Sub Irrigation Farming: How Does it Work?

You A sub-irrigation farming method can be an advantageous watering system for your field crops. Farmers can also use them in controlled env, such as plants in nurseries, commercial greenhouses, and even hydroponic systems.

Moreover, it is essential to note that in outdoor cropping systems – the soil type, permeability, water table, and climatic conditions must be uniquely suited to support such an irrigation system. At times to optimum a sub-irrigation system can be complicated to design and manage for the farmers.

So, here is what farmers need to know about managing and installing sub irrigation as their watering system of choice.

Sub-Irrigation: What Is It?

Sub irrigation is sometimes referred to as seepage irrigation. It is a method of delivering water to plants from below the root zone. It means the process controls the water level below the root level. An effective method of water conservation while also having low labor requirements. Once you install the system, the labor needs are significantly less.

Sub irrigation is sometimes referred to as seepage irrigation. A method of delivering water to plants from below the root zone. It means the process controls the water level below the root level. It is an effective method of water conservation while also having low labor requirements. Once you install the system, the labor needs are significantly less.

How Does it Work?

It is important to note that you will not find sub irrigation in arid or semi-arid systems. They need sufficient moisture to germinate seeds at the surface level. In fact, for sub-irrigation you need areas with high drainage levels that should be farmable too. You also need to install a network of drainage pipes and tiles to move the excess water out of the ground. You can use this excess water to repurpose- adding water when plant growth requires irrigation.

In controlled env agriculture (CEA) systems, such as in commercial greenhouses for crop or horticulture production sub-irrigation is commonly used. In such a setting, you can accomplish it by setting potted plants into a managed water reservoir. Thus allowing capillary action to pull water up into the soil and root system of the plant.

Quite simply, sub irrigation will work through the natural process of capillary action. Which means it wicks moisture upwards through the soil. In simple terms, it pulls water upwards. In the case of greenhouse and horticulture systems, the irrigation system pulls the water up through the growing medium.

Growers or farmers can manage how close the water level is below their plant’s root zones. In this fashion, they can encourage effective wicking without flooding the field. As a result, the process creates over-saturation, which is detrimental to healthy crop growth. So with the help of this irrigation system, you can grow healthy plants.

Sub Irrigation Versus Surface Irrigation: The Difference

Many of you may have this question. The difference between surface and sub irrigation – is that in the case of sub irrigation, they will move up to the plant root zone. In contrast, in the case of surface irrigation, the water will move down to the plant root zone

All other types of irrigation systems, other than sub-irrigation, are a type of surface irrigation. It even includes natural rainwater – which is accomplished through surface irrigation. You may, at times, confuse sub-surface irrigation with sub-irrigation. But you need to understand that it is a method of surface irrigation, not sub-irrigation.

Note that sub-surface irrigation is a type of drip irrigation. In the case of sub-surface irrigation – the drip irrigation lines are buried just below the top surface of the soil. But the water is still delivered down toward the plant roots.

Sub-Irrigation Systems and Their Parts

Note that sub-irrigation is a method of irrigating crops and potted plants from the bottom up – rather than the top to down. You can design the sub-irrigation system in different ways – depending on whether you will use it for field cropping or commercial greenhouse.

Sub Irrigation – in Field Cropping Systems

Sub irrigation in field cropping systems – often uses controlled water by adding or draining water from the water table. As you know, the water table raises or lowers the groundwater level. Farmers usually use a system of pipes, pumps, drainage tiles, and valves to control water flow into the groundwater system.

It is also important to note that as sub-irrigation is often dependent upon water being able to wick up through the soil, this system will only work for specific soil types. Moreover, you can also use the system for particular field conditions.

Your soil should be highly permeable, meaning it should have good capillary action that will actually encourage the water to move up rapidly and also laterally. Note that in case of silt or clay layers in soil are not suitable for sub-irrigation. The reason being these types of layers often tend to slow down the capillary rise. Finally, such soil types tend to become impermeable.

In contrast, very fine, sandy loam top soil that usually does not have a layer of impermeable subsoil generally does not support enough permeability to support your crop’s irrigation needs.

Sub-Irrigation to Saturation Method

In this technique, the farmer will add water through drainage tiles until saturation – to the soil surface. Next, the water will start draining out if you open the outlet valve.

Many farmers do not encourage this method because it might lead to significant water run-off. It also leaches the fertilizers and salts into the root zone, thus leading to the degradation of water quality.

Controlled Injection Sub-Irrigation

A specific amount of water is usually injected into sub-irrigation tiles when the soil will reach the predetermined soil matric potential or SMP. SMP is generally a measurement of the availability in the soil profile. It measures how much water it can hold for plants to plant uptake and use. The injected water will move through the soil via capillary rising. It happens in a period of about two – four hours – all depending on the soil type, delivery method, and initial wetness.

Constant Water Level Sub-Irrigation

This method of sub-irrigation will use a float valve to maintain a constant level of water in the topsoil. Salt that gets accumulated in the soil will use the method – as it is a significant problem.

Sub-Drainage Mode

It is draining enough, but not too much, water out of a field. You can open and block the drainage tiles to maintain a high water table level. Remember that a high water table will support capillary rising to the plant root zones. In addition, three other factors might affect irrigation. Appropriate soil types, a high water table, the design, field slope, and engineering of the field are equally essential to make this type of system work.

Greenhouse and Nursery Sub-Irrigation Methods

Note that sb-irrigation is commonly used in commercial greenhouse production. The reason being it is a labor-efficient and plant-healthy method to irrigate. At the same time, it allows a grower to capture and reuse water and nutrient run-off. Note that sub-irrigation is generally referred to as a ‘zero runoff’ system, especially in commercial greenhouse production.

Capillary Mat Systems

You can place the potted plants on a thick fabric mat that lye on an impermeable surface. You should keep the moist continuously via a slow application of drip water. Plants will slowly wick up moisture from the mat through holes at the pot’s bottom.

Trough System

You should place the potted plants along the edge of a metal or plastic trough. You should install it at a very slight slope from one end of the other. Next you should pump water containing a nutrient solution into the trough which will flow down the length of the trough. The process is encouraged by gravity. Pots will wick up moisture from the trough. You can use the water captured at the lower end of the trough and also recycle it back through the system.

Flood Floors

You can design a flood plain on a watertight concrete floor. Next place the potted plants on the floor. You should install slotted PVC pipes in the middle of the floor, which will funnel the water and nutrient solution from large holding tanks onto the floor. Then after a set period, it will allow the plant to wick up the moisture. Note that once the valve flips, and the water will drain back into the holding tanks for reuse. You should follow a smooth follow so that the water forms spots.

Pros and Cons of Sub Irrigation

Advantages of Sub-Irrigation

Conserves Water and Nutrients – Sub-irrigation is highly resource-efficient, especially in commercial greenhouse operations. In field cropping, it may depend on several factors.
Saves on Labor – Once a system has been set up, it requires very less labor.
Can Be Used as a Drainage System

Disadvantages of Sub-Irrigation

Requires Uniform Soil Types and Level Fields – Uniformity is the key to successful irrigation.
It Can Lead to Salt Build-Up – The irrigation method can lead to an unhealthy build-up of salt in the topsoil.
It Requires Adequate Water Supply

Conclusion

It is important to note that farms that use sub-irrigation techniques use canals, pumping stations, gates, and weirs that often lower or raise the water level accordingly. You will notice that this method of irrigation is widely used in greenhouses. The reason is that potted plants are often watered from below. Interestingly, most professional gardeners prefer to maintain plants utilizing this form of irrigation. The reason being they tend to respond better than to other watering methods.