Studies On The Optimization Techniques Of Tobacco Floating-seedling System In Panzhihua

To improve the floating breeding technology and to increase the rate of sound seedlings,combined with the tobacco production and ecological conditions in Panzhihua, the research has been carried out to study the optimized technologies in tobacco floating breeding,. This research has been separately carried out a series of comparison experimental, including comparison experiments of sprouting coated seeds, floating breeding medium, breeding fertilizer, seedling raising pan, different sowing stages, changes of temperature, leaf-cutting, seedling-hardening without water, depth of nutrient solution, different covering ways after sowing, choices of seedling breeding sheds, application of CuSO4·5H2O and breeding by different ways. The primary research result as follows.The sprouting coated seeds germinated5-7days earlier than those normal seeds, and the field stage have varying degrees of advance,,which would benefit for avoiding negative influences on plants later growth suffering from low temperature.Using sprouting coated seeds in low temperature areas in Panzhihua is to avoid the abnormal low temperature damages in plants later maturity.The optimal physical characteristics of breeding medium were organic matter contained, medium particles with1-3mm diameter, capacity of0.26, total pore at60-70%. With the basis of70%peat and15%vermiculite, adding15%perlite is an ideal formula.If the concentration of total N increases from200mg/kg which Panzhihua have been used to300mg/kg in floating system, it will help to coordinate of tobacco plant growth and produce sound seedlings.The optimal choice of the floating pan is the one with55cm in length,33cm in width,6cm in thickness and160seedling holes, and the capacity of each hole was26m3.It is better to choose the medium and seedling-raising pans with good thermal conductivity.Located at1800m above the sea level along Anlinghe River, late January to early February is the suitable period for sowing seedlings breeded by floating in Panzhihua tobacco growing areas.For overcoming low temperature of seedling beds in early seedling stage, baking the water、pans and some other ways would effectively increase the temperature of seedling beds.Leaf-cutting and seedling-hardening would increase the dry weight accumulation of seedlings, make the plants much more uniform and even, strengthen the roots and stems and stress resistance of seedlings and enhance the adaptability in the fields after been transplanted. Besides those, it could increase the lignification degree and stress resistance to avoid and prevent the injured or weak seedlings transplanted in the fields, so as to match the standard of sound seedlings as well.Alternately cutting leaves and stopping water in hardening seedlings was good for roots growth and promoting early growth and quick development in fields. Some materials present that over cutting and hardening or immediate transplanting after cutting and hardening would slow down the growth and cause side effects.When the depth of nutrient solution was lower than8cm, the stability of water temperature was poor and seedlings came out unevenly, and while it was better to keep the depth between10cm to12cm.Compared with small-sized sheds, the medium ones would help seedlings come out earlier with the altitude increasing, the advantage with high rate of seedlings shooting and high uniformity would become much more obvious.Therefore, the medium-sized sheds floating seedling is a professional way suitable for high altitude areas.It played a promotive role in seedlings’growth to use the25-100mg/kg CuSO4·5H2O solution, while an inhibitory role when the concentration was more than200mg/kg. For safety’s sake, when it entered the five true leaves stage in Panzhihua and even the Panxi area, adding50mg/kg CuSO4·5H2O would effectively inhibit the growth of the invalid roots and r the rotated ones coming out from the pan holes,and increase more valid ones.The floating ones would increase the leaf number to27pieces, which is a better seedling way to improve the quality of tobacco leaf production in Panzhihua. The photosynthesis rates of seedlings raised by these three different ways first decreased and then gradually increased during the day before been transplanted to45days after been transplanted. The curve of waterbed tray raising seedlings was relatively flat.. After seedlings been transplanted, the transpiration rates first decreased and then increased, the decline rate of waterbed tray was lower than the other two ways, During the15days after transplantation, content of chlorophyll a+b of plants was gradually increasing, and after this period it increased rapidly. The root vigor was increasing slowly, while of the floating breeding seedlings first increased rapidly, and then decreased a little bit. The total root absorption area and surface activity absorption shared little differences among those seedlings raised by three different ways. The yield per unit, output value, high-class leaf rate, medium-class rate and average price of floating seedlings were the highest, there was little differences in early-cured leaves, nicotine, protein and chlorine among the three. The potassium content had obviously improved. The sensory taste result indicated that different breeding ways have little impact on sensory taste total scores, strength, inflammability and grey, although, the value and quantity of the aroma of leaves produced from floating system had increased.