The present work aimed the development of a low cost servo-valve that answers to an electronic control signal, for variable rates liquid inputs application. A literature research to define which valve type should be used was made. A mechanically activated proportional valve with an electronically controlled servo-engine was designed and evaluated. Since developed the servo-valve, the system was submited to a number of tests .The evaluation of its behavior was obtained in terms of repeatability, hystheresis and linearity. The test was accomplished in a bench, specially developed for this aim. As a result, were obtained three curves of opening percentage as function of flow rate, describing three opening and closing increments in two different work pressures. The servo-valve presented a good repeatability, reasonable hysteresis and a typically quadratic curve. This one maintained the low cost target. These results were very satisfied because the non-linearity and the hysteresis could be easily corrected by software.261142150Boareto, A.E., Cruz, A.P., Luz, P.H.C., (1991) Adubo Líquido: Produção e Uso No Brasil, 100p. , São Paulo: Fundação CargillFixen, P.E., Fluid fertilizers in an evolving agriculture (1994) Anais..., pp. 1-30. , SIMPÓSIO BRASILEIRO SOBRE FERTILIZANTES FLUÍDOS, 1993, Piracicaba. Piracicaba: PotafosJohann, A.L., Cappelli, N.L., Seleção e modelagem matemática de uma válvula dosadora a ser empregada na aplicação de fertilizantes líquidos a taxas variáveis (2003) Anais..., , WOKSHOP DE PÓSGRADUAÇÃO: O WORKSHOP DAS ÁREAS DE CONCENTRAÇÃO, 4., 2003, Campinas. Campinas: Faculdade de Engenharia Agrícola da UNICAMP, 1 CD-ROMMacintyre, A.J., (1997) Bombas e Instalações de Bombeamento. 2.Ed., 635p. , Rio de Janeiro: Livros Técnicos e CientíficosNeto, B.B., Scarminio, I.S., Bruns, R.E., (2002) Como Fazer Experimentos: Pesquisa e Desenvolvimento Na Indústria. 2.Ed., 250p. , Campinas: Editora da UNICAMP(1964) Valves for the Control of Fluids, 344p. , Manchester: C. Nicholls & CompanyUmezu, C.K., (2003) Sistema de Controle de Um Equipamento de Formulação, Dosagem e Aplicação de Fertilizantes Sólidos a Taxas Variáveis, pp. 171f. , Tese (Doutorado em Máquinas Agrícolas) - Faculdade de Engenharia Agrícola, Universidade Estadual de Campinas, Campinas, 2003