Intra-row Weed Research Articles

Integration of Vinegar for In-Row Weed Control in Transplanted Bell Pepper and Broccoli

Vinegar can supplement the existing intrarow weed control options of organic farmers. However, there are two primary limitations to its use in vegetable crops. First, it is costly. Second, vinegar applications that contact the crop can cause injury and yield loss. The aim of this research was to use vinegar to control intrarow weeds in bell pepper and broccoli in a way that product costs would be reduced and crop injury would be minimized. Banded applications were shielded and directed below the crop canopy to reduce weed control costs and minimize contact with crop foliage. Organic paints applied to crop stems were evaluated as potential physical barriers to crop stem injury. Four field trials were conducted in 2009, two in transplanted bell pepper and two in transplanted broccoli. A single application of 200-grain vinegar (20% acetic acid) at 700 L ha−1was applied when weeds were in the cotyledon to six-leaf stage. Applications were made to crops with the lower stems coated in one of two stem protectants, or left uncoated. Hand-weeded and weedy treatments were included for comparison. One day after vinegar application, in-row weed control was 100% in both pepper trials and greater than 96% in the broccoli trials. Two weeks after application, 75% fewer weeds germinated in the vinegar-treated areas compared with the areas that were hand weeded. Neither stem protectant prevented crop injury. Despite pepper foliar injury of less than 5%, stem injury 2 wk after application contributed to a measurable yield reduction. Broccoli injury was limited to instances where overspray contacted the crop canopy. With vinegar, high levels of weed control and the extended duration of that control relative to hand weeding could facilitate improved organic intrarow weed control. However, crop injury must be reliably reduced. Alternative stem protectants may merit evaluation.

Evaluation of an autonomous GPS-based system for intra-row weed control by assessing the tilled area

An automatic tillage system for inter- and intra-row weed control based on real-time kinematic GPS navigation and control has been used to address the problem of mechanically removing weeds within rows of precision seeded crops. The system comprised a side-shifting frame with an attached tine-rotor (cycloid hoe) with eight sigmoid-shaped, vertically directed tines. The individual tines can be released for individual rotation in order to avoid collision with geo-referenced crop plants. The system navigated with reference to pre-defined waypoints for tillage parallel to crop rows and around individual crop plants. The system evaluation was based on quantification of treated areas for uprooting and burial and the corresponding prediction of weed control efficiencies. A single pass of an 80 mm wide row band provided tillage of 30–49% of the intra-row area, with highest coverage at a speed of 0.32 m s−1 and at even plant spacing. A double pass, once on each side of the row in opposite directions, provided higher soil disturbance intensity and resulted in tillage of 31–58% of the intra-row area with highest coverage at a speed of 0.32 m s−1. The intra-row weed control effect was predicted to be up to 20% for a single pass and up to 29% for a 2-way pass treatment both at the white thread to the two-leaf stage of weeds. The result of the prediction is of crucial importance for the considerations of tool designs at the current conceptual stage of the system.

Soil steaming effects on weed seedling emergence under the influence of soil type, soil moisture, soil structure and heat duration

Soil steaming applied in bands is a new technology with the potential to radically lower the burden of hand-weeding intra-row weeds in non-herbicidal vegetable cropping. Preliminary studies with band-steaming have shown effective control of viable weed seeds when the maximum soil temperatures reach 60–80°C. This temperature range has a particular agronomic interest, and the present study aimed at investigating the influence of soil factors and heat duration on weed seed mortality of soil steaming targeting 60–80°C. Two soil types (sand versus sandy loam) and two moisture levels (moist versus dry) were studied in one experiment (expt) while two levels of structure of a sandy loam (coarse versus fine) were included in a second experiment. A third experiment was focussing on the significance of heat duration expressed as the speed of cooling-down after steaming had been stopped. Weed control efficacy was generally greater in sand than in sandy loam and soil irrigation further improved weed control. Steam application to the finely structured soil improved weed control efficacy relative to that obtained with the coarse soil of larger aggregate size. The rapidity of cooling from the maximum temperature did not affect the efficacy of the treatment on weed seed mortality. Based on these experiments, a maximum soil temperature of 80°C should ensure satisfactory weed control under moist soil conditions, especially if the soil is cultivated prior to steaming.

