In-Field Rice Panicles Detection of Different Growth Stages

The present study was part of a comprehensive field plot experiments of double cropping rice (spring and autumn) conducted at location of Research Centre Shapu, in Zhaoqing, Guangdong Province, China (23.16° N and 11.57° E) in 2021. There were 90 plots in the spring rice field experiment (Exp.1) and the autumn rice field experiment (Exp.2), respectively. The size of each plot was 10.8 × 3.5 m2. The experimental plot was designed with three replications. Different strategies for plant growing practices, including three cultivars, five levels of N fertilizers, and two planting densities were applied in each plot. In Exp.1, rice seeds were sown in early May, transplanted in late May, and harvested in early July. Three cultivars included Huahang No.51, Huahang No.57, and Guang8you2156. Two planting densities, namely 30×14 cm2 and 30×21 cm2, were adopted. Five levels of N fertilizers (N0-N4: 0, 45, 90, 180 and 270 kg/ha) with the same amount of P fertilizers (130 kg/ha) and K fertilizers (180 kg/ha) were applied in the experiment (Fig. 1a). In Exp.2, rice seeds were sown in late July, transplanted in early August, and harvested in late October. Three cultivars included Y liangyou3089, Huahang No.57, and Guang8you2156. Two planting densities were the same as those of Exp.1. Five levels of N fertilizers (N0-N4: 0, 90, 180, 270 and 360 kg/ha) with the same amount of P fertilizers (130 kg/ha) and K fertilizers (180 kg/ha) were applied in the experiment (Fig. 1b). A protected planting area with a width of 1 m was provided surrounding the experimental site. To further prevent the diffusion of fertilizers among plots, a guard row of ridge was built on the boundary between two adjacent plots and a plastic wrap covered the ridge. The growing practices, such as irrigation and pesticide application, were performed according to the local standards of rice cultivation to ensure no water stress, disease, or pest stresses in the experiments.