Effects of banana stem and its biochar application on soil aggregate characteristics in the Pearl River Delta

Here, to investigate the effects of banana stem and its biochar application on soil fertility in the Pearl River Delta, the effects of applying 0.5%, 1.0%, and 2.0% banana stem, rice straw, and their biochar on the composition of soil water-stable aggregates were evaluated in soil culture and pot experiments. The mean weight diameter (MWD), geometric mean diameter (GMD), fractal dimension (D), and mean weight specific surface area (MWSSA) were used to evaluate soil aggregate stability. The results revealed the following:1) Water-stable aggregates in the studied soil was dominated by < 0.25-mm micro-aggregates, followed by 1-0.5-mm aggregates, accounting for 29.80%-47.55% and 18.19%-20.08% of the aggregates, respectively. 2) Applying 1.0% and 2.0% banana stem and 2% rice straw significantly increased >0.25 mm macro-aggregate content and soil aggregate stability. Compared with the control treatment, the soil aggregate MWD increased by 45.60%, 62.37%, and 65.50%, respectively; GMD increased by 43.45%, 55.34%, and 60.66% respectively; D decreased by 2.23%, 2.32%, and 2.78% respectively; and MWSSA decreased by 18.14%, 20.09%, and 23.01% respectively. 3) The MWD and GMD significantly positively correlated with >5 mm, 5-2 mm, and 2-1 mm soil aggregate percentages, and significantly negatively correlated with < 0.25-mm soil micro-aggregate percentage. The D value and MWSSA significantly positively correlated with < 0.25-mm soil micro-aggregate percentage, and significantly negatively correlated with >5 mm, 5-2 mm, and 2-1 mm soil aggregate percentages. 4) The results of principal component analysis and difference significance test indicated that applying 2.0% and 1.0% banana stem had a better effect in improving soil aggregate stability, and this effect was not significantly different from that of 2.0% rice straw application; however, the application of biochar did not increase the stability of aggregates in the short term. This study provides a reference for effectively utilizing banana stem waste and improving soil fertility.