By Alhassan, ALH; Kyei-Baffour, N; Agyare, WA; Amponsah, W (2023). Greener Journal of Science, Engineering and Technological Research, 12(1): 34-48.
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Greener Journal of Science, Engineering and Technological Research
ISSN: 2276-7835
Vol. 12(1), pp. 34-48, 2023
Copyright ©2023, the copyright of this article is retained by the author(s)
https://gjournals.org/GJSETR
Department of Water and Environmental Engineering, Faculty of Engineering, Tamale Technical University, Tamale, Ghana.
Department of Agricultural and Biosystems Engineering. College of Engineering, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana.
Type: Research
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In this study, field tests were performed for sprinkler irrigation system. The results indicate that the average Christiansen’s coefficient of uniformity (CU) for the sprinkler for up-stream of the plot was the highest (95.3%) followed by the sprinkler mid-stream (95.1%) and the least was the sprinkler down-stream (75.8%) of the plot. The sprinkler distribution uniformity for the up-stream of the plot was highest (99%) whiles the mid-stream was next with (92.7%) and down-stream was the least with (67.6%). The sprinkler had average discharge is 1.5 m3/ h. The crop water productivity of Ayoyo (Corchorus olitorius) grown under sprinkler irrigation was determined for the up-stream and the mid-stream with both locations having the same value of 0.50 kg/m3 whilst the least was obtained for the down-stream with a value of 0.44 kg/m3. It was recommended that; further elaborate studies be conducted on the subject by considering the effects of different pressures on the performance of sprinkler irrigation system.
Published: 07/11/2023
Alhassan, Abdul Latif Husein
E-mail: joelatey13@gmail.com
Keywords: Sprinkler irrigation, Ayoyo (Corchorus olitorius), Agriculture, crop production, Catch-Can, water use efficiency
Agriculture is a significant consumer of global water resources, accounting for approximately 70-80% of usage (Crovella et al., 2022). However, with water availability diminishing, it has become imperative to enhance water management practices within the agricultural sector. Escalating competition for water resources among agricultural, industrial, and domestic sectors underscores the need for ongoing advancements in water-efficient techniques for crop production. The imperative of efficient water utilization is growing, and alternative irrigation methods such as drip and sprinkler systems hold the potential to substantially optimize the use of scarce water resources in crop cultivation.
Hernandez et al., 2020). Crops like Okra (Abelmoschus esculentus) and Ayoyo (Corchorus olitorius) are particularly sensitive to water stress, especially during flowering and pollination stages. Given their highwater requirements and vulnerability to water stress, especially in light-textured soils, implementing limited or deficit irrigation without incurring yield losses is challenging. Thus, ensuring a consistent and uniform water supply is paramount to enhancing Ayoyo yields. Novel approaches to augment water availability and efficiency are imperative. Embracing irrigation technologies like drip and sprinkler systems, designed to deliver water at a consistent rate, can serve as effective tools for rationalizing and optimizing limited water resources (Smith et al., 2020).
Rainfall is the single most important factor affecting crop production (Rukuni & Carl 2004). The smallholder farming sector in various regions faces a decline in Ayoyo (Corchorus olitorius) yields, primarily attributed to erratic rainfall patterns, the non-uniform water requirements during different growth stages, the sensitivity of these crops to water stress, and the competition for water resources across various sectors due to climate change (Coelho & Or, 1999; Assouline, 2002; Wang et al., 2006).
Sprinkler irrigation is a modern method of irrigation where water is distributed over the field in the form of small droplets, resembling rain, through sprinkler heads or nozzles (Li et al., 2012). This method allows for precise and uniform application of water, reducing water loss due to evaporation and runoff, and increasing water use efficiency (FAO, 2012).
Sprinkler irrigation systems can be classified into different types based on the type of sprinkler head used, such as impact sprinklers, rotary sprinklers, and spray sprinklers (Li et al., 2012). Impact sprinklers are widely used in agricultural fields and operate by using the force of water to drive a rotating arm that distributes water in a circular pattern. Rotary sprinklers operate by rotating a series of arms with nozzles that spray water in a specific pattern, such as full circle or part circle. Spray sprinklers, on the other hand, operate by spraying water in a fine mist or spray pattern, and are commonly used in smaller areas or for landscape irrigation.
