To understand application of thickness compensation type chlorophyll meter in soil and plant analyzer development（SPAD）value determination of cotton

through determination and analysis on 20 strains of different growth periods of cotton leaves at different position of SPAD value distribution after thickness compensation

and leaf thickness

SPAD value

chlorophyll content of 10 trains of cotton in different growth period are measured.At the same time

the correlations between SPAD value and chlorophyll content after thickness compensation are analyzed.The results show that cotton leaf blade tip position is the best measurement position

after thickness compensation

correlation coefficient and significant between SPAD value and chlorophyll content are improved.The Influence of different leaf thickness are somewhat eliminated.The changing trend of chlorophyll content of cotton leaf in different growth periods is reflected more accurately.