Tomato is one of the most popular and widely grown vegetable crops in the world.
It belongs to the genus Lycopersicon which is grown for its edible fruit
(Jones, 1989). The fruit contains high levels of vitamin A, B, C, E and nicotinic
acid and is therefore an important source of vitamins. On the average, the fruit
contains 8% protein 34% minerals (mainly K+ Ca+ and P)
48% total soluble sugars, 9% citric acid and 0.5% vitamin. Tomato has a higher
acreage than any vegetable crop in the world and it requires a high water potential
for both, optimal vegetative and reproductive development (Jones, 1989).
The crop tolerates fairly acid soil and liming is unnecessary unless the soil
pH is below 5. Well drained sandy loam is preferred by the crop. No horticultural
crop has received more attention and detailed study than tomato (Lycopersicon
esculentum). Water deficit decreases tomato growth, yield and quality (Byari
and Al-Sayed, 1999) therefore, proper water management is vital for sustainable
The use of irrigation technology is not widespread but considered to be of
great importance in view of the seasonal and incidental occurrence of drought.
The main consumptive water uses in Ghana are for domestic, industrial and irrigation
purposes. According to SRID (2002), in 2000 about 652
million m3 were withdrawn for irrigation (66%), 235 million m3
for domestic purposes (24%) and 95 million m3 for industry (10%),
giving a total water withdrawal of 982 million m3. Sprinkler irrigation
is a versatile means of applying water to any crop, soil and topographic condition.
It is popular because surface ditches and prior land preparation are not necessary
and because pipes are easily transported and provide no obstruction to farm
operation when irrigation is not needed. Sprinkling is suitable for sandy soils
or any other soil and topographic condition where surface irrigation may be
inefficient or expensive or where erosion may be particularly hazardous.
According to Ismail and Ozawa (2009), in the arid and
semi arid as well as tropical regions, water shortage is a normal phenomenon
and seriously limits the agricultural potential. Therefore, under irrigation
or rain-fed conditions, it is important for the available water to be used in
the most efficient way. Proper irrigation interval can play a major role in
increasing the water use efficiency and the productivity by applying the required
amount of water when it is needed. On the other hand, the poor irrigation interval
can lead to the development of crop water deficit and result in a reduced yield
due to water and nutrient deficiency.
Early in the season when plants are small, it is beneficial to encourage the
roots to explore as much of the soil profile as possible. This maximizes nutrient
uptake and stress tolerance later in the season (Ismail
and Ozawa, 2009).
Jamiez et al. (2000) stated that irrigation
frequencies or different irrigation frequencies or different irrigation intervals
have beneficial effects on water balance fruit quality and fruit production.
Irrigation also plays important role in maintaining sustainable growth of every
crop especially it reduces the wilting which causes 60-80% crop loss but sometimes
excessive water or frequent flooding for longer periods of time affect the yield
of the crop (Gajera et al., 1998).
In this study two sprinkler heads were evaluated and one of them was used to study the sprinkler irrigation intervals on the growth and yield of tomatoes. It represents an effort to quantify the effect of water application on the growth and yield of tomatoes.
MATERIALS AND METHODS
The Study Area
The study was carried out at the University of Cape Coast (UCC) Teaching
and Research Farm from 2006 to 2007. It falls within the Coastal Savanna zone
of Ghana between latitude 050 03N and 050 15N,
longitude 01° 13 W and 01° 13 W. The area is characterized by
a mean annual rainfall, which varies from about 750 to 1200 mm. The area has
two seasons, that is, dry season and wet season. The wet season can also be
divided into two, the minor one and the major one. The major season is from
May to July with a peak in June and the minor season is from September to November
with a peak in October. The dry season is from December to February (Ayittah,
Temperatures are uniformly high throughout the year with an annual average minimum of 30°C. Diurnal variations in temperature are greatest in February and March.
Determination of Etc
The mean daily Eto for the study area was computed using Modified Penman
method (Sam-Amoah, 1996). The Etc was then derived from
the formulae below:
||Reference evapotranspiration (Modified Penman Method)
Total volume of water for the growing period was 31.48 m3.The same amount was used for each of the treatments.
