Template:Chapters 5.9

5.9 - Drip irrigation in a greenhouse

Matthew Kinnear, University of Guelph, Canada

Introduction

Drip irrigation (often called trickle irrigation) involves dripping water onto crops near their base at a very moderate rate. This system is typically made of small diameter plastic pipes fitted with outlets (emitters) which drip at a rate of 2-20 liters per hour (FAO, 2016). It is an efficient way of watering crops to ensure the greatest yield for the least amount of water and gives higher yields of crops as compared to traditional furrow irrigation (Ibragimov, 2007). Drip irrigation can also be easily modified to fit many selected environments and can be utilized for a variety of different crops. Drip irrigation systems can be used for a multitude of different crops, however they are often and effectively used for regional cash crops as an additional source of income. In fact, implementing cash crops within this system might be the best option as they may be needed to offset the cost of supplies depending on the materials used. When implementing this system it is best to know what kinds of cash crops grow well in the region and its soil to maximize yield.

System layout

The system detailed in this chapter utilizes a row line model which distributes water from a single large source into multiple pipelines that align with their crop rows. This form of a drip irrigation system generally allows for an equal distribution of water amongst crops when applied correctly (Frielander, 2013). This system is made up of multiple pipe units known as Mainlines, Submains, Laterals and Emitters that connect to a large Storage Tank. All of these parts in unison allow for water to be efficiently collected, stored, and distributed for use.

Common Layout: http://homesteadlifestyle.com/wp-content/uploads/2013/10/diypvcdripirrigation.png

Storage tank

The first, and most crucial part of assembling this system is setting up the means by which water can be properly stored. Ideally, this would take the form of a large storage barrel (like a rain barrel) which can store water for a long time and is also able to be connected to the pipelines. It is also highly recommended that this storage facility be connected to any type of rain collection system that will take advantage of any local precipitation.

Alternative forms of storage tanks

Although a plastic storage tank is ideal it is not the only option for water storage. Other methods exist that may be more practical and available for use. An example of this would be a Silpaulin trench which utilizes a silpaulin tarp and a large trench dug in the ground. The trench provides the depth needed for storage while the tarp ensures that the water is not absorbed into the ground. Keep in mind that while this form of water storage is practical, it is more labour intensive. It also requires different methods of transporting the water to the pipelines either via pumping or by manual collection.

Silpaulin storage trench: https://www.google.ca/search?q=silpaulin+tunnels&source=lnms&tbm=isch&sa=X&ved=0ahUKEwi3wf3bzr_QAhUL3IMKHbLGBt4Q_AUICCgB&biw=1366&bih=662#imgrc=1FSysA_x9OWc8M%3

Mainlines, submains and laterals

Mainlines, Submains, and Laterals supply water from the Storage Tank into the fields (Figure 1). The idea of Mainlines and Submains is to provide a connection to the source of water which allows the Laterals to distribute water to the crop lines. Mainlines connect directly to the Storage Tank and then split up into two Submains. The Submains allow the water to be split in two directions, covering the width of the crop lines, and allow the water to be distributed by the Laterals. The Laterals are the lines that attach to the Submains and lie over the crop lines. The amount of Laterals corresponds to the amount of crop lines that are in the field. The water is then distributed by the emitters (FAO, 2016)

Emitters

Emitters, otherwise known as drippers, are mechanisms used to operate the amount of water from the laterals to the crops. They are usually spaced more than 1 metre apart with one or more used for a single crops such as trees, however can be modified as needed. For row crops more closely spaced emitters are needed to hydrate each crop properly (FAO, 2016). Multiple different designs of emitters have been produced in recent years however a basic 3.2 mm hole will prove just as useful and more cost efficient.

