Change in Photosynthesis of Spring Wheat with Irrigation Amount and Biochar Amendment

Abstract

【Objective】 Amending soil with biochar can improve soil structure and fertility, but it could make soil slightly hydrophobic. Its combined effect with irrigation on crop growth is not well understood. This paper aims to fill this knowledge gap by using spring wheat as the exemplary plant. 【Method】 The experiment was conducted in a spring wheat field in northern Xinjiang and comprised three irrigation amounts: irrigation amount used by local farmers (w0), reducing w0 by 10% (w1), and reducing w0 by 20% (w2). For each irrigation amount, there were three biochar amendments: no biochar (b0), adding 10 t/hm2 (b1) and 20 t/hm2 (b2) of biochar. For each treatment, we measured photosynthesis and yield of the spring wheat; its relationship with biochar amendment rate and irrigation amount was fitted to pre-defined functions. 【Result】 Biochar application amount affected leaf area index at the flowering stage significantly. Compared to b0w0, reducing irrigation amount combined with a biochar amendment increased LAI by 9.1%~25.41%, and SPAD by 1.7%~10.73% 20 days after the flowering. Irrigation amount had a significant impact on photosynthesis, dry matter accumulation and yield formation. Reducing irrigation amount by 10% coupled with an appropriate biochar amendment promoted material accumulation in the plant during the flowering stage, thereby improving photosynthesis and the ultimate yield. However, when the irrigation amount was reduced by 20%, biochar amendment reduced photosynthesis, with the net photosynthetic rate, transpiration rate, stomatal conductivity and intercellular CO2 concentration decreasing by 11.58%~18.15%, 55.85%~66.3%, 67.42%~75.94% and 16.2%~27.19%, respectively, from the control. Irrigation amount affected the yield more significantly than biochar, but an appropriate biochar amendment can compensate for the yield loss due to irrigation water reduction. In all treatments we compared, b1w1 was most effective, increasing the grain yield by 7.57% compared b0w0. b2w1 was most effective in increasing 1 000-grain weight, and compared to b0w0, it increased the grain yield by 3.36%. 【Conclusion】 The compressive experiment showed that reducing irrigation amount currently used by local farmers by 10% combined with a 20 t/hm2 application of biochar is most effective for saving water and improving spring wheat yield in northern Xinjiang.

Keywords

• spring wheat
• biochar
• water control
• photosynthetic characteristics
• production