Effect of water management on the vivianite content of paddy-rice roots

Figures & data

Figure 1 Dates of water management change and rice (Oryza sativa, L.) root sampling.

Figure 2 Weight loss of synthetic vivianite with heating. Note that error bars are present but are not larger than the symbols used in the plot.

Figure 3 Changes in the amount of extractable phosphorus (P) in 0.1 mol L⁻¹ hydrochloric acid (HCl) and 1 mol L⁻¹ acetic acid (AcOH) from unground and ground synthetic vivianite with time (0, 3, 6, 12, 24 and 48 h) at 105°C (a) and heating temperature (20, 50, 80, 105, and 150°C) for 48 h (b). The error bars represent the absolute deviation from the mean (n = 2).

Figure 4 Changes in soil redox potential values (Eh) with days after transplanting. The error bars show the absolute deviation from the mean (n = 2).

Figure 5 Changes in modified Bray No. 2 phosphorus (P) values in relation to the number of days after transplanting. The error bars represent the absolute deviation from the mean (n = 2).

Figure 6 Optical microscope image of rice (Oryza sativa, L.) roots from the micro paddy field (a) with continuous flooding sampled on September 2, 2010 [104 days after transplanting (DAT)], and (b) with midseason drainage and intermittent irrigation on November 4, 2010 (167 DAT).

Figure 7 (a) Scanning electron microscope image of vivianite crystals on a rice (Oryza sativa, L.) root, and (b) energy-dispersive X-ray analyses of the selected areas of (i) the dotted square and (ii) the dashed square of Fig. 7a. O: oxygen; P: phosphorus; Fe: iron.

Figure 8 Changes in the vivianite content of rice (Oryza sativa, L.) roots in relation to the number of days after transplanting. The error bars represent the absolute deviation from the mean (n = 2). P: phosphorus.