Development and Testing of a Decision Making Based Method to Adjust Automatically the Harrowing Intensity

Abstract

Harrowing is often used to reduce weed competition, generally using a constant intensity across a whole field. The efficacy of weed harrowing in wheat and barley can be optimized, if site-specific conditions of soil, weed infestation and crop growth stage are taken into account. This study aimed to develop and test an algorithm to automatically adjust the harrowing intensity by varying the tine angle and number of passes. The field variability of crop leaf cover, weed density and soil density was acquired with geo-referenced sensors to investigate the harrowing selectivity and crop recovery. Crop leaf cover and weed density were assessed using bispectral cameras through differential images analysis. The draught force of the soil opposite to the direction of travel was measured with electronic load cell sensor connected to a rigid tine mounted in front of the harrow. Optimal harrowing intensity levels were derived in previously implemented experiments, based on the weed control efficacy and yield gain. The assessments of crop leaf cover, weed density and soil density were combined via rules with the aforementioned optimal intensities, in a linguistic fuzzy inference system (LFIS). The system was evaluated in two field experiments that compared constant intensities with variable intensities inferred by the system. A higher weed density reduction could be achieved when the harrowing intensity was not kept constant along the cultivated plot. Varying the intensity tended to reduce the crop leaf cover, though slightly improving crop yield. A real-time intensity adjustment with this system is achievable, if the cameras are attached in the front and at the rear or sides of the harrow.

A Non-Chemical System for Online Weed Control

“…This system uses a combination of approaches for characterizing the harrowing intensity: the sensor-based mechanical weed control [ 14 , 18 ] and the measuring-controlling-regulating [ 13 ]. Both systems presented some limitations such as the use of complex and expensive sensors for plant identification (e.g., photooptic sensors, differential camera), difficult to calibrate sensors for soil density, and the “laboratory processing” required to generate the application maps, which also indicated the off-line operability.…”

“…Variations in crop development, weed abundance, and a hard or a loose soil surface affect the harrowing performance, resulting in crop damage and variations in weed control [ 6 , 12 ]. Research during the last decade has shown that it is possible to assess variations in soil density, weed density, and crop development and automatically adjust the intensity using different approaches and prototype systems [ 12 – 14 ].…”

“…However, the author concluded that working depth was not the best way to characterize the harrowing intensity, in terms of weed control. Engelke [ 13 ] and Rueda-Ayala et al [ 14 ] based their systems on other factors besides soil density, i.e. , weed density and crop growth stage.…”

“…, weed density and crop growth stage. Nevertheless, their prototypes worked mostly off-line using application maps, which were created with data from complex and high-cost sensors such as the photooptic sensors [ 13 ] and bispectral cameras [ 14 ]. Ultrasonic sensors are robust, low cost devices which have been used in weed science research.…”

Mechanical weed control in organic winter wheat

“…In this context, the recent development of site-specific mechanical weed management strategies offer the opportunity to increase the efficacy against weeds and to improve the selectivity to the crops (Melander et al, 2015;Pannacci et al, 2017). In particular, the recent automated harrowing systems designed to vary in real-time the harrowing intensity, on the basis of crop and weeds detection by sensors, have showed to increase the harrowing efficacy and balance the trade-off between crop damage and weed control (Rueda-Ayala et al, 2013). Indeed, harrowing intensity refers to the cultivation aggressiveness of the tines penetrating into the soil surface that can be varied by varying the tine angle relative to a perpendicular axis to the field surface, varying the depth of the implement, varying driving speed or through various consecutive passes on the same day of cultivation (Cirujeda et al, 2003;Rasmussen et al, 2007).…”