| 217 soil samples has been selected from different types of tobacco-growing soils in Chongqing,in which 20 were from limestone earth soil,133 from yellow soil,34 from yellow brown earth soil,18 from purple ochre soil and 12 from black lime soil.The analyses show that most of the soils are a bit acidic and rich in OM that is related to the manure applications by farmers.Among the mass elements,the content of total nitrogen is relatively high and the content of available N is moderate.The contents of the mid-elements such as calcium,magnesium and sulfur,and the trace elements such as iron,manganese,copper,molybdenum and zinc,are abundant for the growth of tobacco.In order to improve the soil quality,a fertilization principle is proposed to control nitrogen,to supplement phosphorus and boron properly,to add potassium,to increase chlorine universally and to inhibit sulfur. |