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Home / Agriculture / Rainguns - The Future of Sprinkler Irrigationby Dr. Anand Titus and Geeta N. Pereira Page 1 | Page 2 Dr.Anand Titus Pereira is a Technical Consultant to Canara Bank. (A Government of India enterprise). The information in this article is not biased toward any single product or manufacturer! Readers are requested to refer the article THE FINE ART OF IRRIGATION IN ROBUSTA ( C. canephora) COFFEE PLANTATIONS and PHYSIOLOGY OF COFFEE FLOWERING for a better understanding of the present article. Shade grown ecofriendly coffee plantations are located in the picturesque evergreen forests of the Western Ghats. These coffee landscapes are known for their beauty all over the world. The natural features of coffee forests include steep mountainsides with altitudes reaching up to 4500 feet main sea level.
Depending on the agro climatic region, Coffee forests are known to receive from a modest 30 inches of rainfall per annum to a high of 300 inches. However, a well distributed annual rainfall is a prerequisite for growing economically sound Arabica and Robusta coffee's. Coffee, being an evergreen bush, requires a high regime of soil moisture during the dry months. In India, coffee usually encounters four to five months of dry spell in a year. The Robusta variety of coffee is more susceptible to drought and needs irrigation to sustain itself compared to the Arabic's. The rainfall inside the coffee mountain is not evenly distributed throughout the year. Due to global warming, the rainfall is uncertain, erratic and altogether unpredictable. Some parts of the coffee forests may receive rainfall for the year in a few days, without another drop of rain for the year. Often the drought that follows the rains is so intense that the surface feeders in both Arabica and Robusta are deprived of residual moisture resulting in poor yields. In some coffee regions of chikmagalur the terrain drops down from 4500 feet main sea level to 400 feet, registering a vertical drop. Setting up a sprinkler system to augment the plants unquenchable thirst for water, under such difficult terrain and mountainous region is indeed a great challenge to engineering skills.
The aim of the present article is to place at the disposal of coffee farmers world-wide, a technical description of the use of rain gun sprinklers inside coffee plantations, which will form a bridge from the results of research to the concerns of practice. We have pioneered a whole new concept of efficient sprinkling for coffee plantations using both impact and non impact sprinkler systems. Our objectives are as follows.
A sprinkler system delivers water to coffee plantations using a net work of main lines, sub mains and lateral lines with emission ducts spaced along their lengths. The aim is to supplement the natural rainfall conducive for inducing blossom. The concept of sprinkler irrigation is to supply the water at the proper time and in sufficient quantities. The timing and the quantity of water are of prime importance in determining the fruit set. If the sprinkling is carried out too early or too late, it will adversely affect the yield. The same thing will happen, if the water is either too little or too much. RAINGUN TECHNOLOGYRain guns provide a promising possibility for sprinkling of small and large holdings in a short time, in situations where the supply of labour is scanty or expensive. Large quantities of water are sprayed on an increasing scale with the help of towers spread out inside the plantation. Rain gun sprinklers operate under low, medium and high pressure systems, rotating at uniform speed and can be adjusted to cover part circle or full circle. The entire sprinkler is driven by gearboxes housed inside the telescopic barrel made up of pressure die cast aluminum body. The rain gun is perfectly balanced and has two discharge outlets. Interchangeable nozzles of different sizes can be fixed depending on the dead length and static head. The main nozzles are provided with an adjustable jet breaker, providing a uniform distribution of rain all over the irrigated area. The second opening is much smaller in size and throws water to an approximate distance of 100 feet, covering the nearby coffee plants. VARIABLE SPEED RAINGUNSWe have also experimented with rain guns equipped with variable speed. These guns are light weight, fitted with turbines and gearboxes and offer two different rotational speeds. The first speed is extremely fast in nature and is particularly useful for sprinkling coffee on the 5th day of flowering. {This particular stage of coffee flowering is very susceptible to damage due to big droplet size of water}. The high speed of rotation results in a fine mist like spray, which is favorable for coffee flowering.
The second speed (slow) is suitable for inducing flowering in coffee. RAINGUNS IN JOE'S SUSTAINABLE FARM, KIREHULLY ESTATEIn the year 2002-2003 we were the first to introduce the Italian rain guns, SKIPPER and MARINER into coffee plantations. In the year 2007, we successfully tried out the GEMINI rain gun.
The main line consists of 12 inches diameter galvanized iron pipes, branching out into 8 inches diameter galvanized iron pipes. The end point is connected to a Y shaped connector connected to two separate 6 inches HDPE pipe line and ending with four inch HDPE lateral lines. The pipe system is so designed in the form of a ring main, so as to avoid water hammer. A specially designed 12 inches non return valve controls the upstream and downstream water pressure. Depending on the elevation and number of pipes required to sprinkle various blocks, we can comfortably operate two mariner jets, throwing water to a distance of 180 feet radius; right up to 220 feet radius. As the deadline and head increases, a single jet operates throwing water to a distance of 180 feet radius. We use a 100 H.P. air-cooled turbo driven engine (diesel) to operate the jets.
Table-a : Rain gun performance under field conditions. SKIPPER
MARINER
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