Simple emitter holes: https://solarbeez.files.wordpress.com/2013/07/drip-watering-siletz.jpg

Alternative Forms of Piping

While drip irrigation is both efficient and produces higher yields, using PVC pipes may require a significant financial investment. While PVC pipes are the most reliable form of water transportation (as they last longer), they are not the only means in which drip irrigation can be produced. If PVC pipe cannot be afforded, the system can still be used with natural low-cost material such as bamboo. Simply use the same method as detailed below (or modify as needed) while replacing PVC pipe + connectors with a bamboo-like alternative (Rainwater Harvesting, 2016). Keep in mind, although bamboo does act as a cheap alternative it is much more susceptible to the elements and may require frequent maintenance.

A drip irrigation system made of bamboo may look something like this: http://www.cseindia.org/userfiles/bamboo_drip.jpg

Here’s a website with step by step procedures: http://permaculturenews.org/2014/02/28/bamboo-drip-irrigation/

Set Up

Step by step procedure

1. Attain supplies (Mainlines, Submains, Laterals, and Storage Tank)

2. Create correct hole size (matching Mainline diameter) in lower level of Storage Tank

3. Attach Mainline to hole in Storage Tank

4. Seal Mainline end within Storage Tank (any form of plug will do)

5. Create and attach Mainline to Submains (if using PVC apply T-connectors)

6. Create 3.2 mm Emitter holes in Laterals relative to crop line spacing

7. Attach Laterals to Submains along crop lines

8. Seal-off all ends on Mainlines, Submains, and Laterals

Similar end product: https://s-media-cache-ak0.pinimg.com/736x/a6/8e/ae/a68eaee4c210cefac1008ab267f2a17e.jpg

Greenhouses

Using a greenhouse for crops is an effective way to keep moisture from evaporating into the atmosphere. Not only do greenhouses retain moisture, they also aid in pest prevention. Coupled with a drip irrigation system, a greenhouse can add benefits such as increased yields and a longer growing season (Agritech, 2016). What is even more appealing about greenhouses is the simplicity involved in making them. Essentially, as long as there is adequate spacing, coverage, and support a simple silpaulin tarp can be made into an effective small-scale greenhouse.

Set up

construct a small greenhouse requires minimal (and likely low cost) materials accompanied by a fairly simple set up process. Mandatory materials are as follows: silpaulin tarp (or similar material), staking pieces, holding materials, and supports. Staking pieces can be simply sturdy sticks (though plastic or metal stakes will work best), holding materials can take the form of nails or string, and supports are typically any form of wood, plastic or metal. In many rural environments (where wood is available) a fairly simple greenhouse can be constructed using local trees and nails or tied bark string. The lumber from the trees is staked around the perimeter of the irrigation system and the tarp is draped over and held into place. (Agritech, 2016)

Step by step procedure

1. Attain Supplies (supports, stakes, holding material, tarp)

2. Lay supports around perimeter

3. Secure cross supports atop perimeter supports

4. Drape tarp across supports (enough to allow excess on the ground)

5. Secure tarp with staking materials

6. Secure tarp on perimeter and cross supports

Examples of basic greenhouses:

https://illuminumgreenhouses.com/portfolio-items/kadogo/#prettyPhoto

http://4.imimg.com/data4/SL/HF/MY-14033358/greenhouse-shading-500x500.jpg

General benefits of drip irrigation systems.

A drip irrigation system complete with greenhouse is a smart investment for those working in the rural agricultural sector due to a multitude of benefits. A study done by USAID in Haiti found that drip irrigation provided an additional $5000 worth of income within 40 hectares of land (USAID, 2014). It is also likely that these types of systems will reduce household energy spending. USAID support in Karnataka, India found that smallholder farmers reduced electric pump use from 84 to 25 hours per week of use. This was enough for one farmer to send his son to college as he was no longer needed to water the fields and there was more money in savings (USAID, 2016). Furthermore a 3 year study by the IDRC in Guyana showed that water usage was reduced by 25% while crop yield increased by 34% in some instances (IDRC, 2014).

Considerations and possible issues

Drip Irrigation within a greenhouse can be a fantastic way to use water efficiently on crops, however there should be some considerations to keep in mind when planning to use this system. The drip irrigation system described in this chapter has taken into account the importance of practicality and efficiency of use, but should be modified for regional situation and needs. Suitable crops, slopes, and soil types also need to be taken into consideration. Building a greenhouse can be equally as challenging in regards to logistics, financial requirements, and available resources.