Sprinkler irrigation is suitable for a wide range of crops, including field crops, vegetables, orchards, and lawns (FAO, 2012). It is particularly useful in areas with irregular or sloping terrain, where other methods of irrigation may be challenging to implement (Li et al., 2012). Sprinkler irrigation can also be used to apply fertilizers and pesticides, which can be dissolved in the irrigation water and distributed evenly across the field, reducing the need for separate applications (FAO, 2012). Several studies have highlighted the benefits of sprinkler irrigation in improving water use efficiency and crop productivity. For example, research conducted in Northern Ghana showed that sprinkler irrigation improved crop yields and water use efficiency for crops such as maize and tomatoes compared to traditional flood irrigation methods (Abdul-Rahaman et al., 2015). Another study in India demonstrated that sprinkler irrigation reduced water consumption and improved crop yields for crops such as wheat, cotton, and groundnut, compared to flood irrigation (Ghosh et al., 2013). However, sprinkler irrigation also has some limitations. It requires higher initial investment compared to other irrigation methods, such as surface irrigation, due to the cost of equipment and installation (FAO, 2012). It also requires regular maintenance to ensure proper functioning of sprinkler heads and nozzles, and can be affected by wind drift and evaporation losses (Li et al., 2012). Proper design, installation, and management of sprinkler irrigation systems, including the use of modern technologies such as pressure regulators, weather sensors, and automated control, can help overcome these limitations and optimize water use efficiency and crop productivity (Abdul-Rahaman et al., 2015; Ghosh et al., 2013). In recent years, there has been increasing interest in the use of sprinkler irrigation as a viable option for farmers in peri-urban areas of Northern Ghana, where water resources may be limited and competition for water may be high (Abdul-Rahaman et al., 2015). The use of wastewater as a potential water source for sprinkler irrigation systems is also being explored as a sustainable option for agricultural irrigation in water-scarce regions (FAO, 2012). Further research and innovation in sprinkler irrigation are expected to contribute to the adoption of more efficient and sustainable irrigation practices for farmers in Northern Ghana and other similar regions. Figure 1 below depicts sprinkler irrigation.
FIGURE 1 Sprinkler Irrigation (Bustan, 2008)
Uniformity of water distribution is a critical factor in the performance of sprinkler irrigation systems. Several factors can affect the uniformity of water distribution in a sprinkler irrigation system. These factors need to be carefully considered and managed to ensure optimal performance of the system. Some of the main factors affecting uniformity in sprinkler irrigation are:
1. Sprinkler Nozzle Selection: The selection of the appropriate nozzle for a sprinkler system is crucial in achieving uniform water distribution. Nozzle size, shape, and type can significantly affect the distribution pattern and precipitation rate of the sprinkler. It is important to select nozzles that are matched to the specific application, including the desired radius of throw, spacing between sprinklers, and the type of crops being irrigated (Hunt et al., 2015). Proper nozzle selection can help achieve uniform water distribution and prevent over-watering or under-watering of plants.
2. Operating Pressure: The operating pressure of a sprinkler system can greatly impact the uniformity of water distribution. Too high or too low pressure can result in uneven distribution patterns, with some areas receiving too much water and others not enough. Properly managing the operating pressure within the recommended range for the specific sprinkler type and nozzle size is essential to ensure uniform water distribution (Pereira et al., 2013).
3. Wind Speed: Wind can have a significant impact on the uniformity of water distribution in sprinkler irrigation systems. Wind can cause water droplets to drift or be carried away from the intended target area, resulting in uneven water distribution. Wind can also cause changes in the distribution pattern and precipitation rate of the sprinkler, affecting uniformity. It is important to consider wind speed and direction when designing and operating a sprinkler irrigation system to minimize the impact of wind on uniformity (Li et al., 2016).
4. Sprinkler Spacing and Overlap: The spacing between sprinklers and the overlap of their spray patterns can affect the uniformity of water distribution. If the sprinklers are spaced too far apart or do not overlap adequately, there may be gaps or overlapping areas with excess water or no water. Proper spacing and overlap of sprinklers should be considered in the design and layout of the system to achieve uniform water distribution across the entire irrigated area (Burt et al., 2015).
