Proceedings International Conference of Agricultural Engineering, Zurich, 06-10.07.2014 – www.eurageng.eu 1/5

Ref: C0706

Experiences on physical weed control in nursery container production

Christian Frasconi, Marco Fontanelli, Michele Raffaelli and Andrea Peruzzi, Department of Agriculture Food and Environment, University of Pisa, via del Borghetto 80, 56124, Pisa, Ita-ly.

Luisa Martelloni, Centro di Ricerche Agro-Ambientali “Enrico Avanzi”, University of Pisa, via vecchia di Marina 6, 56122, San Piero a Grado, Pisa, Italy.

Abstract

Weed control represents a major issue not only in agriculture but also in nursery production of ornamental species. This is also a key problem in nursery container production, where weeds can relevantly affect the aesthetical and commercial value of the plants. Usually this problem is overcome using liquid or granular herbicides or special disks (i.e. co-co-fibre disks) which suppress/avoid weed emergence. However, the use of herbicides is often associated with possible environmental drawbacks while the disks may represent a relevant cost for the farmers. Moreover no natural substances with herbicide action are la-belled in Italy for nursery production at the moment. In this respect, a specific trial has been carried out at the University of Pisa since 2012 in order to test different physical weed control methods, which may be a possible alternative to herbicide application and disk use in nursery container production. The treatment where made in Photinia × fraseri, growth in common commercial pots filled by peat-based potting soil artificially infested by Oxalis corniculata L. Two different physical treatments were compared: - flaming performed with a trolley machine connected to a manual lance equipped with a 10 cm wide open flame rod burner; - steaming performed with a professional steam generator (power 2.4 kW and steam outflow 3.12 kg h-1) equipped with a manual lance and an on purpose designed and realized dis-penser. Two different frequencies were tested for both the thermal applications. This trial is still on-going but the preliminary results showed that steaming could represent a real effective and economically sound system of weed control in nursery container produc-tion. However, further studies to closely evaluate steaming performance and long-period ef-fectiveness as well as generator efficiency are needed in order to optimize this technique.

Keywords: non-chemical weed control, ornamental trees, flame weeding, steam weed-ing

1 Introduction

Weed control represents a major issue not only in agriculture but also in nursery production of ornamental species. Researches carried out in ornamental trees showed that a rational weed management around the stem allowed increasing plant development (Boyd and Rob-bin, 2006). Moreover weeds can indirectly affect the development of other pests like fungi

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and arthropods (Kuhns et al., 2007). Weed control is also a key problem in nursery container production, where weeds can relevantly affect the aesthetical and commercial value of the plants. Usually this problem is overcome using herbicides. However, the use of herbicides is often associated with possible environmental drawbacks. Moreover, no natural substances with herbicide action are la-belled in Italy for nursery production at the moment (Frasconi et al., 2013). Different methods and machines can be used in order to reduce weed competition within a “holistic” approach and physical strategies may replace or integrate chemical applications (Peruzzi et al., 2005; 2006). Mechanical methods consist in the utilization of different tools designed and realized in order to cut, uproot, bury or damage weeds. In example mulches, intra-row rotary harrows, intra-row rotary hoes (like finger weeders) are often used for weed control in open field ornamental trees production. These machines can be coupled to a trac-tor or a straddle frame (Frasconi et al., 2013). Thermal methods can also be applied as alter-native to herbicides (Peruzzi et al., 2009). Open flame, steam or hot water are usually the most common thermal methods, which can be applied also in container production of orna-mental crops (Frasconi et al., 2013). Special mulching disks (i.e. co-co-fibre disks), which suppress/avoid weed emergence, can also be used in container production but may repre-sent a relevant cost for farmers for both purchase and disposal (Frasconi et al., 2013). The aim of this research was to test flame and steam weeding as alternative methods for weed control in nursery container production of ornamental trees.

2 Materials and methods

A specific trial was carried out at the University of Pisa since 2012 in order to test different weed control physical methods, which can represent be a possible alternative to herbicide application and disk use in nursery container production. The treatments were made in Pho-tinia × fraseri, growth in common commercial pots (0.25 m of diameter) filled by peat-based potting soil artificially infested by Oxalis corniculata L. (Figure 1). The infestation was made by 4 portions of rhizome per pot. Each portion contained 10 buds.

