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Improving irrigation efficiency in a semi arid sub tropical environment a. cotton yields and water use efficiency

G.D. Keefer, D.F. Yule, .J.H. Ladewig and D.J. Nickson

Old. Dept. of Primary Industries, P.O.Box 81, Emerald, Old. 4720

There are increasing pressures to optimise crop production by sound irrigation management practices as well as to avoid waterlogging and salinity problems produced by excess irrigation(1).. Following early experiments with cotton at Emerald in Central Queensland (2) an irrigation management research programme was commenced. One objective is to assess different irrigation management strategies in terms of yield per unit of irrigation infiltration (I.W.U.E.).


In the 82-83 and 83-84 seasons, the project was conducted on a cracking clay (Ug 5.12) with decomposing basalt at 80-85 cm. irrigation of each treatment was scheduled on potential crop water use estimated from a crop factor and Class A Pan evaporation model (2). The total amount of irrigation added to each treatment was calculated from measurements (using weirs and flumes) of water on and off plots 12 m x 200 m (furrow slope 1%). It was not possible to replicate irrigation treatments but 16 yield samples of 2 rows x 10 metres were taken from the 4 middle rows of each block.

Results and Discussion

TABLE 1. Cotton yields and irrigation water use efficiency.

Over 2 contrasting climatic seasons the F treatment produced the highest yields but the IF and VIF treatments had higher I.W.U.E. (Table 1).

There are reports that I.W.U.E. can he improved by varying the irrigation deficit with crop development (3). Four additional treatments were included in 83/84 to test this hypothesis. The most promising was the F-1• which with 3 irrigations had a much higher 1.W.U.E. than the F treatment.

1. Smith, R.C.G., Meyer, W.S., Blackwell, J. and Mason, W.K. 1982. Proc. 2nd. Aust. Conf., Wagga Wagga, pp 126-141.

2. Keefer, G.0., Yule, D.F., Ladewig, J. 1982. Aust. Cotton Growers Research Conference Nov. 4-5, 1982, Goondiwindi.

3. Bordovsky, D.G., Jordan, W.R., Hiler, E.A., Howell, T.A. 1974 Agron. J. 66:88

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