5. Sprinkler Height and Angle: The height and angle of the sprinkler can also affect the uniformity of water distribution. Sprinklers that are too high or too low can result in uneven water distribution, with over-watering or under-watering of certain areas. The angle of the sprinkler can also impact the direction and pattern of water distribution. Proper adjustment of the sprinkler height and angle can help achieve uniform water distribution across the entire irrigated area (Jensen et al., 2010).
Several factors can affect the uniformity of water distribution in a sprinkler irrigation system, including nozzle selection, operating pressure, wind speed, sprinkler spacing and overlap, and sprinkler height and angle. Proper management and consideration of these factors are essential to ensure optimal performance and uniformity in sprinkler irrigation systems
Water use efficiency (WUE) is a critical performance indicator in irrigation systems, including sprinkler irrigation. It is a measure of how effectively water is utilized for plant growth and crop production. WUE is typically calculated by dividing the amount of water used by the crop (in units of water volume, such as cubic meters or liters) by the amount of crop yield (in units of crop production, such as kilograms or tons).
The formula for calculating water use efficiency (WUE) is as follows:
WUE = Crop yield / Water applied………………. (1.0)
Where: Crop yield: the total amount of crop produced (in units of crop production, such as kilograms or tons)
Water applied: the total amount of water applied to the crop (in units of water volume, such as cubic meters or liters)
Water use efficiency is an important parameter in evaluating the performance of sprinkler irrigation systems, as it provides an indication of how effectively water is used in crop production. A higher WUE indicates that less water is required to produce a certain amount of crop yield, which is desirable for sustainable and efficient irrigation practices.
It is important to note that WUE can be influenced by various factors, including crop type, weather conditions, soil characteristics, irrigation management practices, and system design. Properly managing and optimizing these factors can help improve the water use efficiency of a sprinkler irrigation system and maximize crop production while minimizing water consumption. Jensen, M. E., Haise, H. R., & Bernardi, A. (2010). Evapotranspiration and irrigation water requirements. ASCE Press. Recent studies have shown that the measure of water use efficiency (WUE) in irrigation systems should be based on the transpiration efficiency (TE) of crops rather than just the ratio of yield to total water use (Ye/ET). The TE approach considers the biomass production in relation to the water that is actually used by the plant, and is affected by factors such as the photosynthetic mechanism of the crop and the vapor pressure deficit (Van Keulen, 2011; Lof, 2012). The TE approach has been found to provide a more accurate indication of the efficiency of water use in crop production.
Soil surface modifications, such as tillage and the retention of surface residue, can also affect WUE by reducing soil evaporation (E) and increasing crop transpiration (T) (Hatfield et al., 2011). Recent studies have explored the potential advantages of using subsurface drip irrigation (SDI) systems, which have been found to reduce soil evaporation (Solomon, 2010).
Therefore, in assessing the efficiency of sprinkler irrigation systems, it is important to consider the transpiration efficiency of crops and the impact of soil surface modifications on reducing soil evaporation and increasing crop transpiration. These factors can significantly affect the overall water use efficiency of the irrigation system, and can inform decisions on the appropriate irrigation system design and management practices for sustainable and efficient crop production.
