J. agric. Engng Res. (1987) 37, 223-227 Use TECHNICAL NOTE of Pulse Irrigation for Reducing Clogging Problems in Trickle Emitters R. C. JACKSON*; M. G. KAY* Various techniques are available to deal with the clogging problem in trickle irrigation. Although one approach is to increase the size of the waterway in the emitters, this can lead to increased emitter discharge and changes in the soil wetting pattern which may adversely affect water availability to plants. There is evidence to suggest, however, that established soil wetting patterns can be maintained at the higher discharges if the flow is pulsed. A laboratory study on a sandy loam soil has demonstrated that pulsed flows up to three times the equivalent continuous flow can be used with little change to the soil wetting pattern. Thus it should be possible to significantly increase emitter sizes and so reduce the tendency for clogging. I. Introduction Trickle (drip) irrigation is a method of applying small but frequent applications of water to crops through small outlets (emitters) located close to the plants. It has many advantages over the more commonly used sprinkler and surface flooding methods such as the potential for greatly improved efficiency in water use and the successful irrigation of crops using saline water on marginal soils (Blackl). However, one major disadvantage of trickle systems is the tendency for the emitters to clog through the accumulation of debris usually carried in the irrigation water. Although various techniques such as filtration and chemical dosing can overcome this problem they can be expensive to install and to operate and they require highly skilled management for their successful use. An alternative approach to the clogging problem is to increase the size of the waterway in the emitters (normally emitter waterways are 0.I to I-0 mm in diameter). However, this may increase the emitter discharge which in turn would change the pattern of wetting in the soil and may adversely affect water availability to the plants. There is evidence to suggest, however, that established wetting patterns in the soil can still be maintained at the higher discharge if the flow is pulsed. The principles of pulsing were first set out by Karmelli and Peri. 2 They described a pulse as consisting of an operating phase (to), during which water is applied to the soil at a discharge (Qv); and a resting phase (tr) when the flow is zero. The average pulsed discharge (Qa) over the irrigation period (to+tr) would be: Q~ = QPt~ (I) to + t r " The average pulsed discharge (Qa) is equivalent to a continuous discharge (Qc). Thus the same amount of water would be applied with a continuous discharge (Qc) as in the pulsed regime provided the irrigation period was (to + tr). * Silsoe College, Silsoe, Bedford MK454DT, UK Received 19 February 1986; accepted in revised form 25 October 1986 223 0021-8634/87/070223+ 05 $03.00/0 9 1987 The British Society for Researchin Agricultural Engineering