Determination of Sprinkler Head Performance
A rubber hose, stand pipe, flow meter with pressure gauge and a sprinkler
head were connected. Forty catch cans were arranged on a 8x8 m field to establish
a grid pattern of 2x0.8 m. Two sprinklers were used in the evaluation. The LEGO
model sprinkler (Tarjuelo et al., 1999) was used
for the first three runs and AGROS model sprinkler (Tarjuelo
et al., 1999) for the last three runs. The cans were initially turned
upside down in their positions in order to test run the sprinkler and the sprinkling
pattern was observed. The cans were then set up correctly and the sprinklers
were turned on. Each run lasted for 1 h and the quantity of water collected
in each catch can was measured using the measuring cylinder. This was used to
determine the depth of catch. The depth of water in the soil was determined
by bringing up soil with the soil auger and measuring the depth of wetness with
a ruler. Soil samples were taken to the laboratory to determine the moisture
content before and after irrigation. Flow rate, operating pressure before and
after irrigation were measured with the flow meter and pressure gauge, respectively.
Nozzle diameters were measured with a caliper.
Sprinkler Head Performance Measures
The sprinkler head performance measures determined included:
||Distribution uniformity: Is usually defined as a ratio
of the smallest accumulated depths in the distribution to the average depth
of the whole distribution. It was determined according to the
Irrigation Association (2005) methodology
||Uniformity coefficient: The coefficient is computed from field
observation of the depths of water caught in open cans placed at regular
intervals within a sprinkled area (ASAE, 2001)
||Scheduling Coefficient (SC): Determines how big the critical dry
area is and the irrigation time required to alleviate this dry area. It
was determined according to Wilson and Zoldoske (1997)
||Precipitation rate: It is usually expressed as the ratio of average
depth readings to test time. Wilson and Zoldoske (1997)
method was adopted for the computation
||Deep Percolation Ratio (DPR): This refers to the loss of water
below the root zone, that is, beyond plant reach. The method used was according
to Senzanje et al. (2000)
Experimental Design for Sprinkler Interval on Tomato Growth
A Randomized Complete Block Design (RCBD) was used. There were 16 plots
and each plot size was 8x8 m. There were eight rows with plant spacing of 1xl
m and plant population per plot was 64.
The Wosowoso variety of tomato was used. It was obtained from a certified
seed company in Cape Coast.
Nursing and Planting
The seeds were nursed and planting was done a month after nursing. Growing
duration was 90 days.
There were four treatments with four replications. The treatments were:
daily application of water (T1), every third day (T2),
every fifth day (T3) and every seventh day (T4). The treatments
were imposed two weeks after transplanting.
Soil water contents were measured before and after irrigation in the laboratory
by the gravimetric method.
Data collected on plant growth included: plant height, number of flowers,
fruit weight, fruit length and number of fruits and stem diameter. There were
five sampling times and measurements were taken on five plants.
The plants were staked and fertilizer application to all treatment was done.
Plants were kept free of weed by repeated hand weeding and insects, pest and
diseases were controlled with fungicide and insecticide.
Harvesting and Fruit Sampling
The fruits were hand-harvested 90 days after transplanting. Fruit dimensions
were determined using a venier caliper.
Method of Analysis
Analysis of Variance (ANOVA) was conducted on the data using MSTATC statistical
package. The means were compared by applying Least Significant Difference (LSD)
at test 5% probability level.
RESULTS AND DISCUSSION
From Table 1, sprinkler model AGROS had the highest uniformity
coefficient (99.20), distribution uniformity (57.67), percolation ratio (0.61),
depth of water applied (5.93) but the lowest scheduling coefficient (1.87) as
compared to LEGO.
From Table 2, both sprinkler models at the same operating pressure (0.18) had the same radius of throw (0.53).
||Field test result for the uniformity coefficient, distribution
uniformity, percolation ratio, scheduling coefficient and depth of water
|| Field test result for operating pressure and radius of throw
|| Irrigation interval and fruit yield
|Means followed by the same letter within the column are not
significantly different at 5 % level of probability
|| Irrigation interval, plant growth and fruit dimensions
|Means followed by the same letter within the column are not
significantly different at 5 % level of probability
Means followed by the same letter are not significantly different at 5%
level of probability.
Fruit yield over here is the mean mass of all harvested fruit. From Table 3, T1 (45.00) had the highest mean fruit yield followed by T2 (27.50), T3 (25.00) and T4 (22.50) in that order. There were significant differences between T1 (45.00) and the other treatments. There were no significant differences between T2 (27.50) and T3 (25.00). There was a significant difference between T2 (27.50) and T4 (22.50) but no significant difference between T3 (27.50) and T4 (22.50). Irrigation interval significantly affected the fruit yield.
