Development of a variable rate lime application system.

Author(s)

Domingos Guilherme Pellegrino Cerri

• Document type: Master's Dissertation
• Press: Piracicaba. , gráficos, ilustrações, tabelas.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 2002-02-06

Examining board members

Luiz Antonio Balastreire; Ulisses Rocha Antuniassi; Walter Francisco Molina Junior

• Advisor: Luiz Antonio Balastreire
• Field of knowledge: Agronomical Sciences - Agricultural Engineering
• Indexed in: Banco de Dados Bibliográficos da USP-DEDALUS; Biblioteca Digital de Teses e Dissertações - USP
• Location: Universidade de São Paulo. Biblioteca Central da Escola Superior de Agricultura Luiz de Queiroz; ESALQ-BC/t631.8; C417d; 78867

Abstract

Most of the conventional lime spreaders available in the Brazilian market distribute lime at fixed rates without considering the spatial variability feature of the field. The purpose of this study was to design and build a variable rate lime application system. The developed system calculates the geographic coordinates of the lime spreader position obtained by a Differential Global Positioning System (DGPS). These coordinates, information on the machine speed and a prescription map of the quantity of lime needed for each area within the field are transferred to a computer. The program in the computer automatically adjusts the position of the machine metering device using a step motor driven by electric impulses generated by an electronic interface. The metering device position was checked through potentiometric sensors. The C++ programming language was used to write the control program for the system, which was tested to evaluate its accuracy. The tests demonstrated a shorter response time when changing from larger to smaller application rates than when changing from smaller to larger rates. In the test to verify the amount of lime effectively applied on the soil, the observed error between the desired amount and the real amount applied did not exceed 3%. The results of the tests indicate that the system operates according to the established goals. (AU)