Figure 1: Photinia × fraseri pots (left) and artificial infestation of Oxalis corniculata (right).

Two different physical treatments were compared: - flaming performed with a trolley machine connected to a manual lance equipped with a 10 cm wide open flame rod burner (Figure 2); - steaming performed with a professional steam generator (power 2.4 kW and steam outflow 3.12 kg h-1) equipped with a manual lance and an on purpose designed and realized dis-penser. The dispenser has a semi cylindrical carter, which allows reducing steam drift (Fig-ure 3). Two different frequencies were tested for both the thermal applications:

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-low/high frequency flaming (6/12 treatments year-1); -low/high frequency steaming (3/6 treatments year-1).

Figure 2: Flaming treatment in Photinia × fraseri pots.

Before each treatment, weed cover percentage was assessed by image analysis using Compu Eye LSA Software (Bakr, 2005). Data were arcsine transformed and analyzed using a one-way ANOVA and a LSD Fischer post-hoc test (at p≤0.05). Pots were arranged in a completely randomized block design. Randomization was 4-fold.

Figure 3: Steam weeding treatment in Photinia × fraseri pots and detail of the carter.

3 Results and Discussion

Both thermal treatments seemed to have damaged neither the ornamental plants of Photinia × fraseri nor the plastic pots. On the other hand treatments seemed to significantly control the aboveground part the weeds. Figure 4 shows the effect of the thermal treatments on Oxalis corniculata. During the experiment pots were colonized also from external weeds, which were included in the visual assessment.

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Figure 4: Effect of flaming (left) and steaming (right) on the artificial infestation of Oxalis corniculata in Photinia × fraseri pots. In Figure 5 the average weed cover values assessed in pots after the first growing season are shown. All treatments significantly controlled weeds with respect to the untreated control. The only significant difference among treatments means was observed between low fre-quency flaming and high frequency steaming, which resulted the least and the most effective option respectively.

Figure 5: Weed canopy at the end of the first growing season (LF/HF=low/high frequency).

4 Conclusions

This experiment is still on-going but the preliminary results showed that steaming could rep-resent a real effective and economically sound system of weed control in nursery container production. However, further studies to closely evaluate steaming performance and long-period effectiveness as well as generator efficiency are needed in order to optimize this technique.

5 Acknowledgements

The authors sincerely thank the Tuscany Region for funding this research within the Regional Project VIS and Mrs. Roberta Del Sarto and Mr. Calogero Plaia for their support.

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6 References

Bakr, E. M. (2005). A new software for measuring leaf area, and area damaged by Tetranychus urticae Koch. Journal of Applied Entomology, 129 (3), 173-175. Boyd, J., & Robbin, J. (2006). Effect of Weed Control on the Growth of Field-grown Shade Trees in Central Arkansas after Four Years. Proceedings of Southern Nursery Association Research Conference, Volume 51, 110-112. Kuhns, L. J., Harpster, T., Selmerr, J., & Guiser, S. (2007). Controlling Weeds in Nursery and Landscape Plantings. The Pennsylvania State University Extension Bulletin, #UJ236, 44. Peruzzi, A., Ginanni, M., Mazzoncini, M., Raffaelli, M., Fontanelli, M., Di Ciolo, S., Verna, P., Casaccia, D., & Recinelli, E. (2005). La gestione fisica delle infestanti su carota biologica e su altre colture tipiche dell’Altopiano del Fucino, Editoriale Pisana, Pisa, Italy. Peruzzi A., Ginanni M., Mazzoncini M., Raffaelli M., Fontanelli M., & Di Ciolo S. 2006. Il Con-trollo fisico delle infestanti su spinacio in coltivazione biologica ed integrata nella Bassa Valle del Serchio, Editoriale Pisana, Pisa, Italy. Peruzzi A., Lulli L., Raffaelli M., Del Sarto R., Frasconi C., Ginanni M., Plaia C., Sorelli F., & Fontanelli M. 2009. La gestione fisica della flora spontanea in area urbana. Felici Editore, Pisa, Italy. Frasconi, C., Benvenuti, S., Fontanelli, M., Martelloni, L., Raffaelli, M., & Peruzzi, A. (2013). Il controllo fisico della flora infestante. Gestione Sostenibile nei Vivai, (Chapter 2).