Irrigation is the best way to ensure continuous food production with an ever-increasing population. However, when designing large irrigation schemes like a 100-acre irrigation design, we must take a lot of care when deciding the components to use to avoid risks of failure. Irrigation schemes of this size can use one type of irrigation method or two or more methods depending on the crops grown.
Water uses for different crops
Plants need water for growth and cooling purposes. It is essential to know the water use, why plants use water, and the factors affecting water use in irrigation. By knowing this, you can be able to avoid over-irrigation and under-irrigation. Crop water use entails two processes, i.e., evaporation and transpiration. The two processes are customarily combined and referred to as evapotranspiration. Transpiration is water loss through the leaves’ stomata, whereas evaporation is water loss through the wet soil or plant leaves’ surface. Plants extract water from the soil using the roots.
Evaporation occurs in the upper soil surface (depths of 3 cm to 5 cm). The evaporation rate is high during the initial stage of crop development, but as the crop grows, the canopy increases, offering shade to the soil surface. The shade helps reduce the evaporation rate in the mid and late stages of crop development.
Uses of water in plants
Plants use water for the following purposes;
- To cool the plant by transpiration.
- Photosynthesis – it is a process by which plants make food.
- Transport of nutrients and organic matter.
- Support system – plants achieve this by helping the plants’ cells remain turgid.
Crop water use determination
We determine crop water use by measuring changes in the soil water content with respect to time. However, the methods involved are tedious, expensive, and time-consuming. We use the crop coefficient and the reference evapotranspiration to quickly determine crops’ water use. The crop coefficient depends on the crop grown and the growth stage of the crops planted. Reference evapotranspiration refers to water use based on the prevailing weather conditions in an area. For instance, Crop water use is an important element when determining the water requirements in a 100-acre irrigation design.
Factors affecting the evapotranspiration rates
The following factors affect the rate of water use in an area;
- Solar radiation – stomata are sensitive to solar radiation. The amount of radiation affects how wide the stomata open, affecting water loss through transpiration. Solar radiation also affects evaporation rates. The higher the solar radiation, the more the evaporation rates
- Air temperature – plants use transpiration to cool the plant. Increased air temperature means high transpiration rates.
- Plant species – different plants have varying growth periods and water uses.
- Growth stage of plants – a fully matured plant will need more water than a recently planted crop. There are three growth stages of plants, i.e., initial stage, mid-stage, and late stage. At the initial stage, the water demand is low, and water loss is mainly through evaporation. In the mid-season stage, the water demand increases because of the flowering and fruiting of the crops. In the late stage, water demand depends on the desired plant conditions during harvesting. If you want fresh produce, the water demand remains the same as the mid-stage. For dry harvested produce, we reduce the water application to achieve that.
- Wind – the presence of the wind increases the evapotranspiration rate. The wind removes moisture from the air creating room for more moisture.
- Relative humidity – when there is high humidity, the rate of evapotranspiration is low. The water loss rate is increased when the humidity is low.
- Degree of surface cover – evaporation is mainly through the soil surface. A high degree of surface cover implies that the evaporation rate will be reduced.
The pump house
The pump house in a 100-acre irrigation design refers to a building built to hold the components of the pumping unit. It is used to protect the pump from external conditions such as freezing. There are two primary water sources, i.e., surface water and groundwater. Surface water refers to water that collects on the ground or in streams, lakes, rivers, oceans, and reservoirs. The surface water is used to replenish the groundwater. Groundwater is water that collects in the spaces between rocks and soil. Groundwater is usually of high quality, but it is best to measure the amounts of iron and manganese in the water. Measurement of these elements is done since they can block drippers or sprinkler nozzles when the concentration in water is high.
Components of a pumping system in a 100-acre irrigation design
The pumping system in a 100-acre irrigation design composes of the following components;
- The pump – the function of the pump is to transfer water for irrigation from one point to another.
- Prime mover – the prime mover is the source of power for the pump. It can be electric motors, diesel/petrol engines, or an air system.
- Piping – to convey the irrigation water into and out of the pump system.
- Valves – control the flow of water into the piping network.
