Localized spraying in oilseeds rape crop with a conventional boom sprayer

As a part of ECOPHYTO plan established by the French government to reduce the use of chemical plant protection products (PPP), specific spraying equipment are needed, for example to spray only the row of the crop. Often these devices have small spray boom widths and they are very expensive. The objectives of the project “PLEVOP” (development of in-row sprayer in oleaginous crops and protein crops), proposed by the technical Institute Terres-Inovia, are to define the conditions for successful localized post-emergence spraying for the herbicide application on the row using large width devices. This work is carried out in connection with a manufacturer of agricultural equipment (the Marechal company), an agricultural cooperative (CAL) and a French public Institution of Higher Education (AgroSup Dijon). The first year, experiences were conducted on oilseed rape crops using GPS-RTK as guidance system embedded on the tractor; the second year, trials were realized on oilseed rape and sunflower using a camera interface placed on the boom as guidance system. Three weeding strategies practices are compared: "full herbicide treatment" vs. "herbicide treatment on the row + inter-row hoeing" and a "no treatment". After weed counting and identification, we evaluated the biological efficiency on weeds and the effectiveness of such operations. Moreover, working with a conventional sprayer for a localized spraying, we have developed an automatic calculator tool to help farmer to determine the required amount of herbicide and water depending on its use conditions (nozzle type, nozzle height, speed of passage, boom height, field size, etc...). Oilseed rape: First trial of localized herbicide treatment with a conventional boom sprayer Experiences were conducted in the Lorraine region in France in 2017-2018 on oilseed rape crop. Plants were treated post-emergence with an herbicide at the stage four leaves. The sprayer was equipped with GPS-RTK as guidance system and the boom width was 16m (Figure 1). The sprayer characteristics were: nozzle=110°, boom height=16cm, spray band=45cm for the full herbicide treatment and nozzle=40°, boom height=27,5cm and spray band=20cm for the localized treatment. The results of this first year of experimentation show that localized treatment and full treatment have much lower infestations than the untreated reference. On the crop row, the infestations of the "localized treatment" and "full treatment" modalities are similar, which shows that on the crop row the localized treatment is as effective as a full treatment. On the inter-row, the modality " herbicide treatment on the row then hoeing" is slightly more infested in weeds than the inter-row of the modality "full treatment", which shows that the hoeing is slightly less satisfying than the full treatment. Nevertheless, when we compare the inter-row of the modality " localized treatment on the crop row and then hoeing in the inter-row" with the inter-row of the untreated reference, we notice a hoeing efficiency that is not negligible. In the modality "full treatment", we observe that the crop row is slightly dirtier than the interrow one can possibly interpret that by an umbrella effect of the rapeseed crop during the 195 treatment. In the untreated reference, we observe that the crop row is less dirty than the interrow; this is probably due to a competitive effect of rapeseed on weeds on the row. Thus, the results of modality "localized treatment on the row then hoeing" on oilseed rape crop are encouraging. The localized treatment area with no hoeing also shows that the treatment on the crop row is not enough to have a good efficiency overall surface and that hoeing is important. That is the complementarity of chemical weeding and mechanical weeding which makes it possible to obtain the 80% efficiency observed. Figure 1: Specific spraying equipment and spraying formula used for the PLEVOP project A Decision Support Tool for localized spraying A single conventional sprayer with a large spray boom (16 m) was used for both "full treatment" and "spot treatment" strategies. In both cases, complex calculations were made to determine exactly the amounts of herbicide and water. So we had to create a decision support tool (DST) to help farmers depending on their own spraying parameters but also to provide information about the environmental benefits of a localized spraying (Treatment Frequency Index (TFI) reduction for example). As an example, considering the spray parameters described previously for both treatment (full and localized) and according a tractor speed of 10km/h, a nozzle output of 0.65l/min and using an herbicide product (2litre/ha) the results of calculation are deduced from the decision support tool. They indicate that: for the "full treatment", 86.7litre of water and 2litre of herbicide are required for a field of one hectare whereas as for the treatment on the row strategy, with a spray band of 20cm, only 0.89litre of herbicide and 86.7litre of water are required for a field of one hectare. Conclusions and Future Outlook We have tested in rapeseed crop, the use of a single conventional sprayer with a spray boom of 16m for a full and localized herbicide treatment thanks to a GPS-RKT type guidance system. The "full treatment" and "localized treatment" modalities were compared to the reference "no treatment". Results were encouraging, demonstrating that "localized treatment on the crop row then hoeing" is as efficient as "full treatment" modality. During experiences, the spraying settings had to be changed for the automatic calculations of herbicide and water quantities. The guidance system with a camera interface has to be evaluated as well. Overall, we developed a decision support tool (DST) in order to assist farmers in the volume calculations of whatever their spraying settings. Thus, environmental benefits have been added to sensitize the farmer to the positive effects of herbicide reduction. We would also like to finalize the decision support tool with an economic cost estimation. Finally, we would like to test our system on other crops (protein crops for example) and using other phytopharmaceutical products.

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