Simulation Of Rice Yield Influenced By Meteorological Factors Under Different Soil Organic Carbon Content And Model Improvement

With the continuous acceleration of global climate change,the stability of food production is an important guarantee for social development and progress.Soil organic carbon content is one of the key contributors of soil fertility,which provides stable soil ecological environment for maintaining agricultural production.At present,the offset of soil organic carbon on climate change has attracted researchers'attention all over the world.In this study,Oryza?version.3?model was used to simulate the effects of different soil organic carbon contents on rice yields under different scenarios of temperature,precipitation,radiations and CO₂ concentration.The algorithm of rice transplanting time effect and dynamic extinction coefficient was improved for rice cropping system in Northern China where the crop yield was normally limited by temperature accumulation and radiation.The main researches are shown as follow:1.ORYZA model could s imulate the annual yield var iability of two experimental sites of rice cropping system in Southern China under different soil organic carbon contents.Except for the simulation of low soil organic carbon content?NPK?in Minhou,the simulations had siginif icant relation with the observations?p<0.01?for other treatments.Therefore,the model can be used to simulate the year to year yield var iability under different soil organic carbon contenta for the rice cropping system in South China China,which provides a conditionfor further simulating of yield changing under the risk of climate change.2.When the changes of mean temperature during the growing period are-1?,+1?,+2?and+4?of normal level:compared with control group,the simulated rice yields were decreasing with the rising temperature;The averaged variation of rice yield for many years has no signif icant relationship with soil organic carbon content.When the total precipitation are-20%,-50%of normal level:compared with control group,the simulated r ice yields were decreasing with the lower precipitation,the averaged yield variation of the high soil organic carbon content treatment is signif icantly reduced by 57%,and the upper and lower limits of CV variation range are lower.When the total radiation in the growth period is-20%,+20%of normal level:compared with control group,the total var iation trend of rice yield at the study site is decreasing,but the dry matter quality on the ground increases with the increase of radiation;in this scenario,the increase of soil organic carbon content has no significant effect on yield variation.When the CO₂ concentration was+30ppm and+60ppm of normal level:compared with control group,the simulated rice yields were increasing with the rising CO₂ concentration;there was no signif icant difference between the treatments,and there was no significant difference in CV fluctuation range.3.After introducing transplanting time effect and dynamic population extinction coefficient into the model,the mean square root error?RMSE?and relative variation?RE?of similating the duration of growth period were only 1.6 days and 1.3%on average,and the RMSE and RE of yield simulation were714 kg/hm² and 9.2%,respectively,which all past the statistic level of model performence.Compared with a constant as group extinction coefficient,introduc ing a dynamic group extinction coefficients improved about 14%of the accuracy for yield simulation.The improved model has a better simulation performance.In conclusion,ORYZA model could be used to simulate the yield change under different soil organic carbon contents in southern rice field and well captured the dynamic change of yield over the years.The increase of soil organic carbon content in rice field could significantly alleviate the yield variation caused by the change of precipitation and radiation,and showed no siginif icant relationship in CO₂concentration and temperature variation scenarios.The improved model based on ORYZA development period model greatly reduced the simulation error of the development durtion and meteorological yield,and had a better simulation capability.