Studies On Magnesium Nutrition And The Control Meathods Of Quality Flue-Cured Tobacco

Field investigation, simulation experiment with repacked soil columns, indoor soil-culture, pot experiment and field experiment were conducted to investigate status of magnesium of soil and tobacco leaf, study the rule of the leaching lose of Mg fertilizer .suggest the magnesium diagnostic indexes in soil and tobacco leaf in Fujian tobacco planting area, and study Mg fertilizer rational application effect.1. The results of the study for 2253 samples of soil and leaf in Fujian tobacco planting area were summarized as follows:the range of the content of exchangeable magnesium in the tobacco soil was 1.80 256.80 mg. kg^-1, and the average of the content was 34. 49 mg. kg^-1. 88. 86% of all soil samples, the content of exchangeable magnesium was lower than 50mg.kg¹. The range of the content of magnesium in tobacco leaf was 0. 06%¹.60%, and the average of the content was 0.24%. 43.00% of the tobacco leaf samples , the content of magnesium was lower than 0.2%.2. The results of an indoor simulating experiment with repacked soil columns showed that magnesium was relatively easily leached from soil, which resulted in the magnesium deficiency of tobacco. The leaching ratio of exchangeable magnesium in soil came up to 27.47%. Separately, the leaching ratios of exchangeable magnesium in the treatments of MgS0₄.7H₂0, Mg(0H)₂, MgO, limestone, alcium magnesium phosphate were 32.88%, 27.30%, 24.08%, 19.26%, 11.86%. Application of K fertilizer(K₂SO₄) promoted the leaching of magnesium. Applicationof N fertilizer increased the leaching of magnesium. Application of Ca fertilizer scarcely affected the leaching lose of magnesium.3. Soil culture experiment results showed that the content of exchangeable magnesium had increased promptly in Paddy field, Tidal Paddy field, Red mud field when MgO, Mg(OH), and MgSO,. 7H,0 were applied. The soil had the highest amount of exchangeable magnesium when Mg(0H)L. and MgS04. 7H20 were applied in 10 days, and the soil had the highest amount of exchangeable magnesium when MgO was applied in 30 days. The ratio of clench in various soils was in the following order: Paddy field (55.97%) > Tidal Paddy field (38.20%) > red mud field (11.20%) when MgSO4. 7H20 was applied in 90 days. The treatments of MgO and Mg(0H)2 had the same rule. The ratio of abstract in various soils was in the following order: Paddy field (20.00%) < Tidal Paddy field (53.32%) , Calcium magnesium phosphate was 22869.15yuan. hnf2, MgS04. 7H20 had the lowest output value (21275. 25yuan. hnf2). Apparent character of the treatments of MgO and Mg(0H)2 were better than others, So MgO and Mg (Oil) ^ were the better choice of Mg fertilizer for Fujian tobacco planting area.6. A field experiment was carried out, the results showed that tobacco plant had symptom of magnesium deficiency remarkablely when rate of MgO was lower than 150kg. hnf2. The content of magnesium was lower than 0.25% in low leaf after roasting, so Mg content, of 0.20% in low leaf of tobacco was recommended preliminary as a critical level after roasting.The output value, yield , mean value .ratio of high class leaves of flue-cured tobacco were improved with increased dosage of MgO in field of magnesium deficiency stress, the range of output value was 39. 88%⁷9. 03%, yield 4. 07%¹6. 20%, mean value 2. 04—3. 1 lyuan. kg"1, high class leaves 24. 36³4. 00 percentage. The rate of 225kg. hm2 MgO...