1. What drip irrigation is
Drip irrigation, also known as micro-irrigation, is an irrigation method that allows you to optimize the consumption of irrigation water in terms of production results and water saving. The irrigation system is a complex system aimed at bringing water to the ground through the use of dripping pipes, i.e. plastic pipes of small diameter that release certain quantity of water on a regular and prolonged basis, with flow rates ranging from 2 to 20 liters per hour.
Thanks to the use of a drip irrigation system, water is released near the plants in order to wet only the part of the soil where the roots grow, with a significant water saving, while overhead irrigation, on the contrary, involves humidification of the entire soil profile.
Implementing drip irrigation system, water supply is more frequent (usually each 1-3 days) and this provides a level of humidity that makes the soil a favorable environment for plants to thrive.
1.1 Suitable crops
Drip irrigation is more suitable for row crops (vegetables, berries), for trees and grapevine plants, where one or more drippers can be provided for each plant. For herbs cultivation this irrigation system is also preferable.
1.1.1. Vegetable crops – vegetables and extensive crops
Vegetables and extensive crops in open field, generally of annual duration, such as: tomatoes, potatoes, courgettes, melons, cucumbers, lettuces, corn, chard, tobacco, seasonal drip tapes from polyethylene are recommended and mostly used.
1.1.2. Fruit growing
For fruit growing, such as olive trees, grapevines and apple trees, drip lines are mostly used, as they can be used for more than one season.
1.2 Suggested slopes for drip irrigation
Drip irrigation is adaptable to any type of slope that can be cultivated. Even in case of fields with slight slopes with cultivations of tree crops and row crops, the use of a drip irrigation system is recommended. Furthermore, thanks to the ingenious system of the pressure compensating dripline that is adapted to all slopes, arable and vegetable crops can also be grown on steep terrain.Crops irrigated with drip tape are generally grown on flat ground, with maximum slopes of 1%, to obtain the optimal yield from the drip irrigation system.
1.3 Suitable soils
Drip irrigation is suitable for most soil types, but some precautions should be taken. On clay soils water must be provided slowly to avoid stagnation and runoff of surface water. A higher flow rate of drip tape will be needed on sandy soils to ensure adequate lateral wetting of the soil. The third soil typology is silty soil or medium-textured soil, which require intermediate conditions. For these reasons, drip tapes are produced in a wide range of flow rates (l / h) of the drippers and distances (cm) from one dripper and the other, in order to adapt to the different types of soils and to the different needs of the crops. 1.4 Suitable irrigation water
One of the main problems encountered with a drip irrigation system is the obstruction of the drip tape. The principle of drip tape working consists in water passing through a narrow labyrinth, before dripping out. In this way, a good uniformity of delivery for long distances is guaranteed, but the labyrinth can be blocked if the water is not clean.
Therefore, it is essential that the irrigation water is free of sediment, for this reason every good drip irrigation system is equipped with an adequate filtration system.
Obstruction can also occur if water contains algae, fertilizer deposits and dissolved chemicals, such as calcium and iron. Filtration can remove some of the substances, but the problem can be complex to solve and require expert intervention or consultation with the equipment dealer.
Scheme/structure of a drip irrigation system
Here is how what a drip irrigation system includes:
- Irrigation controllers
- Water pump
- Irrigation mainline pipes
- Filtration system
- Drip tape or drip line
- Fittings for drip tape/drip line
The irrigation Controller is an automated control unit thanks to which the quantity and frequency of daily water administration can be established. It is composed of valves to control the discharge and pressure in the entire system.
The pump takes water from the source and provides the right pressure into the piping system.
Irrigation mainline pipes are usually made of PVC or polyethylene and are preferably buried.
Filtration system to eliminate water impurities. The filtration system is essential to safeguard the drip tape from obstruction due to the impurities present in the water. The choice of filter sizes based on the quantity and quality of the water is very important. Furthermore, these accessories require periodic cleaning and backwashing operations. Filters can be divided as follows:
- Hydrocyclones or vortex separators.
- Grit filters.
- Screen filters such as net filters or disc filters.
It is also possible to connect fertilizer injection (Venturi) and water regulators as well as control devices to this system.
