1 Paper presented on International Conference of “Balanced Nutrient Management For Tropical Agriculture”, 12-16 th April 2010, Swiss Garden Resort&Spa KUANTAN, PAHANG, MALAYSIA FERTILIZER MANAGEMENT FOR IMPROVING LOWLAND SAWAH PRODUCTIVITY IN INDONESIA: INTEGRATED PLANT NUTRIENT MANAGEMENT SYSTEM 1 Sri Rochayati and Husnain Indonesian Soil Research Institute, Agency for Agricultural Research and Development Ministry of Agriculture-Indonesia Jl. Juanda No. 98 Bogor, Indonesia Telp/Fax: +62 251 8321608 Email : sri.rochayati@gmail.com ; husnainuut@yahoo.com ABSTRACT Declining rice yields are strongly related to soil quality degradation particularly nutrient depletion. Nutrient depletion can be attributed to insufficient fertilizer use and imbalanced fertilization. As in many developing countries, Indonesian’s use of fertilizer in sawah soil is not well balance at present and therefore causes several problems such as low rice productivity, environmental pollutions and land degradation. Continuously rice cropping system without returning sufficient amount of nutrient uptake by rice plant could exhausted soil nutrient. On the other hand, excessive amount of fertilizer applied such as urea caused N pollution of soil, water and environment. Nitrogen fertilizer use in Indonesia has seen continued increases since the late 1960s and it reached 2.3 million Mg year -1 (in 2004), however P and K consumption have not followed the same trends as N consumption. As the result, rice productivity has fluctuated and stagnated over the past decade. Recently, improving rice productivity through integrated plant nutrient management system (IPNMS) program was recommended. The IPNMS is mainly based on balanced fertilization combines with organic matter application in to the sawah soil. Balance fertilization contributes to fertilizer use efficiency by keep a balance between nutrient requirement and uptake by rice plant. At the same time, it seeks to maintain a balance between nutrient supply for plant and natural nutrient pools and soil conditions. Site specific fertilizer recommendation based on soil testing was resulted in increasing rice yield and fertilizer use efficiency in sawah soils in Java Island. However, sustainable rice production is not only depending on the balance input and output of nutrient, but also soil organic matter (SOM) status. Principally, organic fertilizer supports soil fertility maintenance and creates a better soil environment for intensive farming by improving chemical fertilizer effectiveness and supplying micro nutrient. At present in Indonesia, farmers are rarely applied organic matter such as rice straw or manure into sawah soil which caused depletion of SOM. Therefore, IPNM practices could substantially support fertilizer management program to improving lowland sawah soil productivity in Indonesia. Key words: lowland sawah, balanced fertilization, IPNMS, fertilizer use efficiency 1. Introduction Concerns are growing about the long term sustainability of agriculture. Both the over- and underapplication of fertilizer and the poor management of resources have damaged the environment. In