Monitoring the plant density of cotton with remotely sensed data 多o”based jon the sats from ent of the r J bu June9:N=4.364EVI+0.686 R2-0.75 8 June25h:N.=3.185EV7+0.148 R2-0.63 9 i .15 2 : w Fig.3.Relationship between PDC and DEVI 3.2 PDC Estimation with DEVI get DEVI on the corresponding time.It is shown in Fig.3.the determination coefficients of the linear equation between PDC and DEVI are 0.34 reaching the great significant level on May 24,and on the contrary the linear disappears when EVI estimated PDC on May 24.In addition,the determination coefficients rise from 0.23 to 0.27 on June 9 and from 0.3 to 0.34 on June 25.And the linear still disappears on July 11.The estimation models on PDC with DEVI as below:Monitoring the Plant Density of Cotton with Remotely Sensed Data 95 PDC estimation based on the data from middle emergence stage. As shown in Fig.2, coefficient of the linear equation between PDC and EVI rise to 0.75 for June 9th and 0.63 for June 25th when the data from middle emergence stage is only used, but unfortunately, the determination coefficient hasn’t still reach the significant level on May 24th and July 11th. The estimation models on PDC with EVI as below: June 9th : Nu = 4.364EVI+0.686 R2 =0.75** (8) June 25th : Nu = 3.185EVI+0.148 R2 =0.63** (9) Fig. 3. Relationship between PDC and DEVI 3.2 PDC Estimation with DEVI PDC estimation based on the data from three emergence stages. EVI on May 24th, June 9th, June 25th and the July 11th, respectively minus EVI on April 22th get DEVI on the corresponding time. It is shown in Fig.3, the determination coefficients of the linear equation between PDC and DEVI are 0.34 reaching the great significant level on May 24th, and on the contrary the linear disappears when EVI estimated PDC on May 24th. In addition, the determination coefficients rise from 0.23 to 0.27 on June 9 and from 0.3 to 0.34 on June 25th. And the linear still disappears on July 11th. The estimation models on PDC with DEVI as below: