| The nitrogen fertilizer is important on the growth, physiology process and quality of flue-cured tobacco. Flue-cured tobacco can absorb the NH4-N, NO3-N and urea from soil. But when different forms of nitrogen enter the tobacco plants, they are different in transportation and character of assimilation in tobacco plants, also different in synthesis of material in tobacco leaves. Different sources of nitrogen fertilizer effect quality of tobacco leave greatly. However, none of nitrogen fertilizer, can exist in with they original forms for a long time. When they enter the soil, they are changing all the time. So studies every kind of fertilizer, particularly NH4-N fertilizer and urea, on its nitrification character and the effect of tobacco's growth and quality of tobacco leave, have great significance on rational application of fertilizer guidance, special fertilizer production, reduction the cost of produce and improvement of the economic benefit.The results of soil incubation experiment of (NH2)2CO, NH4HCO3, NH4NO3, (NH4)2SO4,NH4H2PO.4, and (NH4)2HP04 indicated: after nitrogen applied into soil 5 days, the treatments of the highest content of ammonium nitrogen were that of (NH2)2CO and NH4H2PO4, 121.50mg/Kg and 120.56mg/Kg, respectively, higher than that of the treatment of check(CK); after urea applied into soil 5 days, amide nitrogen in soil of (NH2)2CO treatment was 2.78 mg/Kg, this indicated that a majority of urea had been inverted to ammonium nitrogen. When nitrogen applied into soil 15 days, the content of nitric nitrogen of (NH2)2CO and NH4HCO3 treatments increased 78.70mg/Kg and 86.66mg/Kg than the content of the 5th day; but the content of ammonium nitrogen still maintained at higher level. At this moment, the ordet of the rate of nitrification of every kind of nitrogen fertilizer treatment is: NH4HCO3 > (NH2)2CO > NH4NO3 > (NH4)2HPO4> NH4H2PO4> (NH4)2SO4. When nitrogen applied into soil 30 days, compared to CK the content of ammonium nitrogen of (NH2)2CO, NH4NO3 and NH4HCO3 treatments were only higher 2.4-7.0 mgs/ Kg. It indicated that a majority of three kinds of nitrogen fertilizers already had been converted into nitric nitrogen at that time. The changes of soil pH-value after all kinds of nitrogen fertilizer applied into soil were different. When urea entered into soil 5 days, its soil pH-value had risen to 6.11, then continuously decreased, in the 15th day 0.22 units lower than that of CK, in the 80th day 0.33 units lower than that of CK. After nitrogen applied into soil 30-day, pH-values of (NH4)2SO4, (NH4)2HPO4 and NH4H2PO4 treatments(4.15,4.11,4.20, respectively) were lower than those of other treatments. During the period of 30-80 days every kinds of nitrogen fertilizer entered into soil, pH-value slowly and stably changed.The results of experiment of pot culture indicated: application of NH4HCO3, NH4NO3 and (NH2)2CO into soil promoted the tobacco plants to grow rapidly, the maximum area of leaves was 32.8-43.4% bigger than that of CK after transplantation 30 days, and they had more 1.8-3.0 leaves per plant than that of CK. But the tobacco plant grew slowly with the applied of (NH4)2SO4, (NH4)2HPO4 and NH4H2PO4 into soil. The order of the yield (root, stem and leaf) in all treatments with application different nitrogen fertilizer was: (NH2)2CONH4HCO3> NH4NO3>(NH4)2SO4>NH4H2PO4> (NH4)2HPO4. At the treatments of application with (NH2)2CO, NH4HCO3 ,NH4NO3 and (NH4)2SO4, the difference among the total amino acid, asparaginic acid and arginine of tobacco leaves were trivial. At the treatment of application NH4H2PO4, the content of the total amino acid, asparaginic acid and arginine of tobacco leaves was higher than that of other treatments.The result of field experiment indicated: the treatment with the highest yield and output is with 25%NO3-N+25%urea+50%NH4-N, 178.5 Kg/acre, 1781.6 Yuan/acre, respectively. Application the 100% urea made the ratios of high-quality tobacco leaf 3.6-16.6 percent lower than that of other treatments. The reducing sugar of leaves of all treatments was that...
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