Abstract
Natural forest soils promote sustainable production of the plant community by recycling ecosystem nutrients. To understand the nutritional characteristics of forest soils as a reference for conservation agriculture, which aims at reducing the use of fertilizer and enhancing biodiversity, we studied moderately moist Brown Forest Soils and Black soils on the footslopes of forested hills. We applied the criteria for desirable soil properties for crop and orchard lands as promoted by the Ministry of Agriculture, Forestry and Fisheries of Japan. Contents of organic matter and available nitrogen in the forest soils were 2 to 3 times those in agricultural soils. However, the pH in the forest soils was low, at about 5, and the concentration of exchangeable cations was also low, at around 10 cmolc kg-1. To understand how the nutrient characteristics of the forest soils form, we compared aspects of agricultural management, for example, the application of compost and lime, with the amount of litterfall and nutrients in the O layer. The productivity of the forest soil seems to be maintained by a lack of disturbance, which favors the predominance of the fungal community in the acidic soil in the absence of fertilizer use, the formation of soil aggregates by soil macrofauna, and the accumulation of nutrients in tree organs. To enable sustainable soil management on agricultural land with reduced fertilizer use, we will need to replicate the overall biological functions seen in the forest soils.
