Effects of biochar application on soil potassium dynamics and crop uptake

摘要

Biochar has been suggested as a possible means for enhancing soil fertility, including soil potassium (K). However, understanding of the effects of biochar on soil K dynamics remains limited. In this study, a pot trial was conducted to investigate the influence of biochar application (0, 5, 10, and 25 g kg(-1) soil) on soil K dynamics and crop K uptake under a winter wheat-maize rotation in two types of soil (an Alfisol, which contained a high initial available K and an Entisol, which contained a high abundance of 2 : 1 K-bearing minerals). Changes in soil K in various forms following biochar application and cropping were determined, and their contributions to plant K uptake were evaluated. Soil microbial activity, especially the development of K-dissolving bacteria (KDB), was evaluated to obtain insights into its effects on the weathering of K-bearing minerals in the soils. During the wheat growth period, crop K uptake was more enhanced (13.6-40.5% higher) in the Alfisol than in the Entisol due to the higher availability of water-soluble and exchangeable K, while K fixation occurred in the Entisol because of the higher content of 2 : 1 K-bearing minerals. During the maize period, crop K uptake was generally higher in the Entisol soil due to the release of non-exchangeable K. In addition, biochar application enhanced the growth of KDB in both soils, which was associated with changes in soil pH and water-soluble K. However, improved mineral K release was observed only in the Entisol. It is concluded that biochar application could be a feasible soil amendment to improve soil K availability, but crop K uptake responses may vary depending on soil types. Soils abundant in 2 : 1 K-bearing minerals tend to prolong biochar effects on crop K uptake. Biochar application enhanced the growth of KDB, which may facilitate mineral K weathering in soils with abundant K-bearing minerals.