RICE SCIENCE ›› 2012, Vol. 19 ›› Issue (2): 143-152.

• Research Paper • Previous Articles     Next Articles

Estimating Crop Coefficient in Intermittent Irrigation Paddy Fields Using Excel Solver

  1. 1Department Civil and Environmental Engineering, Bogor Agricultural University, Kampus IPB Darmaga 16680, Indonesia; 2Experimental Station for Irrigation, Research Center for Water Resources, Ministry of Public Work, Bekasi West-Java, Indonesia; 3Department of Global Agricultural Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-Ku, Tokyo 113-8657, Japan
  • Online:2012-06-28 Published:2012-04-18
  • Contact: Chusnul ARIF

Abstract: The current study proposes a novel method using Excel Solver to estimate, from limited data, crop coefficient (Kc) in paddy fields under intermittent irrigation (II). The proposed method was examined in a field experiment conducted at Karang Sari Village, Bekasi, West Java, Indonesia during the first rice season of 2007/2008 (December 2007 to April 2008) in the rainy season. As the control, continuous flooding irrigation (CF) was applied to the conventional rice cultivation fields. Based on the observed water storage, Excel Solver was used to estimate crop evapotranspiration. Estimated crop evapotranspiration was used to compute Kc value, then the average Kc values at each growth stage were compared with that for the CF treatment. The estimation method was evaluated by comparing estimated crop evapotranspiration and the crop evapotranspiration derived by the well established FAO procedure. Excel Solver estimated crop evapotranspiration accurately with R2 values higher than 0.81. Accordingly, more than 81% of the FAO crop evapotranspiration was described by the proposed method. Thus, Kc value could be well determined from those estimated crop evapotranspiration. Under the II treatment, the average Kc values were 0.70, 1.06, 1.24 and 1.22 for the initial, crop development, reproductive and late stages, respectively. These values were lower than those under the CF treatment for initial and crop development stages because of a minimal soil evaporation and intense dryness during these stages. However, average Kc values under the II treatment were higher than those under the CF treatment at the reproductive and late stages, indicating that the II treatment promoted more plant activity particularly for dry biomass production as indicated by a greater number of tillers per hill.

Key words: crop coefficient, evapotranspiration, intermittent irrigation, excel solver, water balance