Figure 2. Map of Sagnarigu Municipal Area (GSS, 2021)
The Sagnarigu Municipality has 79 communities, comprising of 20 urban, 6 peri-urban, and 53 rural areas. The district covers a total land size of 200.4km2 and shares boundaries with the Savelugu-Nanton Municipality to the north, Tamale Metropolis to the south and east, Talon District to the west and Kumbungu District to the north-west. Geographically, the district lies between latitudes 90 16’ and 9o34’ North and longitudes 00 36’ and 00 57’
The sprinkler system plot or field were also divided into three (3), that is: the up-stream, mid-stream and down-stream. Data were collected for all the three (3) streams and analysed using the various equations of uniformity test. This data was used to evaluate the performance of the sprinkler system. They were thirty-six (36) catch-can arranged in each stream. Field data were collected two times in a day, that is; morning (from 7am-7:30am) and evening (from 4pm-4:30pm). The peak crop water requirement of Ayoyo (Corchorus olitorius) is 7.5mm/day with a discharge of 1.5 m3/h
2.2.1 Discharge Measurement
The volumetric discharge was measured with the aid of a flexible water hose and a 17-litre bucket. The time taken to fill the bucket was recorded and used to determine discharge using Equation 2:
………………………………………………….[2.0]
Where
v is the volume of water collected in litres(l)
t is the container filter time(s) and
q is the spring flow discharge in l/s
2.2.2 Crop Water Productivity
The assessment of crop water productivity (WP) involves a fundamental metric, typically defined as the marketable yield divided by the total crop evapotranspiration (Etc). However, it’s worth noting that from an economic perspective, as well as from the viewpoint of farmers, the focus often centers on maximizing yield while optimizing the use of irrigation water resources (Nagaz et al., 2013). This pragmatic perspective leads to the calculation of WP as the yield in kilograms per hectare divided by the total volume of irrigation water in cubic meters per hectare, encompassing the period from transplanting to harvest. In the case of Okra cultivation, which employed drip irrigation, the fresh pod yield from each stream was meticulously determined once the green pods reached maturity. This involved a systematic harvesting routine, with pods collected every two days throughout the harvest period. To quantify the yield accurately, an electronic scale was employed to weigh the harvested pods for each respective stream. Conversely, for the ‘Ayoyo’ crop cultivated using sprinkler irrigation, the focus was on assessing the fresh leaf yields when the leaves reached maturity. Similar to the Okra, electronic scales played a crucial role in precisely weighing the harvested leaves for each respective stream. This is illustrated in the Equation 3:
Where; WP=crop water productivity in (kg/m3)
Y= yield in (kg/ha) and TIW= total irrigation water in (m3/ha)
Data recorded for both the drip and sprinkler irrigation were used to determine the distribution patterns, discharge efficiencies and uniformity parameters presented in the succeeding sections.
Discharge efficiency, Ed, is the relationship between the water collected by the catch-cans and water discharged by the sprinkler and the drip systems. The difference between the actual discharge and the water collected is attributed to evaporation and drift losses during the irrigation event, mainly as a result of environmental conditions (Montero et al., 2002):
The mean application rate (mm/h),
Where q in mm3/h; sm and slin m
…………………… [6]
Where, is the mean water depth collected in all catch-cans, n is the number of cans and xiis the water depth collected by a catch-can, I (Christiansen, 1942 as in Keller and Bliesner, 1990).
The pattern efficiency (PE), is the ratio of the mean of 25% of the samples nearest to the lowest, M25, to the mean of all the measured samples. This parameter is also known as the distribution uniformity (DU):
Three widely-used parameters for measuring emitter discharge uniformity are: Flow variation, (Qvar), Uniformity coefficient (UC) and coefficient of variation (CV).
Emitter flow variation qvar was calculated using the equation:
Flow variation,
……………………… [8]
Where: Qmax = maximum emitter (drip hole) flow rate
Qmin = minimum emitter (drip hole) flow rate
Uniformity coefficient, UC, as defined by Christiansen (1942) and modified to reflect a percentage, was calculated using the equation:
Uniformity coefficient,
………. [9]
Where: q = discharge in (m3/s)
Mean of discharge (q) in (m3/s)
n = number of (drip holes) emitters evaluated.
…………………………………. [10]
Where: s = standard deviation of (drip flow) emitter flow rate
Mean of discharge (m3/s)
For the purpose of conducting the irrigation test, standardized cans with identical dimensions, measuring 84mm in diameter and 130mm in height, were meticulously selected. It is noteworthy that the guidance of irrigation experts regarding the recommended number of cans per test zone, typically ranging from 16 to 20 cans, was adhered to, as advised by Wilson and Zoldoske in 1997. Additionally, in line with the recommendations set forth by the Irrigated Crop Management Centre in 2002, which advocate for a minimum of 30 cans, each with a minimum height of 100mm, to assess sprinkler irrigation uniformity, this study thoughtfully employed 36 catch-cans. This number of catch-cans ensured the evaluation of the water distribution pattern for sprinkler irrigation while maintaining compliance with established standards. In the context of field and laboratory tests, catch-cans are commonly arranged in either a rectangular grid or in one or more radial configurations. For the specific test conducted in this study, the decision was made to employ the full rectangular grid setup. This choice was made based on the rationale that it provides more representative and reliable data, particularly when there are prevailing wind conditions during the test. Figure 3 depicts catch-cans used to collect water in Ayoyo farm.
