Effects Of Continuous Cropping Loss On Phosphorus Form And Availability In Tobacco Growing Soil

Phosphorus is one of the three elements of plant nutrition,also known as the life element.The abundance and deficiency of phosphorus nutrition is particularly important for plant growth and development.In this study,11 representative soils in main tobacco-producing areas of Hunan Province were selected as the research objects.Through pot experiment,the phosphorus forms in tobacco-planting soil and their changes under continuous planting depletion were studied,and the relationship between phosphorus forms and soil available phosphorus was revealed,so as to objectively and scientifically analyze the sources and main forms of available phosphorus in tobacco-planting soil to provide scientific basis for the availability analysis of phosphorus in tobacco-planting soil and the rational application of phosphorus fertilizer in Hunan Province.The main results are as follows:1.The proportion of inorganic phosphorus in the main tobacco-planting soil in Hunan Province is 45.8%～77.8%,which is in the main position,and organic phosphorus accounts for 22.2%～54.3%.The content of inorganic phosphorus is as follows: O-P > Fe-P > Ca-P > Al-P,among which the content of O-P is the highest,accounting for 26.9%～46.6% of the total inorganic phosphorus,followed by Fe-P,accounting for 21.0%～40.5%.The content of Al-P and Ca-P is lower,accounting for only 2.9%～25.5% and 4.4%～26.4% respectively,and most of the soil is about 10%.The content of Al-P and Ca-P in tobacco-planting soil is complementary,that is,the content of Al-P is higher,and the content of Ca-P is relatively low.Among the organic phosphorus components,the main organic phosphorus is medium stable organic phosphorus and medium active organic phosphorus,accounting for 78.8%～91.6% of the total organic phosphorus,of which the proportion of the middle active organic phosphorus is the largest,accounting for 42.3%～78.9%,which is the dominant component of soil organic phosphorus.The organic phosphorus of medium stability was the second,accounting for 12.3%～42.5%.The content of active organic phosphorus is low,which only accounts for about 10% of total phosphorus.The organic phosphorus content of high stability was the lowest and the proportion was the least,accounting for only 1.1%～6.9%.2.After the soil phosphorus consumption decreased after four crops in 3 years,the content of available phosphorus decreased significantly.Although some of the soil had a slight increase after the first tobacco harvest,the increase was smaller than that of the initial soil.The decrease of the soil available phosphorus content after the three crops increased quarterly,accounting for 3.9%～19.2%,5.2%～22.1% and 8.3%～27.2%respectively.3.After the soil phosphorus consumption decreased after four crops in 3 years,the total inorganic phosphorus decreased by 0.5%～24.7%.The content of Al-P in the inorganic phosphorus component of soil decreased by 15.6%～46.9%,and the decrease of the soil with high Al-P content in the initial soil was larger,and the decrease of the soil with low Al-P content in the initial soil was smaller.The reduction rates of Al-P during the next three tobacco harvests were 0.3%～12.5%,2.2%～20.4%and 0.01%～30.8% respectively.The Fe-P content of soil decreased by 1.3%～7.4%,which was not significantly different from the initial soil.The content of soil O-P decreased by 4.3%～42.9%,the first three decreased one by one,the largest in the first,the second and the third,which decreased by 2.6%～47.4%,0.5%～26.0% and2.4%～25.5%,respectively.When the fourth crop of tobacco was harvested,the soil O-P content had a trend of rebound at the bottom.The change trend of Ca-P content in different tobacco-planting soil was different,and there was no significant difference from the initial soil.The lower content soil(treatment)decreased 2.72～7.67 mg/kg,while the soil with higher content increased by about 10%.4.After after four crops in 3 years of tobacco-planting consumption,the total amount of soil organic phosphorus decreased by 3.6%～14.6%.The content of active organic phosphorus decreased by 19.5%～58.4%,and showed that the first one decreased sharply,with the decrease of 9.7%～42.2%,and the change range of the three successive periods decreased significantly,which were 1.2%～12.4%,1.0%～28.0%and 0.3%～14.0%,respectively.The content of organic phosphorus in medium stability decreased,with the range of 5.4%～24.3%.The content of organic phosphorus in high stability also decreased,and the change trend of different soil and different stubble was different.The content of active organic phosphorus in the medium was relatively stable and changed little.5.The results of correlation analysis show that the changes of total inorganic phosphorus,total organic phosphorus,Al-P,Fe-P and active organic phosphorus in Hunan tobacco-planting soil are significantly or extremely significantly related to the changes of available phosphorus.Therefore,they may be the main source or contributor of available phosphorus in Hunan tobacco-planting soil.