- End-use equipment – refers to the component that uses pumping power. It can be a heating system, sprinklers, drip emitters, etc.
Pump power sources
The type of power source to choose for your pump depends on the availability and accessibility of the power source. However, power sources for water pumps are electricity, diesel/ petrol, and solar power. Electricity is best used for areas with reliable electricity supply. In addition, advantages of using electricity are reduced labor costs, and the system has high efficiency.
We use diesel/ petrol-powered generators for areas with no or unreliable electricity supply. Solar-powered pumps save on energy costs. Their power depends on solar radiation, and the initial cost of installing the system is high. By installing batteries, you can save the power available during the day and use it to run the pump when the solar radiation is low or at night.
The function of the pump in a 100-acre irrigation design is to push water through the system. It is essential to know the different components of a pump. This knowledge is advantageous when it comes to replacing worn-out or damaged parts. The members of a pump are;
- Casing – the casing is the outer shell of the pump. Its principal function is to protect the inner components from external conditions. The material used to make the housing should be firm and resistant to harsh external conditions.
- Impeller – consists of a rotating disc connected to a shaft with a set of vanes. The disc rotates, creating the energy required to induce flow in the system
- Motor – this component is the power source of the pump. It can be alternating current (AC) or direct current (DC) powered, fuel, hydraulic, solar, or steam powered.
- Shaft – the shaft connects the impeller to the motor. It transmits the power to the impeller creating the necessary force to induce flow.
- Volute – it is the inner casing that contains the impeller. It collects and discharges the irrigation water.
- Bearing assemble – offer mechanical support allowing continuous impeller rotation.
- Hub – the hub forms a connecting part for the engine.
- Seal – the seal protects the bearing assembly from the irrigation water.
Types of pumps
There are various types of pumps available in the market. The choice of type of pump depends on the use, power source, and the power of the pump. For a 100-acre irrigation design, you will need to use a powerful pump to achieve the necessary flow rates. Types of pumps available in the market include;
- Floating pumps – they are submersible or turbine pumps attached to a float. The pump hangs beneath the float, and the pump delivers water through a pipe connecting to it.
- Booster pumps – manufacturers build these pumps primarily for improving water pressure in the system.
- Turbine pumps – consists of a centrifugal pump mounted underwater and connected to a motor on the surface. These pumps are excellent and efficient for use in large schemes.
- Submersible pumps – submersible pumps are placed at the bottom of the water source. Unlike turbine pumps, the pump and motor are part of a single unit.
- End suction centrifugal pumps – they are widespread in the market. Manufacturers mount the pump at the end of a motor and it requires priming before the first use. The pump has an advantage in portability since it is easy to carry.
- Centrifugal pumps – these pumps use an impeller to create the necessary force to push the water up the system. They need priming before the first use.
- Displacement pumps move water through displacement. Examples of these pumps are rotary and piston pumps.
Factors to consider when selecting a pump for a 100-acre irrigation design.
The wrong choice of a pump in a 100-acre irrigation design can have profound financial implications. Purchase of a low-performance pump will mean the water supply to the plants won’t be enough resulting in yield losses. A high-performance pump will mean more pumping costs. The factors to consider before purchasing a pump for irrigation are;
- The pump discharge – discharge refers to the amount of water the pump supplies.
- The pressure – refers to the internal energy of water due to pressure on the pipe walls.
- Suction head – it refers to the distance a pump can suck water from a water source.
- Friction head – friction head is the loss in water pressure resulting from friction between the flowing water and the pipe walls. Irrigation pipes’ length, diameter, surface smoothness, and material affect the friction head in an irrigation system.
Estimated flow rate across a 100-acre irrigation scheme
To estimate the flow rate across a 100-acre irrigation design, we firstly determine the crop water requirements. Precisely, the crop water requirements vary depending on the species, growth stage, and environmental conditions. Crops grown in hot areas will need more water than those in cool regions. Water demand is usually expressed in terms of depth. To get the total volume of water required per day we multiply the total area by the crop water demand. Assuming the crop water demand is 6mm/ day, the volume of water plants need in a day is.
