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. 2018 Mar 8;8:4398. doi: 10.1038/s41598-018-22637-7

Figure 2.

Figure 2

Changes of total N stocks over time at 0–20 cm depth for Tamale (a) and Ouagadougou (b). Means were calculated irrespective of irrigation water quantity and quality levels because they had no significant effects on N stocks (means ± sd; n = 16). Values after biochar additions (between 0 and 0.5 years) are calculated and have no standard deviation.