FIGURE 3: Catch-Cans Used to Collect Water in Ayoyo Farm (Field Studies, 2023)
The materials used for the research were:
• ½ inch (0.0127m) PVC pipe 6m in length
• ½ inch (0.0127m) end caps
• ½ inch (0.0127m) elbow
• ½ inch (0.0127m) tap
• 2 mm drill bit
• Hydro sensor II (used to monitor the soil moisture content of the field)
• Geotextile layer (used in association with soil, has the ability to separate, filter, reinforce, protect, or drain)
• Flexible copper wire (core)
• Storage tank (2000Litres, use to store water)
• Metal stand raise height of water flow for the storage tank (height of the metal stand is 2.5m)
• Funnel (used to channel liquid or fine-grained substances into containers with a small opening)
• Recordable rain gauge (Truchek_200, commercial name) (used to measure rainfall)
• Measuring tape (used to measure distance)
• Measuring cylinder (used to measure volume of liquids)
Stop watch (used to measure the amount of time elapsed from a particular time when it is activated to the time when the piece is deactivated)
• Collection cans (used to collect water)
Fittings or pipe connector fittings
Spray tubes
Flow control devices
Filters
Micro spray tubes 40mm
Offtake valves and saddles 40mm
P.E end cap 32mm
Air release valve 1 inch
Composite soil samples were meticulously collected at a depth of 30cm from distinct locations at the site, considering up-stream, mid-stream, and down-stream positions for subsequent analysis of various physical and chemical soil properties. These analyses were performed at the Savannah Agricultural Research Institute (SARI) soil laboratory in Nyankpala. Notably, the soils in the area displayed a limited depth, averaging less than 30 cm due to the presence of hardpan and lateritic outcrops. Several essential soil physico-chemical properties were examined, including pH, CEC (Cation Exchange Capacity), potassium (K), calcium (Ca), nitrogen, and soil texture. Total nitrogen content was determined using the Kjeldah method (Bremner and Mulvancy, 1982), while phosphorus (P) levels were analyzed using the Bray-P solution method. Additionally, potassium (K) concentrations were ascertained using the flame photometer method recommended by the United States Salinity Laboratory Staff (1954). pH and organic carbon (OC) content were determined using the Walkley and Black technique (1934), while calcium (Ca) and magnesium (Mg) were assessed via the Ammonium acetate method (Motsara and Roy, 2008; Ogunddare et al., 2015; Peter, 2018). These analyses were conducted to ensure soil suitability for drip irrigation. In addition to laboratory assessments, on-site soil water infiltration tests were carried out, encompassing both up-stream and down-stream locations. These tests aimed to determine the maximum infiltration capacity or hydraulic conductivity of the soils in their natural environment. Unbiased plotting positions were employed for the collected data. Knowledge of soil infiltration rates was vital not only for calculating crop water requirements but also for selecting appropriate drip emitter discharge rates to prevent surface water runoff and water wastage at the Zagyuri site within the drip irrigation system. The double ring infiltrometer method was utilized for the field infiltration rate measurements, requiring specific equipment, including the double ring infiltrometer, wooden support for driving the rings into the soil, a mallet, bucket, measuring jug, stopwatch, notebook, measuring tape or ruler, and an adequate water supply. The method involves two concentric metal rings, with measurements taken within the inner cylinder to assess soil infiltration properties. The outer cylinder serves to guide water flow downward and prevent lateral spreading during the test.
The procedure for the infiltration test is as follows:
Drive the 30cm diameter ring at least 15cm into the soil, using timber to protect the ring from damage. Maintain a vertical ring position, with approximately 12cm protruding above the ground.
Install the 60cm ring into the soil or construct an earth bund around the 30cm ring, ensuring it reaches the same height as the ring. Place hessian inside the infiltrometer to protect the soil surface during water pouring.
Initiate the test by rapidly pouring water into the 30cm ring until it reaches a depth of approximately 70-100mm. Simultaneously, add water to the space between the two rings to create a water barrier that prevents lateral water spread.
Record the starting time of the test and note the water level on the measuring rod or ruler.
After 1-2 minutes, record the drop in water level within the inner ring on the measuring rod and replenish the water to restore it to the original level. Maintain a consistent water level outside the ring, similar to the inside.
Continue the test until the drop in water level remains consistent over the same time interval. Initially, take frequent readings (e.g., every 1-2 minutes) and gradually extend the intervals between readings (e.g., every 20-30 minutes) as the test progresses.
