Effects Of Simulated Acid Rain And Nitrogen Application On Soil Acidification Of Tobacco Planting Area In Zunyi

In recent years,soil acidification in southern China gradually serious with acid deposition and excessive application of chemical fertilizers,and the soil acidification of tobacco fields in the southwest region has become an important bottleneck of restricting the sustainable development of tobacco agriculture.In order to reveal the mechanism of soil acidification in the tobacco field in southwest region,and to clarify the acidification effect of human activities on the tobacco field soil and its control strategies,laboratory soil columns and field simulated acid rain experiment were used to systematically study the effects of simulated acid rain and nitrogen application conditions on the typical tobacco fields soil in Zunyi?yellow soil and paddy soil?through buffer capacity,leaching of base ions,soil enzyme activity and tobacco growth.To initially clarified the acidification mechanism and acidification effects of tobacco fields.The main conclusions are as follows:1.Studies on the two types of soil buffer capacities and chemical properties showed that the acid-base buffer capacity of Zunyi yellow soil was higher than that of paddy soil.Among the 13 basic chemical indexes,11 indexes in paddy soil had a correlation of more than 0.9 with acid-base buffer capacity,which were respectively available potassium,pH,CEC,available phosphorus,organic matter,exchangeable Ca²⁺,exchangeable K⁺,exchangeable Al³⁺,exchangeable H⁺,exchangeable Na⁺,exchangeable Mg²⁺.Five indexes in yellow soil had a correlation of more than 0.9 with acid-base buffer capacity,which were CEC,organic matter,available phosphorus,pH,and exchangeable H⁺.2.The effect of acid rain with different pH values on the two types of soil acidification was studied by soil column simulation experiment.The results showed that the content of inorganic nitrogen and exchangeable base ions(Ca²⁺,Mg²⁺,K⁺and Na⁺)in the leaching solution increased with the decrease of pH value of the eluent.The influence of acid rain on 20?40 cm soil layer was less than 0?20 cm soil layer.Soil pH,CEC,exchangeable base ions and urease activity of the two types of soil decreased with the decrease of the eluent pH value.The exchangeable acid,exchangeable H⁺,exchangeable Al³⁺increased with the decrease of the eluent pH value.The invertase activity decreased first and then increased as the eluent pH value decreased.And the order of soil base ions after leaching was:Ca²⁺>Mg²⁺>K⁺>Na⁺.Compared with the initial pH value of soil,the soil pH increased slightly with the eluent was pH 5.6 and pH 7.0.3.Studies on the effect of acid rain with different pH values and different nitrogen fertilizer types on soil acidification showed that under the interaction of acid rain and nitrogen application,the content of inorganic nitrogen and base ions in the leaching solution of the two types of soil increased significantly with the decrease of eluent pH value,and the acid production of NO₃^-leaching was greater than that of NH₄⁺.Under different nitrogen fertilizer treatments,the total amount of NO₃^-in the leaching solution of the two soils was shown as potassium nitrate>ammonium sulfate>urea.Compared with the single acid rain treatment,the pH value,exchangeable base ions and enzyme activity of the soil were further decreased,and the exchangeable acid,exchangeable H⁺and exchangeable Al³⁺content were further increased.Under the same pH eluent treatment,both soils were treated with urea had the highest pH,followed by potassium nitrate and ammonium sulfate,while the ratio of exchangeable Al³⁺to exchangeable acid was ammonium sulfate>potassium nitrate>urea in different nitrogen fertilizers treatment,the total exchangeable base was potassium nitrate>urea>ammonium sulfate,the urease activity of the soil was urea>ammonium sulfate>potassium nitrate,and the activities of invertase were ammonium sulfate>potassium nitrate>urea.It could be seen that under acid rain conditions,the application of ammonium nitrogen fertilizer would aggravate the process of soil acidification.4.Studies on the effects of simulated acid rain on tobacco growth and soil acidification in tobacco fields showed that the growth of flue-cured tobacco under natural rainfall treatment was slightly better than that of distilled water treatment,but the acid rain of pH3.5 significantly inhibited the growth of tobacco,reduced the agronomic characteristics and biomass characteristics of roots and stems in the budding stage of flue-cured tobacco.Meanwhile,it reduced the soil pH value,CEC and total amount of base at the budding stage of flue-cured tobacco,and increased the content of exchangeable acid and exchangeable Al³⁺.This showed that the low pH acid rain had negative effects on the soil ecological environment and tobacco growth in tobacco fields.