Drip tapes and drip lines are special pipes equipped with drippers or labyrinths inside, used to deliver water in a uniform and controlled manner to the roots of the plants. Usually the delivery holes are places at min 10cm up to 1meter distance with one or more emitters used for each single plant / tree. For row crops, longer spacing may be used. The diameters are between 16 and 22 mm with wall thicknesses ranging from 1.2 to 0.15 mm. As the thickness gradually decreases, it is possible to divide them into rigid, semi-rigid and flattened pipes:
- Drip Tapes: these pipes are also called “flattened”. They are made up in Polyethylene and the wall thickness goas form 0.375 mm to 0.15 mm. At a first sight these pipes look like a ribbon, indeed they have the shape of a real pipe only when they are operating. The drip tapes are more suitable for annual extensive vegetables farming.
- Drip lines: they are rigid and semi rigid pipes with wall thickness until 1,2 mm. They can be used in multiannual applications and farming, like for example the fruit growing.
- The fittings for drip irrigation or connectors are used to connect drip tapes with each other and with the main hydric line.
Different types of drip irrigation system
There are 2 types of drip irrigation system:
- Surface drip irrigation system: it is the more common and known at international level. From the main pipe line begin a net of drip tapes that bring water to the plants. The drip tapes can be rigid, for long distance farming, or flexible, for arboreal and annual farming because they have to be substitute periodically.
- Underground irrigation system: it is a drip irrigation system with the drip tapes placed underground. In this way the drippers touch directly the roots, that have to be watered. This kind of irrigation system is also known as sub-irrigation.
In any case, regardless of the type of system that has been chosen, a drip irrigation system can be easily automized. The water can be moistened also every day, if needed, and this creates favourable conditions for the plant’s growth.
3.1 Wetting pattern
Unlike the surface irrigation and the rain irrigation, the drip irrigation allows to water only the root zone. The wetting pattern, that develop from the water dripping on the ground, depend from the plumbing and also from the ground.
Benefits of drip irrigation systems
There are many reasons to prefer a drip irrigation system:
- Better and constant output of water;
- Big water saving: no evaporation, no downflow, no waste;
- It can be used in every kind of ground;
- Energy saving: drip irrigation works with low pressure;
- Efficient use of fertilizers and farming protection;
- Less weather dependence, indeed it can help minimize the effects of climate change. The drip irrigation system allows to increase the cultivation productivity making it easier and more efficient.
It is the eco-friendliest irrigation method in the world: it is efficient under a hydric and energetic point of view. Indeed, it allows to save water, a valuable and vital resource, to save energy, to save money, it increases the health of plants and it makes the planning process easier, thanks to the flexibility and the capability to adapt at different orographic areas.
Moreover, at the end of their service life, polyethylene pipes and drip tapes are completely recyclable and do not contribute to an increase in the amount of plastic waste.
For example, rain irrigation systems have the 75% of water efficiency, while drip irrigation systems reach the 90% or more.
In rain irrigation systems, water is pumped in a too fast way, so it’s not completely absorbed by the ground and it can be taken away by the wind. Moreover, the water can create paddles dangerous for the plant’s roots.
In drip irrigation systems, the speed of water allows the ground to absorb drips slowly and it maintains a homogeneous moisture level. The fact that water drips directly on the plant’s roots remove the risk of wind dispersion.
Drip irrigation systems are easy to plan and to install. There is no need of a digging of trenches and the pipe outside is suitable for every landscape and context. It can be used for hanging baskets, for vegetable gardens, even for flowerbeds.
Even though it is mostly used professionally for field crops, it’s also a good choice for the do-it-yourself lovers, also because it can be installed individually and it can help saving money.
Summing up, drip irrigation systems are a happy choice for the environmental health and it can be used in every land plot. Moreover, it is a cheap solution suitable for every kind of investment.
4.1 Benefits for plants
Thanks to drip irrigation system, pants receive water and nutrients in a well-balanced way.
Drip irrigation systems allow to water plants and provide nutrients with small quantities, but frequently. This guarantees perfect growth conditions that help to have the best production performance.
This is why plants are more productive with drip irrigation:
– Homogeneous availability of water and nutrients;
– The amount of water and nutrients are tailored for the plant’s growing needs;
– No soil saturation and good soil aeration;
– Avoid the high salinity from an excessive fertilizer application;
– No foliage wetting that may cause fungal diseases.