Study On The Difference Of Annual Light Energy Resource Ulitization In Different Paddy-upland Rotations

Many countries around the world are facing the contradiction of the increasing population and the limiting cultivated land,therefore,how to use the limited cultivated land to produce enough food is facing big challenges.The available light energy resources are limited in farmland ecosystems.How to increase the utilization light energy efficiency and the light energy production efficiency through reasonable planting systems,cultivation measures,field management,etc.under limited light energy resources to increase system output,wich has been the key issues that need to be solved and studied by many scholars.In this study,five paddy-upland rotations of garlic-rice,wheat-rice,bean-rice,rapeseed-rice and potato-rice were studied based on the planting systemin 2016-2018,the characteristics of crop acceptance of radiation,transformation and fixation were studied.Based on the distribution characteristics of meteorological factors,the characteristics and differences of annual light energy utilization and the differences of light energy distribution and variation in different paddy-upland rotations were analyzed,and the correlation between light energy utilization and environmental factors was analyzed.The size and seasonal distribution of the annual radiation use efficiency of the five rotation modes were clarified.The main results are as follows:(1)The overall change law of the annual light energy of Chengdu Plain: the average total radiation is more in rice season,the average total radiation is less in dry season,the scattered radiation is higher than direct radiation from April to mid-October,and the proportion of scattered radiation is as high as 68.67%~75.37% during the rice growing season(May-September).(2)High-efficiency light energy utilization crop population characteristics: the leaf area index is large,the coverage of the group is also large,the canopy light energy interception rate is high,the canopy light energy interception is large,the group photosynthetic capacity is strong,and the dry matter and energy accumulation are high.The canopy structure of crops with different paddy-upland rotations resulted in differences of the population light energy interception,dry matter and energy accumulation,which in turn affected the light energy utilization efficiency.The light energy interception rate,leaf area index and population photosynthetic potential of garlic-rice pattern were the highest after rice seeding,and the garlic-rice rotation population had stronger photosynthetic capacity and more light energy interception,which improved radiation use efficiency.The differences were significant in dry matter and energy accumulation during the growth stage of different paddy-upland rotations,which in turn affected the radiation use efficiency.The dry matter and energy accumulation and the proportion of the rice season from the jointing stage to the heading stage were the largest,and the rice was from the jointing stage to the heading stage.The accumulation of matter and energy significantly affected the radiation use efficiency;the dry matter and energy accumulation of garlic-rice and bean-rice rotations in the dry season increased first and then decreased,while the dry matter and energy accumulation of the bean-rice and garlic-rice rotations were negative in April.The dry matter and energy accumulation of the wheat-rice,rapeseed-rice and potato-rice rotations gradually increased.(3)Differences in light energy utilization and influencing factors: The annual radiation use efficiency can reach 0.48%~0.81%,which is expressed in the wheat-rice>rapeseed-rice>garlic-rice>potato-rice>bean-rice rotation,and the difference is significant or extremely significant level;among them,the radiation use efficiency can reach 1.02%~1.39% in rice season;the radiation use efficiency is 0.20%~0.94% in dry season.The annual light energy production efficiency ranged from 0.29% to 0.47%,and the garlic-rice,wheat-rice and potato-rice patterns were higher or significantly higher than the rapeseed-rice and bean-rice patterns;the light energy production efficiency of garlic-rice pattern in dry season is greater than or significantly greater than other rotations.The light energy production efficiency of garlic-rice pattern in rice season is greater than or significantly greater than other rotations.The light energy utilization and production efficiency are significantly positively correlated with the average temperature,and the correlation with the average temperature difference and rainfall is not obvious;the radiation use efficiency,light energy production efficiency and the proportion of scattered radiation are positively correlated,and the correlation is achieved,extremely significant and significant level.