Enhancing sugar beet yield and quality in Northeast China: Investigating the synergistic impact of sugar mill filter mud and biochar on black soil

In this study, different ratios of sugar beet sugar factory filter mud and biochar in different proportions were used to assess the effect of incorporating filter mud into the field on soil quality and its influence on two distinct sugar beet (Beta vulgaris) varieties: high-yielding KWS9147 and high-sugar KWS1176. The experiment was conducted in 2022 at the Hulan Campus of Heilongjiang University in Harbin City, Heilongjiang Province, China. Eight treatments were employed, including CK1 (no filter mud or biochar application), CK2 (20 t/ha biochar), T1 (16.67kg/ha filter mud), T2 (16.67 t/ha filter mud + 20 t/ha biochar), T3 (33.33 t/ha filter mud), T4 (33.33 t/ha filter mud + 20 t/ha biochar), and T5 (50kg/ha filter mud). For sugar beets, parameters such as the SPAD value (Soil and Plant Analyzer Development, represents the relative content of chlorophyll), disease resistance (root rot and brown spot), tuber yield, and sugar content were evaluated. Soil analysis included nitrogen content, available potassium content, available phosphorus content, and soil sucrase, urease, and phosphatase activities. Results indicated that the combined application of 16.67 t/ha filter mud and 20 t/ha biochar had a positive impact on the growth indices, tuber yield, sugar content, effective phosphorus, and quick-acting potassium content in KWS1176. In contrast, for KWS9147, the most favorable effect was achieved with the application of 16.67 t/ha filter mud. This treatment improved plant leaf growth, increased tuber yield and sugar content, reduced root rot incidence, elevated alkaline dissolved nitrogen content in the inter-root soil, and enhanced soil phosphatase activity. Biochar application did not contribute significantly to these improvements. Therefore, returning sugar mill sludge to the field demonstrated its potential to enhance soil quality, promote the yield of sugar beet varieties, and improve resistance to root rot while also providing an eco-friendly solution for managing environmental issues related to sludge accumulation.