Response in Physicochemical Properties of Tobacco-Growing Soils and N/P/K Accumulation in Tobacco Plant to Tobacco Straw Biochar

Abstract

The purpose of this study was to investigate the response of physicochemical properties of tobacco-growing soils and N/P/K accumulation of tobacco plant to tobacco straw biochar. Two contrasting tobacco-growing soils of paddy soil (Ultisol in USDA taxonomy) and brown soil (Alfisol in USDA taxonomy) were selected to conduct the pot experiments. Five addition rates (w/w) of tobacco straw biochar of 0%, 1%, 2%, 4%, and 10% without or with tobacco (Nicotiana tabacum) were applied in a greenhouse. The 7.41–35.90% increase of soil field capacity, 0.71–15.11% increase of total porosity, 3.40–17.55% increase of capillary porosity, 15.98–293.13% increase of organic matter, 6.52–58.75% increase of available phosphorus, 109.07–1789.70% increase of potassium, 3.23–147.71% increase of exchangeable cation, and 12.13–48.48% increase of soil pH were observed after biochar addition. And this improvement increased with the increasing application rate. The same trend was also found in the tobacco N/P/K uptake in the biochar application range of 0–4% and subsequently decreased at 10% rate. Meanwhile, biochar decreased the soil bulk density of 0.68–14.06%. The step regression equation showed that the exchangeable potassium and aluminum for Ultisol as well as the exchangeable potassium and hydrogen for Alfisol were the predominant factors that determined the soil pH. According to the PCA results, exchangeable calcium > exchangeable potassium > exchangeable cation > pH > organic matter > exchangeable magnesium > available potassium > available phosphorus and organic matter > exchangeable potassium > available phosphorus > exchangeable cation > available potassium > pH > exchangeable calcium had a significant impact on soil fertility of Ultisol and Alfisol, respectively. Finally, a comprehensive evaluation of soil fertility by PCA revealed that ST10 (10% rate, w/w) performed best, followed by the ST4 (4% rate, w/w) in both soils. The application of tobacco straw biochar, with appropriate rate, is an effect method to improve physicochemical properties of tobacco-growing soil and N/P/K uptake of tobacco plant.