Methodology Study On Real-time Measurements Of The Maize Stalk Lodging Angle And Corresponding Pull Force Angel

Stalk lodging has become one of the important factors for achieving high and stable yield of maize.Enhancing the maize stalk lodging resistance is one of the essential ways to improve maize yield,to facilitate harvest mechanization and to breed new varieties.Agricultural scientists have been trying to solve this problem by raising the lodging resistance of corn stalks.However,it is very inaccurate to evaluate the lodging properties with a single physical variable of maize.In this paper,the pull force applied on the maize stalk was used to simulate the action of natural wind,and the pull force was corrected to the force whose direction is perpendicular to the stalk according to the measured pull force angle and the stalk lodging angle.A portable instrumentation for monitoring the maize stalk lodging resistance in real-time was designed to judge the maize stalk lodging properties.It is great significance to agricultural scientists who can screen out the parent sample with strong stalk lodging resistance to breed new maize varieties.Maize stalk lodging is comprehensive and complicated.It is not only related to the external environmental factors but also related to the characteristics of the maize itself.Maize stalk lodging is mainly caused by external factors resulting in maize stalk from the natural vertical to the ground upright state to the permanent break dislocation phenomenon.At present,internationally,researchers have launched a lot of projects on measuring the maize stalk lodging resistance,such as,maize stalk elasticity assay,maize stalk root pullout method,wind tunnel test method,maize stalk crushing strength test,maize root strength assay,maize morphological method,maize solubility test and maize chemical assays.Among those,the method of measuring the strength of maize stalk can effectively simulate the natural wind action,and determine the lodging characteristics of maize stalk according to the mechanical equivalent principle.Based on the review of domestic and foreign techniques for the determination of lodging resistance of maize stalks,the paper puts forward the newly technical principle of measuring the anti-bending strength parameters of maize stalk.A new type of portable,low-cost and real-time test instruments in field was designed.This instrument enables real-time monitoring and recording the maize stalk bending angles,pull force angle,pull force F,elastic modulus E,and the stalk bending stress.According to the measured real-time angles,the anti-bending equivalent pull force applied on maize stalk is calculated,which avoids the influence of different pulling direction.It can accurately simulate the change of natural wind acted on maize stalk during the stalk bending process.The experimental results show that the maize stalk lodging resistance can be carried out according to the acquisition of the stalk lodging angle,pull force angle and pull force in real-time of maize stalk.For the different density of five varieties of maize stalks measured in September 2015,from the view of the agronomic characteristics and mechanical characteristics of measurement results,the average maximum bending stress was 2.35 Mpa from the maize with plant densities of 60000 plant/ha and the average maximum elastic modulus was 218.6Mpa.However,compared with the five different varieties in plant density of 75000 plant/ha,the average maximum bending stress was 1.96 Mpa and the average maximum elastic modulus was 150.04 Mpa.Therefore,the lodging resistance of maize stalk in plant density of 60,000 plant/ha was significantly better than that of maize stalks in plant density of 75,000 plant/ha.Besides,the lodging angle,the pull force angle and the corresponding pulling force of five varieties with different plant densities were also obtained when the equivalent reached the maximum,and the lodging resistance of the maize with low plant density was obtained,which shows that the lodging properties of lower planting density maize is higher than the high planting density and its lodging angle is slightly smaller than the high planting density of maize stalk.Finally,the paper introduces the principal component analysis(PCA)algorithm,by calculating the scoring matrix and load factor of each sample to classify measured samples reasonably.It further explains that the necessary reasons for high lodging resistance varieties should be planting closely controlled.For the experiment of six different varieties tested in Xinxiang,in September 2016,Fisher discriminant analysis(FDA)was used.In the case of error elliptical confidence of 90%,we can distinguish 1445,1448 and 1454 easily,while the remained three samples' error elliptical have a large overlapping area,indicating that is not clearly differentiated,which means that their lodging ability is similar in some extent,and the classification of maize varieties with different lodging capability are realized.