The establishment and management of cover crops are common practices widely used in irrigated viticulture around the world, as they bring great benefits not only to protect and improve the soil, but also to control vine vigor and improve the yield quality, among others. However, these benefits are often reduced when cover crops are infested by Cynodon dactylon (bermudagrass), which impacts crop production due to its competition for water and nutrients and causes important economic losses for the winegrowers. Therefore, the discrimination of Cynodon dactylon in cover crops would enable site-specific control to be applied and thus drastically mitigate damage to the vineyard. In this context, this research proposes a novel, automatic and robust image analysis algorithm for the quick and accurate mapping of Cynodon dactylon growing in vineyard cover crops. The algorithm was developed using aerial images taken with an Unmanned Aerial Vehicle (UAV) and combined decision tree (DT) and object-based image analysis (OBIA) approaches. The relevance of this work consisted in dealing with the constraint caused by the spectral similarity of these complex scenarios formed by vines, cover crops, Cynodon dactylon, and bare soil. The incorporation of height information from the Digital Surface Model and several features selected by machine learning tools in the DT-OBIA algorithm solved this spectral similarity limitation and allowed the precise design of Cynodon dactylon maps. Another contribution of this work is the short time needed to apply the full process from UAV flights to image analysis, which can enable useful maps to be created on demand (within two days of the farmer´s request) and is thus timely for controlling Cynodon dactylon in the herbicide application window. Therefore, this combination of UAV imagery and a DT-OBIA algorithm would allow winegrowers to apply site-specific control of Cynodon dactylon and maintain cover crop-based management systems and their consequent benefits in the vineyards, and also comply with the European legal framework for the sustainable use of agricultural inputs and implementation of integrated crop management. efficient use of farm inputs (e.g., pesticides, fertilizers, water, labor, fuel, etc.) and, consequently, reducing potential environmental impacts caused by the over-application of inputs [1]. Moreover, PV strategies enable farmers to fulfill decision making with regard to the European Union's (EU) Directives included in the Common Agricultural Policy concerning both the digitizing of agriculture and the sustainable use of agricultural inputs, which foster the development of alternative strategies that limit or optimize their usage. PV strategy implementation involves identifying the intra-and inter-crop-field spatial variability and the causes that determine such variability, as well as designing optimal site-specific management strategies accordingly [2]. One of the most innovative technologies that can be employed to quantify this variability is the use of Unmanned Aerial Vehic...

Ground cover management in vineyards in Spain is focused on minimizing soil erosion and compaction. Such practices have influenced the weed community structure in the inter-rows, contributing to the spread of the high noxious weed Cynodon dactylon (L.) Pers. This fact highlights the need for further investigation of the interaction between ground cover practices and weed control techniques. In this study, the effect of four different ground cover managements (M) in the inter-rows on C. dactylon population dynamics (changes in coverage and frequency) was assessed over three seasons (2015–2017): (M1) a no-till spontaneous vegetation ground cover managed by shredding; (M2) a no-till spontaneous vegetation ground cover managed by shredding plus herbicide application, (M3) tilled soil and spontaneous vegetation growing; and (M4) tilled soil and a barley cover crop seeded (Hordeum vulgare L.). Cynodon dactylon and the other weeds responded differently to the various weed control methods. After three seasons, the barley cover crop was the most efficient management system to control C. dactylon and other weeds. Final soil cover in barley cover crop and tilled soil with spontaneous vegetation were 0.5% and 1.1%, respectively, compared to 3.7% and 7.7% obtained by spontaneous vegetation shredded with and without herbicide application, respectively. In addition, total weed frequency varied from 9.7% for barley cover crop to 45.8% for spontaneous vegetation only shredded. Weed community composition changed due to the pressure exerted by each management and the adaptive strategy of the different species. This study highlights the importance of knowledge of how vegetation management influences weed flora to improve the sustainability of wine grape production systems.

Crop rotation in winter cereals in semiarid Mediterranean climates is highly desirable to prevent weed infestations, but the climatic conditions make it difficult to implement alternative crops to winter cereals. Camelina (Camelina sativa (L.) Crantz) is an interesting option, as it is able to produce profitable yields thanks to its tolerance to cold and drought. In this work, three autumn–winter sowing dates (SD1, October; SD2, December; SD3, January) and two sowing rates (R1, 8 kg ha–1; R2, 11 kg ha–1) were chosen to evaluate the effectiveness of these cultural methods to control weeds over three seasons, and to determine effects on camelina seed yield. Results showed that a significant reduction of weed coverage was obtained by delaying the sowing date. Sowing rates did not show differences in weed coverage. In contrast, no apparent yield penalty was observed among sowing dates and rates. These results show that the introduction of camelina as a rotational crop in semiarid Mediterranean climates is a feasible option for helping to suppress winter weeds, as well as to provide productive seed yield in these climatic conditions.