The collected data were subsequently analyzed using the well-known Kostiakov infiltration equation (Kostiakov, 1932). This model suggested a formula which assumes that at time t=0, the infiltration rate is infinite and at time t the rate approaches zero. This equation is given by:
Where;
I = Cumulative infiltration rate
M = A measure of initial rate of infiltration and structural condition of the soil
t = time
n = Index of soil structural stability
Taking the logs of both sides gives:
Figure 4 Infiltration Test Conducted at Zagyuri Site (field studies, 2023)
The average infiltration rate for the site is 160.25 mm/h. The results of the infiltration test suggest that the soils of the site belong to hydrologic soil group A/B. Group A is sand, loamy sand or sandy loam types of soils while Group B is silt loam or loam (Nielsen et al., 2017) it has a moderate infiltration rate when thoroughly wetted. It has low runoff potential and high infiltration rates even when thoroughly wetted. These soils have high to moderate rate of water transmission. This also, means that a 160.25 mm/h layer of water on the soil surface will infiltrate in one hour. This rate also falls above 13 – 76 mm/h which was started by Waller and Yitayew (2016) to be the range of sandy loam soils. The infiltration rate of 160.25 mm/h indicates a relatively high rate of water absorption by the soil. This could be beneficial for irrigation practices, as it suggests that the soil can quickly accept and distribute water to plant roots. High infiltration rates can reduce the risk of runoff and water wastage, leading to improved irrigation efficiency. This is consistent with the findings of (Badr et al.,2022) who concluded that the soil with a high infiltration rate can support efficient irrigation methods like surface or subsurface drip irrigation, enabling better control over water application and reducing water losses due to runoff. As such the soils are suitable for sprinkler irrigation. The detailed results are showed in figure 5, figure 6 and Table 1.
Table 1. Soil Physico-Chemical Properties Results
(1:2.5 H2O)
Total N
(mg/kg)
(cmol/kg)
Sand
Silt
Clay
5.40
(Field studies, 2023)
Figure 5 Downstream Infiltration Curve (F=70.5mm/H) (Field Studies, 2023)
Figure 6 Upstream Infiltration Curve (F = 250 Mm/H) (Field Studies, 2023)
3.2.1 pH
The pH values for both up-stream and down-stream treatments are slightly acidic, with up-stream having a pH of 5.3 and down-stream having a pH of 5.4. These values indicate a soil pH that is within an acceptable range for most crops. However, specific crop requirements and soil amendment recommendations should be considered to optimize soil pH for desired plant growth.
3.2.2 Organic Carbon Content (%O.C)
The organic carbon content is an important indicator of soil fertility and nutrient availability. The up-stream treatment has an organic carbon content of 0.38%, while the down-stream treatment has a slightly higher value of 0.47%. These values suggest that the down-stream treatment may have slightly higher organic matter content, indicating a potentially higher fertility level. Adequate organic matter in the soil is crucial for nutrient retention, water holding capacity, and overall soil health. Soils with organic carbon values between 0.5 and 1.5% are considered to be low in organic carbon content by Tadese (1991). Thus, the soil of the site was found to be less than 3% indicating the soil health to be poor (Tequam and WSP, 2017).
3.2.3 Total Nitrogen (%N)
The total nitrogen content is essential for plant growth and is an important component of soil fertility. The up-stream and down-stream have the same values for total nitrogen content of 0.04 (%N). Soil TN availability of < 0.05 % as very low, 0.05 – 0.12 % as low, 0.12 – 0.25 % as moderate and > 0.25 % as high was classified by Tadese (2017). According to this classification, analysis of soil samples indicated a very low level of total N indicating that the nutrient is a limiting factor for optimum crop growth. This is in agreement with similar studies which reported Nitrogen to be the most limiting soil nutrient because of its high volatility and the fact that it can be easily leached (Kebede, 2019).
3.2.4 Phosphorus (P), Potassium (K), Calcium (Ca), and Magnesium (Mg)
The concentrations of these macronutrients in the soil play a vital role in plant growth and development. In the Upstream treatment, phosphorus, potassium, calcium, and magnesium are reported as 64.47 mg/kg, 110.4 mg/kg, 133.6 mg/kg, and 126.5 mg/kg, respectively. The Downstream treatment shows slightly higher concentrations for these nutrients, with values of 69.36 mg/kg, 114.29 mg/kg, 162.56 mg/kg, and 137.89 mg/kg, respectively. These values suggest that the downstream treatment may have a slightly higher nutrient availability compared to the upstream treatment, which can positively impact plant growth and productivity.
