图3 炭肥互作对主要生育期大豆茎干物质积累的影响 图柱上标不同的字母表示在0.05的水平上差异显著。 Fig. 3 Interaction effects of biochar and fertilizer on dry matter accumulation of soybean stem at main growth stages Bars subscripted by different letters are significantly different at the 0.05 probability level among treatments.