College of Agriculture, Hunan Agricultural University/Southern Regional Collaborative Innovation Center for Grain and Oil Crops in China, Changsha 410128, China
Abstract：Rape is the largest domestic plant oil source in China. It is necessary to apply appropriate micro fertilizer in field production to improve yield and quality. It is very important to build a model which can quickly screen the micronutrient fertilizer to improve the yield of rape. In this research, the spectral reflectance of high oleic acid rape “FanMing No.1” in the whole growth period under different micro fertilizer conditions was measured by ground object spectrometer. And chlorophyll content was accurately determined by ethanol extraction method. The correlation between spectral reflectance, chlorophyll content and final yield was analyzed. The yield test showed that the application of micro fertilizer could increase the yield of rape and the content of chlorophyll at the bolting stage. It could increase the yield of a single plant by up to 2%. The correlation analysis of spectral parameters and chlorophyll showed that the correlation between chlorophyll content and spectral parameters was high at 550 and 720 nm, which indicated that the spectral parameters could be used to predict yield and screen out the micro fertilizer which could improve the yield of rape. The correlation analysis of chlorophyll content and yield showed that the correlation between chlorophyll content and yield was high at the bolting stage. The correlation analysis between the spectral parameters and the yield showed that there was a significant negative correlation between the reflectivity of 550 and 720 nm and the yield. The correlation analysis between the spectral parameters and the yield showed that there was a significant negative correlation between the reflectivity of 550 and 720 nm and the yield. Comprehensive analysis of fertilization, spectral parameters, yield and chlorophyll changes showed that the linear equation of the correlation coefficient between the spectral parameters 550 and 720 nm and yield could be used to screen the micro fertilizer, and the linear equation was y=-32.362x+33.097, y=4.069 5x+35.386, y=28.849x+23.735, y=-19.023x+31.005, y=12.447x+24.586, and R2 was greater than 0.6. Comprehensive analysis of fertilization, spectral parameters, yield and chlorophyll changes showed that the yield of rape increased when the linear equation R2≥0.6, which was stimulated by the spectral parameters 550 and 720 nm and the yield correlation coefficient, was applied. The results show that the spectral parameters of bolting stage can be used to predict the yield and then screen out the micronutrient fertilizer that can improve the yield of rape, which will increase the sample size to further detect the correlation and carry out subsequent verification. In view of the high efficiency of the process with no chemical reagents and destructive sampling of the samples and low cost, the establishment of the model is of great significance for the rapid screening of the formulation of high oleic acid rape micronutrient fertilizer, which provides a theoretical basis for screening the micronutrient fertilizer and promoting the yield of rape.