Tomato Growth and Dimensions
From Table 4, T1 (2.85) had the highest stem
diameter followed by T4 (2.78), T3 (2.73) and T2
(2.69). There were no significant differences between T1 (2.85) and T4 (2.78).
There were differences between T1 (2.85) and T2 (2.69),
T3 (2.73). Irrigation interval significantly affected the fruit lengths.
The T1 (2.85) had the highest fruit length followed by T2
(2.69), T3 (2.73) and T4 (2.78).
From Fig. 1, T1 had the highest flower number of 2.781 followed by T3 (2.776), T2 (2.627) and T4 (2.301). The lowest flower number was registered by T4 of 2.301. It was observed that flower number increases as irrigation interval decreases with the exception of T3 (2.776) which resulted in increased flower number.
The results for flower number for all the treatments were statistically analysed and there were no significant differences among the irrigation intervals.
Deep Percolation Ratio
Comparing the deep percolation ratio for the two sprinkler heads, the AGROS
had the highest. The differences could be due to the sprinkler model or the
nozzle diameter (Senzanje et al., 2000) and subsequently
the impact of droplets on the soil surface.
Christiansens Uniformity Coefficient and Distribution Uniformity
The main difference between Coefficient of Uniformity (CU) and Distribution
Uniformity (DU) is that, CU is a measure of the absolute difference from the
mean divided by the mean while DU is the ratio of the smallest accumulated depths
in the distribution to the average depths of the whole distribution. From the
experiment, CU values were very high and this can be attributed to the definition
of CU and DU. It was in agreement with Wilson and Zoldoske
(1997) who did a research on sprinkler system and their findings were DU
value for rotor system was 70% or higher and 50% or above for spray-head system.
|| Flower number and irrigation interval
It should be emphasised that the results obtained during the study were under
a particular field and climatic conditions at the time of the test. Since wind
has a large impact on the distribution of irrigation water, a test conducted
in lesser wind conditions may have shown better results for distribution uniformity.
Irrigation Interval, Growth and Yield Parameters
In this present experiment irrigation interval had an influence on fruit
yield. This is in agreement with Byari and A1-Sayed (1999)
who found a reduction in fruit mean mass due to increased irrigation intervals
(1, 2, 3, 5) and their findings were explained by the fact that plants were
under water stress because irrigation interval has a major influence on the
soil moisture profile. Irrigation interval in this work had a significant effect
on yield indicators. Again, Pulupol et al. (1996)
and Byari and Al-Sayed (1999) ascribed poor plant yield
to plants grown under water stress or increased time of irrigation intervals
between successive irrigation.
These differences in irrigation interval may be enough to cause water to be
a limiting factor for yield of tomatoes. Several researchers have reported that
frequency of irrigation and quantity of nutrient in solution provided to plants
affect yield (May and Gonzales, 1994; Peet
and Willits, 1995; Singandhupe et al., 2002).
Data from this study revealed that plant height mean for T1 was
greater than T2 and T3 and this in agreement with
Olalla and Valero (1994) who reported that plant height increased with decrease
of irrigation interval and vice versa.
Stem Diameter and Fruit Length
Plants that were irrigated every day resulted in significantly larger stem
diameter and fruit length as compared to irrigation interval of every third,
fifth and seventh day. This was in agreement with Byari
and Al-Sayed (1999) who found a reduction in stem diameter and fruit length
due to increased time of irrigation intervals between successive irrigation.
He explained his findings by the fact that plants were under water stress. However,
it was clear that tomatoes reacted, positively to the frequency of application
of irrigation water.
Candido et al. (1999) reported that drought
reduces fruit growth and size and excessive fluctuations in soil moisture content
may induce physiological disorders such as blossom end rot and this was in agreement
with the present study. Ponce et al. (1996) reported
plants under any kind of stressed conditions tends to shortened their life span
and try to complete their life cycle in hasten which causes the minimum flowering
and fruiting of plants.
Sprinkler head AGROS performed better than LEGO. Irrigation interval of one day, using the same amount of irrigation water, had a significantly higher plant height, stem diameter, fruit mass, fruit length, fruit number, flower number than intervals of 3, 5 and 7 days.
Author wish to express my sincere thanks and appreciation to Dr. L.K. Sam-Amoah and Rev. Dr. J.D. Owusu-Sekyere for their encouragement, tireless supervision, valuable advice, assistance and patience throughout this research.