3.2.5 Cation Exchange Capacity (CEC)
The CEC indicates the soil’s ability to retain and exchange cations, which are essential for nutrient availability to plants. The Upstream treatment has a CEC of 10.89 cmol/kg, while the Downstream treatment has a higher CEC of 12.65 cmol/kg. A higher CEC implies that the soil has a greater capacity to retain and release nutrients to plants, which is beneficial for crop production.
3.2.6 Soil Texture
The soil texture provides information about the relative proportions of sand, silt, and clay particles in the soil. The up-stream treatment is classified as sandy loam, with 54% sand, 25.6% silt, and 20.4% clay. The down-stream treatment is classified as loam, with 43.43% sand, 29.71% silt, and 27.29% clay. These soil textures indicate different water-holding capacities and drainage characteristics, which can influence plant growth and management practices. The result is in harmony with Buri et al., 2012; Shaibu et al., 2017 who reported that soil textures within the Northern zones are dry and vary from sand through sandy loam to silt and are relatively poor in clay content.
The spraying tube used for this study was a 100 m flexible tube but 80 m was used on the field. The distance between two spray tube is 3 m. There are specified holes created across the tubes and there are 30 holes per line and 10 lines. The distance between two holes is 30 cm (0.3m).
Figure 7: Design of the Spray Tube System
3.4 Sprinkler Uniformity Coefficient
The coefficient of uniformity from the up-stream was evaluated as 95.3%, which was comparatively higher than that of Keller & Bliesner (1990) observed elsewhere (85%). Also, the coefficient of uniformity from the mid-stream was evaluated as 95.1% which was also comparatively higher than that of Kellers &Bliesner (1990) observed elsewhere (85%). The down- stream was also evaluated as 75.8% which was comparatively lower than that of Keller &Bliesner (1990) observed elsewhere (85%). The low down- stream value for the uniformity coefficient can be attributed to the lower volume of water received at the down-stream. Also, the results obtained from the studies agreed with the results attained by Batchelor at el., (2014) which had high CU at the up-stream followed by mid-stream and the down-stream had the least CU. This is illustrated in figure 8.
Figure 8 Sprinkler Uniformity Coefficient (Field Studies, 2023)
The distribution uniformity was also evaluated from the data gathered. The up-stream distribution uniformity was evaluated as 99%, the mid-stream was 92.7% and the down-stream was also evaluated as 67.6%.
These figures showed that, the distribution uniformity for the up-stream and mid- stream was high; this means that the water was distributed uniformly across the field except the down-stream which was low as 67.6%. The low down-stream value for the sprinkler distribution uniformity can be attributed to the lower volume of water received at the down-stream. Also, the results obtained from the studies agreed with the results attained by Batchelor et al., (2014) which had high DU at the up-stream followed by the mid-stream and the down-stream had the least DU. This is illustrated in figure 9
Figure 9. Graph Showing Sprinkler Distribution Uniformity (field studies, 2023)
The mean application rate from the sprinkler irrigation system was 3.75 mm\h. The average soil infiltration rates observed was 160.25 mm/h. Thus, this particular sprinkler could perform without runoff. The results obtained from the studies agreed with the results attained by Valenzuela et al., (2017) which had mean application rate of 3.74 mm/h.
There was difference in Ayoyo (Corchorus olitorius) fresh leaves yield under sprinkler irrigation. The up-stream recorded the higher yield of 900 kg/ha followed by the mid-stream of 880 kg/ha and the down-stream of 544 kg/ha. The differences in yield are attributed to the amount of water received by each of the stream. The results obtained from the studies agreed with the results attained by Valenzuela et al., (2017) which was in a range of 760 kg/ha-900 kg/ha. The results obtained from the studies also agreed with the values attained from FAO (2020) which was in a range of 700 kg/ha-930 kg/ha. However, the results obtained from the studies were lower than the results recorded by Nagaz et al., (2013) in Tunisia which were in the ranged of 1000 kg/ha-1200 kg/ha. This could be due to differences in geographical locations. The up-stream and the mid-stream recorded the same values of crop water productivity of 0.50 kg/m3 and the down-stream recorded the least crop water productivity value of 0.44 kg/m3. The crop water productivity results also agreed with the results attained by Valenzuela et al., (2017) which was in a range of 0.43 kg/m3-0.50 kg/m3. The crop water productivity results agreed with the values attained from FAO (2020) which were in the ranged 0.39 kg/m3-0.67 kg/m3. This is illustrated in Table 2.
