Optimization Of Cultivation Technology For Oats In Alpine Region Using APSIM Model

In the desert steppe area of the Middle East of the Qinghai Tibet Plateau,the climate is arid and rainfall is limited,where the natural grassland has a low carrying capacity.Shortage of forage in winter and spring restricts the development of local animal husbandry.It is a key problem for local industry to improve the yield and resource utilization efficiency of the main cultivated forage oats by field management.The purpose of this study is to put forward the optimal cultivation and management mode of oats through field experiments and APSIM model simulation to provide basis for efficient and high-quality production of oats.The experiment was carried out in Jintai ranch,Chaka County,Qinghai Province from 2017 to 2018,and used a completely randomized block design.In 2017,two fertilization treatments were set,namely,low fertilizer(60 kg N ha^-1)and high fertilizer(120 kg N ha^-1).In 2018,four water treatments were set up based on fertilization treatments in 2017.There were 8treatments in the experiment,which were irrigation of 50 mm only in flowering stage（treatment I1）,50 mm in tillering stage and jointing stage（treatment I2）,50 mm in tillering stage,jointing stage and flowering stage（treatment I3）and no irrigation（treatment NI）,respectively.Based on the experimental data,the APSIM model was calibrated and validated,and the oats yield and water use efficiency under different sowing dates,irrigation and fertilization scenarios were analyzed.Finally,the sowing time,irrigation and fertilization schemes suitable for the efficient production of oats in the Tibetan Plateau were proposed.The main results are as follows:（1）Increasing irrigation and fertilization can significantly improve oats the dry matter yield,and reducing irrigation properly can improve the water use efficiency of oats.The dry matter yield of oats can be effectively increased by applying appropriate amount of nitrogen fertilizer under the condition of no irrigation.In 2017,the dry matter yield of oats treated with high-level fertilizer was the largest,which was 6.5 t ha^-1,and the water use efficiency was 32.9 kg ha^-11 mm^-1.Under the condition of irrigation in 2018,The dry matter yield of the treatment of nitrogen 120 kg ha^-11 was the highest(8.5 t ha^-1),and the water use efficiency was 21.9 kg ha^-11 mm^-11 with irrigation 50 mm at tillering stage,flowering stage and jointing stage respectively.In the two-year experiment,the protein content of oats in the flowering stage was higher than that in the milky stage,but the dry matter yield in the milky stage was significantly higher than that in the flowering stage.In 2017 and 2018,it was 32.9%-36.7%and 16.0%-49.1%higher than that in the flowering stage,respectively.And the crude protein yield was 10.2%-10.3%and 8.7%-37.4%higher.Higher dry matter and crude protein yield could be obtained by harvesting at milk maturity.Therefore,in the process of APSIM model calibration and simulation,the final yield was the yield at milk maturity.（2）The model of APSIM-oats was calibrated and verified by field test data.The NRMSE of the simulated and measured values of dry matter yield and soil water storage were 16.6%and 2.7%respectively,and the RMSE were 0.56 t ha^-11 and 4.9mm,respectively.R² were 0.969 and 0.955 respectively.In 2018,the RMSE of simulated and measured values of four key phenological stages（seedling stage,flowering stage,filling stage and milk maturity stage）were 1,3,4 and 7 days respectively,and R² was 0.960.During the validation process,the NRMSE of the simulated and measured oats dry matter yield and soil water storage were 19.7%and4.1%respectively.RMSE were 0.72 t ha^-11 and 7.5 mm and R² were 0.945 and 0.938,respectively.The RMSE of the simulated and measured values of the four key phenological periods in 2017 were 1,1,5 and 5 days and R² was 0.999.The comprehensive simulation results showed that APSIM model can simulate the growth of oats in high cold area.（3）According to the local sowing date of about May 15,we set the sowing ahead of 10,20 and 30 days（May 5,April 25 and April 15）,and 10,20,30 and 40 days behind schedule（May 25,June 4,June 14 and June 24）on the basis of the meteorological data of the test site in 2017-2018.And the effects of sowing date on dry matter yield,water consumption,water use efficiency and days of growth period were analyzed.The simulation results showed that proper late sowing is conducive to the accumulation of dry matter yield of oats in the Qinghai Tibet Plateau,and made the water consumption of oats higher（2018）,but when there was less rainfall in 2017,the water consumption of early sowing oats was higher than that of late sowing oats.The water use efficiency of oats increased with the delay of sowing date,and the earlier and later sowing would lead to the longer growth period of oats.The results of comprehensive analysis and simulation showed that the risk of drought and frost disaster could be reduced and the yield and water use efficiency of oats could be improved by delaying sowing properly in the desert steppe area of Qinghai Tibet Plateau.（4）On the basis of the experiment,16 irrigation combinations（irrigation gradients of 30,40,50,60 and 70 mm）and 5 nitrogen application gradients(30,60,90,120 and 150 kg N ha^-1)of different phenological stages（tillering,jointing and flowering）were set up,with 80 irrigation and fertilization scenarios.The results showed that considering the resources saving and effective utilization and the seasonal distribution of rainfall was uneven in Qinghai Tibet Plateau,the best irrigation times and fertilization amount for planting oats in this region were 2 times and 90 kg ha^-1.In the less rainfall year,the irrigation quota of 70 mm is the most suitable,while the optimum irrigation quota is 60 mm in the more rainfall year.Using crop model+weather forecast+technical guidance+farmers’experience can further improve the irrigation and fertilization system.In conclusion,the study analyzed the effect of water and fertilizer management on the dry matter yield,crude protein yield and water use efficiency of oats through two years field experiment,and calibrated and verified the APSIM oats model in the alpine region of the Qinghai Tibet Plateau on the basis of field experiment,which provided a basis for the application of the model in this region.Moreover,Based on the APSIM model,the changing rules of dry matter yield and water use efficiency of oats under different sowing time,irrigation and fertilization conditions were discussed,and the optimized sowing time and irrigation fertilization system were put forward.The results can provide a basis for the cultivation and management of oats in the arid and semi-arid areas of the eastern margin of the Qinghai Tibet Plateau.