Volume of water plants need in a day (100-acre) = × 400,000 m2
= 2400 m3/ day
Assuming 20 hours of irrigation in a day, then the daily volume of water we need is;
Flow rate per hour = = 120 m3/hour.
Using drip irrigation in this area with a flow rate of 2 liters per hour and spacing of 0.2 m by 0.6 m on the laterals, we can obtain the application rate.
Water application rate =
You can get the application time by dividing the crop water demand by the application rate, i.e.,
Application time = = 0.375 hrs/ 22.5 minutes
If the field is irrigated as one whole field, then the discharge we need will be;
Estimated flow for the whole field= = 6400 m3/ hr
To get the number of shifts that you can use, you divide the crop water requirements with the application time.
Number of shifts = = 16 shifts
If we divide the plot into 16 plots, each irrigated in one shift, then the area and discharge of each shift are;
Area per shift = = 6.25 acres
Discharge per shift = 6.25 × 4,000 m2 × = 150 m3.
To get the flow rate per shift, we divide the discharge per shift by the application time.
Estimated Flow per shift = 400 m3/ hr
Estimated irrigation hours for a 100-acre irrigation design
To get the actual irrigation hours you will need for a 100-acre irrigation design using the above requirements, we use the number of shifts and application time.
Estimated irrigation hours = the number of shifts × application time.
= 16 shifts × 0.375 hrs
= 6 hours
Use of automation for cost efficiency
We automate irrigation systems to ensure efficient water and nutrient supply to the plants. The system carries out irrigation operations with no or minimal human intervention. Automatic systems use sensors, timers, or computers to control the water and nutrient flow in the system. The system uses sensors to determine the right time to apply fertilizer and water to the plants. The sensors send the information to the computer, which decides when to irrigate depending on the data. Irrigation timers are the brain of an automatic irrigation system. Timers can be mechanical, electronic, or hybrid.
Automatic irrigation systems reduce the labor cost on a farm. The computer decides when to irrigate and supply nutrients depending on the data collected. This reduces the labor needed to operate the farm. The system releases water to the plants in the right quantities reducing water wastage. Efficient water use means less water pumping. This helps reduce the pumping costs. The system also controls the fertilizer application, reducing wastage and saving on costs.
The incorporation of a pest detection system helps detect the presence of pests early on. Control of the pests early on is much easier and cost-effective. An automatic system helps increase the quantity and quality of yield. The risk of losses is reduced significantly, ensuring farmers get returns on their investment. The use of automation in 100-acre irrigation design is necessary to help reduce production costs.
Size of filtration unit for 100-acre irrigation design
Filtration is the removal of suspended contaminants from irrigation water to avoid blocking the system. Water quality determines the filtration requirements, chemical injection, and management of the filtration system. The filtration system blocks three main groups of contaminants, i.e., biological, chemical, and physical contaminants. Biological pollutants include algae. Chemical contaminants include scale or precipitates, while physical contaminants include grit or suspended soil particles. To determine the filtration system, water emitters, and maintenance programs in a 100-acre irrigation design, you should conduct a water analysis.
The types of filters available for irrigation systems are;
- Media filters – media filters use sand and gravel to remove contaminants. We use them in surface water sources, especially in wastewater treatment. They are more suitable for the removal of organic compounds. Backwashing cleans the media filters.
- Disc filters – these filters contain a series of flexible, grooved discs stacked together. The screen size ranges from 40 to 400 mesh and is best suited for high flow rates. They are capable of cleaning physical and biological contaminants. Although when cleaning organic pollutants, they clog faster than when removing sand particles. They utilize little water when backwashing than other filters.
- Screen filters – they use a flexible or rigid wire woven screen to separate contaminants from water. Depending on the size of the filter, washing can either be done manually or by backwashing. We use screen filters when the amount of contaminants is little to average.
- Hydro-cyclone sand separators – these centrifugal filters separate water according to the difference in densities. They are helpful when separating large particles, i.e., 50 microns or larger, from irrigation water. The filter contains a sand collector at the bottom, which is easy to open and clean. Irrigation water filtration using this filter can be made more efficient by combining its use with screen or disc filters.
