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Modeling

Modeling the Effects of Water Temperature on Rice Growth and Yield under a Cool Climate

I. Model Development

^a Faculty of Agriculture, Iwate University, 3-18-8 Ueda, Iwate, 020-8550, Japan
^b Department of Global Resources, National Institute for Agro-Environmental Sciences, 3-1-1 Kannondai, Tsukuba, 305-8604, Japan
^c Graduate School of Agriculture, Hokkaido University, N9, W9, Kita-ku, Sapporo, 060-8589, Japan

^* Corresponding author (shimn{at}iwate-u.ac.jp)

For paddy rice (Oryza sativa L.), water temperature (T_w) is a major determinant of growth and yield. In rice paddies, T_w is higher than the air temperature (T_a), and this difference significantly affects production, especially in cool climates. However, there is no model to evaluate the effects of T_w on rice yield. To simulate temporal and regional differences in rice productivity under such climates, we developed a simple mechanistic growth model that accounts for the effects of T_w based on the results of previous field trials. The rate of crop ontogenetic change was linearly related with T_w before the heading stage. Leaf area was expressed as a function of leaf emergence and tillering, and leaf senescence was expressed as function of ontogenetic change and spikelet fertility. Radiation use efficiency was less affected by T_w than by leaf area, and its change with respect to ontogenetic changes was expressed using nonlinear functions. Spikelet fertility, which strongly determines grain yield, was expressed as function of cumulative cooling degree-days (below a threshold temperature), water depth, and the height of developing panicles. This model covered the major processes that are affected by T_w, and can be used for evaluating the role of T_w on rice growth and yield under a cool climate.

Abbreviations: DAT, days after transplanting • DVI, developmental index • DVR, developmental rate • HU_t, heat units for tiller number • LAI, leaf area index • LN, leaf number on the main culm • RPW, ratio of panicle weight to total biomass • RTN, relative tiller number • RUE, radiation use efficiency • T_w, water temperature • T_a, air temperature • TLNI, total leaf number index

Received for publication November 25, 2006.

This article has been cited by other articles:

				H. Shimono, T. Hasegawa, T. Kuwagata, and K. Iwama Modeling the Effects of Water Temperature on Rice Growth and Yield under a Cool Climate: II. Model Application Agron. J., September 10, 2007; 99(5): 1338 - 1344. [Abstract] [Full Text] [PDF]