ABSTRACT

Since 1970, most of the tobacco has been cultivated using conventional tillage system in Southern Brazil. No long-term soil degradation assessment on tobacco crop has been performed, particularly, on soil erodibility. The objectives of this study were to evaluate the aggregate stability, soil erodibility, and physico-chemical soil changes, as a function of the time of tobacco cultivation i.e. chronosequence (forest, 3, 10, 15, 20, 25, 30, and 40 yr). Several tests for aggregate stability, soil physicochemical, and soil organic matter determination were applied. The dry mean weight diameter of aggregate decreased more than twice from 3.6 mm to 1.6 mm. While the aggregate stability decreased five times from 36.7% to 6.8% following the tobacco chronosequence. The organic matter content decreased abruptly i.e. 57% under tobacco cultivation. Inversely, the pH, cations and particularly, phosphorous concentration, increased three times on older tobacco plots (≥ 25 yr). Surprisingly, an increase of 23% in silt size fraction due to re-organization of particles makes the soil more erodible along the chronosequence. Forty years of soil cultivation with tobacco, using conventional tillage methods caused significant soil physical-chemical degradation. Therefore, a soil conservation policy must be adopted urgently on tobacco crop areas in Southern Brazil.

摘要

自 1970 年以来，巴西南部大部分烟草都使用传统耕作系统种植。尚未对烟草作物进行长期土壤退化评估，特别是对土壤可蚀性的评估。本研究的目的是评估总体稳定性、土壤可蚀性和物理化学土壤变化，作为烟草种植时间的函数，即时间序列（森林、3、10、15、20、25、30 和 40年）。对骨料稳定性、土壤理化和土壤有机质测定进行了多项测试。骨料的平均干重直径从 3.6 mm 下降到 1.6 mm 的两倍多。而在烟草时间序列之后，总稳定性从 36.7% 下降了 5 倍至 6.8%。有机质含量急剧下降，即在烟草种植下下降了 57%。反之，较老的烟草地块（≥ 25 年）的 pH 值、阳离子，尤其是磷浓度增加了三倍。令人惊讶的是，由于颗粒的重组，淤泥尺寸分数增加了 23%，这使得土壤在时间序列上更容易被侵蚀。40 年的烟草土壤种植，使用传统的耕作方法导致了显着的土壤物理化学退化。因此，巴西南部烟草种植区必须紧急采取水土保持政策。使用传统的耕作方法会导致显着的土壤物理化学退化。因此，巴西南部烟草种植区必须紧急采取水土保持政策。使用传统的耕作方法会导致显着的土壤物理化学退化。因此，巴西南部烟草种植区必须紧急采取水土保持政策。