Modeling the effects of cool water on growth and grain yield in rice

水温（Tw）可以通过各种生长过程限制水稻产量。通过田间试验，建立了一个简单的模拟模型，以评价不同Tw条件（17-26℃）下Tw对水稻生长和产量的影响。该模型涵盖了Tw对发育速率、叶片外观、分蘖和茎伸长的影响。叶面积估计值来自主茎上的叶数和分蘖数的乘积。辐射利用效率表示为发育阶段的函数。收获指数被确定为小穗育性的函数，这是估计与冷却度天的基础上，无论是Tw或空气温度取决于发育中的穗的垂直位置。我们在1990-1999年在北海道的四个地点（比浦、岩见泽、札幌和大野）对模型进行了测试。估计的产量通常与测量的产量很好地一致，其范围为19至677 gm^<-2>，均方根偏差（RMSD）为79 gm ^<-2>（n=33）。基于热平衡的Tw估计模型（Kuawgata等人，2001）估计了四个位置的Tw，RMSD约为1℃，残差无指示性趋势。据估计，札幌过去10年的平均Tw比Ta高3.8℃，Tw之差相当于约300 gm^<-2>的粮食产量，表明北海道水稻生产力的显著“水毯”效应。区域产量的变化主要是由于太阳辐射，但风速，影响Tw也有显着的影响。模拟结果表明，在其他气候条件不变的情况下，气温每升高3℃，札幌的Tw可增加1.3℃，粮食产量可增加6%。

Water temperature (Tw) can limit rice yield via various growth processes. A simple simulation model was developed to evaluate the effects of Tw on rice growth and yield based on the field trials conducted under different Tw conditions (17-26℃). The model covers the effects of Tw on the developmental rate, leaf appearance, tillering and culm elongation. Leaf area estimates were derived from a product of leaf number on the main culm and tiller number. Radiation use efficiency was expressed as a function of developmental stage. Harvest index was determined as a function of spikelet fertility, which was estimated with the cooling degree-days based on either Tw or air temperature depending on the vertical position of the developing panicles. We tested the model at four locations (Pippu, Iwamizawa, Sapporo and Oono) in Hokkaido for 1990-1999. The estimated yields were generally in good agreement with the measured yields that ranged from 19 to 677 gm^<-2> with the root mean square deviation (RMSD) of 79gm^<-2> (n=33). The Tw estimation model based on the heat balance (Kuawgata et al. 2001) estimated those at the four locations with a RMSD of about 1℃ with no indicative trend in the residuals. Tw averaged for the past 10 years was estimated to be higher than Ta by 3.8℃ in Sapporo, the Tw difference being equivalent to about 300 gm^<-2> of grain yields indicating the marked "water blanket" effect on rice productivity in Hokkaido. The regional yield variation was largely attributed to solar radiation, but wind speed that affects Tw also had a significant effect. A simulation indicated that a rise in air temperature by 3℃ could result in a 1.3℃ increase in Tw and a 6 % increase in grain yield in Sapporo, if other climatic conditions were unchanged.