Predicting dry matter production of high yield rice at Yunnan Southwest China using ORYZA 1 model
1998
Xuhua Zhong | Shaobing Peng | Jifeng Ying | Sheehy, J.E. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Field experiments were conducted in a tropical environment at IRRI and in a subtropical environment at Yunnan, Southeast China in 1995 and 1996. Leaf area index, leaf nitrogen content, and above ground dry matter were measured at key growth stages. Daily radiation and air temperature were monitored. With these data as input, gross photosynthesis, maintenance respiration, and growth respiration were estimated using the ORYZA 1 model. The dry matter produced by IR72 was 17.8 t/ha at IRRI and 24.0 t/ha at Yunnan in 1995, while 16.2 t/ha at IRRI and 24.1 t/ha at Yunnan in 1996. The highest biomass of 29.7 t/ha was achieved by Shanyou 63 at Yunnan. The ORYZA 1 model well-estimated dry matter production at IRRI, but underestimated dry matter production at Yunnan. The discrepancy in IR72 was 18 percent in 1995 and 13 percent in 1996, and 28 percent in Shanyou 63 in 1996. A subroutine was developed to account for the effect of the diurnal temperature cycle on maintenance respiration. The maintenance respiration coefficient for stems and sheaths used in the ORYZA 1 model was too high, resulting in an overestimation of maintenance respiration. This, in turn, caused an underestimation of dry matter production and low growth efficiency. By setting the maintenance respiration coefficient of stems and sheaths to zero, the estimation of dry matter production at Yunnan was dramatically improved. However, the model with parameters modified overestimated dry matter production at IRRI. The possible reason for the overestimation were discussed
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