| The integration of agricultural machinery and agronomy has always been a short board in China.As a major oilseed rape production country,China's mechanized harvesting level is not high.The main reason for the for the above problem is the mismatch between the harvester requirements and the pod shatter resistance and plant branching characteristics.Low pod resistance,entanglement caused by excessive branches and inconsistent pod maturity lead to large harvest loss.Among them,the large header loss caused by the poor shatter resistance is the main proportion for the excessive mechanized harvest loss.In order to obtain the quantitative size of pod shatter resistance and the characteristics of plant type and branch structure suitable for mechanized harvesting,and screen the typical rape varieties suitable for mechanized harvesting,so as to reduce the mechanized karvesting loss.This paper adopted the research method of combining agricultural machinery and agronomy,based on biology,morphology,genetics,collision mechanics and random process theory,to carry out a detailed study on the pod shatter resistance and the characteristics of plant type and branch structure.Research work includes:1.The characterization method of pod shatter resistance was studied.Based on the actual working conditions of mechanized combined harvesting,a two degree of freedom random(2-DOF)collision method was put forward,which is convenient for field testing and can truly reflect the field pods property at harvest time,and the reasonable test collision parameters were also determined through experiments.This method is compared with the shaking table random collision method and the ripping method proposed by the predecessors.Through EDEM simulation,it is found that the steel balls movements under the 2-DOF collision method were faster and more uniform than the steel balls movement under the shaker collision method,and there is no slipping phenomenon.By using the three test methods to test the pod shatter resistance of different rape varieties under the same conditions,and compared and analyzed the stability and discrimination of the test results under each method,it was found that the 2-DOF collision method had better repeatability and higher discrimination on pod shatter resistance among varieties.A comparative experiment on the pod shatter resistance in the field pods and the after indoor water balance pods showed that the real-time detection of the pods under the same level moisture content in the field has significantly lower pod shatter resistance than the indoor water balance pods,which indicates that the pods field test can better reflect the true pod shatter resistance during harvest.Therefore,the 2-DOF collision method is a more reliable test method for evaluating the pod shatter resistance.2.The 2-DOF collision method was used to test the pod shatter resistance of the whole rape plant.Pearson correlation and grey correlation method were used tocomprehensively analyze the correlation between pod morphological characteristics(pod length,pod width,pod thickness,pericarp,length,pod volume and the thousand-seed weight,etc.)and plant type characteristics(plant height,diameter of main stem,number of branches,starting height and relative height of the lowest branch,branch length and branch angle,branch concentration,diameter and thickness of pod layer,etc)and the pod shatter resistance.The pericarp,thousand-seed weight,pod thickness and volume,and plant relative branch height were found to be significantly correlated with pod resistance,which can be strengthened by breeding.The influences of rape varieties,pod location,pod size and planting year on the pod resistance were also studied.It was found that rape varieties and pod location had significant influence on the pod size and pod shatter resistance.For the field grown rape plants,the shatter resistance of branched pods was significantly higher than that of main inflorescence pods,and the resistance on top and bottom of main inflorescence was lower.Therefore,avoid hitting the top of the plant during the harvesting process is necessary and focus on the middle siliques when spraying dehydrating agent is resonable.3.The pod shatter resistance and plant type branching structure of rape suitable for mechanized harvesting were studied.In order to determine the resistance value for low-loss harvesting of the reel,the impact force on the rape was analyzed through the measurement and wireless transmission of stress change of the tine.The impact forces of the tine of harvester reel at low,medium,and high speeds were obtained,and the mathematical relationship between the pod shatter resistance index(SRI)of the 2-DOF method and the craking resistance force(F)of the ripping methodis established.Combined with the test results of tine impact force,the pod shatter resistance index of field pod meeting the harvest expectation of header was 0.583.Through the plant type statistics and morphological analysis of the tested varieties,it was found that the branch structure of rape varieties was dominated by supernumerary branches,The higher height of the lowest branching,the better the development of pod and hold the higher the yield.Combined with the working principle and process of combine harvester,the plant type suitable for mechanized harvesting is characterized by low plant height,less branches,concentrated pod layer,compact plant type,full seeds and strong lodging resistance.The transcriptome analysis of the materials obtained in this study was also carried out.Transcriptome sequencing was carried out on the meristem of stem tip of less branched mutants and wild-type varieties,and the division zone of varieties with the greatest difference in shatter resistance,to investigate significant differentially expressed genes related to less branch and shatter resistance.It is speculated that the branch development of rape may be related to cell division cycle and cytokinesis,and the shatter resistance may be related to plant photosynthesis and flowering period.This provides a new research basis for the formation of branches and the regulation of shatter resistance at the molecular level,so as to promote the breeding of mechanized cultivation varieties.4.According to the characteristics of easy broken pod and multi-branched plant type in oilseed rape,an harvesting reel with improved tine trajectory,considering the reel working process and a function suitable for oilseed rape,is proposed in this study.The improved tine,of which angle can be continuously adjusted to adapt to the plant structure and meet the operating requirements of the reel in the stages of pushing the reel into the crops,feeding plants into the auger,and releasing the reel.The kinematics of the tine trajectory between the new and standard reels were calculated and a simulation comparative analysis was performed,which proved that the improved reel satisfies the theoretical requirements and the range of action of the reel tine is larger every week.Single-factor field experiments were conducted for the two types of reels.The test results demonstrated that the proposed reel has a lower header loss rate and is significantly affected by the reel speed than the reel height or machine forward speed.This shows that the improved reel is more conducive to rape harvesting.The screened variety of C6009 with higher shatter resistance and suitable plant features for mechanized harvesting was planted in large areas and harvested by machines for verification.Through the comparative experiment of mechanized harvest in the field,it was found that the loss rate of header and the impurity rate of grain after harvest were lower than those of the commercial variety YY12.The selected characteristics of rape are beneficial to reduce harvest loss. |
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