Dynamics of mineral nitrogen, water-soluble carbon and potential nitrification in band-steamed arable soil

Steaming of narrow soil bands prior to sowing is a new technique that reduces the need for intra-row weeding in herbicide-free row crops. However, the steam treatment may eliminate both weed seeds and non-target soil organisms, thereby affecting the nutrient cycling in the soil. This study tested the effect of band-steaming on N and C dynamics in a sandy loam soil that was steamed in situ to maximal temperatures of 70–90°C using a prototype bandsteamer. Soil samples (0–5 cm depth) were collected during 90 days from band-steamed soil, undisturbed control soil, and control soil treated just mechanically with the bandsteamer. In the steamed soil, ammonium concentrations increased from 1.1 to 20.3 μg NH4+-N g−1 dry weight during 28 days. This coincided with an immediate and persistent inhibition of potential nitrification (33–61% inhibition during 90 days). Assays of the temperature response of potential nitrification confirmed the temperature sensitivity and showed an optimum temperature of 27.1°C and a temperature coefficient (Q10) of 1.9. The effects of band-steaming on concentrations of nitrate and water-soluble carbon were divergent and stimulatory, respectively, but generally not statistically significant. Mechanical effects of band-steaming were negligible. The observed ammonium surplus could be of agronomic benefit and should be evaluated in integrated studies of the effects of band-steaming on crop growth and plant N uptake.

Kameragestütztes Regelkonzept einer mechanischen Hacke für Zuckerrüben

Mechanical weed control is currently limited to application in organic agriculture. Technically, intra-row weed control is problematic and still requires a high amount of manual labour. The aim of the project presented here is to design a mechanical hoe for intra-row weed control. For this purpose a camera-based control system was developed that determines the position of the plant in real-time and controls the hydraulically-driven implement in accordance to the position of the next plant. Consequently, it is possible to determine the exact position of the plant, from the picture that is taken by the camera, in real-time and independently of the speed within stage of development BBCH 10 to BBHC 14 of the sugar beet.

Effects of band-steaming on microbial activity and abundance in organic farming soil

Band-steaming of arable soil at 80–90 °C kill off weed seeds prior to crop establishment which allows an extensive intra-row weed control. Here we evaluated the side-effects of in situ band-steaming on soil respiration, enzyme activities, and numbers of culturable bacteria and fungi in an organic field soil. The results showed that mechanical disturbance created by band-steaming could be neglected as a mediator of microbial changes. Also, soil pH and water content was unaffected by band-steaming. Effects of band-steaming on in situ soil respiration and basal respiration, respectively, were insignificant or slightly stimulatory ( P < 0.05). Fluorescein diacetate hydrolysis and arylsulfatase activity were significantly ( P < 0.001) inhibited by 25 and 38%, respectively, and only showed weak recovery during 90 days after band-steaming. Bacterial colony-forming units increased after soil steaming whereas the number of fungal propagules was reduced by 50% ( P < 0.001). This reduction persisted at a level of 38% after 90 days ( P < 0.001). Evaluated in relation natural environmental stresses, band-steaming showed ecologically tolerable short-term effects, but with weaker recovery potential and therefore possible long-term effects. However, band-steaming affects only a minor volume of the plough layer (<10%) and long-term effects may be minimal due to annual tillage (mixing) of the soil. In conclusion, the side-effects on soil microbiology may not disqualify band-steaming as an option in organic farming systems.

RTK GPS mapping of transplanted row crops

This study demonstrated the feasibility of using a real-time kinematic (RTK) global positioning system (GPS) to automatically map the location of transplanted row crops. A positive-placement vegetable crop transplanter retrofitted with an RTK GPS receiver, plant, inclination, and odometry sensors, and an on-board real-time data logger were used for transplant mapping in the field during planting. Sensing the location where each plant was placed in the soil using an absolute shaft encoder mounted on the planting wheel proved to be more robust and accurate than using an infrared light beam sensor to detect the stem location of each plant immediately after planting. Field test results showed that the mean error between the plant map locations predicted by the planting data and the surveyed locations after planting was 2 cm, with 95% of the predicted plant locations being within 5.1 cm of their actual locations. Along-track errors were greater than transverse-track errors indicating that some improvement in plant map accuracy might be obtained by characterization of dynamic planting effects on final plant location. Overall, the system was capable of automatically producing a centimeter-level accuracy plant map suitable for use in precision plant care tasks such as intra-row weed control.

