Abstract
The site specific application of fertilizers to maintain crop growth is an essential part of precision agriculture and is required to minimise the cost of production whilst preserving the environment. The objective of this study was to develop a fertiliser rate control system, using a real-time fertiliser discharge sensor to enable variable-rate application with a significant reduced error compared to current systems. Experiments were carried out to modify the mechanical fertiliser rate adjustment system of pneumatic seeder for the automatic control of the fertiliser output rate. The results of this study indicated that: (a) the automatic setting of the target fertiliser rate and periodic checks and control of output rate could be performed efficiently, (b) the system could be significantly used for variable-rate applications with overall system errors in the range of +/- 5%, (c) the control system response time to step change adjustments is within the range of 0.95-1.90 s, and (d) selecting check distance intervals of more than 3 m will enable the developed system to perform the check and control processes precisely. Further experiments under field conditions are essential in order to confirm these results and perform any modifications needed to optimise system performance. (C) 2008 IAgrE. Published by Elsevier Ltd. All rights reserved.