Role Of Biofertilizer On Regulating Soil Nutrition And Improving Quality Of Tobacco Leaves

Tobacco is one of the most important economic crops and is widely plantedthroughout China. Over years, large amounts of synthetic fertilizers and pesticideshave been applied to farmland for the purpose of obtaining a high yield; however, theindiscriminate use of chemical fertilizers and pesticides has caused a series ofnegative impacts on croplands. It has increased soil contamination with heavy metalsand residual pesticides which damaged the soil eco-environment, thereby destroyingthe microbial community structure, making crops more prone to diseases and reducingsoil fertility. All these unfavorable circumstances not only have serious implicationsfor tobacco leaves quality, but also impede the sustainable development ofagriculture.In the present study, a combination of organic fertilizer, soil ameliorant andbiofertilizer was used in preparing a novel type of biofertilizer which containedPhanerochaete chrysosporium and Bacillus thuringiensis （BFPB）. Rapeseed cake wasused as the microorganism carrier, and bentonite was added for improving soil waterand nutrient conservation. To determine the effect of P. chrysosporium and B.thuringiensis, respectively, two other biofertilizers were prepared as follows:（i） oneprepared according to BFPB without B. thuringiensis （BFP）; and （ii） the otherprepared without P. chrysosporium （BFB）. All these biofertilizers were used as basefertilizer with the purpose of improving soil conditions for the growth of Yunyan87.As control, pure rapeseed cake was used at the same way with biofertilizers. Soilsamples were collected during the tobacco growth season, including resettli ng growthstage, vigorous growing period, topping, and maturity stages of lower, middle, andupper leaves to exploring the influence of biofertilizers on soil nitrogen-supplying.Mature lower, middle, and upper leaves were collected for analysis of tobacco quality.Experiment results showed that biofertilizer had no influence on soil totalnitrogen. By contrast, soil available nitrogen and enzymes were deeply affected bybiofertilizer. NO₃^--N content and nitrate reductase activity in biofertilizer-amendedsoil increased by92.3%and42.2%, respectively, compared to those in the control,whereas the NH₄⁺-N and urease activity decreased by37.8%and29.3%, respectively.Nitrogen uptake was improved in the early growing stage, but this phenomenon wasnot observed during the late growth period. The biofertilizer caused an increase of total nitrogen in lower and middle leaves compared with control, while a decrease oftotal nitrogen was observed in upper leaves. Protein concentration in different tobaccoleaves had similar fluctuation to that of total nitrogen in response to biofertilizer. Thebiofertilizer can also reduce the nicotine content in tobacco leaves, with a maximumdecrement of16%–18%being observed in the in upper leaves. This study is importantfor the development of new biofertilizer and its application in improving soilecological environment and tobacco quality.