S Mohan

Crop coefficients (Kc) were estimated for cotton, sorghum and millet for tropical South India based on lysimeter measured actual evapotranspiration (ET) and reference crop ET computed by the modified Penman method. The estimated crop coefficients were 0.46, 0.70, 1.01, and 0.39 in the four crop stages for cotton. Kc value of the last stage was significantly lower than the FAO Kc value. The estimated Kc values were considerably lower than FAO crop coefficients in the third and fourth stages for sorghum, for which the estimated stagewise Kc values were 0.42, 0.71, 0.62 and 0.23. For millet, the estimated Kc values for four stages were 0.51, 0.78, 0.87 and 0.50 and found to differ markedly from FAO Kc values. Crop coefficient relationships with respect to time were developed using mean crop coefficients derived from multi-year data. The developed crop coefficients and relationships would be of great use for the estimation of crop water requirements under tropical climatic conditions. © 1994.

Due to the complexity of irrigation management problems, reliance on experience and experts is necessary for effective decision-making in this domain. Expert systems (ES) are efficient means for providing decision support to tasks that primarily require experience-based knowledge. This paper reviews the adoptability and suitability of ES applications in the domain of irrigation management. Core concepts of ES are briefly discussed. A detailed review of the existing applications of ES is presented under three classes of ES applications: (a) expert systems proper, (b) intelligent front-ends, and (c) hybrid systems. This review of literature shows that the ES approach is applied more recently to broader domain areas in contrast to the earlier systems that were focused on narrower domain problems. Additional research on ES application to domains such as real-time irrigation scheduling, reservoir operation involving stochastic nature of inflows and evapotranspiration demand, and integrated operation of irrigation system components is needed to evolve guidelines for optimal water use. The problem of handling multiple experts to evolve decisions that are less biased than an individual expert needs to be addressed. A methodology that takes into account the uncertainty of the ES decisions is also warranted. Further, there is a need for practical evaluation of the quality of recommendations made by the ES which would result in the successful implementation of the ES. © 1997 Elsevier Science B.V.