Filtration variables in a 100-acre irrigation design.
Several variables affect the type of filtration system to use. Some of these factors are;
- The flow rate – the irrigation system’s water flow rate will determine the cartridge’s size and the size of the filter inlet and outlet. The pipe sizing mostly determines the size of the inlet and outlet.
- Differential pressure – this refers to the difference in water pressure between the inlet and outlet of the filter. We consider the housing and cartridge differential pressures for irrigation systems sensitive to pressure drops.
- Location – the space available for the filter will determine the size of the filter.
- Viscosity – this factor determines how water flows in the filter and the pressure the system needs to push the water through the filter. High viscosity means high pressures to push irrigation water through the filter. The downside to this is that the increased pressures can force some of the contaminants through the filter.
- Contaminants – Different filtration systems have their advantages when it comes to filtering out various contaminants. Disc filters are suitable for high volumes of water while media filters are more suitable for filtering organic contaminants.
Determination of filter size for a 100-acre irrigation scheme.
The filter for use in a 100-acre irrigation design should be able to filter out contaminants from the water without any problems. The factors to consider when selecting the size of filter to use are the inlet and outlet dimensions, the pressure rating, the type of filter, and the mesh size. The mainline pipe diameter determines the size of the filter to use. This filter already has the requirements to meet the flow from the diameter of such a pipe. The area is large; hence you will need large pipes to handle the pressures and volumes of water. We recommend the use of disc filters when the discharge is high.
Automatic fertigation system
Fertigation is the injection of fertilizers, amendments, or other water-soluble products into an irrigation system. Automatic fertigation systems deliver just the right amounts of water and fertilizer at the root zone of the crops. The system uses sensors in the soil to detect soil moisture levels and substrate quantities. When the substrate quantity in the ground is low, a signal is sent to the computer, which supplies current to the solenoid valve. Moreover, the solenoid valve enables the mixing of dissolved fertilizer with the irrigation water. Since solenoid valves are fast, the efficiency of the automatic fertigation system is high. The solenoid valves to use in this system are three-way solenoid valves.
The advantages of using automatic fertigation systems in 100-acre irrigation design are;
- High yields – use of sensors and timers ensures the plants get the required quantities of water and fertilizer, increasing the yields.
- The system is convenient – the farmer must not be present to activate the system. It is done automatically, and monitoring the system through the phone or computer is possible.
- Smart irrigation timers and sensors enable some systems to vary the amount of fertilizer application throughout the growing period depending on the demand.
- Optimization of fertilizer application – sensors monitor the substrate quantity in soil and alert the computer when the level goes low. The computer then allows fertilizer application.
- Cost -saving on production – an efficient fertilizer supply reduces wastage, reducing the amount of fertilizer you use.
- Reduced nutrient leaching – the system only supplies the required quantities of fertilizer to the plants. This reduces the leaching of nutrients into the soil.
- Automated fertigation systems provide the farmer with the fertilizer use data enabling the farmer to make well-informed decisions concerning fertilizer application.
Soil health in relation to the automatic application of fertilizer
Continuous planting and harvesting of crops gradually decrease the nutrients available in the soil. To ensure continuous high yields, farmers use either fertilizers or natural decomposition to replenish the soil nutrients. Fertilizer application is a preferred way of replenishing nutrients since it is fast-acting and a farmer can add specific nutrients depending on the deficit. Fertilizers help ensure adequate food supply in the world. However, overuse of chemical fertilizers has serious consequences on soil, animals, plants, and human health. The increasing population poses a threat to food security; hence the need to improve agricultural production. One way of doing this is by using automatic fertigation systems. Not only does it ensure plants get adequate nutrients, but it also protects the environment from the harmful effects of fertilizer overuse.
Some of the harmful effects prevented by the use of automatic fertigation systems are;
- Increased soil acidity – an increase in soil acidity reduces the crop intake of phosphate, raises the concentration of harmful ions, and inhibits crop growth.
- Humus content reduction – a loss in humus content reduces the ability of the soil to store nutrients.
- Over-application of nitrogen fertilizers for long periods kills the balance between the three macro-nutrients. These nutrients are nitrogen, phosphorus, and potassium. The loss in nutrient balance will result in reduced yields.
