| The study aims at a systematic evaluation and the application of Agricultural Production System Simulator (APSIM) to lucerne planting zones in Ningxia Hui Autonomous Region, China. With data collected from Touying Base of Guyuan Agricultural Institute; Hecaogou Village, Laotang Township, Tongxin County; Helanshan Pasture Farm; Ma’erzhuang Township, Yanchi County; Pilot Base of Yanchi Agricultural Institute; and the Northern Ningxia Semi-Arid Pilot Zone at Jiatang Township, Haiyuan County, developed by Northwest Agriculture and Forestry University, the model was verified in terms of how well the model was applied to lucerne production in the above zones, under different irrigation conditions, and involved in grass-crop rotation systems at Haiyuan County especially. The verified model was further analyzed in terms of how lucerne production and soil moisture varied with climate. Through a careful analysis, major findings include the following:(1) APSIM’s main parameters were determined specifically for the lucerne planting zones in Ningxia, including those for Guyuan variety, Meiguodaye and E3006 variety for the first time, thereby leading to the model with localized parameters to simulate the plant’s growth, irrigation and rotating accuracy;(2) the parameters were adjusted and verified in Guyuan for the first time and the plant’s period of growth, production of dry plant and soil moisture were also verified through an analysis of data collected from Touying Base, Hecaogou Village and Helanshan Pasture Farm; and results show that the R2 was between 0.71 and 1 and D between 0.85 and 0.99, which indicates that the simulated and observed data are significantly correlated and consistent; correlation is also found between production of dry plant and overall soil moisture when the former had 7.1%higher simulated data and the latter 10.1% on average, which indicates that the verified model can be well applied to the Ningxia planting zones;(3) irrigation conditions were verified in Yanchi through an analysis of data collected from Ma’erzhuang Township and the Pilot Base of Yanchi Agricultural Institute; and results show that the R2 was between 0.56 and 0.89, D between 0.96 and 0.99 and NRMSE between 17% and 48%, which indicates that the simulated and observed data are significantly correlated and consistent; and that irration volume and frequency tend to take the same effects on the production of dry plant and the verified model can work well for simulating the plant’s production in different irrigation conditions;(4) the parameters for the crop varieties were determined for the first time in Haiyuan through an analysis of data collected from the Northern Ningxia Semi-Arid Pilot Zone at Jiatang Township; of the model’s eight Lucerne-wheat-rice rotation systems, WWW and MMM were adjusted; other six systems were verified and analyzed and results show that the production had the R2 between 0.83 and 0.98, D between 0.94 and 0.99, but NRMSE between 21.1% and 29.8% simply for five of them; and that the soil moisture had the R2 between 0.52 and 1, D between 0.94 and 0.97, but NRMSE between 27.4% and 38.3% simply for five of them; it is indicated that the simulated and observed data are significantly correlated and consistent in both the production and soil moisture;(5) through the model simulation, effects of climate changes was analyzed on the plant production and soil moisture with no irrigation between 1981 and 2010 in the four zones of Ningxia and significant differences are found; little correlation is found beween the rainfall during the period of growth and the production relying simply on the rainfall, which indicates no significant linear correlation between them; but such significance is found between the rainfall during the period of growth and the soil moisture due to the R2 of 0.7 and 0.6 in Tongxin and Yinchuan repectively, which indicates that the annual rainfall is the major contributor to soil moisture in such arid and semi-arid zones;(6) the verified model was put into use in different irrigation conditions and results show that irrigation is a major factor in an increased production of Lucerne in Ningxia arid and semi-arid zones and a sharp increase is possible; changes in both volume and ET showed similar tendency and significant correlation is found (p<0.01) with a coefficient of 0.826; but efficiency of Lucerne’s water consumption is found not proportional to irrigation volume and it is a tendency that a fall goes after a rise at the start, which is significant to the planting of Lucerne.(7) with the verified model simulation, correlation between soil moisture and crop production in grass-crop rotation systems under different climates were analyzed between 2000 and 2011 and a comparative analysis was then for a prediction from 2039 till 2050; results show that soil moisture will significantely decrease while crop production will increase to some extent, which can attribute to a possible reduction of rainfall as well as a possible increase of sun radiation in the future;(8) through a combination of GIS and APSIM, climate factors, in terms of average rainfall, sunlight hours, and minimal and maximal temperatures, were well determined in the whole period of growth as well as in different phrase of the period with data collected from the 21 meteorological observations by using the inverse distance weighted method; and the space-time distribution of Lucerne production in the eight zones were analyzed and results show that rainfall is a major but not the only decisive climate factor in the plant’s production; a proper increase in soil moisture will contribute significantly to the plant’s increased production during its branching and blooming phrases; the majority of Guyuan, Xijie and Haiyuan and some parts of Yanchi, Zhongning and Tongxin are considered to be dominant Lucerne planting zones for a higher production in better conditions. |
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