Evaluation Of Climate Suitability Of Direct Seeding Rice In Zhejiang Province Based On ORYZA2000 Model

Zhejiang Province is the main rice-producing province in China.Direct-sowing rice,featured by energy-saving,labor-saving and simplified cultivation,has expanded cultivation area in Zhejiang Province and currently accounts for 36%of the total rice cultivation in Zhejiang Province.However,the yield of direct-sowing rice fluctuates obviously under the influence of meteorological conditions.In view of such circumstances,it is an important measure to carry out climate suitability evaluation of direct-sowing rice to ensure high and stable yield.For this reason,an experiment with 10 sowing dates was conducted at the agrometeorological experimental station of Longyou in Zhejiang province in 2016-2017,in which the rice variety of Yongyou15 was used.During the experiment,the effect of sowing date on the growth and yield of direct-sowing rice were analyzed,the parameters of ORYZA2000 model were calibrated and verified,and adopted the meteorological data of 22 meteorological stations in Zhejiang Province from 1988 to 2017 in combination with the ORYZA2000 model to obtain the simulated growth period,yield and optimum sowing time of direct-sowing rice in different regions of Zhejiang Province.This model simulated three growth stages of rice,adopted statistical approach to determine the weighting factors of light,temperature and precipitation suitability at different growth stages,and used the climate suitability model to analyze temporal spatial distribution of light,temperature,water and climate suitability in Zhejiang Province.The results are as follows:(1)Later or early sowing date lowered the leaf area index,crop photosynthesis potential,growth rate,and dry matter accumulation in different developmental stages of direct-sowing rice,and reduced yield and conversion rate of dry matter of stem and leaf.Later or earlier sowing time had no significant effect on the TKW(Thousand Kernel Weight)of direct-sowing rice,it reduced the number of effective panicle number,grain number per panicle and seed setting rate of direct-sowing rice which finally contributed to the significant reduction in the yield of direct-sowing rice.The optimum direct sowing date for Yongyou 15 variety in Longyou,Zhejiang,was the middle of May.Earlier or later planting(in early May or late May)may lead to a decline in rice production,and late sowing will easily lead to low temperature in the later growth period,which will seriously affect the yield.(2)After calibration,the NRMSE of leaf dry weight,stem dry weight and spike dry weight of the model were 32.4%,28.6%and 31.1%respectively,and the NRMSE of total biomass and yield were 31.9%and 8.19%respectively,showing that the model performed well in simulating the growth processes and biomass of direct-sowing rice.The model was used to simulate the direct-sowing rice in different regions of Zhejiang Province.And the results showed that the optimum sowing date of direct-sowing rice in Zhejiang Province was distributed like this:later in west and earlier in east.Among them,the optimum sowing date in northern Ningbo and southern Wenzhou came the earliest,the date sequence of the optimum sowing date is 118 DOY,that is,the end of April,while the optimum sowing date in Quzhou and southern Hangzhou came the latest,the date sequence of the optimum sowing date is 132 DOY,that is,the mid-May.In addition,the date sequence of the optimum sowing date in Shaoxing,eastern Jinhua,northern Wenzhou and Taizhou is 123 DOY and around,and the optimum sowing date in other areas was basically in early May.(3)The overall temperature suitability and climate suitability in Zhejiang Province showed a downward trend,and the temperature suitability showed a significant downward trend.The light suitability basically remained same,while the precipitation suitability showed a slight upward trend.By analyzing the suitability of temperature,light and precipitation at each growth stage,it was found that the main meteorological factors and impact stages of restricting the growth and development of direct seeding rice were different in different regions.From the perspective of different areas,it can be seen that the most suitable areas for directsowing rice were the west of Quzhou,the border area between Taizhou and Wenzhou and the south of Huzhou,the suitable areas were the southern Hangzhou,Lishui,northern Wenzhou,Jinhua and Taizhou,followed by Shaoxing and southern Wenzhou.Ningbo and northern Hangzhou are unsuitable areas for direct-sowing rice cultivation.