Crops

Drip irrigation is best suited for high value row crops (carrots, etc.), tree and vine crops where each emitter will be able to effectively water each crop. Typically cash crops are farmed using drip irrigation as greater capital will be produced and greater product will be made per crop. Therefore, it is recommended that this system is utilized with local profit-based crops (FAO, 2016).

Slopes

Drip irrigation can be reasonably modified to any arable slope. Normally the crop would be planted along a soil line and the laterals (dripping pipes) would then be laid atop the crops. This is done to minimize changes in emitter discharge as a result of land elevation changes (FAO, 2016).

Soils

Drip irrigation is generally suitable for most soils, though there are some precautions needed for certain soils. For instance, water on a clay soil must be applied moderately to avoid surface water ponding and runoff. In contrast, more sandy soils require a higher discharge rate in order to ensure adequate lateral wetting of the soil (FAO, 2016).

Greenhouse construction

As previously stated, a greenhouse is a fantastic way to maximize water efficiency on crops, however there are some challenges associated with building one. Mainly these challenges take the form of materials available such as a silpaulin tarp or proper supporting and holding materials. If someone would like to build a greenhouse they must have the proper materials for it, some of which may be difficult to acquire based on location. If the user does not live in an area which is abundant in trees then lumber may have to purchased, something not everyone can afford. Even more so might be the difficulty to acquire a silpaulin tarp. A properly sized silpaulin needs to be manufactured, sold or donated. If the user cannot acquire/afford this important piece of material then they should consider whether the cost of construction outweighs the benefit.

Possible suppliers

iDE: https://www.ideglobal.org/

iDE provides users with low-cost international products as well as provides instructions on home-made low-cost technologies that can be easily adopted.

Jain Irrigation : http://www.jains.com/PS/index.htm Here’s a fantastic website that can provide low-cost product for both the drip system as well as the greenhouse which it also shipped internationally

References

1. Brouwer, C., Prins, K., Kay, M., and Heibloem, M. (1988) Chapter 6. Drip Irrigation. In Irrigation Water Management: Irrigation Methods. Food and Agriculture Organization, Rome.

2. FAO (2016). Drip Irrigation. Retrieved November 23, 2016, from http://www.fao.org/docrep/s8684e/s8684e00.htm#Contents

3. Friedlander, L., Tal, A., & Lazarovitch, N. (2013). Technical considerations affecting adoption of drip irrigation in sub-Saharan Africa. Agricultural Water Management, 126, 125-132.

4. Ibragimov, N., Evett, S. R., Esanbekov, Y., Kamilov, B. S., Mirzaev, L., & Lamers, J. P. (2007). Water use efficiency of irrigated cotton in Uzbekistan under drip and furrow irrigation. Agricultural Water Management, 90(1-2), 112-120.

5. IDRC. (March, 2011-August, 2014). From farm to fork: improving nutrition in the Caribbean. Retrieved December 01, 2016, from https://www.idrc.ca/sites/default/files/sp/Documents%20EN/Connecting-productivity-nutrition-and-health-106525-EN.pdf

6. Krishnamurthy, Ravindra. (2014). Bamboo Drip Irrigation. Retrieved December 02, 2016, from http://permaculturenews.org/2014/02/28/bamboo-drip-irrigation/

7. TNAU (2001) Low Cost Greenhouses for Vegetable Production-Agritech.tnau.ac.in. Retrieved November 23, 2016, from http://agritech.tnau.ac.in/agricultural_engineering/greenhouse.pdf

8. USAID. (2014, March 21). Haiti: Drip Irrigation Makes New Farm Possible. Retrieved December 02, 2016, from https://www.usaid.gov/what-we-do/water-and-sanitation/from-the-field/drip-irrigation

9. USAID. (2016, 10 March). Drip Irrigation Helps Farmers Save. Retrieved December 02, 2016, from https://www.usaid.gov/results-data/success-stories/drip-irrigation-helps-farmers-save