LPG Flaming—A Safe Post-Emergence Weed Control Tool for Direct Seeded and Bulb Onion

Alon Horesh,Zvi Peleg,Karam Igbariya,Ran Nisim Lati

doi:10.3390/agronomy9120786

Alon Horesh, Zvi Peleg + Show 2 more

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https://doi.org/10.3390/agronomy9120786

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Abstract

The demand for pesticide-free food has increased the need for sustainable organic farming. Onion (Allium cepa L.) is an important vegetable crop cultivated worldwide. The available weed control tools for intra-row weeds following onion emergence are limited. This study aimed to evaluate the potential use of liquefied petroleum gas (LPG) flaming as a pre- and post-emergence weed control method for both direct-seeded onion seedlings and transplanted onion bulbs. The safety of cross-row, where the flames are targeted to the intra-row area from both sides of the row, and broadcast flaming for bulb onion was compared. Cross-row flaming at twelve days after planting had no effect on onion dry weight, while broadcast flaming-treated plants’ dry weight was reduced by 36% as compared to controls. For the cross-row technique, the tested burners’ angle (45° and 30°) and inter-burner distances (30 and 40 cm) had no impact on weed control efficacy, and similar control levels, between 55% (15 cm) and 45% (10 cm), were observed 15 cm from both sides of the row-center. Direct-seeded onion cultivars were treated at various growth stages. The pre-crop-emergence stage was completely safe for the crop, and the second leaf stage exhibited a wide range of tolerance levels to flaming treatment across the different onion cultivars, with dry weights ranging between 39 and 117% compared to non-treated control in the flaming sensitive and tolerant cultivars, respectively. These results were validated under field conditions using the two most tolerant cultivars (Orlando and Browny); no yield reductions were observed for either cultivar when treated from the third leaf stage. In bulb onion, flaming had no impact on dry weight of shoots or roots when applied from four weeks after planting. This study demonstrates, for the first time, the potential of using flaming as a post-emergence weed control tool for direct-seeded and bulb onion, and at earlier time points than previously shown. Cross-row flaming proved effective for controlling intra-row weeds and can lower weeding costs. Future research should evaluate the safety of sequential applications and test complementary control methods for the initial growth stages.

Highlights

Onion (Allium cepa L.) is an important vegetable crop, grown in most parts of the world via direct seeded, bulb or transplanted cultivation [1,2,3]
Comparison of the cross-row versus broadcast flaming techniques demonstrated that cross-row flaming 12 days after planting (DAP) had no significant impact on crop safety, while broadcast treatment led to a significant (p = 0.001) 36% reduction in shoot dry weight (DW) in treated versus control plants
When treated 19 DAP, none of the main factors nor the interaction between them had a significant impact on the crop safety (p > 0.414), suggesting that the differential impact of the tested flaming techniques on crop safety is relevant at early growth stages only and that developed plants are more tolerant

Summary

Introduction

Onion (Allium cepa L.) is an important vegetable crop, grown in most parts of the world via direct seeded, bulb or transplanted cultivation [1,2,3]. Weeds remain the central challenge hindering widespread adoption of organic agro-systems [11], owing to the limited availability of non-chemical weed control options [2,3]. While cultivation is a common mechanical control practice, the shallow root system of onion can be damaged by the cultivator blades resulting in crop injury and yield loss [1]. Previous studies reported on the potential use of the other mechanical method, vertical brushes, which provided 74% weed control when combined with pre-emergence harrowing or flaming in bulb onion [2]. The limited control level achieved by these methods, coupled with the lack of control options for intra-row weeds (weeds growing within the crop row) emphasize the need to adopt new non-chemical control tactics that will be safe and effective for organic onion, for intra-row weeds

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