Design and realization of an innovative automatic machine able to perform site-specific thermal weed control in maize

This PhD thesis contains a detailed introduction on the state of the art of precision agriculture. The introduction is a brief guide to the technologies used in precision agriculture such as global navigation satellite system (GNSS), computer vision, remote and proximal sensors, Geographic Information System (GIS), Variable-Rate Application (VRA) and yield monitoring systems. In the introduction are also described in details the techniques for site-specific weed control and focuses on the most innovative methods for automatic detection and discrimination of crop and weeds, including the existing automatic or autonomous machines for precision chemical or physical weed management. The last chapter of the introduction concerns with a detailed description of the RHEA (Robot Fleets for Highly Effective Agriculture and Forestry Management) Project. The RHEA Project is really innovative as application of precision agriculture because focused on the design, development and testing of a fleet of heterogeneous and autonomous robots working together according to a proper use of innovative technologies. The first chapter of the experimental part of the thesis concerns with the description of the innovative automatic machine designed and realized within the RHEA Project at the University of Pisa in order to perform site-specific thermal weed control in maize. This implement is able to perform mechanical non-selective treatment in the inter-row space and site-specific flaming in the intra-row space of heat-tolerant crops. According to the Description of Work of the RHEA Project the machine was adjusted in order to properly work in maize planted at 0.75 m of inter-row. Preliminary tests in order to verify the management of actuation devices and sensors by the PLC, the coupling with the ground mobile unit and the integration with the perception system for weed and row detection (that make the machine autonomous) were satisfying, although further research activities are needed in order to optimize all the sub-systems and verify their integrated functioning. In the second chapter of the experimental part a research carried out at CiRAA “E. Avanzi” of the University of Pisa aiming to evaluate the field performances of the hoeing flaming system is described. The field trial aimed to test the tolerance of maize (Zea mays L.) to cross flaming and the effectiveness in weed control as influenced by LPG dose and maize growth stage at the time of treatment. The obtained results showed that maize flamed with cross burners proves to have a high heat tolerance even if treated with high LPG doses because, despite of the reduced growth observed during the first month after the treatment, plants successively recovered and produced as much as the untreated ones. Differences in maize yield were observed as a consequence of flaming effectiveness in controlling weeds according to their stage of development and the used LPG dose. As a matter of fact, dicot weeds at seedling stage are more sensitive than well developed plants and high LPG doses resulted in a higher weeding effect. Finally, it is possible to state that the future use in the field of the automatic machine realized within the RHEA Project, besides allowing to perform site-specific flaming, will assure to obtain satisfying levels of weed control and good results in terms of maize yield.