
applied on the soil and the Ca2+ content in fruits |
 |
Values are Mean±SD (n = 4). f.w.: fresh weight, *Values
are statistically different from T0 at p<0.05 |
In a similar study, foliar applications of calcium salts were also shown to
increase Ca2+ levels in tomato fruits (Garcia
et al., 1995). It is well known that mineral ions absorbed by roots
are transported in long distances in the xylem concurrently with water (Opik
et al., 2005). Most plants can also absorb mineral nutrient applied
to their leaves as sprays and this mode of uptake is most effective when the
nutrient solution remains on the leaf as a thin film (Taiz
and Zeiger, 2006). As indicated by the negative correlation between the
dose of Ca(NO3)2 used and the Ca2+ content
in fruits, the former was in inverse ratio to the latter. Thus, tomato plants
could no longer absorb calcium ions or transport them in growing fruits when
high doses of Ca(NO3)2 were applied on the soil. The mechanisms
whereby Ca2+ or NO3- could at high concentration inhibit
the absorption of the former ion by roots of tomato plants are not known. Nevertheless,
Ca2+ has been shown to be very effective in the enhancement of the
uptake of nitrate by barley seedlings under saline conditions. At 800 kg ha-1
of Ca(NO3)2 Ca2+ might thus, to the detriment
of its own absorption, enhance the uptake of NO3- by tomato plants.
The mechanisms whereby liquid fertilizers containing Mg2+ triggered
an increase in Ca2+ content in tomato fruits are not yet known. An
increase in the level of Ca2+ in banana fruits after treatment by
dipping in MgSO4 solution has also previously been observed (Aghofack-Nguemezi
and Dassie, 2007).
In most of cases where tomato plants received fertilizers containing Mg2+,
magnesium ion contents in fruits produced by these plants were significantly
higher than those observed in the extracts of fruits from control plants (Table
5). In this context, when compared to the control, higher contents in Mg2+
ions were found in fruits produced by tomato plants that received T9 (N/P/K
+ calcium nitrate at 200 kg ha-1 + SMMS), T12 (N/P/K +
calcium nitrate at 400 kg ha-1 + SMMS), T13 (N/P/K + calcium
nitrate at 400 kg ha-1 + SMCS + SMMS) or T15 (N/P/K +
calcium nitrate at 800 kg ha-1 + SMMS). However, the content of Mg2+
also significantly increased in tomato fruits produced by plants that received
only fertilizers containing Ca2+, namely T1 (N/P/K + calcium
nitrate at 200 kg ha-1) or T5 (N/P/K + SMCS).
Table 5: |
Effects of fertilizers containing calcium and/or magnesium
on the yield, diameter, duration of the ripening period (DRP) and that of
shelf-life (DSL) of tomato fruits, and correlations between ion contents
and DRP or DSL |
 |
Values are Mean±SD (n = 4), d.a.h.: Days after harvesting,
d.a.r.: Days after ripeness, *Values are statistically different from T0
at p<0.05 |
These results indicated that as it generally the case for most of mineral
nutrients (Taiz and Zeiger, 2006; Opik
et al., 2005), Mg2+ could be absorbed through the leaves
of plants and then transported into developing tomato fruits. The mechanisms
whereby fertilizers containing Ca2+ triggered an increase in Mg2+
content in tomato fruits are not yet known.
No significant difference could be observed between the total yield and the
diameter of tomato fruits produced by plants which received fertilizers containing
Ca2+ and/or Mg2+ and that of fruits produced by control
plants (Table 5). In contradiction to these results, Hao
and Papadopoulos (2003) reported that Ca2+ at 300 mg L-1
and Mg2+ at 20 mg L-1 nutrient solutions led, respectively
to increase and decrease in tomato fruit yield. In a ferrallitic sandy loam
soil, tomato fruit yield was significantly increased by liming with CaO at a
pH of 5.2 while at a pH of 5.7 and above liming had little effects; under those
conditions applied Mg2+ had no effect on fruit yield (Asiegbu
and Uzo, 1983). Suplementary calcium enhanced fruit yield in strawberry
cultivars grown at high NaCl salinity (Kaya et al.,
2002).
