Development of machines for flaming weed control on hard surfaces

Weed control is a major issue not only in agriculture but also on hard surfaces in urban and suburban contexts. Weeds can cause serious damage to urban structures and are often considered as a sign of neglect. Moreover, citizens are becoming increasingly aware of environmental pollution and its potential risks for their health. Flaming represents a concrete alternative to herbicide applications on hard urban surfaces. Flaming can also be a good alternative to mechanical means (e.g., string trimmers) which can seriously damage surfaces because they are too intense and in any case are often not effective. The aim of this work is to describe LPG fed flaming machines designed and built at the University of Pisa, Italy. Liquefied Petroleum Gas (LPG) is a flammable mixture of hydrocarbon gases– propane and butane. Four different machines were developed and tested in four different urban and sub-urban contexts. A small backpack flamer equipped with a manual lance was tested on a stonewall, a trolley machine with a manual lance was used to clean the base of ornamental trees, a self-propelled machine was tested in a railway station, and a mounted machine was used in a suburban cycle way. Flaming was compared to the ordinary weed control systems such as using herbicides or mowing. The results showed that flaming can be both less expensive and more effective (on average less that 1 € m-2 year-1 maintaining weed cover below 5% to 6%) than the ordinary treatments in urban areas. Flaming was more effective than mowing in the suburban area but much more expensive, thus an integrated approach would be advisable in this context. Future research should be devoted to improving the efficiency of the treatment, using for example, new burners with secondary air and precision agriculture technologies

Mechanical weed control on small-size dry bean and its response to cross-flaming

Dry bean (Phaseolus vulgaris L.) can be a profitable crop for farmers; however controlling weeds effectively without a decrease in yield remains a problem. An example where mechanical weed control is difficult to conduct is dry bean ‘Toscanello’, which is a small sized high-income niche product growing low to the ground. Concerning intra-row weed control, also flame weeding could be an opportunity but the dry bean heat tolerance needs to be studied. The aims of this research were to study the weed control efficacy of a spring-tine harrow and an inter-row cultivator in this bean variety, and to test the tolerance of dry bean cultivated under weed-free conditions to cross-flaming applied with different liquefied petroleum gas (LPG) doses. Flame weeding was applied at BBCH 13 and BBCH 14 bean growth stages by pairs of burners producing direct double flame acting into the intra-row space, with bean plants placed in the middle. The results suggest that the spring-tine harrow used two times at BBCH 13 and 14, respectively, lead to a yield similar to that of the weedy control. The inter-row cultivator could be an opportunity for small-sized dry bean crops producers, enabling them to obtain a similar yield compared to the hand-weeded control. Concerning the bean tolerance to cross-flaming the results showed that bean flamed at BBCH 13 stage had little tolerance to cross-flaming. Bean flamed at BBCH 14 stage was tolerant until an LPG dose of 39 kg/ha, giving yield responses similar to those observed in the non-flamed control

Cross-flaming application for intra-row weed control in maize

Flame weeding is the most common thermal intra-row weed control method used in agriculture as an alternative to herbicides in heat-tolerant crops. Within the seventh framework program project “Robot fleets for Highly Effective Agriculture and Forestry Management” (RHEA), the University of Pisa was responsible for the development of an automatic machine for intra-row cross-flaming in maize (Zea mays L.). This study focused on the selection of a range of liquid petroleum gas (LPG) doses able to control weeds without affecting crop yields, for the basic calibration of the machine. Tests were conducted in 2012 and 2013 during the growing cycle of maize both in weed-free and real-field weedy conditions. Five biological LPG doses (0, 52, 65, 104, and 130 kg ha-1) were applied at different maize growth stages once (2- and 5-leaf) and twice (2-leaf the first time and 16 days after the first time). The response of maize and weeds to cross-flaming was evaluated in terms of grain yield, weed density after flame weeding, and weed dry biomass at harvest. Log-logistic models were used to describe the responses of different growth stages of maize and weeds to single and repeated applications of LPG doses. Overall response of maize yield to flame weeding was influenced by LPG dose, number of flame weedings, maize growth stage, and presence of weeds. The results of this study indicate that two cross-flaming treatments applied separately with an LPG dose ranging from 36 to 42 kg ha-1 can provide an acceptable level of weed control in maize, enough to ensure economically acceptable yields

Physical weed control in urban hard surfaces and turfgrasses.

