| Take Zhongyan100 as material,three humic acid and three nitrogen applying levels were designed in a pot experiment to study the effects of interaction between different levels of humic acid and nitrogen on the flue-cured tobacco growth and soil quality.Discuss the difference between humic acid and nitrogen on the dry matter and nitrogen accumulation,the root activity of flue-cured tobacco and the aggregate compositions,available nutrition,urease activity of soil,the chemical composition,petroleum ether extracts and aroma constituents of flue-cured tobacco leaves.The main conclusions are as follows: 1.Effects of interaction between humic acid and nitrogen on flue-cured tobacco growth:Tthe interaction between humic acid and nitrogen had a significant effect on the accumulation of dry matter in flue-cured tobacco,especially at 60 days after transplanting,the highest dry matter accumulation was treated with H3N3,compared with the control?H1N1?increased by 1.1 times.The results of dry matter accumulation in different parts of flue-cured tobacco showed that total accumulation and accumulation of dry matter in different parts of flue-cured tobacco were significantly higher than those in blank control?H1N1?.The stem accumulation of H2N3 was 1.5 times higher the control;while the root,leaf and total accumulation of H3N3 were 1.4,1.0,1.1 times higher than the control,respectively.The results of variance analysis showed that the effects of humic acid and nitrogen fertilizer on root,stem,leaf and total accumulation were extremely significant.The effect of interaction between humic acid and nitrogen fertilizer was only significant on leaf and total accumulation,and the effect of dry matter accumulation on root and stem was not significant.The results of the study on root activity of flue-cured tobacco showed that under different humic acid and nitrogen levels,the variation trend of root activity of all treatments were nearly the same,showing “M” type.And the root activity was the highest at 45 d and 75 d after transplanting,respectively.The results of variance analysis showed that the effect of humic acid on root activity of flue-cured tobacco at 30,75 and 90 days after transplanting was extremely significant.The effect of nitrogen fertilizer on root activity of flue-cured tobacco at 30 and 75 days after transplanting was also extremely significant,while reached the significant level at 90 d after transplanting.The root activity of the interaction between humic acid and nitrogen reached the extremely significant level at 30 d and 75 d after transplanting.The results of nitrogen accumulation in flue-cured tobacco showed that the nitrogen accumulation of flue-cured tobacco under different humic acid levels increased with the increase of nitrogen application rate,except H2N2 treatment.As for the uptake and accumulation of nitrogen in different parts of flue-cured tobacco,the accumulation of H2N3 was 2.5 times higher in roots than the control and the accumulation of H3N3 in stem,leaf and total accumulation were 3.2,1.4,2 times higher than the control,respectively.The results of variance showed that the effects of humic acid and nitrogen fertilizer on nitrogen accumulation of root and stem as well as total accumulation all reached the extremely significant level,and the effect on leaf nitrogen accumulation was significant.The effects of interaction between humic acid and nitrogen on nitrogen accumulation of leaf and total accumulation reached the extremely significant level,but the effect on nitrogen accumulation of root and stem were not significant.2.Effects of interaction between humic acid and nitrogen on soil propertiesThe treatment of the dry sieve is mainly composed of large aggregates,the large aggregates contents of H2N2,H2N3,H3N2 and H3N3 in the interaction of humic acid and nitrogen fertilizer were 2.0%,4.7%,4.7% and 2.9%,respectively,higher than the control treatment?H1N1?.The treatment of the wet sieve is mainly composed of micro aggregates.The mean weight diameter of H3N2 reached a maximum of 0.66 mm,which was the same as dry sieve.The effect of interaction between humic acid and nitrogen on the main nutrient status of soils at different growth stages was different.Except for H1,the contents of available nitrogen of N3 were 17%,1.2 times higher than those of N1 at 90 days after transplanting.The effects of interaction between humic acid and nitrogen on available nitrogen were significant after 60 and 75 days after transplanting and reached a very significant level after 90 days transplanting.As for the available phosphorus,the content of single application of nitrogen was less than the control;while the content of application of humic acid only and the interaction between humic acid and nitrogen were 12%,1.1 times higher than the control,respectively.The effects of interaction between humic acid and nitrogen on available phosphorus were significant after 45 and 90 days after transplanting and reached a very significant level after 60 and 75 days transplanting.The content of available potassium in each period under different humic acid levels were the lowest in N1 treatment and the highest in N3.After 90 days transplanting,the treatment of H1N3,H2N3 and H3N3 were increased by 21.9%,29.5% and 25.9%,respectively,compared with the control?H1N1?.The interaction between humic acid and nitrogen had a very significant on the content of available potassium in each period.In terms of organic matter,the interaction between humic acid and nitrogen was only significant at 45 days after transplanting.The changes of urease activity in the whole growth period were similar.The results of analysis of variance showed that humic acid had a very significant effect on soil urease activity at 60 days after transplanting,and had significant effect on 75 d.Nitrogen had significant effects on urease activity at 30 and 90 days after transplanting.The interaction between humic acid and nitrogen had significant effects on the urease activity at 30 d and 60 d after transplanting,while had a very significant effect on 75 d.During the whole growth period,the invertase activity was similar in all treatments,and reached the highest level at 60 and 75 days after transplanting.At 60 days after transplanting,the N3 treatment were the highest under the H1 and H2 levels,which were 45%,62% and 37%,50% higher than N1,N2 treatment,respectively.While under the H3 level,the N2 treatment was the highest,59% and 4% higher than N1,N3 treatment,respectively.The interaction between humic acid and nitrogen had significant effect on the invertase activity at 30 days after transplanting,had a very significant effect at 60 and 75 days after transplanting.3.Effects of interaction between humic acid and nitrogen on the quality of flue-cured tobacco leavesThe results showed that humic acid has an extremely significant impact on reducing sugar,chlorine,potassium,total sugar,sugar-nicotine ratio,ratio of potassium to chloride and has a significant impact on total nitrogen of middle leaves of flue-cured tobacco.It also has extremely impact on nicotine,chlorine,sugar-nicotine ratio,ratio of potassium to chloride and significant impact on potassium,Ratio of potassium to chlorine of upper leaves.Nitrogen has extremely significant impact on each indicator of middle leaves except nitrogen-nicotine ratio.While nitrogen has extremely significant impact on nicotine,chlorine,total nitrogen,sugar-nicotine ratio,nitrogen-nicotine ratio and significant impact on reducing sugar,ratio of potassium to chloride of upper leaves.The interaction between humic acid and nitrogen has extremely significant impact on each indicator of middle leaves and has extremely significant impact on reducing sugar,nicotine,chlorine,total nitrogen,sugar-nicotine ratio,nitrogen-nicotine ratio and significant impact on potassium of upper leaves.In addition,the content of petroleum ether extract in upper leaves treated by humic acid and nitrogen?H2N3?was 20.4% higher than that of the control?H1N1?,and the mineral element was also improved,which indicated that the interaction between humic acid and nitrogen fertilizer was beneficial to the coordination of chemical composition and the quality of tobacco leaves.The results showed that the interaction between humic acid and nitrogen fertilizer was beneficial to improve the main aroma content of tobacco leaves,and the total content of H2N3 was the highest in the middle and upper leaves.Based on the research above,when the interaction between humic acid was H3(900mg·kg-1)level and the nitrogen was N2(40mg·kg-1)or N3(120mg·kg-1)level were better to the growth of flue-cured tobacco and the improvement of soil properties.As for the quality of tobacco leaves,the treatment H2N3(humic acid 300 mg·kg-1+nitrogen 120 mg·kg-1)was better. |
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