Effect of Humic Acid on Soil Physical and Chemical Properties in Tobacco Field

Field experiments were carried out to research the effect of Humic acid on soil physical and chemical properties in tobacco fields at Jiaxian County,He'nan Province in 2006-2007.The results showed that after humic acid was used,soil ability to maintain moisture increased,especially in fast growing period;soil bulk density decreased and soil degree of porosity increased.Application of humic acid can improve available nitrogen,available phosphorus,available potassium and organic matter content of the seasonal soil,but there was no significant difference in available nitrogen and organic matter content between the treatments and the control.Compared with fertilizer treatment,application humic acid could increase soil nitrogen validity in the whole growth period;soil available phosphorus content was higher than the control,especially in rosette stage it was 5~20 mg/kg more than the control.The content of soil available potassium kept a high content level at latter stage of tobacco growth.The effect of treatment T2(750 kg/hm2) was the best.