ABSTRACT

To clarify the effects of long-term fertilization on the depth profile of plant nutrients and soil acidity in non-allophanic Andosols, a soil survey was conducted on fertilized grassland and adjacent secondary forest in Kuju highland, Oita Prefecture, Japan. Both of the experimental plots had been managed as a semi-natural grassland (managed by cutting, mowing, and burning for raising cows) before mid of the 1960s, and then, the former had been converted into reclaimed grassland with applying agricultural materials such as fertilizers, manure, and lime, and the latter had been abandoned which resulted in secondary succession into the secondary forest. The comparison of the depth profiles between the two plots revealed that the applied Ca²⁺ and Mg²⁺ reached at least 100 cm depth of the non-allophanic Andosol profile. The soil pH was increased at least at the depth of 100 cm, and the plant-toxic level of soil acidity (≥12 mmol kg⁻¹), which is one of the characteristic properties of non-allophanic Andosols, was decreased in the fertilized grassland soil. Soil available P was also observed to be increased at least 80 to 100 cm depth, although the mobility was smaller than those of exchangeable cations and soil acidity. Other soil chemical properties, such as cation exchange capacity, total C and N contents, pyrophosphate-extractable Al (Al_p) and Fe (Fe_p), acid-oxalate-extractable Al (Al_o), Fe (Fe_o), and Si (Si_o), Al_p/Al_o ratio, and Al_o + 1/2 Fe_o, were not significantly altered by the modern grassland management activities. This study reveals considerable loss of plant nutrients from the fertilized grassland soil of a non-allophanic Andosol during a half-century. The loss of plant nutrients should be reduced for sustainable agriculture and conserving the natural environment.

摘要

为阐明长期施肥对非脂溶性安多溶胶中植物养分深度剖面和土壤酸度的影响，对日本大分县九重高原的施肥草地和邻近次生林进行了土壤调查。2个试验地在1960年代中期以前都作为半天然草地（割、割、烧养牛）进行管理，之后利用农资等农资改造为开垦草地。化肥、粪肥和石灰，而后者已被废弃，导致次生演替进入次生林。两个图之间的深度剖面的比较表明，施加的 Ca ²⁺和 Mg ²⁺达到非脂溶性 Andosol 剖面的至少 100 厘米深度。土壤 pH 值至少在 100 cm 深度增加，土壤酸度（≥12 mmol kg ^-1）的植物毒性水平（非脲素安多溶胶的特征之一）在施肥后降低。草原土壤。还观察到土壤有效磷至少在 80 至 100 厘米深度增加，尽管流动性小于可交换阳离子和土壤酸度的流动性。其他土壤化学性质，例如阳离子交换能力、总 C 和 N 含量、焦磷酸盐可提取的铝 (Al _p ) 和铁 (Fe _p )、酸草酸盐可提取的铝 (Al _o )、Fe (Fe _o ) 和的Si（硅_ø），铝_p/Al _o比率和Al _o + 1/2 Fe _o没有被现代草原管理活动显着改变。这项研究揭示了半个世纪以来，非脲素 Andosol 施肥的草地土壤中植物养分的大量流失。为了可持续农业和保护自然环境，应减少植物养分的损失。