Fig. 6From: Biochar and biofertilizer reduced nitrogen input and increased soybean yield in the maize soybean relay strip intercropping systemSoil urease activity and soil nitrate reductase activity under different organic material and nitrogen levels. Note: Fig. A and B represent soil urease activity and soil nitrate reductase activity, respectively. The growth stage, nitrogen treatment, fertilizer treatment, and significant signs same as described in Fig. 2Back to article page