- Toxic build-up of heavy metals in the soil – continuous overuse of certain fertilizers can result in tox metal build-up. These toxic metals are uranium, cadmium, and arsenic. The heavy metals pollute the soil and they can accumulate in the fruits, grains, and vegetables. When we consume these products, serious health issues can arise.
- Pollution of water sources – overuse of fertilizers will result in washing away of excess fertilizer by leaching or runoff. The water will direct the fertilizer to underground water sources or surface water sources. Fertilizer presence in water sources results in excessive growth of algae which use up oxygen in the water when they respire and decompose. An increase in the number of algae reduces the oxygen available in the water leading to the deaths of fish.
The use of automatic fertigation helps prevent all the problems mentioned above. Lastly, this system ensures plants get fertilizer in the right quantities and time avoiding overuse. It helps ensure proper soil health conditions while increasing the yields.
The pressure rating on mainline and subsequent laterals in a 100-acre irrigation design.
Irrigation pipes deliver water through the entire irrigation system. They make up a large portion of an irrigation system, making their selection very crucial to the operation of the scheme. In a 100-acre irrigation design, the pipes should be able to withstand the maximum operating pressures and convey water without excessive pressure loss or gain. You should ensure proper connection at pipe joints to avoid pressure loss through leakages. The selection of mainline pipes is dependent on economics, friction loss, and flushing concerns. During flushing, the piping network should be able to withstand the flushing velocities. Flushing velocities are usually about 0.3 m/second.
The prices of pipes available at Eunidrip irrigation systems are;
|Irrigation pipe prices
|Cost per meter
Pressure rating recommendations on laterals.
The pressure at the laterals will differ depending on the irrigation method. Drip irrigation and subsurface irrigation usually have low water pressures at the laterals. Sprinkler irrigation and center pivot irrigation experience high water pressures at the laterals.
|The recommended size of lateral pipes for drip irrigation
|Length of laterals
|Lateral flow rate
|40 m -50 m
|40 m -70 m
|60 m -80 m
|80 m -120 m
|90 m – 120 m
Irrigation methods applicable in a 100-acre irrigation design
Irrigation is the artificial application of controlled amounts of water to assist in crop production or grow landscape plants. It is one of the methods preferred nowadays to increase food production. The advantages that arise from using irrigation in crop production are;
- Increased quality and quantity of yields.
- Soil erosion prevention.
- Improved crop health.
- Optimization of fertilizer usage.
- Inhibits weeds growth.
- Eliminates water deficiency.
- Acts as a shield against famine.
There are various irrigation methods available that are applicable in a 100-acre irrigation design. The major irrigation methods available are; surface, sub-surface, drip, sprinkler, and center pivot irrigation. At Eunidrip Irrigation Systems, we supply and install all irrigation types available. We have qualified and well-trained staff and you can be assured of high-quality work.
Surface irrigation involves the application of large volumes of water by the force of gravity over a farm. Types of surface irrigation methods you can use are basin, furrow, and border irrigation. We use surface irrigation methods in soils with poor infiltration rates, i.e., clay soils only. There is some earth movement involved when building bunds or trenches to control the water flow in the areas. Water flows into the irrigation area and is controlled by the use of gates or pipes. The use of surface irrigation methods is mostly applicable where there are large volumes of water and the available soils are clayey. The methods are relatively cheap to install, but they do not conserve water and a lot of it is lost to the atmosphere.
Sub-surface irrigation is a method that delivers water directly into the soil layers. It can be either natural or artificial. People cannot control natural sub-surface irrigation since it involves water seeping from underground water, lakes, streams, or rivers into the soil. It is a cheap method but it is not possible to control the amount of water supplied to the plants. Artificial sub-surface irrigation involves the supply of water to the plant root zone by the use of pipes underneath the soil. The main advantage of this system is that you eliminate water losses through evaporation. We normally use this method in areas with hot climates or areas where there are inadequate amounts of water. Problems encountered when using this method are possible leakages in the pipes due to rodents or heavy machinery. This method is feasible in a 100-acre irrigation design since it conserves moisture reducing water pumping costs.
