Weed management is a crucial issue in agriculture, resulting in environmental in-field and off-field impacts. Within Agriculture 4.0, adoption of UASs combined with spatially explicit approaches may drastically reduce doses of herbicides, increasing sustainability in weed management. However, Agriculture 4.0 technologies are barely adopted in small-medium size farms. Recently, small and low-cost UASs, together with open-source software packages, may represent a low-cost spatially explicit system to map weed distribution in crop fields. The general aim is to map weed distribution by a low-cost UASs and a replicable workflow, completely based on open GIS software and algorithms: OpenDroneMap, QGIS, SAGA and OpenCV classification algorithms. Specific objectives are: (i) testing a low-cost UAS for weed mapping; (ii) assessing open-source packages for semi-automatic weed classification; (iii) performing a sustainable management scenario by prescription maps. Results showed high performances along the whole process: in orthomosaic generation at very high spatial resolution (0.01 m/pixel), in testing weed detection (Matthews Correlation Coefficient: 0.67–0.74), and in the production of prescription maps, reducing herbicide treatment to only 3.47% of the entire field. This study reveals the feasibility of low-cost UASs combined with open-source software, enabling a spatially explicit approach for weed management in small-medium size farmlands.

Highlights- Efficacy of UAVs and emergence predictive models for weed control has been confirmed. - Combination of time-specific and site-specific weed control provides optimal results.- Use of timely prescription maps can substantially reduce herbicide use.   Remote sensing using unmanned aerial vehicles (UAVs) for weed detection is a valuable asset in agriculture and is vastly used for site-specific weed control. Alongside site-specific methods, time-specific weed control is another critical aspect of precision weed control where, by using different models, it is possible to determine the time of weed species emergence. In this study, site-specific and time-specific weed control methods were combined to explore their collective benefits for precision weed control. Using the AlertInf model, which is a weed emergence prediction model, the cumulative emergence of Sorghum halepense was calculated, following the selection of the best date for UAV survey when the emergence was predicted to be at 96%. The survey was executed using a UAV with visible range sensors, resulting in an orthophoto with a resolution of 3 cm, allowing for good weed detection. The orthophoto was post-processed using two separate methods: an artificial neural network (ANN) and the visible atmospherically resistant index (VARI) to discriminate between the weeds, the crop and the soil. Finally, a model was applied for the creation of prescription maps with different cell sizes (0.25 m2, 2 m2, and 3 m2) and with three different decision-making thresholds based on pixels identified as weeds (>1%, >5%, and >10%). Additionally, the potential savings in herbicide use were assessed using two herbicides (Equip and Titus Mais Extra) as examples. The results show that both classification methods have a high overall accuracy of 98.6% for ANN and 98.1% for VARI, with the ANN having much better results concerning user/producer accuracy and Cohen's Kappa value (k=83.7 ANN and k=72 VARI). The reduction percentage of the area to be sprayed ranged from 65.29% to 93.35% using VARI and from 42.43% to 87.82% using ANN. The potential reduction in herbicide use was found to be dependent on the area. For the Equip herbicide, this reduction ranged from 1.32 L/ha to 0.28 L/ha for the ANN; with VARI the reduction in the amounts used ranged from 0.80 L/ha to 0.15 L/ha. Meanwhile, for Titus Mais Extra herbicide, the reduction ranged from 46.06 g/ha to 8.19 g/ha in amounts used with the ANN; with VARI the reduction in amounts used ranged from 27.77 g/ha to 5.32 g/ha. These preliminary results indicate that combining site-specific and time-specific weed control, has the potential to obtain a significant reduction in herbicide use with direct benefits for the environment and on-farm variable costs. Further field studies are needed for the validation of these results.

Weed behaviour in crop fields has been extensively studied; nevertheless, limited knowledge is available for particular cropping systems, such as no-till systems. Improving weed management under no-till conditions requires an understanding of the interaction between crop residues and the seedling emergence process. This study aimed to evaluate the influence of maize and wheat residues, applied in three different quantities (1, the field quantity, 0.5, and 1.5-fold amounts of the field quantity), on the emergence of eight weed species: Abutilon theophrasti, Amaranthus retroflexus, Chenopodium album, Digitaria sanguinalis, Echinochloa crus-galli, Setaria pumila, Sonchus oleraceus, and Sorghum halepense. The experiment was conducted over two consecutive years. The results showed that the quantities 1 and 1.5 could suppress seedling emergence by 20 and 44%, respectively, while the quantity 0.5 seems to promote emergence by 22% compared with the control without residues. Weed species showed different responses to crop residues, from C. album showing 56% less emergence to S. halepense showing a 44% higher emergence than the control without residues. Different meteorological conditions in the two-year experiment also exhibited a significant influence on weed species emergence.

