Use of long-term soil monitoring database for management of arable land in Japan

In 2008 a database was established of the results of about 20 years of continuous long-term soil monitoring of all prefectural agriculture experiment stations in Japan. This database contains data on rates of applied chemical fertilizer and organic matter (rice straw, animal manure compost, and rice straw compost), crop yields, and soil properties, and has a data retrieval function. Using the database I investigated how fertilizer management affects crop yields and soil properties. Organic matter application increased rice yields and improved soil properties such as total carbon and nitrogen content, CEC, and bulk density, and indicated that restoring rice straw (5 - 6 Mg ha-1) to the field is comparable to applying 10 Mg ha-1 compost for improving soil properties. The relationships between total carbon and nitrogen content, CEC, and bulk density were highly correlated. In contrast, total carbon content and exchangeable bases and available phosphorus were not interrelated. These relationships mean that total carbon content affects chemical and physical soil properties, especially the properties related to fundamental soil fertility in paddy fields.