Photo courtesy USDA ARS Photo credit David Nance Variable-flow irrigation sprinkler head |
In this article, we'll look at several different types of irrigation systems, starting with some of the oldest and simplest, which will lead us to an understanding of the more complex systems in operation today. But, first, let's take a closer look at what plants need in order to grow well.
A place to grow
Plants grow in many different places - from plain old dirt to richly fertilized soil. A branch of horticulture known as hydroponics even uses specially prepared solutions of mineral salts as a plant's growing space. Either way, as long as there's somewhere to put down roots and a plentiful amount of the right nutrients, a plant will do its best to grow.
The right temperature
After planting a seed, just the right temperature is needed for it to germinate and begin to grow. Some seeds need warmer temperatures than others to germinate. By relying on our knowledge of seasonal temperatures, it's easy to know when to plant what. And, if mother nature isn't agreeable, you can always make use of greenhouses and other artificial systems to get the temperature just right.
Air and light
Plants make their own food using a process called photosynthesis. During photosynthesis, the chlorophyll-containing green parts of the plant trap light energy and use it to perform a series of chemical reactions. The process involves carbon dioxide, and so plants also need plenty of air. We usually rely on the sun to provide light for our plants.
The plant absorbs carbon dioxide from the atmosphere, draws water up through its roots and uses light to photosynthesize sugars, which it uses as food. It excretes oxygen as a by-product of the process. Without water, photosynthesis cannot take place. |
Water
Water is essential to plants. It carries important nutrients from the soil and is an important trigger for germination and the process of photosynthesis. Without water, plants simply won't grow.
Irrigation systems provide water. When it comes to watering plants in our yards or gardens, most of us don't always like to rely on the weather -- we may use watering cans or sprinkler systems. This is irrigation at its simplest level. And while this is fine for the home gardener, when you're a farmer trying to water an entire field these methods become impractical. So, how about flooding the field? It sounds drastic, but the ancient Egyptians made extensive use of the practice. Two thousand years ago, Herodotus wrote that Egypt was "the gift of the Nile." Diverted into large, flat-bottomed basins, the river Nile provided excellent irrigation for Egyptian crops, and Herodotus was well aware that without the Nile, the Egyptians wouldn't have enjoyed such productive farming methods.
Photo courtesy USDA ARS Photo credit Keith Weller Agronomist Larry Heatherly examines early maturing variety of soybean plants growing in a flood-irrigated field in Mississippi. |
Although the basin method is still popular, there are more refined methods of irrigation in use today:
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