Ripening and Senescence of Fruits
The number of days elapsed between the mature green stage and the red-ripe
stage of fruit ripening was greatly affected by treatments of tomato plants
in the farm with fertilizers containing Ca2+ and/or Mg2+
(Table 5). Nearly all these fertilizers combinations induced
a prolongation of the duration of the ripening period of tomato fruits. Apart
from tomato fruits produced by plants that received T3 (N/P/K + calcium
nitrate at 800 kg ha-1), T14 (N/P/K + calcium nitrate
at 800 kg ha-1 + SMCS), T15 and T16 (N/P/K + calcium nitrate
at 800 kg ha-1 + SMCS + SMMS), fruits produced by plant that received
all other fertilizers containing Ca2+ and/or Mg2+ had
a longer duration of ripening period than those from control plants. The length
of time between the red-ripe stage and the trickling of 100% of tomato fruits
(the shelf-life) was mostly significantly prolonged by the applications of T8
(N/P/K + calcium nitrate at 200 kg ha-1 + SMCS), T9 (N/P/K
+ calcium nitrate at 200 kg ha-1 + SMMS), T10 (N/P/K +
calcium nitrate at 200 kg ha-1 + SMCS + SMMS), T11 (N/P/K
+ calcium nitrate at 400 kg ha-1 + SMCS), T12 (N/P/K +
calcium nitrate at 400 kg ha-1 + SMMS) and T13.
The positive correlation between Ca2+ content and the duration of ripening period of tomato fruits was more pronounced (r = 0.68) than that found between the magnesium content and this period (r = 0.05). The positive correlation between the Mg2+ content and the duration of the shelf-life was more marked (r = 0.1) than the correlation found between Ca2+ content and the duration of the shelf-life (r = 0.05) (Table 5).
Obviously, calcium nitrate at doses ≤400 kg ha-1 or foliar spray
of Manvert Calcium induced increases in Ca2+ content and subsequently
a delay of the ripening process of tomato fruits. When soil application of Ca(NO3)2
was associated to foliar spray of Manvert Calcium and/or Manvert Magnesium,
both the ripening of mature green tomato fruits and the trickling of red ripe
fruits were subsequently retarded. This means that even if no synergistic effect
of soil application of Ca(NO3)2 and foliar spray of Manvert
Calcium on Ca2+ content in fruits was observed, the combination of
both types of fertilization could lead to an increase in the duration of ripening
period as well as a delay of the onset of senescence of red-ripe tomato fruits.
It has previously been demonstrated that fruit from tomato plants expressing
Arabidopsis Thaliana H+/cation exchangers have more Ca2+ and prolonged
shelf life when compared to controls (Park et al.,
2005). Postharvest calcium applications on loquat (Akhtar
et al., 2010) and peach fruits (Manganarisa et
al., 2007) retained their firmness, thereby delaying the ripening process.
It is well established that calcium ion can delay the ripening and senescence
by stabilizing cell membrane and increasing the rigidification of monolayers.
Moreover, the Ca2+-mediated cross-linking may occur as bridging between
phospholipids, between phospholipids and corboxyltails of embedded membrane
proteins and between phospholipids and cytoskeletal. Magnesium ion affects the
electrostatic cross-linking between membranes components to a lesser extend
than calcium ion (Leshem, 1991). There are also several
calcium-pectate interactions which make the cell wall firmer (Carpita
and McCann, 2000). It is not yet known why combination of application on
the soil and foliar spray of fertilizers containing Ca2+ (e.g., T8
and T11) induced a retardation of both the ripening and the senescence
of tomato fruits while soil application of Ca(NO3)2 (e.g.,
T1 and T2) or foliar spray of Manvert Calcium (e.g., T5)
alone led only to the increase in duration of the ripening period. The fact
that combinations of soil application of Ca(NO3)2 with
foliar spray of Manvert Magnesium (e.g., T9) also led to increases
in both the duration of ripening period and that of shelf-life could be explained
by the additional effects of Mg2+. Indeed, due to their divalent
character, Mg2+ and Mn2+ can with lesser effectiveness
play physiological roles ascribed to Ca2+ (Ward
et al., 2005; Leshem, 1991) or quite different
roles (Fanasca et al., 2006). The appropriate
Mg2+ concentration in the nutrient solution required for the production
of winter greenhouse tomato crop was lower than that of Ca2+ (Hao
and Papadopoulos, 2004). High proportion of Ca2+ as related to
K/Ca/Mg ratio in the nutrient solution was reported to improve fruit yield and
reduce the incidence of blossom-end rot whereas high proportion of Mg2+
rather resulted in the increase of total antioxidant activity in tomato fruits
(Fanasca et al., 2006). The retarding effect
of foliar spray of Manvert Magnesium alone on the ripening process could be
related to increases in Mg2+ and Ca2+ contents in tomato
fruits.
CONCLUSION The most striking features of field application of fertilizers containing Ca2+ and/or Mg2+ were increases in the duration of flowering of plants and in calcium contents in the extracts and the subsequent prolongation of the duration of mature green stage of tomato fruits. Combinations of soil application of Ca(NO3)2 at doses ≤400 kg ha-1 with foliar spray of Manvert Calcium and/or Manvert Magnesium solutions were the most efficient in inducing the delay of ripening and senescence of tomato fruits. Calcium ion seemed to be a key player in the modulation of the ripening process while Mg2+ could rather play an important role in the regulation of the senescence of tomato fruits.
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