Weed management is a major issue not only in agriculture but also in cities and in public and sport turfs. Weed development often generates negative aesthetic effects, a sense sloppiness, mechanical damages to hard surfaces, the reduction of visibility for drivers, the reduction of the quality of the quality of the turf, and can make difficult for pedestrians to walk. Specific trials were carried out in order to develop and set up machines and techniques for weed control in urban and sub-urban areas and on turfs

Application of precision flaming to maize and garlic in the RHEA Project.

Flame weeding is actually a well known and used physical treatment according to the increase in concerns about the effects of herbicides on human health and the environment and in the light of the new European laws. Flaming historically, was used at first as a pre-emergence treatment, both prior to planting and before crop emergence. Alternatively, flaming can be used also selectively after crop emergence or planting in tolerant species. Although inter-row weeds can be effectively controlled through mechanical cultivation, weeds that grow in the row are more difficult to control as, in some cases, cultivation is both ineffective and causes unacceptable levels of crop damage. This work aims to describe the specific machine for mechanical-thermal weed control which is being realized by the University of Pisa within the RHEA project. This machine is able to perform mechanical and thermal treatments at the same time in order to remove weeds mechanically from the inter-row space and perform in-row selective and precision flaming. The project is still on-going and the machine has not been fully realized and tested yet, thus no data is available at the moment

LPG burners for weed control

This article reports on the results of a study carried out on three prototypes of open flame burners for thermal weed control. Their performance is reported in terms of flame temperature and length, in order to ascertain the best ratio between primary and secondary air, and liquefied petroleum gas (LPG) consumption. To find the best ratio between primary and secondary air, the length and temperature of the flame were recorded for each of the three burners, examined by varying the inlet sections of the primary air and secondary air. The data on temperature and the flame length of each burner were processed using multiple regression analysis. The LPG consumption was determined with one of the burners using 10 different pressures in combination with three nozzles. The data obtained were subjected to non-linear regression using two gaseous outflow models. The various combinations of primary and secondary air inlet sections affected the values of the flame length and temperature. In general, the best combinations of primary and secondary air inlet for flame temperature did not correspond to those for flame length. However, this experiment showed that the inlet of secondary air is critical for the performance of this type of burner, in terms of flame temperature. The fuel consumption trial showed that the model proposed for the gaseous outflow is suitable for describing the values of LPG consumption collected during the trial. © 2015 American Society of Agricultural and Biological Engineers

Thermal weed control in Photinia x Fraseri “Red Robin” container nurseries

A near-zero tolerance policy on weeds by markets for nursery crops calls for weed-free container-grown plants, and forces growers to frequently remove weeds. Thermal weed control could represent a novel method to control weeds in shrubs from container nurseries, thus avoiding the use of herbicides and mulches. The aims of this study were to develop custom-built machinery for thermal weed control in container nurseries and to test the weed control efficiency of flame weeding and steaming in Photinia x fraseri "Red Robin" containers. A liquefied petroleum gas (LPG) fed flamer and a steamer with a dedicated diffuser were built. Four treatments were applied for a total period of 24 months: steaming once every four months, steaming once every two months, flame weeding once every two months or once a month. Temperature values measured at different depths in the substrate after thermal applications were recorded and analyzed. Photinia x fraseri features (height, diameter, and dry biomass) and aesthetic parameters as affected by thermal treatments were also evaluated. The trend in temperature values of the substrate over time followed a two-phase exponential decay. All the thermal treatments lead to a continuous near-100% weed control level, which is the level required by growers for aesthetic reasons. No damages caused by heat on Photinia x fraseri were observed. Container nursery producers could thus adopt thermal methods as a substitute for chemical solutions for weed control management

Design of an automatic machine for variable rate application of flame weeding on maize.

