SAR Data Assimilation for Crop Biomass Simulation Based on Crop Growth Model

Biomass from SAR data was assimilated into crop growth model to describe relationship between crop biomass and crop growth time to improve estimation accuracy of biomass. In addition, inverse model was established in order to estimate biomass according to relationship between biomass and backscattering coefficients from SAR data. Based on cost function, parameters of growth model were optimized as per conjugate gradient method, minimizing the differences between estimated biomass and inversion values from SAR data. The results indicated that the simulated biomass using the revised growth model with SAR data was consistent with the measured one in time distribution and even higher in accuracy than that without SAR data. Hence, the key parameters of crop growth model could be revised by real-time growth information from SAR data and accuracy of the simulated biomass could be improved accordingly.

Studies on crop growth modelling and simulation models in China

There is a close relationship between agricultural production and environmental meteorological conditions. In the study of the correlation between them, the simulation models are paid more attention to the crop growth. In this paper the development of the studies on the crop growth dynamic simulation model in China is briefly reviewed. The relationships between meteorological conditions and each process of crop growth (such as photosynthesis, respiration, accumulation and distribution of assimilation products and growth of leaf area) are studied and simulated basing on the results from field experiments. Preliminary models for rice, wheat, maize and soybean have been developed, and some investigations about modelling methods, procedures and parameters in simulation models are made.

Calibration and validation of SiBcrop Model for simulating LAI and surface heat fluxes of winter wheat in the North China Plain

The accurate representation of surface characteristic is an important process to simulate surface energy and water flux in land-atmosphere boundary layer.Coupling crop growth model in land surface model is an important method to accurately express the surface characteristics and biophysical processes in farmland.However,the previous work mainly focused on crops in single cropping system,less work was done in multiple cropping systems.This article described how to modify the sub-model in the SiBcrop to realize the accuracy simulation of leaf area index(LAI),latent heat flux(LHF)and sensible heat flux(SHF)of winter wheat growing in double cropping system in the North China Plain(NCP).The seeding date of winter wheat was firstly reset according to the actual growing environment in the NCP.The phenophases,LAI and heat fluxes in 2004–2006 at Yucheng Station,Shandong Province,China were used to calibrate the model.The validations of LHF and SHF were based on the measurements at Yucheng Station in 2007–2010 and at Guantao Station,Hebei Province,China in 2009–2010.The results showed the significant accuracy of the calibrated model in simulating these variables,with which the R2,root mean square error(RMSE)and index of agreement(IOA)between simulated and observed variables were obviously improved than the original code.The sensitivities of the above variables to seeding date were also displayed to further explain the simulation error of the SiBcrop Model.Overall,the research results indicated the modified SiBcrop Model can be applied to simulate the growth and flux process of winter wheat growing in double cropping system in the NCP.

Simulation and Validation of Rice Potential Growth Process in Zhejiang Province of China by Utilizing WOFOST Model

A crop growth model of WOFOST was calibrated and validated through rice field experiments from 2001 to 2004 in Jinhua and Hangzhou, Zhejiang Province. For late rice variety Xiushui 11 and hybrid Xieyou 46, the model was calibrated to obtain parameter values using the experimental data of years 2001 and 2002, then the parameters were validated by the data obtained during 2003. For single hybrid rice Liangyoupeijiu, the data recorded in 2004 and 2003 were used for calibration and validation, respectively. The main focus of the study was as follows： the WOFOST model is good in simulating rice potential growth in Zhejiang and can be used to analyze the process of rice growth and yield potential. The potential yield obtained from the WOFOST model was about 8100 kg/ha for late rice and 9300 kg/ha for single rice. The current average yield in Jinhua is only about 78% （late rice） and 70% （single rice） of their potential yield. The results of the simulation also showed that the currant practice of management at the middle and late growth stages of rice should be reexamined and improved to reach optimal rice growth.

作物生长模拟模型研究和应用

作物生长模拟模型研究和应用宇振荣（北京农业大学农业生态环境系，１０００９４）ＳｔｕｄｉｅｓｏｎＣｒｏｐＧｒｏｗｔｈＭｏｄｅｌｌｉｎｇａｎｄＩｔｓＡｐｐｌｉｃａｔｉｏｎ．￥ＹｕＺｈｅｎｒｏｎｇ（ＤｅｐａｒｔｍｅｎｔｏｆＡｇｒｏ－Ｅ－ｃｏｌｏｇｉｃａｌＥ...

Applications of Decision Support System:A Case Study of Solanaceous Vegetables

Crop simulation models constitute the major proportion in decision support systems.A large number of crop models have been developed for potato and few for tomato and peppers.In the literature,thirty three crop models have been reported to simulate potato,nine for tomato and six for peppers.Some of these models dealt with the climate change scenario and others with the crop management practices such as sowing time,irrigation,nitrogen,and insect-pests management.The most evaluated and applied models for potato include;SUBSTOR,and LINTUL-Potato,whereas CROPGRO-tomato model is the most tested and applied for tomato.The AQUACROP is the most widely used model to simulate the water dynamics.The CROPGRO model has been tested for elevated temperatures and CO_(2) under greenhouse conditions for tomato.In tomato and peppers,almost similar models have been applied for field conditions as well as under greenhouse environments with some modifications.Nitrogen dynamics has been widely tested by employing the EU-Rotate-N model for tomato and peppers.Simulation studies dealing with changing climate conditions are rare in potato and are not found for tomato and peppers.To modify potato,tomato and peppers models for climate impact studies,it is required that they are(a)calibrated and evaluated with new cultivars under various agro-environmental conditions and(b)assessed under varying field conditions under changing climates and crop management practices,including temperature increases,water and nutrient management and their interactions.These comprehensive model studies and modifications need a collaborative international effort and a multi-year,large scale field research studies on potato,tomato and peppers.

Influence of Climate Change on Winter Wheat Growth in North China During 1950-2000

The crop model World Food Studies (WOFOST) was tuned and validated withmeteorological as well as winter wheat growth and yield data at 24 stations in 5 provinces of NorthChina from 1997 to 2003. The parameterization obtained by the tuning was then used to model theimpacts of climate change on winter wheat growth for all stations using long-term weather data from1950 to 2000. Two simulations were made, one with all meteorological data (rainfed) and the otherwithout water stress (potential). The results indicate that the flowering and maturity datesoccurred 3.3 and 3 days earlier in the 1990s than that in the 1960s due to a 0.65℃ temperatureincrease. The simulated rainfed yields show that the average drought induced yields (potential minusrainfed yields) have decreased by 9.7% over the last 50 years. This is to be compared with a 0.02%decrease in yield if the precipitation limit is lifted. Although the precipitation during thegrowing season has decreased over the last 50 years, the drought effects on the rainfed yieldsremained to be practically unchanged as the spring precipitation did not decrease markedly.