Water-Stable Aggregates of Strongly Acidic Allophanic Andosols affected by Heavy Application of Fertilizers
Nobuhiko Matsuyama, Hirotsugu Konno, Choichi Sasaki, Chihiro Kato, Haruki Fujisawa, Eiji Sakaiya

This research was performed to assess water-stable aggregates of strongly acidic allophanic Andosols affected by heavy application of fertilizers. A long-term field experiment with successive application of lime and fertilizers began in 1940 at the Fujisaka Branch of the Aomori Agricultural Experiment Station. The exchange acidity y1 of the fertilizer plot for topsoil (0-13cm), subsoil (13-21cm), and subsoil (21-42cm) showed strong acidity. The potato yields in 2014 were 0.93 kgm-2 for the fertilizer plot and 3.12 kgm-2 for the lime+fertilizer plot. Strongly acidic allophanic Andosols with accumulation of acidic materials showed dissolution of part of the active Al fraction in the soil causing Al toxicity. The percentages of water-stable aggregates of the uppersubsoil layer (13-21cm) in the fertilizer plot were 39.9%±4.9% for the < 0.125 mm fraction, 17.4%±1.2% for the 0.125-0.25 mm fraction, 30.5%±3.5% for the 0.25-0.5 mm fraction, 9.3%±0.5% for the 0.5-1.0 mm fraction, 2.1%±0.3% for the 1.0-2.0 mm fraction, and 0.7%±0.4% for the > 2.0 mm fraction. The micro aggregate increased because of the decrease in the amount of roots by Al toxicity in the strongly acidic subsoil of the fertilizer plot. The taproot areas were estimated as 11.4 cm2 for the fertilizer plot and 14.4 cm2 for the lime+fertilizer plot on radiographs. The taproot area in the fertilizer plot was relatively low. Thus, we confirmed that the macro aggregate was decreased by restricting of the root system in the strongly acidic allophanic Andosols and the pores formed by roots were relatively small.

Full Text: PDF     DOI: 10.15640/jaes.v5n1a5