Drip Technology

John Roberts
Roberts Irrigation Products, Inc.

History

Drip irrigation technology is best understood by examining its history, the major developments, and what type of future innovations will happen. What is drip irrigation? It is a method of uniformly delivering water and nutrients to a plant’s root zone in the precise amounts required to meet the needs of the plant. “Drip tapes” and “In-Line” emitters are the most commonly used products for this type of irrigation. Drip irrigation allows a grower the ability to apply water and put chemicals and fertilizers directly to the plant.

Drip irrigation has met the need of growers who wanted a higher control of irrigation than what was previously used in the market. It was adaptable to new growing practices such as the use of plastic mulch and it helped to reduce the use of pesticides and fertilizers. It has given arid or drought ridden areas of the world the ability to grow crops with very limited water supplies. According to the United Nations, one third of the world’s population lives in countries that are experiencing moderate to high water stress, and by 2025 it is estimated that as much as two thirds of the world’s population (5 billion) could be living in countries under water stress conditions.

Drip irrigation history can be dated back thousands of years, depending on what is defined as drip irrigation and how primitive it is. The origins have been said to be from Egypt or even somewhere in Asia. During the 1700’s, there were reports of people experimenting with primitive forms of drip irrigation. Drip irrigation, in its current form, was pioneered in the 1940’s in England, but not until the introduction of polyethylene plastics in the late 1960’s did drip irrigation begin to gain recognition as an effective system that increases crop yields, reduces water consumption, and reduces the requirements for fertilizers and chemicals.

The list of major accomplishments in drip irrigation includes; Chapin Watermatics who supplied polyethylene tubing to water plants and flowers grown in greenhouses in the 1950’s, Sterling Davis who installed the first field experiment with subsurface micro irrigation on lemons and oranges in 1963 and Norman Smith who invented Dew Hose drip tape in 1964. In 1969, Bernarr Hall began to conduct trials using surface drip irrigation on strawberries and tomatoes along with plastic mulches, near San Diego, California. Drip technology was commercialized and widely adopted in the 1980’s by companies both in the United States and Israel. The 1990’s can be seen as the decade that used more innovative engineering to improve on the existing irrigation devices. One example of this is the introduction of turbulent flow emitters. These tapes were a significant improvement over earlier generations of drip tapes and because of their ability to keep contaminants suspended they greatly decrease plugging. In addition to the major development of new technology, the last decade was a period where companies reached out to develop new markets around the world. This decade also saw the entry of many new manufacturers into the industry and a more competitive marketplace.

The history of irrigation has also had many milestones in the past fifty years and the overall irrigation statistics are crucial to understanding where this industry will go. Worldwide, total irrigated land has increased from 96 million hectares in 1950 to 225 million hectares in 1985 and 271 million in 1998. This represents an increase of 282% in a forty-eight year period. The largest increases, on a percentage basis, took place in Europe and Africa. According to Food and Agricultural Organization of the United Nations, 40% of the global food production comes from 17% of cropland that is irrigated. In the United States, 15% of the harvested land is irrigated and the irrigated land produces 38% of the total crop value. In both cases irrigated lands provide a disproportionate amount of food production and they are necessary for the survival of our growing population.

The adoption of drip irrigation has been considerable in the last twenty years and during these years the percentage of annual increase has out paced other methods of irrigation. Over the past decade, the average annual growth rate of drip and micro products has been approximately 8%. Sprinkler and Gravity both had smaller increases at 3%. Looking at the statistics closer, they demonstrate several individual trends for each type of irrigation method. The growth in gravity irrigation mostly took place between the late 1980’s and 1990 and has been declining ever since. Sprinklers were just the opposite. In the early 90’s, the growth rate for sprinklers was declining, and then it turned around and sprinklers have lead the growth for the past few years. Even with drip irrigation’s consistent increase over ten years, drip and micro irrigation only accounts for approximately 5% of irrigated land in the United States. Two of the most influential reasons that drip is not a larger percentage of irrigation methods are because of economics and the lack of education on these types of products. Drip is still a new method of irrigation to many growers. Even some of the growers who have tried drip do not use it to its fullest potential. Most growers take several years to get comfortable with drip products and then they start to utilize fertigation and chemigation techniques.

The Advantages and Disadvantages of Drip Irrigation

The use of a drip irrigation system holds many advantages, but to get the best return on the substantial investment, the system must be well maintained and managed properly. Good irrigation scheduling is critical to achieving top yields and quality. Drip systems lend themselves to facilitating crop water demands and allow the crop to be engineered. Field measurements show that drip irrigated vegetable farms often apply 30%-50% less water than used by furrow application. Drip irrigated systems do not wet the entire field surface and as a result reduce evaporative water losses, which translates to efficient use of water. Because less water is needed, a smaller water source is used, lower pumping pressures and lower flow rates are used to make for a more environmentally friendly irrigation system. In addition to using less water, the crop yields and the quality of the crop increases. Much of this is due to the manager’s ability to control the irrigation scheduling to more closely match the crop’s water needs without wetting plants, fruit or vegetables.

