英文摘要 |
Remote sensing is widely used in agricultural field during recent years. This study explored the changes of vegetation indices of ‘42’ broccoli under water-saving experiments. The broccoli seedlings were planted in open field in plastic containers under three different substrate volume water contents (VWC) at VWC35%, VWC25% and VWC15%. Thermographic camera was used to record the temperatures of plants, while multispectral camera was used to capture spectral images of plants growth. All treatments were terminated as floral initiation appeared. All the images were calibrated and used in calculating vegetation indices, including normalized difference vegetation index (NDVI), normalized difference red edge index (NDRE), canopy chlorophyll content index (CCCI), normalized difference based on NIR and green reflectance (NDNG), and optimized soil adjusted vegetation index (OSAVI). After planting 50 days, the vegetation indices of VWC 15% treatment were significantly lower than that of VWC35% and VWC25%. After planting 28 days, the temperature of VWC 15% treatment was significantly higher than that of VWC35% and VWC25%. The correlation between the difference of each vegetative index between treatments and the plant temperature of normalized by current temperature at the same day increased with the planting days. On the 34 day after planting, NDVI and OSAVI were significantly correlated with the earliest leaf canopy temperature after temperature normalization R2≧0.64. And during the cultivation period, the NDVI of VCW35% and 25% were both higher than 0.79, and the OSAVI were also higher than 1.18. Therefore, the NDVI value of 0.79 and the OSAVI value of 1.18 can be the critical indicators for detecting whether broccoli is under drought stress. Water-saving cultivation can improve the water use efficiency of broccoli, and with the use of plant temperature and vegetation index, the water status of crop can be quickly obtained, the cost of field management can be reduced, and the water required by crops can be more accurately provided. |