An automatic operative machine for variable rate application (VRA) of flame weeding on maize was designed and built at the University of Pisa within the European Project “Robot fleets for Highly Effective Agriculture and forestry management” (RHEA). The machine was designed to conduct non-selective mechanical weed control between the crop rows and site-specific VRA of flaming in the intra row space. Flame weeding is applied by a pair of burners liquefied petroleum gas (LPG) fed, which work cross to the row, and is activated automatically only in presence of weeds. The machine was coupled with an autonomous tractor equipped with an optical sensor for real-time row crop and weed detection. Specific hardware and software provide information about the weed cover percentage detected and send these data to the operative machine. The LPG dose that has to be applied is chosen in real-time between two doses identified in the calibration phase to be effective on weed cover percentages lower or higher than 25%. In the case of 0% weed cover, burners are switched off. The burners ignition system was designed to be almost instantaneous in order to minimize all delays, which elapse between weed detection and the presence of the flame in the area that have to be treated. The almost instantaneous burners ignition system allows also to avoid the use of a pilot flame, which would be switched on for all the effective working time of the machine. The operative machine is equipped with and automatic steering system, which according to directional movement of two metallic wheels, allows maintaining the same trajectory of the autonomous tractor, and avoiding the accidental damage of the crop. A study aimed to find the optimal LPG doses for an effective weed control and which not lead to yield losses, as a consequence of damages occurred to maize plants treated at different development stages, was conducted in 2012 and 2013 at the experimental farm of the University of Pisa. Maize and weeds response to the application of five LPG doses was evaluated in terms of yield, weed density after the application and weed dry biomass at harvest. The optimal LPG doses estimated were useful for the automatic operative machine calibration. The site-specific VRA of flaming and the use of an almost instantaneous burners ignition system allow to reduce the LPG consumption compared to a continuous application and the presence of the pilot flame during turning, leading to a reduction of costs for the thermal weed management of heat-tolerant crops. The operative machine represent a new technology for precision agriculture, which if integrated with a proper perception system, independent from the autonomous tractor for the receiving of information needed for the automatic regulation of the LPG dose, could work coupled with a common tractor

Transplanting for conversion to warm season turfgrass.

Warm season turfgrass species (like bermudagrass) seem to be very suitable to Mediterranean climate conditions. They also give an excellent wear resistance to the sport pitches. Transplanting of pre-cultivated warm season turgrass plants (similar to horticultural nursery) is a promising technique which can be efficiently used for turf conversion. It is based on the quick ground cover capacity of these species by means of stolons and rhizomes. Transplanting can be performed both in tilled and untilled soil. A working yard for the conversion of a professional football pitch was assessed in order to evaluate the performaces. The transplant was performed with a 4-row mechanical transplanter which had been adjusted to work in the untilled mowed football pitch. The mechanical transplanter accommodates 4 back-seated operators and 4 walking operators who can manually transplant the plants in case of failure. The working speed of the tractor was less than 1 km h-1, theoretical working time was about 15 h ha-1, actual working time was 28 h ha-1, thus the work efficiency was about 0.52. Fuel consumption was about 28 kg ha-1. Such a low efficiency was due to the difficulty of the operators to remove the plants from the trays and supply the transplanter’s delivery system. In this concern, an automatic transplanter was modified in order to work in untilled soil within a second specific trial. This machine had an automatic system for removing the plants from the trays, like the most advanced robotic transplanters for vegetable crops. Moreover, a specific system for plant deposition in untilled soil was developed by mounting a double disc in front of the furrowers. Plant deposition was tested and a maximum variation of 6 cm in the row was assessed with respect to the expected value. This gap is completely in accordance with this kind of crop