Effect Of Straw Return To The Field On The Organic Matter Of Tobacco Soil And Its Mineralization Characteristics

The content of organic matter of tobacco soils was large different in the south of Hunan. The range of the content of organic matter is 24.63-60.27 g/kg. The relation between the content of organic matter and the supply of the soil nitrogen was not direct proportion. The area which had large content of organic matter always had low mineralization of the soil nitrogen. So, on the base of the difference of the physical and chemical properties of the tobacco soil and the soil mineralization characteristic in Hunan, to study the relationship between the groups of organic nitrogen and the mineralization of organic matter in the different systems of fertilization. Collecting 14 different soil patterns which were straw return to the field of tobacco rice rotation in the south of Hunan province to be subject of studying. Study the effect of straw return to the field of tobacco rice rotation on the organic matter and its mineralization characteristic. The main results were as follows:1. The disposal of straw return to the field can enhance the content of organic matter, the total nitrogen, the alkali-hydrolysable nitrogen, available phosphorus and available potassium. The increasing ranges of them were 23.62%,19.21%,19.64%,23.53% and 27.98%. However, the disposal of straw return to the field just had a significant effect on the soil organic matter and total nitrogen (F=6.30). The disposal of straw return to the field can enhance the carbon content of humus acid, fulvic acid, and humin in soil. The increasing ranges of them were 13.57%,15.94% and 26.02%. The disposal of straw return to the field had a significant effect on the carbon content of humin, F=6.05(F0.05=5.99), and not to the carbon content of humus acid and fulvic acid (F0.878).2. The disposal of straw return to the field which could improve the content of groups of organic nitrogen (expect Amino sugar nitrogen) in soil in general. The increasing ranges of the content of Amino acid nitrogen, Unknown hydrolysable nitrogen, and Unhydrolysable nitrogen were 12.5%,2.5%,55.1% and 17.5%. But the increasing range of the total nitrogen was 19.2% after straw return to the field. Then, the proportion of the groups of organic nitrogen in total nitrogen were declined expect Unknown hydrolysable nitrogen. The descend rang of Ammonia nitrogen, Amino acid nitrogen, Amino sugar nitrogen, Unhydrolysable nitrogen were 0.68%,2.48%,0.65%,1.10%. And the increasing range of Unknown hydrolysable nitrogen was 4.91%. So the main effect of straw return to the field was to improve the content of Unknown hydrolysable nitrogen. The main effect on the content of Ammonia nitrogen, Amino acid nitrogen, Unhydrolysable nitrogen was the different physical and chemical properties of soils. Straw return to the field which enhanced correlation coefficient(r) between Ammonia nitrogen, Unknown hydrolysable nitrogen, Unhydrolysable nitrogen and organic matter, total nitrogen, alkali-hydrolysable nitrogen. They had significant relation (r>0.811), even extremely significant relation (r>0.917). Straw return to the field which weakened correlation coefficient(r) between Amino acid nitrogen, Amino sugar nitrogen and organic matter, total nitrogen, alkali-hydrolysable nitrogen.3. The content of soil experiment mineralization potential was between 416.67 mg/kg and 1428.57 mg/kg. And the content of soil theory mineralization potential was between 233.24 mg/kg and 1194.33 mg/kg. The disposal of straw return to the field had not a significant effect on the soil experiment mineralization potential, F=1.48(F0.05=5.99). And it had a significant effect on the soil theory mineralization potential, F=11.71(F0.05=5.99). So the disposal of straw return to the field could significantly enhance soil mineralization potential in theory. The soil mineralization rate constant was between 0.0401-0.4931. However, it had not significant effect on the soil mineralization rate constant (k), F=0.33(F0.05=5.99). The soil mineralization rate constant was the inherent physical constant in soil. It could not have a significant change with the different system of fertilization. Generally, the faster of the mineralization rate, the larger of the soil mineralization rate constant. To the tobacco soil, the larger of the soil mineralization rate constant, the better to need of the grow rhythm of tobacco.