It is easy to pick out a drip field because the crop is so consistent. All of the plants are growing at the same height and look nearly identical. This is because drip irrigation uniformly and efficiently delivers chemicals and fertilizers to the crop. The other feature that you will notice about drip fields is that there are fewer weeds and less disease. Diseases may be lessened because foliage is not wetted and the soil moisture can be better controlled. Drip irrigated fields also give the grower more access into their field. The irrigation can continue up to and even during cultural operations such as cultivation, spraying, or harvesting. Finally, the drip system is one of the most versatile systems allowing a grower to irrigate small or irregularly shaped fields.

If there are so many positives of this technology then why aren’t all farmers using it more extensively? There are several factors that have slowed the adoption of these products including initial costs, changing of cultural practices, increased management and maintenance, disposal of the product and the stability of their own market. To use drip, a grower has to go through a learning process on how to use the product and trust that it will work. Increased management and maintenance is mostly due to monitoring of the system. Just the fact that they have been farming a specific way for many years has been an obstacle. Cultivation, planting, and harvesting practices may need to be adapted to accommodate use of drip irrigation. One of the key factors necessary for farmers to try new methods is the economic situation of their crop. Good markets help foster experimentation in growing practices. In bad markets, growers run their businesses very conservatively, relying on familiar cultural practices.

Most of the disadvantages can be overcome with good system design, proper installation, and good management. The Initial costs may be more expensive on a per acre basis than furrow irrigation because of the filters, pumps, regulators, valves, gauges, and mainlines that are purchased the first year the farm is changed to drip irrigation. Tape and incidental fittings are reoccurring costs and could be replaced as much as once a year or as little as every 10 years. Management of the system becomes more crucial because a critical delay in the operation of the system or infrequent inspections of the system may cause crop damage. The frequent irrigation associated with drip irrigation also requires water to be readily available. Another issue is that germinating a crop may be more difficult depending on the buried depth of the tape or the crop grown. Management training is recommended for drip irrigation. There are other issues to deal with like rodents, insects or human damage of drip tape that may cause leaks and require repairs. Pest control should be managed in all fields to minimize the risk of problems. Keeping the emitters unplugged is key to the success of drip. Good water supply, proper filtration, and a quality design can make the system much less susceptible to plugging. The water supply should have a water quality analysis done to identify possible problems with the water. Problems can be mitigated by use of good filtration and/or chemical treatments.

Measurement

Drip irrigation requires more measurement that other forms of irrigation. Measurements should be made on flow rates, water pressure, differential pressures across filters, pH levels, and chemical levels in the water. If these types of measurements are taken on a regular basis, any problems will be detected and alleviated before there is any damage to the crop. Most manufacturers have detailed guidelines of how all of the components of the system should be functioning. Proper monitoring of these rates will help insure that the irrigation system is performing at the same level throughout the entire crop season.

Uniformity

One of the most important aspects of using drip irrigation technology is measuring how well it is working. Emission Uniformity is a measure of how evenly irrigation water is distributed across a field. Emission Uniformity is important because it allows a grower to design the most efficient irrigation system. There are a number of factors that affect Emission Uniformity, but two major factors are system design and emitter clogging. While there have been no radical innovations in drip products in the last year or two, most manufacturers have made continual improvements to quality. Several manufacturers now have excellent products with Cvs of .05 or less. When you are working with drip you should monitor the uniformity to insure that you will get the most consistent crop and maximum crop yield. Well-designed systems can deliver an EU of 90% or better. Drip is the most uniform method of irrigation and because of this it is the most efficient.

The population and the stress it is putting on our water supplies

The fact is that the world’s population is increasing and potable water supplies are becoming more valuable. There is some daunting information out there that shows that we have to be more efficient with our water. Populations in Asia and Africa are increasing at a rate of 1.8% and 3.1% respectively, while the per capita production of food stuffs are increasing by only 1.3% in Asia and decreasing by 1.1% in Africa. According to a study by Stanford University and the Global Water Policy Project in Cambridge, Mass., humans have tripled their water usage over the last forty years, amounting to 54% of what can feasibly be captured. By the year 2025 researchers project that humans could use as much as 70%. Even as farmers are being asked to produce more food, they will be asked and then forced to do so with less water consumption.

The population has been growing at a tremendous rate. From the beginning of time until 1960 the population had only increased to 3 billion people. From 1960 to 2000 the population has grown to 6.1 billion, a doubling of the population in 40 years. While population increases, the amount of usable water does not. The population is also migrating to the large cities of the world. Fewer people will actually grow their own food. The population Growth since 1973 has decreased the per person potential water availability from 12.9 down to 7.6 thousand m3. The greatest reduction was in Africa, Asia and South America.

The population on Earth is going to grow continually for the next 15 years. The population is estimated to grow from 6 billion people to 8.1 billion people by 2015. This is an increase of 33%. The Food and Agriculture Organization of the United Nations states that to meet the demand three factors will have to occur. The first is increasing agricultural yield. Second an increase in the use of arable land. And last there needs to be increased cropping intensity. The organization predicts that 69% of increases will come from increased yield, 12% will come from increased intensity and the rest will come from new arable lands. Approximately 80% of the developing world’s potential arable lands are in areas with sub-humid or semi-arid climates with erratic rainfall. It is going to be drip irrigation that allows the world to meet their increased yields.

