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Digital archive of theses discussed at the University of Pisa


Thesis etd-03182024-163331

Thesis type
Tesi di dottorato di ricerca
Thesis title
Comparison and evaluation of innovative techniques and equipment for weed management in conservative organic farming systems
Academic discipline
Course of study
tutor Prof. Fontanelli, Marco
  • autonomous mowers
  • biodiversity
  • conservation agriculture
  • mowing
  • non-chemical weed control
  • organic farming
  • reduced tillage
  • residential gardens
  • vegetable crops
  • vineyard under-row area
Graduation session start date
Release date
Up to the present time, agriculture encountered a multitude of challenges, including the impacts of climate change, environmental deterioration, resources depletion and biodiversity loss. Organic farming could be a solution to these challenges by promoting soil health and biodiversity. However organic farmers still rely on conventional intensive tillage to carry out various agricultural operations and most importantly to control weeds. To restrict the related disadvantages, reduced or no-tillage has been proposed in organic agriculture. Nevertheless, conservation tillage in organic farming presents some difficulties one of these is the greater weed pressure. Among the mechanical weed control methods available in various agricultural contexts, mowing and reduced tillage allow the stability of the soil to be preserved. It is necessary to identify equipment and management systems suitable for various contexts, which carry out effective weed control, guarantee good operational performance in terms of time and energy consumption and environmental sustainability. 5 trials were conducted in which the performance of innovative equipment and management systems were evaluated.

1) In the area under tree rows of alley cropping systems, coarse plant material as well as pruning material or stones may be present, so the use of a mower equipped with chains as cutting a tool could be advantageous. A mower designed for under-row weed control in orchards, equipped with an automatic tree-skipping mechanism, was modified by replacing blades with chains with the aim of evaluating its performance in an alley cropping system. A first trial was carried out in an open field to preliminarily compare the chain mower with the version equipped with blades in relation to different settings of working speed (1.6 and 2.4 km·h−1) and rotation speed of the cutting tool (1830 and 2500 rpm). Weed biomass reduction, weed cover reduction, weed height reduction, weed biomass regrowth, and clipping size were assessed. In a second trial, the performance of the mowers with different setting configurations was assessed in an alley cropping system under a more critical environmental condition for mowing, i.e., the presence of dew. Weed biomass reduction, weed cover reduction, weed height reduction, and the mowers’ field capacity with different working speed settings were assessed. No major differences emerged between the mowers, and the chain mower performance was comparable to that of the standard blade mower. The setting with the high working speed and high rotation speed of the cutting tool turns out to be the best compromise, obtaining a weed biomass reduction of 59.6%, a weed cover reduction of 40.9%, and a higher field capacity compared to the setting with the low working speed, with an increase of 47.9%.

2) In the Mediterranean area, vineyard soils are often characterized by a high stone content. In these contexts, where tools commonly adopted for under-row weed control are frequently damaged, the utilization of a chain mower could be a preferable alternative. This research aims to compare a modified mower with chains with other tools commonly employed that control weeds through tillage, such as motorized discs, blade weeder, and rollhacke. Weed control effectiveness, effects on weed flora composition, soil compaction, and operative efficiencies were evaluated. The chain mower allowed us to obtain encouraging results of weed biomass reduction (55.4 and 25.4%, between and around vine trunks, respectively), weed height reduction (35.9%), and weed cover reduction (79.2%), comparable to the other tools. All the tools showed a lower weed control efficacy around vine trunks rather than between them (weed biomass reductions of 24.8% and 52.6%, respectively). Results regarding the effect on weed flora composition seem to confirm this trend. Despite the higher chain mower field time (3.78 h ha−1) and fuel consumption (24.24 kg ha−1) compared to the blade weeder and the rollhacke, its versatility in stony soil and its lower impact on soil (soil penetration resistances of 1602.42 and 2262.83 kPa in 2022 and 2023, respectively) compared to the other tools make it a potentially advantageous implement for under-row weed management in vineyards.