Table 2 Crop Water Productivity of Ayoyo
(m3/ha)
(kg/ha)
(kg/m3)
The average infiltration rate for the site is 160.25 mm/h. The results of the infiltration test suggest that the soils of the site belong to hydrologic soil group A/B. Group A is sand, loamy sand or sandy loam types of soils while Group B is silt loam or loam. It has a moderate infiltration rate when thoroughly wetted. It has low runoff potential and high infiltration rates even when thoroughly wetted. These soils have high to moderate rate of water transmission. This also, means that a 160.25 mm/h layer of water on the soil surface will infiltrate in one hour.
From the determined sprinkler mean application rates (MAR) (4.63mm/h) and the basic soil infiltration rate (160.25mm/h), the impact sprinkler tested in this study was suitable and could therefore be used satisfactorily without runoff. Both the up-stream and the mid-stream could also be employed satisfactorily without any runoff.
Also, there was difference in Ayoyo (Corchorus olitorius) fresh leaf’s yield under sprinkler irrigation. The up-stream recorded the higher yield of 900kg/ha followed by the mid-stream of 880kg/ha and the down-stream of 544kg/ha. The differences in yield are attributed to the amount of water received by each of the stream. For the crop water productivity of Ayoyo under sprinkler irrigation system, the up-stream and the mid-stream recorded the same value of 0.50kg/m3 and the down-stream recorded the least value of 0.44kg/m3.
For the sprinkler irrigation system, the up-stream data produced higher/better results than the mid-stream and the down-stream for all the parameters studied i.e. mean application rate (MAR), coefficient of uniformity (CU) and pattern uniformity or distribution uniformity (PE/DU). Also, the up-stream data from the sprinkler gave very good results as regards, the coefficient of uniformity (CU) and pattern uniformity or distribution uniformity (PE/DU) which were above standard values stated in literature. For the soil texture analysis, he up-stream treatment is classified as sandy loam, with 54% sand, 25.6% silt, and 20.4% clay. The down-stream treatment is classified as loam, with 43.43% sand, 29.71% silt, and 27.29% clay. These soil textures indicate different water-holding capacities and drainage characteristics, which can influence plant growth and management practices. The total nitrogen content is essential for plant growth and is an important component of soil fertility. The up-stream and down-stream have the same values for total nitrogen content of 0.04 (%N). Soil TN availability of < 0.05 % as very low, 0.05 – 0.12 % as low, 0.12 – 0.25 % as moderate and > 0.25 % as high. The organic carbon content is an important indicator of soil fertility and nutrient availability. The up-stream treatment has an organic carbon content of 0.38%, while the down-stream treatment has a slightly higher value of 0.47%. These values suggest that the down-stream treatment may have slightly higher organic matter content, indicating a potentially higher fertility level. Adequate organic matter in the soil is crucial for nutrient retention, water holding capacity, and overall soil health. The pH values for both up-stream and down-stream treatments are slightly acidic, with up-stream having a pH of 5.3 and down-stream having a pH of 5.4. These values indicate a soil pH that is within an acceptable range for most crops.
I am grateful to all those who in diverse ways contributed to the successful completion of this research work. I thank the Almighty God, to whom all knowledge, wisdom and power belong for sustaining me in good health, sound judgement and strength to move on. Special appreciations go to my brother Mr. Ishmael Alhassan who helps in analyzing of the data. I also thank Ghana government for timely disbursing the book and research allowance which is used for publication of research works.
Alhassan, ALH; Kyei-Baffour, N; Agyare, WA; Amponsah, W (2023). Evaluation of the Performance of Sprinkler Irrigation System for Ayoyo Cultivation using Wastewater at Zagyuri in Sagnerigu Municipal in the Northern Region of Ghana. Greener Journal of Science, Engineering and Technological Research, 12(1): 34-48.
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