Abstract
Long term tobacco planting leads to soil acidification. A ten-year experiment with various fertilization treatments (no fertilization (CK), chemical fertilizer (CF), organic-inorganic compound fertilizer (OCF), and organic fertilizer (OF)) was carried out between 2010 and 2020 in a continuous cropping system of Nicotiana tabacum in the brown soil of eastern China, to assess the effects of organic fertilizer on the improvement of tobacco planting soil acidification. The results indicated that treatments OCF and OF reduced the soil exchangeable acid content, of which the exchangeable aluminum showed the largest reduction by 51.28% with the OF treatment. In contrast, treatment CF showed more significant increases in exchangeable aluminum (Al) and Al saturation, and also apparently increased soil NO3−-N, NH4+-N and nitrification potential (NP) than other treatments. Treatments of OCF and OF significantly increased the total amount of exchangeable base (EBC) by 37.19% and 42.00% compared with CF, respectively. Redundancy analysis (RDA) showed that NP, NH4+-N, and NO3−-N were the important factors indicating soil acidification, while EBC and exchangeable K were the significant factors restricting soil acidification. Inevitably, OCF could improve the soil organic carbon pool and labile organic carbon pool. The structural equation model (SEM) showed that OCF treatment increased the soil organic carbon pool mainly by inhibiting soil nitrification and reducing the content of exchangeable Al. In conclusion, both OF and OCF treatments were effective methods to alleviate tobacco planting soil acidification, however OCF had more advantages in improving soil organic carbon pool.
Highlights
Soil acidification is one of the most important factors limiting nutrient uptake and crop yields
After ten years of continuous fertilization, it was found that the changes of organic fertilizer (OF), organic-inorganic compound fertilizer (OCF), and CK treatments were relatively minor, and the soil pH value of the OF treatment was the highest in each year
The application of organic fertilizer increased soil pH by 0.18 units in 2020 compared with 2010, while the application of chemical fertilizer alone led to a sharp decrease in soil pH by 0.84 units
Summary
Soil acidification is one of the most important factors limiting nutrient uptake and crop yields. Soil acidification can lead to the accumulation of aluminum (Al) and deficiencies in phosphorus (P), potassium (K) and other nutrients in tobacco field soil [3]. Concerning the quality of tobacco, soil acidification can reduce the total sugar, protein, and aroma substances in tobacco leaves, increase metals ions such as aluminum, iron, and manganese, and is not conducive to the growth of tobacco or the formation of high-quality tobacco leaves [4]. It is urgent to solve the problem of soil acidification in tobacco fields, so as to ensure the further improvement of soil productivity and tobacco quality
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