With water comes life, beauty, sustainability, and responsibility. The most widely used irrigation methods are the five that this blog will cover. Mother nature provides the oldest way of watering, rainfall. Rain can be erratic from heavy downpours to sparse amounts. It needs to be controlled. The absence of regular rainfall throughout history has created conditions that have threatened farmers crops and even civilization's survival. There is very little we can do to control rain as it varies from year to year, season to season, and week to week. The need for water storage and irrigation ingenuity becomes necessary. Here are five techniques that have been developed to give all of us a chance to manage and benefit from this most precious commodity, water.
Furrow irrigation is used for row crops where the raised part of the row called the ridge are where the crops are planted. The lower row or furrow is where the water flows. The roots of the plants naturally grow down to the moist soil near where the water flows. Water is fed to the field from a large pipe or a ditch at the beginning or head of the furrows. Water is often pumped out of a nearby lake, pond, stream, or river. The furrows can be as deep as 12 inches or as shallow as a few inches. When a pipe is used as the header (top of the row) to feed water to the furrows, a “T" pipe fitting is used at the beginning of each row with a short length of pipe attached to it to direct the water down the furrow. This method of irrigation is used where there is an unlimited supply of water and the terrain is relatively flat.
Sprinkler irrigation generally used on farms where the water supply is plentiful, where the soil has the ability to hold water, and where the ground undulates or is not level. The downside of these high pressure sprinklers or guns is the high rate of evaporation in arid areas or during times of extremely hot or windy weather. To obtain 100% uniform coverage sprinklers must be set up so the result is 100% spray overlap because the area next to the sprinkler often gets little or less water than the areas away from the sprinkler head.
Subsurface irrigation is similar to drip irrigation in that the water flows through poly tubing 6"-12" under the soil surface with factory installed emitters that are inside the tubing. Here we are talking about using subsurface irrigation for lawns. The tubing has emitters (usually with an herbicide embedded in the emitters) that are evenly spaced at intervals usually 12" apart. If the soil is sandy, you may want the emitters spaced more closely. The water is kept on long enough so that the soil gets evenly saturated. Less evaporation, less weeds, and being not subjected to windy weather are three advantages of subsurface irrigation. On large farms the water is pumped into ditches that are up to 100 feet apart. The water then seeps into the ground thus maintaining the height of the water table and allowing the crops roots to reach the moisture. The western arid farming regions of Utah, Colorado, Idaho, and California use sub irrigation on areas of large acreage.
Drip irrigation has been around for thousands of years from its primitive days in the Middle East and China to modern times when the micro irrigation industry was born. The goal of drip is to deliver water directly to the root zone and minimize evaporation. Water is distributed thru a series if tubing and emitters or sprayers. In ancient China during the first century BCE the use of unglazed pots called Ullas were filled with water and the water would soak thru the pot slowly to irrigated for a week or more. The use of plastic emitters was developed in Israel by Simca Blass in 1959 and became the now worldwide irrigation company called Netafim. These days Drip tape has become the most widely used drip irrigation product for acreage of row crops on farms. Drip irrigation is also used in commercial greenhouses, and residential gardens. Most drip irrigation systems employ some type of filter to prevent clogging of the small emitter flow path. Liquid fertilizers can be run through a drip system when using a fertilizer injector. This method of irrigating and fertilizing is called fertigation. If managed correctly, water application efficiency in a drip system should be high. Weed growth, soil erosion, and labor costs are lessened and fields with irregular shapes are easily accommodated. For home gardeners drip irrigation allows the gardener to use a battery timer and a precise schedule of the amount of time a garden gets watered and the days it will get watered. It will free the homeowner to leave for the weekend or longer while the drip system is on automatic. For a compendium of information, instruction, videos, examples of system layouts, and pre-assembled kits of all sizes go to www.dripworks.com.