Studies On The Causes And Control Technologies Of Salt Accumulation In Surface Soil Of Tobacco-Planting In Hunan

In this study, the salt accumulation in surface soil and its correlation with the contents of majorelements in tobacco leaf were analysed, the intensity and regularity of salt accumulation in surface soiland the composition of ions, their effects of growth and development on tobacco, quality on tobaccoleaf were definituted. Effects of the technological measures which as changing the suitable morphologhof fertilizer, reasonable irrigation way and mulching straw on salt accumulation in surface soil werestudied. The goal is providing scientific basis and effective actions of active prevention the saltaccumulation in surface soil or the secondary salinization,promoting the sustainable development oftobacco production. The main results were reported as follows:1.The distinct salt accumulation was observed in surface horizon of soils after the tobacco leaveswere harvested. The total salt concentration ranged from 3770.4 mg/kg to 4526.9 mg/kg, the averagereached 4169.5 mg/kg, which is near the intensely salinized soil. The total salt of three tobacco fields insurface soil is Hengyang＞Yongzhou and Chenzhou＞Zizhizhou; NO₃^-, SO₄^2-, Ca²⁺ and K⁺ consisted ofmain ions in surface soil after tobacco leaves were harveasted, which accounted for 93.77% of total saltamount; NO₃^-, SO₄^2-, Ca²⁺ and Na⁺ consisted of main ions in surface soil in the rice-rice rotation fields,which accounted for 95.16% of total salt amount; The total salt of three tobacco soils (which of differentfarming systems) are the tobacco-rice rotation＞the tobacco dryland＞the rice-rice rotation.2.In the southern of Hunan, the Ca²⁺,SO₄^2-,Cl,K⁺ and Mg²⁺ accumulation in surface soil willdecreased the contents of Ca, S,Cl,K and Mg in tobacco leaves, but the NO₃^- and Na⁺ accumulation insurface soil have little effect on the contents of these ions. In the western of Hunan, the Na⁺,SO₄^2- and Cl^-accumulation in surface soil will decrease the contents of Ca, S and CI in tobacco leaves, theK⁺,Mg²⁺,NO₃^- and Ca²⁺ accumulation in surface soil have little effect on the contents of these ions. Theresult of correlation test is the amount of ions in surface soil and the relative elements in tobacco leavesis inconspicuousness(r＜r_0.05).3. The effects of water movement on salt accumulation are great. More salt accumulation in surface soil was obtained in the treatments of water move-up than that of move-down, it can explainthat water move-down can reduce the total salt in the surface soil, and alleviate the pressure of saltaccumulation in surface soil; Salt accumulation in surface soil can be decreased by the treatments ofwater move-down because of salt washing with water, the amount of salt in water seepage has relationswith the concentration of salt and characteristic of ions in soil, the K⁺,Ca²⁺,SO₄²⁺ and NO₃^- consisted ofmain ions in water seepage. The effects of different directions of water movement on biologicalcharacteristics of flue-cured tobacco are not great.4.The effects of different morphologhs of potassium fertilizer on biological characteristics offlue-cured tobacco are not great, K⁺,Ca²⁺,SO₄^2- and NO₃^- consisted of main ions in surface soil of thedifferent growth periods in the flue-tobacco, the contents of Na⁺ and Mg²⁺ are also high in vigorousgrowing period, it can explain that these kinds of ions are easily accumulated in the soil surface. Theyield can be increased when KNO₃ application combined with K₂SO₄ and the irrigation water aresimultaneous.5.The salt content in surface soil can be decreased by 1.8%～22.2% because of straw covering.The vigorous growing stage is shorten, plant height, the leaves and the leaf areas are increased, thequantity and quality of tobacco leaf are increased. The activity and vigor of root system are alsoincreased.