重庆市植烟区土壤镁素含量状况及施镁效应研究

通过野外采样和田间试验对重庆市植烟区土壤交换性镁含量以及施镁效应进行了研究。结果表明，1）重庆市植烟区土壤普遍存在着缺镁的现象，土壤交换性镁含量平均值仅为1.11 cmol/kg（n=334），变幅为0.15～4.50 cmol/kg； 5种主要类型土壤的交换性镁平均含量（cmol/kg）依次为黄棕壤1.51＞黄壤1.20＞紫色土0.83＞水稻土0.41＞石灰土0.30； 其交换性镁含量在缺镁临界值（1.0 cmol/kg）以下的土壤样本数分别占27.78%、54.51%、72.22%、100%和100%。2）施镁对烤烟具有显著增产、提高中上等烟比例以及增加产值的效应，烤烟产量、产值、均价和中上等烟比例均以T4处理为最高（MgSO4·7H2O 244.90 kg/hm2），且与其它各处理表现出显著性差异。3）各施镁处理中，烟叶总氮、蛋白质和烟碱的含量均低于CK处理，而总糖和还原糖含量则高于CK处理； 钾素含量与施镁量的增加均呈现出极显著性负相关（彭水r=0.9824，石柱r=0.9893），烟叶化学成分的协调性也同样以T4处理最佳。

Studies on soil Mg content and effects of Mg application in tobacco planting areas of Chongqing

The objectives of this study were to investigate the contents of soil exchangeable magnesium and the effects of magnesium application on tobacco production in tobacco planting areas of Chongqing by using the methods of field sampling and field experiments. The results show that the average content of soil exchangeable magnesium is about 1.11cmol/kg (n=334), and the range is from 0.15 to 4.50 cmol/kg in Chongqing tobacco planting areas. The average contents of soil exchangeable magnesium of the five main soil types are pale brown soil, 1.51cmol/kg; yellow soil, 1.20 cmol/kg; purple soil, 0.83 cmol/kg; paddy soil 0.41 cmol/kg; and lime soil, 0.30cmol/kg. The percentages of magnesium deficiency soil samples for the 5 soil types are about 27.78%, 54.51%, 72.22%, 100% and 100%, respectively. Which indicates the phenomenon of magnesium deficiency is common in tobacco planting areas of Chongqing. The application of magnesium fertilizer can increase the yield, the ratio of mid-grade and high-grade tobacco leaves and the output value significantly. The yield, output value, average price and the ratio of mid-grade and high-grade tobacco leaves of the T4 treatment (MgSO₄·7H₂O 244.90 kg/ha) are the highest, and there are significant differences between the T4 treatment and the CK, T1, T2, T3 and T5 treatments. Among the magnesium application treatments, contents of total nitrogen, protein and nicotine of leaves are lower than those of the CK treatment, while contents of total sugar and reductive sugar are higher than those of the CK treatment. There are negative correlation between content of K₂O of leaves and the rates of the magnesium fertilization. In addition, the chemical composition of the T4 treatment is the best.