The brazilian agriculture has expanded and improved its techniques in the last decades as well as the mechanization of sugarcane cultivation. Overall, the mechanization cost of this cultivation is the highest of the total cost of production in relation to other crops. That cost consists of several elements such as the cost of the harvester. This study aimed to develop a mathematical model that represents the operational cost of the harvester in relation to its operating life and agricultural productivity, parameters that are associated with its operational capacity. Simulations of this cost were conducted, raging the operating life of harvesters between 0 and 17,900 h, and the agricultural productivity of the cultivation from 50 to 130 Mg ha-1. The results indicated an operating cost between R$ 7.23 (BRL) and R$ 26.43 Mg-1. It was verified that the operational cost is inversely proportional and nonlinear to productivity, and also directly proportional and nonlinear in relation to the age of the harvester.

Resumo O controle da aplicaç ão de fertilizantes visando à otimizaç ão da operação é uma parte essencial da agricultura de precisão e traz consigo a economia de insumos, aumento da produção e preservação do solo. Os dosadores atuais possuem uma característica oscilatória na taxa de aplicação, comprometendo assim a uniformidade de distribuição do fertilizant e. Este trabalho teve por objetivo a validação de um sistema de controle c íclico para o acionamento de um dosador helicoidal de fertilizantes.

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