Conyza bonariensis is one of the most problematic weed species throughout the world.It is considered highly noxious due to its interference with human activities, and especially the competition it poses with economically important crops. This research investigated the temperature requirements for seed germination of four populations of C. bonariensis with distinct origin and the influence of daily alternate temperatures. For this, a set of germination tests were performed in growth chambers to explore the effect of constant and alternate temperatures. Seeds of the four populations (from Lleida, Badajoz and Seville, Spain and Bahía Blanca, Argentina) were maintained at constant temperatures ranging from 5-35ºC. The final germination and cardinal temperatures (base, optimum and maximum) of each population were obtained. We also tested the influence of daily alternate temperatures on final germination. To do so, seeds were exposed to two temperature regimes: 5/15, 10/20, 15/25, 20/30 and 25/35ºC night/day temperature (intervals increasing 5ºC, with constant oscillation of 10ºC) and to 18/22, 26/24, 14/26, 12/28 and 10/30ºC night/day temperature (intervals with average of 20ºC, but increasing the oscillation in 4ºC between intervals). In general, all populations behaved similarly, with the highest germination percentages occurring in the optimum temperature range (between 21.7ºC and 22.3ºC) for both constant and alternate temperatures. In general, climatic origin affected germination response, where seeds obtained from the coldest origin exhibited the highest germination percentage at the lowest temperature assayed. In addition, we observed that the alternate temperatures can positively affect total germination, especially in oscillations that were further from the average optimum temperature (20ºC), with high germination percentage for the oscillations of 15/25, 20/30, 18/22, 16/24, 14/26, 12/28 and 10/30ºC in all populations.

Cover crops and mulches have become an alternative for soil management in vineyards due to the agronomic, environmental, and economic advantages, especially the possibility of weed control. Implicitly to this objective lies the idea of assessing the potential herbicide effect of the allelochemicals released by different cover crop and mulch species. With this objective, the present work evaluated the phytotoxic effects of 12 aqueous extracts of selected species with potential use as a cover crop or mulch: a Bromus species mixture (B. hordeaceus L. and B. rubens L.), Festuca arundinacea Schreb., Hordeum murinum L., H. vulgare L., Vulpia ciliata Dumort.,  Medicago rugosa Desr., M. sativa L., Trifolium subterraneum L., T. incarnatum L., Phacelia tanacetifolia Benth., Sinapis alba L., and Pinus sylvestris L.,on the germination and early growth of three troublesome weeds (Conyza bonariensis (L.) Cronquist, Aster squamatus (Spreng.) Hieron, and Bassia scoparia (L.) A. J.). The different in vitro bioassays showed that aqueous extracts of some species significantly inhibited or reduced germination and root and shoot growth of the target weed species in a dose-response manner. Germination of A. squamatus and C. bonariensis was reduced by 100-80% by the different extracts applied at 50% concentration, and completely blocked at 100% concentration, except for M rugosa extract to which both species showed less sensitivity. Root elongation of A. squamatus was absolutely inhibited under every extract and concentration, whereas C. bonariensis root growth showed only some tolerance to the crude extracts of F. arundinaceaand P. sylvestris. Bassia scoparia was relatively tolerant to the aqueous plant extracts, except for T. subterraneum crude extract, which reduced total germination by 80%; otherwise, B. scoparia showed higher general sensitivity of shoot growth than the other two weed species. The chemical profiles of phenolic compounds of the aqueous extracts were obtained and identified by HPLC-DAD, the phenolic profiles of H. murinum, V. ciliata, and M. rugosa being reported in this work for the first time. Using stepwise regression, the influence of certain phenolic compounds from the aqueous extracts on the germination and early growth of weeds was predicted. Among other significant compounds, the flavonoid naringenin identified in T. subterraneumaqueous extract at 8.09 µg·mL-1 was predicted to underlie its specific phytotoxicity on B. scoparia germination. These results support the use of cover crops and mulches in weed management and can help to select the most suitable species to adopt according to the target weed species. Highlights The phytotoxic nature of the aqueous extracts of twelve conventional and novel cover crops and mulch species was demonstrated on three troublesome weed species in vineyards. Phenolic acids and flavonoids of the twelve aqueous extracts were identified and quantified by HPLC-DAD, and, by regression analysis, some allelochemicals were postulated as responsible for the phytotoxic effects. The water-soluble phenolic profiles of three potential cover crops, namely Hordeum murinum, Vulpia ciliata, and Medicago rugosa, are reported for the first time. In vitro germination and early root growth of Conyza bonariensis and Aster squamatus were almost entirely restricted by any of the twelve plants' aqueous extracts and presumably by the joint action of their particular allelopathic compounds. Bassia scoparia germination was relatively much less sensitive to the extracts, except for Trifolium subterraneum, for which the flavonoid naringenin was predicted to underlie its specific phytotoxicity.