Irrigation: main interest in money

Press, 1 May 1981, Page 18

Irrigation: main interest in money

By

JOHN GOULTER,

journalist,

Lincoln College

A four-day conference and exposition on irrigation with some 1500 in attendance and over 200 exhibits of irrigating equipment is, by anyone's standards, a vast affair. The AGRI-TURF Irrigation Exposition, held annually by the United States Irrigation Association, attracts visitors from throughout the United States and around the world. They come to see one of the largest displays of irrigation equipment that there is: One of the visitors to the 1981 exposition held in February at Salt Lake City, Utah, was a New Zealander, Graham Harrington, an agricultural engineer with the Ministry of Agriculture and Fisheries. He is stationed at the New Zealand Agricultural Engineering Institute at Lincoln College.

Mr Harrington is at present in the United States on a year’s study tour supported by a grant from the Lincoln College Foundation. His visit to the exposition is one of the highlights of his. visit so far, and not merely from an engineering point of view. ‘“lt was quite clear that technical matters were important at the conference,” he says, “but the main interest was the process of running a business to make money.” Energy use was a major concern. With increasing demands on water resources, research is being done on deficit irrigation. One scheme discussed was deliberately under-designed, knowing that yields would be reduced. However, the profit to the farmer with his low cost, low water-use system

was the same as with a scheme designed for full irrigation. “In other words, the same dollar profit for less capital, less water, and less energy,” reports Mr Harrington. Over-watering was shown to be doubly inefficient, wasting water and leading to loss of fertiliser. Nitrogen fertiliser is particularly vulnerable to this leaching, causing subsequent problems of groundwater pollution. Information on the type and timing of nitrogen applications was discussed, as well as suggestions to reduce fertiliser applications when.irrigation water contained ap-

preciable amounts of nitrate. All aspects of irrigation were represented at the expo, with manufacturers using “every strategy imaginable” to attract customers to their exhibits. One of the most successful soft-sell techniques Mr Harrington reports was of one exhibitor who mounted your instant photo in a key ring while you waited. Surface irrigation, though, “tends to be the poor relation,” not having the glamour of large expensive machinery or the innovations of drip irrigation. The surface irrigation session was low key and poorly attended.

Mr Harrington reports on some sophisticated technology. Some of the trickle systems featured a controller with a feed back system and liquid crystal display to identify problems rapidly and toreadily control the multivalve irrigation and fertiliser application system. Many irrigation controllers show the impact of microprocessors, with units ranging in price from ?60 to $60,000 replacing the old electro-mechanical systems. . Among the side-roll irrigators, Mr Harrington was keen to . inspect the McDowell company’s- model, which shows a parallel development to the N.Z. Agricultural Engineering Institute’s model, recently shown to local farmers at a field day. The two machines share the basic concept of end

drivers with booster units along their length, The major difference is that the United States model draws itself along a fixed cable instead of coiling the cable up on a winch drum. It is designed to use a longer length of hose than the N.Z.A.E.I. machine, and it requires less labour. The disadvantage is the higher pressure needed for the hose. The McDowell company has five prototype models in the field, and they will convert existing models for $15,000. Also at AGRI-TURF Mr Harrington saw a range of water turbine driven plastic sprinklers. Having no arm to interfere with the sprinkler jet, they can be made to give any desired sprinkler pattern. He has sent one of the sprinklers to the N.Z.A.E.I. for testing.

Other sprinkler nozzles included a diffuser nozzle designed to assist jet break-up on a low pressure sprinkler, and another designed to give a constant flow despite variations in water pressure. These nozzles can help with the layout of systems in awkward or hilly positions, or where a sprayline is undersized. There was also a lot of electrical equipment on display. One unit which showed potential for New Zealand was a three phase generator which converts from a single phase power supply. “In outlying areas I could see this unit being used to avoid the high cost of a single phase motor or the additional cost of three phase power reticulation,” says Mr Harrington.