Effects of long-term application of organic matter and soil improvement fertilizer on paddy rice, 1: Changes of growth and yield of rice, nutrients uptake by rice, and chemical properties of soils

Effects of long-term application of organic matter (harvested rice straw or rice straw compost) and/or soil improvement fertilizer (calcium silicate and/or fused magnesium phosphate, etc.) on the crop yield and nutrients uptake of rice (Oryza sativa, var. Nipponbare) and the chemical properties of soil were examined. The experiments were carried out from 1975 to 1997 in three different paddy fields: Azuchi Gley soils of the Central Station, Adogawa Brown Lowland soils of Western Branch Station, and Kinomoto Gley soils of Northern Branch Station. The average potential for brown rice production in plots without application of organic matter (OM) and soil improvement fertilizer (SIF) and nitrogen fertilizer in the cropping season was 3.8 in Azuchi, 3.0 in Adogawa, and 3.3 Mg/ha/y in Kinomoto field, respectively. Continuous incorporation of OM and/or SIF in autumn increased brown rice yield on an average by 5-7% in Azuchi after 1981, 5-14% in Adogawa after 1983, and 5-15% in Kinomoto after 1992, respectively, as compared to plots without OM and SIF application. In Kinomoto located in a snowy area, spring incorporation of OM two months before cultivation decreased that effect below 4% until 1991. The contents of soil organic carbon and nitrogen in the plots without OM application declined gradually during the experiment years, whereas continuous application of harvested rice straw (7-8 Mg/ha/y) or rice straw compost at the rate of 10 Mg/ha/y enabled maintenance of original levels. Continuous application of SIF containing phosphate and silicate increased their available contents in soils to suitable levels or above. The brown rice yield was closely related to the uptake amounts of nitrogen, potassium and silica, respectively, the average rates of uptake derived from annually applied OM and/or SIF during 1988-1997 was estimated to the range of 16-29% for nitrogen, 0-8% for phosphorus, 8-28% for potassium, and 18-39% for silica, respectively