This method is the best for irrigation in terms of water conservation. We can apply it in a 100-acre irrigation design depending on the crops. Drip irrigation involves the supply of controlled amounts of water at the root zone of the plant. Emitters deliver the water to the plants at an average rate of two liters per hour. The emitters are sensitive to blockages; hence you will need to filter the water before entering it into the piping system. When it comes to designing the 100-acre farm, the layout of the pipes depends on the topography and shape of the farm. The basic rules are, that you should place the mainline along the slope and laterals across the slope. The use of this method has many advantages such as increased yields, controlled weed growth, reduced soil erosion, reduced labor costs, efficient use of fertilizers, and control of pests and diseases.
The initial costs of installing this system are high, however, the savings done on production costs afterward are worth it. At Eunidrip Irrigation Systems, our installation cost of drip irrigation per acre varies depending on the number of driplines per bed.
|Drip irrigation cost per acre
|Number of driplines per bed
Sprinkler irrigation makes use of sprinkler nozzles to distribute water in the form of artificial rain. The sprinklers can apply a uniform amount of water over a large area depending on the type of sprinkler. When using this system, earth movement is not necessary. You should use a filter to remove contaminants that can block the sprinkler nozzles. The choice of this method in a 100-acre irrigation design depends on the crops grown, the weather conditions dominant in the region, the type of soil, and available funds. precisely, You cannot use sprinkler irrigation to grow water-sensitive plants like beans and tomatoes. This is because these plants tend to get sick when exposed to too much water on their leaves. The climatic conditions of an area affect the efficiency of water application using sprinklers. In windy areas, there is a non-uniform application of water on the farm.
Sprinkler irrigation is most suitable for areas with sandy soils. This is because the water will infiltrate more quickly reducing the amount of water lost through evaporation. Sprinklers need pumps to achieve the high pressures necessary to distribute water. The introduction of pumps means increased production costs in irrigation. Despite the pumping costs, this method is very efficient depending on the usage. Its use can assure you of high returns. However, to ensure the long life of sprinkler irrigation, you should follow the necessary maintenance practices. At Eunidrip irrigation systems, we can help you know where to use sprinkler irrigation, and supply and install the whole system at affordable prices. The cost of installing a sprinkler irrigation system on a one-acre farm starts from KES. 150,000.
Center pivot irrigation
Center pivot irrigation uses sprinklers or a series of sprinklers that rotate about a pivot. These systems are fully automated and the system covers a large area. Water application varies along the length of the pipeline with more water being applied at the end of the pipeline than near the pivot. Some more advanced systems use GIS and GPS to map out the area and distribute water according to the demand in each area. The use of this irrigation system demands large vast areas making it suitable for use in a 100-acre irrigation design.
Crops that you can grow using this method are sugarcane, orchards, maize, potatoes, small grains, alfalfa, and vegetable crops. The major factor that affects the choice of this system is the cost. Center pivot irrigation has a high starting and operational cost. Truly, this limits its use to commercial farmers only. Before deciding on using center pivot irrigation, you should ensure you have enough information to reduce risks. Eunidrip irrigation systems have experienced staff who can advise you on center pivot irrigation, helping you secure your investment. Pivot irrigations are large irrigation projects that require large areas starting from 100 acres. The cost of installation of center-pivot irrigation ranges from KES. 3,000,000 to KES. 10,000,000 depending on the area and equipment.
Eunidrip Irrigation systems’ role in the design, supply, and project implementation.
Eunidrip irrigation systems is amongst the leading irrigation companies in Kenya. We deal in irrigation, greenhouse design and construction, borehole drilling, shade net structure development, and plastic mulch supply. We also offer products as well as consultation services to ensure our clients get customized solutions to their needs.
In irrigation, we design, supply, and install all types of irrigation systems. We deal with various sizes of projects from a quarter an acre to 100-acre irrigation designs. We offer customer-friendly prices for all our products. Our customers can access us through our online shop or our physical store located at George Morara Road, Nakuru town. You can also contact us through our telephone lines or via WhatsApp in case of any inquiries.