Fig. 6From: Microwave pyrolyzed sewage sludge: influence on soil microbiology, nutrient status, and plant biomassSoil pH and dehydrogenase activity (DHA) of substrate treatments amended with biochar made of sewage sludge, sawdust, and zeolite. Mean ± standard deviation (error bars) calculated from independent values (n = 4), different letters express the statistical differences at significance level p ≤ 0.05.Back to article page