Field management practices can alter the physical and chemical properties of the soil, also causing changes to the seed bank. Alterations can also occur to the soil microbial community, which in turn can increase or diminish the process of weed seed decay. In this research, the issue of seed degradation was studied in an undisturbed and a no-till soil, trying not only to uncover where seeds are more degraded, but also to investigate the microbial activities that could be involved in this process. Six different weed species, commonly found in northern Italy, were used: Abutilon theopharsti, Alopecurus myosuroides, Amaranthus retroflexus, Digitaria sanguinalis, Portulaca oleracea and Sorghum halepense. Seed decay was tested in two different sites, a no-till field and the adjacent buffer zone. Soil microbial activity was also measured using the Fertimetro, an approach based on the degradation of cotton and silk threads buried in the soil for one week. Degradation of the buried seeds was higher in the no-till field soil than in the buffer strip for all the studied species as was the microbial cellulolytic activity. Even though the buffer strip soil is an undisturbed habitat and resulted as having higher organic matter, the no-till soil conditions appeared more unfavourable to seed viability. Our findings suggest that no-till management can improve weed seed suppression in the soil. Moreover, cellulolytic microorganisms play an important role in seedbank longevity, so cellulolytic activity surveys could be used as an early monitoring bioindicator for weed seed suppression in soil.

<p>Weeds are one of the major problems in agriculture, they can reduce yield, interfere with harvest and serve as hosts to possibly harmful organisms. For a successful agricultural production, weed issue must be tackled in the begging, during the germination-emergence phase. With different management systems weed seed bank is exposed to different field conditions which may favour or obstruct the germination. One of these conditions is the presence or the absence of crop residues on the soil surface, very common in the newer agricultural practices, such as Conservation Agriculture. In this work the germination of eight weed species: <em>Abuthilon theophrasti</em>, <em>Setaria glauca</em>, <em>Digitaria sanguinalis</em>, <em>Sorghum halepense</em>, <em>Amaranthus retroflexus</em>, <em>Sonchus oleraceus</em>, <em>Chenopodium album</em> and <em>Echinochloa crus-galli</em>, was examined under the residues of two crop species maize (<em>Zea mays</em>) and wheat (<em>Triticum sp.</em>). For each weed species 200 seeds were used, while three different quantities of residues were used for the two crops, the quantity measured in one square meter of the field (1), half of that quantity (0,5) and a half more than the one measured in the field (1,5), plus control, without residues. The experiment was conducted at the experimental farm of the University of Padova in Legnaro (PD) in a 8x2x3 factorial design with three blocks, plus three control repetitions. Seeds of each weed species were sown in an area of 20 cm<sup>2</sup>. Before the beginning of the experiment, the soil from the designated areas was removed and sterilized at 105°C in order to prevent contamination by the seeds already present in the soil. Once the soil was sterilized and restored to the field, the seeds were sown on the surface of the soil and covered with the respective quantity of the respective crop residue or left uncovered in the case of control. The experiment started on December 2018, and the seeds were left undisturbed during the winter, imitating natural conditions. Seeds started germinating on March 2019 and were controlled twice a week until the end of germination process, all germinated plants were removed and counted. ANOVA and LSD analysis were performed on cumulated germination data. Only quantity of residues and weed species resulted significant as factors (p-value < 0,000). The results showed that the quantity 1 and 1,5 can reduce the germination from 10 to 30% respectively, while quantity 0,5 can in fact increase germination by 15%. As for the weed species, they were all more inhibited by the higher concentrations of residues, but in respect to control it was observed that some of them seemed to be favoured by the low presence of residues <em>S. halepense</em> and <em>A. theophrasti</em>, not particularly influenced were <em>A. retroflexus</em>, <em>E. crus-galli</em> and <em>S. oleraceus</em>, while <em>C. album</em>, <em>D. sanguinalis</em> and <em>S. glauca</em> showed major germination rate reduction. In conclusion, to obtain the weed inhibitory effect, it seems very important to pay particular attention to the homogeneity of the distribution of the crop residues on the soil surface, low residue density areas could favour weeds.</p>