       E. Bortolazzo 1 , V. Tabaglio 2 , M. Ligabue 1 1 Forages Department, Research Centre on Animal Production – C.R.P.A S.p.A, Italy, e.bortolazzo@crpa.it 2 Institute of Agronomy and Field Crops, Università Cattolica del Sacro Cuore, Piacenza, Italy, vincenzo.tabaglio@unicatt.it Introduction The objective of this research was to develop an Internet service for farmers and technicians for dynamic fertilisation management. The software estimates real nitrogen requirements for crops based on soil characteristics and daily weather data. The advantage of this service is that it makes it possible to update the advice while the crop is growing in line with pre-set production goals and real weather conditions. Thus, the N-Balance can be calculated in three different ways: as a forecast, work in progress or final balance. The research has been done within the LIFE OptiMa-N Project, conducted by CRPA and funded by the European Commission, the Emilia-Romagna Region, the Provinces of Parma, Reggio Emilia and Modena and three companies working in the area of water purification. Materials and Methods The programme was developed in four stages: 1-Analysis and formalisation of reference mathematical models. 2-Design and construction of databases and stored calculation procedures. 3-Development of the software application and user recognition system with login and password. 4-Estimation service test through a network of 43 4N-trials. Each trial compares 3-N rates (balance rate – 30 kg N ha -1 (N 1 ), balance rate (N 2 ), balance rate + kg N ha -1 (N 3 )) with an unfertilized plot (N0) in order to identify the optimal experimental rate. The network offered a wide variety of situations for an effective service calibration, problem identification and solving. The software was based on the Simplified Nitrogen Balance Sheet adopted by the Emilia- Romagna Region (1). Each term in the calculation algorithm was analysed resulting in improvements in precision and simplicity. (1) Nnex = Na - (Np + Nm + Nr + No-Nl) Where: Nnex= N to be supplied by fertilizers Na = N rate needed to reach a crop production objective Np = N available in soil Nm = mineralised N Nr= N residue from the past crop No = N residue from past organic fertilizers Nl = N leached by rain The main modifications applied to the equation were: i) the introduction of the nitrates content in soils to calculate the mineralised N and ii) a correction of mineralised N based on real temperature changes. Once the equation was definitive, the databases as well as algorithms were constructed and then it was developed the Internet application which produced other advantages useful for a dynamic fertilisation tool such as i) the possibility of acquisition of weather data automatically for the from Meteorological Service (Emilia-Romagna region), ii) the possibility of storage of the chronological data for individual farms and iii) three modes of calculation: as forecast, work in progress or final balance.