3) Mechanical under-row weed control in the vineyard emerges as a sustainable choice compared to chemical control, with tillage-based approaches proving especially efficient. Rollhacke, finger weeder, and blade weeder are valid alternatives to commonly used implements that cause excessive soil disruption and display suboptimal efficiency. The trial aimed to compare different under-row weed control strategies in terms of weed control efficacy and operational performance. Among these, in ST1 a tool-holder equipped with both rollhacke and finger weeder was used at the first and second intervention; in ST2 rollhacke was used at the first intervention and blade weeder at the second one; in ST3 firstly was used the tool-holder equipped with rollhacke and finger weeder, then the blade weeder; in ST4 rollhacke was used first and then the tool-holder equipped with rollhacke and finger weeder. Weed height, weed cover, and weed biomass were evaluated before the first and after the second intervention. Total field time, fuel consumption and CO2 emissions of each strategy were assessed. ST1 proved to be the best compromise in terms of weed control effectiveness and operational performance compared to the other strategies. Indeed, ST1 achieved tendentially a lower weed height (20.42 cm) and weed biomass around vine trunks (105.33 g d.m. m-2) compared to the other strategies. In terms of total field time, fuel consumption and CO2 emissions, ST1 recorded intermediate values equal to 3.85 h ha-1, 15.29 kg ha-1, and 48.72 kg ha-1, respectively.

4) The development of a fully automated robotic weeder is currently hindered by the lack of a reliable technique for weed-crop detection. Autonomous mowers moving with random trajectories rely on simplified computational resources and have shown potential when applied for agricultural purposes. This study aimed to evaluate the applicability of these autonomous mowers for weed control in globe artichoke. A first trial consisting of the comparison of the performances of three different autonomous mowers (AM1, AM2 and AM3) was carried out evaluating percentage of area mowed and primary energy consumption. The most suitable autonomous mower was tested for its weed control effect and compared with a conventional weed management system. Average weeds height, weed cover percentage, above-ground weed biomass, artichoke yield, primary energy consumption and cost were assessed. All the autonomous mowers achieved a percentage of area mowed around the 80% after 180 min. AM2 was chosen as the best compromise for weed control in the artichoke field (83.83% of area mowed after 180 min of mowing, and a consumption of 430.50 kWh·ha−1·year−1). The autonomous mower weed management achieved a higher weed control effect (weed biomass of 71.76 vs. 143.67 g d.m.·m−2), a lower energy consumption (430.5 vs. 1135.13 kWh·ha−1 ·year−1), and a lower cost (EUR 2601.84 vs. EUR 3661.80 ha−1 ·year−1) compared to the conventional system.

5) Enhancing biodiversity within turfgrass systems is pivotal for amplifying ecosystem services in urban landscapes. Gaining information on the impact of lawn management with autonomous mowers on the lawns floristic composition is crucial to improve the biodiversity of this common green space. In this study, an autonomous mower used with a reduced mowing frequency and a more sporadic ordinary management with a riding rotary mower were compared in terms of effect on three dicotyledonous species (Phyla nodiflora, Lotus corniculatus and Sulla coronaria) transplanted on stands of bermuda and manila grass. Regardless of the management system, P. nodiflora achieved the best results in terms of survival on both turfs (74.92 and 58.57% in manila and bermuda grass, respectively). In bermuda grass a higher percentage of surviving individuals was observed for the ordinary management (42.59%), rather than with autonomous mower (9.10%), while no differences emerged on manila grass. On both manila and bermuda grass, a higher value of average percentage of coverage of the single individual was observed for the ordinary management (1.60 and 0.37%, respectively) compared to the management with the autonomous mower (0.55 and 0.08%, respectively). P. nodiflora achieved a higher percentage of individuals with flowers with the ordinary management rather than with autonomous mower both on manila grass (60.73% and 33.90%, respectively), and on bermuda grass (48.66 and 3.32%, respectively). Nevertheless, despite a lower impact on the planted species was observed with the ordinary management, encouraging results were obtained with autonomous mower such as the percentage of surviving individuals for P. nodiflora (33.95%), and L. corniculatus (22.08%) on bermuda grass and, in particular on manila grass, the percentage of individuals with flowers for the same planted species (33.90 and 13.59%, respectively). Furthermore, in terms of operative performance, the primary energy consumption over the year of the autonomous mower is lower compared to riding rotary mower both on manila grass (with values of 200.04 and 614.97 kWh ha-1 year-1, respectively) and bermuda grass (with values of 177.82 and 510.99 kWh ha-1 year-1, respectively).