Objectives The purpose of this study was to investigate effects of straw biochar application on sorghum biomass and nutrient contents as well as soil physico-chemical properties under different water condition.
Methods A pot experiment was carried out in greenhouse. Jinza 34 was selected as the tested sorghum cultivar, and calcareous cinnamon soil was used as the tested soil. Three water levels including normal water (W1, 85% of the water holding capacity), mild water stress (W2, 65% of the water holding capacity) and severe water stress (W3, 45% of the water holding capacity), and five straw biochar application rates (0, 0.5%, 1%, 3% and 6%) were used in this experiment. The sorghum biomass, height and nutrient contents (N, P, K, Ca, Mg, Fe, Mn, Cu and Zn) as well as soil pH, EC and fertility condition were investigated at 70 days after sorghum seedling emergence.
Results Water stress restricted the sorghum growth and decreased sorghum biomass and height. Straw biochar applied at 0.5% significantly increased the sorghum biomass under the severe water stress, while the sorghum biomass was decreased as straw biochar was applied more than 1%. Compared with the normal water treatment, water stress decreased P content and increased K, Ca, Mn and Zn contents of sorghum. The application of straw biochar increased the K and Zn contents, and decreased the N, P and Mg contents of sorghum. At the end of experiment, the available Mn and Zn were decreased with the decrease of water supply. The application of straw biochar significantly increased the soil available K and Zn contents. However, the exchangeable Mg, available Mn and Fe were decreased when straw biochar was applied more than 1%.
Conclusions Under the experimental condition, straw biochar applied at rate of 0.5% has beneficial effect on K and Zn absorption and sorghum growth under water stress condition, but excessive (> 1%) use of straw biochar inhibited the sorghum growth.
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