Summary
Cover crops can suppress weeds within agricultural fields due to competitive and allelopathic effects. Glasshouse experiments were conducted to evaluate the relative proportions of ...allelopathic effects to the total weed inhibition. Six different cover crop species were combined with three weed species in the presence or absence of active carbon over a period of four weeks. Active carbon was used as an adsorbent for allelopathic substances in the soil. Our study revealed that the competition between cover crops and weeds shifted, possibly due to the minimisation of allelopathic effects by active carbon in the soil. We assume that the degree of cover crops allelopathic effects on weeds is species‐specific, both on the side of cover crops and on the weed side. The cover crops Raphanus sativus, Fagopyrum esculentum and Avena strigosa showed the highest allelopathic weed suppression with up to 28%. Additionally, Stellaria media turned out to be the most sensitive weed against allelopathic effects induced by all cover crops, except for Linum usitatissimum and Guizotia abyssinica. The knowledge about the contribution of competitive and allelopathic effects by cover crops would help to create cover crop mixtures with high weed suppressive ability.
Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Primarily, spatial information ...allows a potential reduction in herbicide use, when post-emergent herbicides are only applied to field sections with high weed infestation levels. This paper presents a system for site-specific weed control in sugar beet, maize, winter wheat, winter barley, winter rape and spring barley. The system includes on-line weed detection using digital image analysis, computer-based decision making and Global Positioning System-controlled patch spraying. In a 2-year study, herbicide use with this map-based approach was reduced in winter cereals by 6-81% for herbicides against broad leaved weeds and 20-79% for grass weed herbicides. Highest savings were achieved in cereals followed by sugar beet, maize and winter rape. The efficacy of weed control varied from 85% to 98%, indicating that site-specific weed management will not result in higher infestation levels in the following crops.
Summary
Reliable in‐season and in‐field tools for rapidly quantifying herbicide efficacy in dicotyledonous weeds are missing. In this study, the maximum quantum efficiency of photosystem II (Fv/Fm) ...of susceptible and resistant Papaver rhoeas and Stellaria media populations in response to treatments with acetolactate synthase (ALS) inhibitors were examined. Seedlings (4–6 leafs) were transplanted into the field immediately after the application of the ALS inhibitors florasulam, metsulfuron‐methyl and tribenuron‐methyl. The Fv/Fm values were assessed 1–7, 9 and 14 days after treatment (DAT). Based on the Fv/Fm values of all fluorescing pixels in the images of herbicide‐treated plants, discriminant maximum‐likelihood classifiers were created. Based on this classifier, an independent set of images were classified into ‘susceptible’ or ‘resistant’ plants. The classifiers’ accuracy, false‐positive rate and false‐negative rate were calculated. The Fv/Fm values of sensitive P. rhoeas and S. media plants decreased within 3 DAT by 28–43%. The Fv/Fm values of the resistant plants of both species were 20% higher than those of the sensitive plants in all herbicide treatments. The classifier separated sensitive and resistant plants 3 DAT with accuracies of 62–100%. False‐positive and false‐negative classifications decreased with increasing DAT. We conclude that by the assessment of the Fv/Fm value in combination with the classification sensitive and resistant P. rhoeas and S. media populations could be separated 3 DAT. This technique can help to select effective control methods and speed up the monitoring process of susceptible and resistant weeds.
Massa D, Krenz B & Gerhards R (2011). Target‐site resistance to ALS‐inhibiting herbicides in Apera spica‐venti populations is conferred by documented and previously unknown mutations. Weed ...Research51, 294–303.
