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. 2017 May 19;7:2185. doi: 10.1038/s41598-017-02278-y

Figure 4.

Figure 4

Changes in soil inorganic-N over time. Concentrations of extractable (a) ammonium-N (b) nitrite-N and (c) nitrate-N under near saturated (−1 kPa) or field capacity (−10 kPa) soil moisture conditions, following urea application (+N) or nil urea application (−N). Symbols are means (n = 4) with vertical error bars the standard error of the mean. Asterisks *,**,***indicate significant differences between moisture treatments under urea treatments at P < 0.05, P < 0.01, and P < 0.001, respectively.