Current Technology

Drip Irrigation products are manufactured a number of different ways, especially when it comes to the actual emitter which regulates the water flow to the plant. Drip emitters are designed in numerous ways, including emitters that are molded into the tape itself and emitters that are inserted manually onto the supply tube. Today, there are several types of drip irrigation emitters that are used including integral emitters, in-line emitters and attached in-line emitters, on-line emitters, microtubes and porous pipe.

The integral emitters are mostly utilized in drip tapes because they give a higher performance at a reasonable cost. Drip tapes are the fastest growing drip irrigation products. The emitters are formed during the manufacturing process of the tape and are made from the same material. Drip tapes range in wall thickness from 4 to 25 mils. The thinner tapes are more commonly found in single season applications and the heavier walled materials are found in multi-year or permanent applications.

The in-line emitters are made with a coupling type device that allows the connection of two lengths of tubing or hose while providing an outlet at the point of the union. The use of in-line emitters has become less popular with the development of the attached in-line emission products.
The attached in-line emitters are either welded or glued into the interior of a tape or hose product during the manufacturing process. A hole is made on the exterior of the product to allow the water to exit. Frequently the attached in-line emitter is made of a different material than the tube.

On-line emitters are attached by a barbed inlet coupling that is put through a hole in the supply line and connects the supply line with the emission device through a supply tube. On-line emitters can also be attached directly to the supply line itself, in the case of certain brands of drip tape or hose. Another choice is microtubes that have a long small diameter, laminar flow tube inserted into a larger supply hose. The flow rate is controlled with the friction loss by extending or shortening the tube. Finally, porous pipe emits water all along the length of the tubing. There are thousands of places per foot where water weeps out of the tubing. Each of these types of drip irrigation products seem to have their niche depending on the crop and its permanency.

The Future of Drip

Drip irrigation manufacturers are going to use new types of materials, products with impregnated fertilizers or chemicals, products that impact the environment less and products that are part of computerized systems.

With the rise in the costs of plastics, recycled materials are going to be more attractive. Used drip tape will become a more recycled product too. There has been a boom in companies that are asking for agricultural recycled materials and they are using it to make products for other markets. Drip tapes and all plastic products in agriculture will be recycled into new products in our industry and for other industries. The next step after recycling products is to build a product that does not need to be recycled. The next major generation of tapes will be made of materials that will decompose into the soil when the crop is finished. The idea is that when a grower finishes his crop, he could just plow in the tape and let it decompose into a beneficial ingredient for the next crop. To do this the industry is going to have to look at making the products out of natural materials.

The new drip products will have to handle recycled water, new chemicals, and new types of biologicals. As the political environment will dictate, we will need to make products that can handle water that is much more contaminated than now. The materials we use will have to work in conjunction with new biologicals. How are these new biologicals and our materials going to react? The manufacturers must continue designing products that adapt to other outside influences including governmental, environmental, and the economics of the agricultural industry.

New product innovations will bring precision agriculture to a new level. There will be a point where a grower can control each emitter or each emitter would act independently, depending on the condition of the soil it is in. The emitter will measure the moisture level and then irrigate automatically to maintain the most beneficial watering schedule. The future systems will monitor each plant automatically and deliver to the plant the exact requirements including fertilizers, chemicals and biologicals.

Another trend that has started, but will not see a major impact for many years, is the increased injections into drip irrigation. In the 1990’s, much of the research done on drip tape was to prove how efficient it can be and where it can be used. Now much of the research is working on how chemicals, fertilizers and biologicals can used in drip irrigation. We are in a period where chemicals such as Methyl Bromide will no longer be available and researchers are searching for new formulas and methods to replace these existing methods. Drip irrigation and other plastic products, such as mulch, are going to play a key role in the new answers. We have just entered an era where many new chemicals, biologicals and fertilizers are going to be introduced and the new products have to be compatible with them.

There will be many debates about levels of government regulation of farm chemicals, but greater regulation is coming on a worldwide basis. Rather than fight the inevitable, we must develop economical ways to farm within the constraints of coming regulation. Trials are underway in various parts of the country using reclaimed water for both landscape and agricultural applications. Sub-surface drip irrigation may be the preferred water delivery method of reclaimed water, because it minimizes plant and human contact issues and the associated risk of pathogen contamination. Irrigation run off and leaching have now been identified as sources for contamination of both surface and ground water resources. Excessive pumping has also led to salt water intrusion in some areas. Farmers must apply only the amount of water the plant needs.

Industry Responsibility

The manufacturers of irrigation products need to work together to develop new markets and inform growers of the total benefits of drip irrigation. We must build in enough profit to maintain innovation and make products more environmentally friendly. We must also let our governments and the general public knows how valuable drip irrigation and plastic products are. The ability of the industry to keep developing new products and to promote drip irrigation will help insure these products will continue to be used, and in the bigger picture, the world demand for food will be met.