Effect of Synthetic Soil Aggregates as a Soil Ameliorant to Enhance Properties of Problematic Gray ('Jahgaru') Soils in Okinawa, Japan

摘要

Synthetic aggregates (SA) were developed using low productive red soil, paper, and starch waste and then utilized as a soil ameliorant to improve poor physical and chemical properties of a gray soil ("Jahgaru"). The gray soil was amended with SA at 10, 20, 30, 40, and 50% and then used for the cultivation of French marigold (Tagetes patula). The SA addition enhanced bulk density, porosity, water-holding capacity, hydraulic conductivity, pH, organic matter, and carbon (C) content of original gray soil. Plant height, number of flowers per plant, shoot fresh weight, shoot dry weight, root length, root fresh weight, and root dry weight in 30% of SA addition were the greatest and were increased by 1.5, 2.9, 3.5, 4.7, 3.4, 4.3, and 9 times, respectively, compared to gray soil. It can be concluded that developed SA can be utilized as a soil ameliorant to improve poor physical and chemical properties of gray soil.