Figure 7.

Available P in Spodosol and Alfisol soils affected by different application rates of CNPs. F0B0, control (without fertilizers and CNPs); F0B200, without fertilizers and with CNPs at 200 mg kg⁻¹ soil; and FB0, FB50, FB100, FB200, FB400 and FB800 represent those with and CNPs at application rates of 0, 50, 100, 200, 400 and 800 mg kg⁻¹ soil, respectively. Error bars represent the standard error of the mean (n = 5). The letters a, b, c, d and e indicate statistically significant difference at p < 0.05 within each group comparison between the treatments. Bars with no common letters are significantly different (p < 0.05).