Effect Of Different Humic Acid Levels On Soil Characteristics And Leaf Quality Of Flue-Cured Tobacco

pot and field Experiments were carried out to study the effect of the different humic acid dosage on soil properties and quality of Flue-Cured Tobacco.The results are as follows.Soil water retention capacity was strengthened after using the humic acid,it has a little influence of the containing water ability at the beginning of the growth development period.But it can increase the soil water content of fast-growing stage,lower bulk density of soil,enhance soil porosity.Compared with the treatment of single application of fertilizer,using humic acid can increase soil available nitrogen content and improve the validity of soil nitrogen duringing whole growing period.Soil available phosphorus content of the treatments using humic acid were higher than the control,especially was higher than the control 5-20 mg/kg,increased in rosette stage.Using humic acid increased soil available potassium content,especially in the anaphase of the tobacco growing process remained a higher soil available potassium content.Soil organic matter content increased after using humic acid and to 750 kg·hm^-2 is the best effect.After using the humic acid,adequate supply of phosphorus can increase the leaf phosphorus content during budding stage.Providing adequate potassium fertilizer from fast-growing stage to mature stage can increase leaf potassium content.Providing enough calcium in soil in rosetter stage and budding stage can increase leaf calcium content.Giving enough magnesium in fast-growing stage and budding stage,especially in budding stage can increase leaf magnisium content.Giving more iron in soil in budding stage and mature stage can increase leaf iron content. Applying manganese fertilizer in rosette stage can increase upper leaf manganese content,and giving manganese fertilizer in budding stage can increase cutters and lower leaf manganese content.After using the humic acid,the quantities of soil bacteria,epiphyte,actinomyces, phosphate-degrading bacteria,potassium silicate-degradeing bacteria,aminate-degrading bacteria were higher than those in the control.Humic acid levels had positive relations with the mount of actinomyces and aminate-degrading bacteria in 0.01 level,and applying 750kg·hm^-2 of humic acid was better ??? growing of soil micro-organism. The activities of soil sucrase,urease,phosphatase were higher than those in the control after using the humic acid,and the treatment T2(750kg·hm^-2) were the highest which increased 13.58 %,20.93%,and 205.26%。NRase activity of T2(750kg·hm^-2) was the highest among all the treatments except 75 days after transplanting that lower than T4(1500kg·hm^-2).The chlorophyll content of tobacco leaves increased firstly and decreased then.The MDA content increased quickly at first and then decreased a little and the content of CK were the highest among all the treatments.Root activity increased sustaining till to the max content at 50 days after transplanting and then has a falling trend till to 70 days and has another increasing trend and then another falling trend.The root volume and root fresh weight of the treatments which using humic acid were higher than CK.The aroma contents of the upper leaves and the cutters were higher than the lower leaves. The aroma contents of T2 and T3 has the same changing trend during the growing process and T2 was the highest and CK was the lowest.Using humic acid can make the inner chemical components of leaves more harmony and increased the total sugar and reducing sugar contents.Contrast to CK,the ratio of reducing sugar and total sugar increased 6.98%,5.57%,6.01%and 4.00%respectively and the quality of other treatments have a difference at 0.05 or 0.01 level to CK.The quality of T2 was the best and its total sugar and reducing sugar increased 8.2%and 19%,total nitrogen,nicotine and starch decreased 22.47%,9.67%and 28.4%contrast with CK.The dosage of humic acid have a positive correlation with total sugar,reducing sugar,the ratio of total sugar and reducing sugar, and have a negative correlation with total nitrogen,and a significant negative correlation with starch and nicotine.The humic acid dosage have a positive correlation with boron,manganese,phosphorus,zinc, calcium,potassium and magnesium contents of the lower leaves and copper,iron contents was negatively correlated.The humic acid dosage have a positive correlation with boron,copper, manganese,phosphorus,calcium and potassium contents of the cutters and iron,zinc,magnesium contents was negatively correlated.The humic acid dosage have a positive correlation with iron, zinc,calcium,potassium and magnesium contents of the upper leaves and boron,copper, manganese,and phosphors contents was negatively correlated,and boron and phosphorus contents reached to 0.01 level.