Amending Soil with Biochar to Improve Accumulation and Translocation of Dry Matter after Anthesis in Winter Wheat

Abstract

【Background】 Winter wheat is a staple crop in China, but in many parts of the country rainfall during its growth season cannot meet its demand for water. Irrigation is, therefore, essential to safeguarding winter wheat production. The increasing disparity between water supply and demand has become a challenge in food production, and using saline water and brackish water as a supplementary irrigation water source has thus attracted increasing interest despite their risk of soil salinization. 【Objective】 The purpose of this paper is to experimentally investigate the feasibility of amending soil with biochar to ameliorate the risk of soil salinization induced by irrigation with saline water. 【Method】 The experiments were conducted in a rain-shelter and compared different combinations of biochar amendment and saline water with salt content 5 g/L: Freshwater irrigation (CK), saline water irrigation without biochar amendment (B0), saline water irrigation with 15t/hm2 biochar amendment (B15), saline water irrigation with 30 t/hm2 biochar amendment (B30), saline water irrigation with 45 t/hm2 biochar amendment (B45). In each treatment, we measured the change in soil properties and dry matter accumulation and translocation after the anthesis stage. 【Result】 Biochar amendment significantly improved soil properties, with bulk density of the top 0~20 cm soil decreasing by 2.27%~8.33%, and the associated porosity, organic matter increasing by 4.52%~13.47% and 30.02%~111.12%, respectively. In the meantime, it also reduced the sodium adsorption ratio in the top 0~20 cm and the root zone (0~40 cm) soils by 23.88%~33.27% and 22.34%~30.80% respectively. Amending soil with biochar at 15 t/hm2 facilitated salt leaching and reduced salt accumulation in the topsoil induced by saline water irrigation, but when the applied biochar exceeded a threshold, a further increase in biochar application could increase salt content and salt accumulation in the topsoil. It was also found that amendment with biochar under salt stress could alleviate premature senescence, promote photosynthesis, in addition to maintaining high leaf area index, leaf area duration and stomatal conductance. Biochar was able to improve dry matter accumulation and translocation in the vegetative organs before the anthesis stage, and maintain a good dry matter production capacity after the anthesis stage, thereby improving grain weight and harvest index. Compared with B0 without biochar amendment, B15, B30 and B45 increased grain yield by 9.18%, 7.73% and 2.74%, respectively. 【Conclusion】 Biochar amendment can improve soil properties and increase the yield of winter wheat when irrigated with saline water, but it needs to be used with care as over-application biochar could lead to salt accumulation and inhibit plant growth. In our study, applying biochar at 15 t/hm2 is optimal to reduce salt accumulation and improve crop yield.

Keywords

• winter wheat
• brackish water irrigation
• biochar amendment
• photosynthesis
• dry matter accumulation and translocation