Summary
In this study, whole‐plant bioassays were performed on 72 Apera spica‐venti populations that have survived application of acetolactate synthase (ALS)‐inhibiting herbicides in recent years. Molecular genetic analysis of the ALS gene revealed a Thr mutation at Pro197 within 67 populations. Sequencing of the whole ALS gene from wild‐type and resistant plants not carrying the above‐mentioned mutation revealed the presence of a Leu mutation at Trp574 within two populations and an Asn mutation at Pro197 within two populations. As the Pro197‐Asn amino acid substitution is reported for the first time in a field‐selected weed population, a Cleaved Amplified Polymorphic Sequences (CAPS) marker was developed for its quick detection. In addition, one novel mutation was found within a population that coded for a His substitution at Arg377. Enzyme assays confirmed a significant reduction in inhibition of ALS activity compared with the wild type. This population showed resistance to sulfonylureas (SUs) and cross‐resistance to sulfonylaminocarbonyltriazolinones (SCTs) and triazolopyrimidines (TPs) within the whole‐plant bioassays. ALS protein sequence alignments from weedy and cultural plants revealed that the Arg377 is highly conserved among known wild‐type enzymes. In agreement with existing literature concerning the structure and mechanisms of inhibition of plant ALS, this mutation is probably involved in target‐site resistance to ALS inhibitors. Our results suggest that further single‐nucleotide polymorphisms impairing proper herbicide performance might be selected within field populations in the near future, making the short‐ and long‐range evolution of target‐site resistance difficult to predict depending solely on herbicide use history.
Summary
Information on temporal and spatial variation in weed seedling populations within agricultural fields is very important for weed population assessment and management. Most of all, it allows a ...potential reduction in herbicide use, when post‐emergence herbicides are only applied to field sections with weed infestation levels higher than the economic weed threshold; a review of such work is provided. This paper presents a system for site‐specific weed control in sugarbeet (Beta vulgaris L.), maize (Zea mays L.), winter wheat (Triticum aestivum L.) and winter barley (Hordeum vulgare L.), including online weed detection using digital image analysis, computer‐based decision making and global positioning systems (GPS)‐controlled patch spraying. In a 4‐year study, herbicide use with this map‐based approach was reduced in winter cereals by 60% for herbicides against broad‐leaved weeds and 90% for grass weed herbicides. In sugarbeet and maize, average savings for grass weed herbicides were 78% in maize and 36% in sugarbeet. For herbicides against broad‐leaved weeds, 11% were saved in maize and 41% in sugarbeet.
•A task controller commanding ISOBUS sprayer and using external spatial data.•WFS and WMS as a decision support during a task execution.•Outlined dynamic application task for precision farming.•Farm ...machinery standardisation and FMIS software components need adjustment.
Field operations relating to arable farming are often very data intensive tasks. An increasing number of regulations have been set to ensure food safety and environmental aspects. Also, the number of tools for the best practice management applied in precision agriculture is growing. However, there are yet no standardized, automated methods for a compliance management used in situations where circumstances change and are dependent on the specific location. Therefore compliance checks during the work progress online or on demand are difficult to achieve and the temporal accuracy can be very poor. In this work, we have developed a task controller (TC) prototype with an ISOBUS-compatible process data messages to be able to utilize multiple external services such as WFS (Web Feature Service) during a spraying operation. The WFS was set up in Germany to provide geodata while the actual task execution was performed in Finland. We developed a possibility to use and integrate external data from different sources in the TC on the tractor. Methods presented in this article serve as the basis for the development of multiple tools that can be used for improving farming system development, the environmental risk reduction of agricultural production and compliance checks. Existing information sources such as on board sensors, weather and forecast information, disease pressure, spatial environmental risks and real time remote sensing can be combined for new solutions of this kind. The development of technical standards for the seamless data exchange in the agricultural domain is therefore crucial. In this work, we are focussing on spatial data exchange between heterogeneous IT systems as a component of on-field machinery used in precision management.
