Effects of Different Tillage Depths on Soil Physical Properties and the Growth and Yield of Tobacco in the Mountainous Chongqing Region of China

Abstract

Tobacco (Nicotiana tabacum L.) is the most important cash crop in the mountainous Chongqing region, where mini rotary tillers are widely used for land preparation. The decline in tobacco yields has been partially attributed to deteriorating soil physical properties and the formation of plough pans as a result of the repeated use of the mini rotary tiller. The objective of this study was to evaluate the effects of different tillage depths on soil physical properties and the growth and yield of tobacco. Three tillage depths were evaluated: mini rotary tillage to 15 cm (T15) as a control, medium-deep tillage to 25 cm (T25), and deep tillage to 35 cm (T35). Total porosity, capillary porosity, and soil water content were measured for each treatment, and the root distribution, agronomical traits, and dry matter accumulation were monitored at different growing stages. Tobacco yield and output value were determined following the harvest. Compared to T15, T35 significantly increased total porosity and capillary porosity in the 10–40 cm soil layer and soil water content in the 0–40 cm soil layer, while T25 improved soil physical properties but not significantly. T35 significantly promoted dry matter accumulation and root, stem, and leaf growth compared to T15, while differences in some agronomic traits between T25 and T15 were not significant. Compared to T15, T35 and T25 increased the tobacco yield by 17.2–18.9% and 8.0–10.1%, respectively, and increased the output value by 44.4–46.4% and 29.2–32.6%, respectively. The results indicate that deep tillage improves soil physical properties, breaks plough pans, stimulates root growth, and increases tobacco yield and output value.