Comparing Sensor-Based Adjustment of Weed Harrowing Intensity with Conventional Harrowing under Heterogeneous Field Conditions

Michael Spaeth,Roland Gerhards,Matthias Schumacher

doi:10.3390/agronomy11081605

Abstract

Setting the right intensity is crucial for the success of post-emergence weed harrowing in cereals. The percentage of crop soil cover (CSC) correlates with the selectivity of weed harrowing. Therefore, real-time camera-based measurements of CSC offer a novel approach to automatically adjust the intensity of harrowing. The intensity of harrowing is varied by hydraulic steering of the tine angle. Five field experiments in cereals were conducted at three locations in southwestern Germany in 2019 and 2020 to measure the effect of camera-based harrowing (2020) and conventional harrowing on weed control efficacy (WCE), crop density, and grain yield. For this purpose, pair-wise comparisons of three fixed harrowing intensities (10°, 40°, and 70° tine angle) and three predefined CSC thresholds (CSC of 10%, 20%, and 60%) were realized in randomized complete block designs. Camera-based intensity adjustment resulted in more homogeneous CSC across the whole plot (6–16% less standard deviation variation) compared to conventional fixed settings of the tine angle. Crop density, WCE, crop biomass, and grain yield were significantly higher for camera-based harrowing than for conventional harrowing. WCE and yields of all automatic adjusted harrowing treatments were equal to the herbicide control plots. Camera-based harrowing provides a robust technology for effective weed management with a lower risk of crop damage than conventional harrowing.

Highlights

The current problems with herbicide resistant weeds [1], the adverse effects of herbicides on the environment, their residues in the food chain [2], and the decline of agrobiodiversity [3] can be associated with the frequent use of herbicides
This study presents a pair-wise comparison of conventional harrowing with camerabased harrowing using a decision-support-system based on crop soil cover (CSC) [9]
Rueda-Ayala et al, Krustjens et al, and Rueda-Ayala et al [10,17,18,20] reported that incorrect intensities in mechanical weeding increased crop and yield losses. This explains the higher yield and lower crop losses of camera-based harrowing compared to conventional harrowing

Summary

Introduction

The current problems with herbicide resistant weeds [1], the adverse effects of herbicides on the environment, their residues in the food chain [2], and the decline of agrobiodiversity [3] can be associated with the frequent use of herbicides. Maximum WCE reached 62% if pre- and post-emergence harrowing were combined [5]. The working mechanism of harrowing implies a whole field cultivation within and between crop rows, and it needs to be balanced between maximum weed control and minimal crop damage. A high selectivity in cereals is only achieved if CSC remains constantly in the range around 20%, which the crop can compensate for by higher growth rates after harrowing [8,9]. Conventional harrowing with a fixed intensity may cause crop damage at locations with light soils and less crop coverage and low WCE in areas with high crop coverage and heavy soils. Harrow intensity needs to be adjusted continuously to achieve high selectivity over the entire field

Objectives

Methods

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Conclusion