Summary
Due to the steadily increasing number of putative herbicide‐resistant weed populations, the demand for rapid in‐season tests is rising. In this study, we introduce a new quantitative ...herbicide‐resistance test system based on chlorophyll fluorescence imaging analysis of photosynthesis‐related parameters. Susceptible and herbicide‐resistant populations of Alopecurus myosuroides (black‐grass) were cultivated in multiwell tissue culture plates containing nutrient agar and different dosages of fenoxaprop‐P‐ethyl and mesosulfuron+iodosulfuron. The maximum quantum efficiency of the PSII was measured 3 h after transplanting (HAT) and then for seven days every 24 h. Data of maximum quantum efficiency of the PSII were compared with standard whole‐plant pot tests and molecular tests for target‐site mutations. It was possible to fit dose‐response curves and calculate corresponding resistance factors for ED90 for all populations tested using the chlorophyll fluorescence imaging. It was possible to distinguish between resistant and susceptible populations. The results of the chlorophyll fluorescence imaging corresponded well with the standard whole‐plant pot tests in the glasshouse. However, populations with proved target‐site mutations did not differ from other herbicide‐resistant populations in the maximum quantum efficiency values of the PSII. We conclude that the chlorophyll fluorescence imaging provides reliable data on herbicide resistance for both modes of action tested in a shorter time and using less space, compared with standard whole‐plant pot tests in the glasshouse.
Gutjahr C, Sökefeld M & Gerhards R (2012). Evaluation of two patch spraying systems in winter wheat and maize. Weed Research52, 510–519. SUMMARY: Fifteen field experiments were conducted in winter ...wheat and maize to analyse the spatial distribution of weed species and to evaluate two systems of site‐specific weed control. Fields were divided into cells and weed densities for all weed species were counted in each cell. Weed species were then grouped into annual broad‐leaved species, grass weeds and Galium aparine in winter wheat and annual broad‐leaved species, grass weeds and perennials in maize. Weed control thresholds were set for each group of weed species and different herbicides were sprayed in cells where the weed control threshold was exceeded. All three weed species groups were distributed heterogeneously within and between the fields, with densities ranging from 0 to more than 2000 plants m−2. Site‐specific weed control was realised with a GPS‐controlled multiple‐tank sprayer, containing three separate spray lines for each of the three application maps. In winter wheat, site‐specific weed control using a multiple‐tank sprayer resulted in 70% untreated area compared with uniform applications across the whole field. Simulated site‐specific weed control using a conventional sprayer with a tank mixture only resulted in 37% untreated area. In maize, 47% of the area remained untreated using the multiple‐tank sprayer and 6% using a conventional sprayer and tank mixtures. Efficacy of site‐specific weed control was good in all fields. The results demonstrate the need for combining weed mapping and new application technologies for patch spraying.
Summary
Herbicide resistance in Alopecurus myosuroides causes severe problems in Western European cropping systems. Costs of herbicide resistance were investigated in this study by analysing variable ...production costs and sales revenues. Three farms were selected for this study, with winter wheat as the dominating crop in all farms. Resistance in A. myosuroides populations was verified at all locations. Four farming approaches were simulated over a period of 20 years: (i) continuing the actual cropping system without increase of resistance, (ii) continuing the actual cropping system with increase of resistance, (iii) changing cropping practice to overcome resistance and (iv) changing cropping practice to prevent resistance. Contribution margins representing the proportion of sales revenue that is not consumed by variable costs were calculated for all approaches. Comparative static simulations showed that average contribution margins in a cropping system with more than 60% winter cereals and reduced tillage practice dropped from 807 € ha−1 a−1 without herbicide resistance to 307 € ha−1 a−1 with herbicide resistance. Alopecurus myosuroides population densities increased to more than 1000 plants m−2. Diverse crop rotations, including spring crops, clover–grass leys and intensive tillage, suppressed A. myosuroides populations, and average contribution margin was 630 € ha−1 a−1. Preventive methods with rotations of winter cereals and spring crops with less clover–grass leys resulted in an average contribution margin of 691 € ha−1 a−1. In conclusion, rotations of winter cereals and spring crops combined with inversion tillage and herbicides provide stable yields and can prevent weed population increase.
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