Systematic design of an autonomous platform for robotic weeding

The systematic design of an autonomous platform for robotic weeding research in arable farming is described. The long term objective of the project is the replacement of hand weeding in organic farming by a device working autonomously at field level. The distinguishing feature of the described design procedure is the use of a structured design approach, which forces the designer to systematically review and compare alternative solution options, thus preventing the selection of solutions based on prejudice or belief. The result of the design is a versatile research vehicle with a diesel engine, hydraulic transmission, four-wheel drive and four-wheel steering. The robustness of the vehicle and the open software architecture permit the investigation of a wide spectrum of research options for intra-row weed detection and weeding actuators.

Chemical and Non-Chemical Weed Control in Wide Row Lupins and Chickpeas in Western Australia

Organic crops are on the increase worldwide and weed control is one of the main problems since chemicals cannot be used. Wide row lupin sowing systems (greater than 50 cm wide rows) are becoming common in Western Australia (WA) and this allows growers to control inter–row weeds by inter-row cultivation for organic crops or spraying non-selective herbicides using shielded sprayers. In this study, inter-row shielded spraying was found to be the most effective treatment for annual ryegrass control in the 66 cm wide rows, but future herbicide resistance will be a major limitation. With shielded spraying, some form of intra-row weed control will still be necessary to significantly reduce weed seed set. Automatic tractor steering control would also be essential for commercial growers to adopt shielded spraying. In 2006, inter-row cultivation reduced annual ryegrass biomass by 63% and the number of annual ryegrass heads by 43%, but this did not result in a significant increase in lupin yield. To be most effective, it is suggested that inter-row cultivation should be done relatively early while the weeds are small, and when the soil is relatively warm and dry with rain not predicted for a day or two. In 2006 and 2007, inter-row shielded spraying with glyphosate gave the best ryegrass control averaging 94%. Weed seed head trimming or cutting weeds above the crop prior to weed seed maturity may be a useful non-chemical method to reduce the number of weed seeds set if the weed seed is above the crop canopy and the cutting height is well controlled. Indian hedge mustard (Sisymbrium orientale) seed collected in the 2005 chickpea harvest samples was reduced by around 35% with all trimming treatments. In 2006, the late flower trimming reduced the seed number of wild oats and volunteer wheat in chickpeas. Lupin and chickpea grain yield was slightly reduced by trimming in 2005, but with improved height control did not reduce yields in 2006. Given the difficulties in controlling weeds by the growers due to widespread development of herbicide resistance in these weeds within the WA wheatbelt, this novel non-chemical way of weed control is a viable promising option to reduce the soil weed seed bank.

The development and assessment of the accuracy of an autonomous GPS-based system for intra-row mechanical weed control in row crops

Highly selective mechanical weed control within crop rows as an alternative to herbicide treatment requires the accurate guidance of tools around individual crop plants. The objectives of the research presented in this paper were to develop and optimise a novel self-propelled and unmanned hoeing system for intra-row weed control based on real-time kinematic global positioning system (RTKGPS) navigation, and to evaluate its performance under field conditions. The system comprised an autonomous tractor and a side-shifting frame, both equipped with RTK-GPS, and an attached cycloid hoe, which is a tine-rotor with eight sigmoid-shaped, vertically directed tines that can be released to allow individual rotation in order to avoid collision with geo-referenced crop plants. The system navigates with reference to predefined waypoints for hoeing parallel to crop rows and around individual crop plants. Field experiments using plastic sticks as artificial crop plants, placed with a mean within-row spacing of 0.2 m and variation typical under field conditions, confirmed that the system reliably performed hoeing within crop rows without colliding with the plastic sticks at forward velocities up to 0.52 m s−1. The side-shift enabled control of the transverse position of the cycloid hoe and was able to follow the row line with an accuracy of ±16 mm (P = 0.95) at 0.31 m s−1 and ±22 mm (P = 0.95) at 0.52 m s−1 forward velocity. Tines intruded into the required uncultivated zone, which had a radius of 10 mm from the centre of individual plants, with a maximum distance of 9 mm for 18 out of 1224 observations. Sufficient accuracy of the real-time positioning and control system was provided by using a Kalman filter, signal processing of the tilt data, and control algorithms developed for the side-shift and cycloid hoe control systems.

Reducing intrarow weed numbers in row crops by means of a biennial cultivation system

Intrarow weed emergence in row crops can be reduced by means of a biennial cultivation system that is based on an exhaustion of the weed seedbank in the upper soil layer of crop-free bands established in a preceding cereal crop, year I, before the row crop, year II. In this study, a series of field experiments is presented focusing more specifically on the influence of prevention of weed seed shedding and of different cultivation tactics in the system on intrarow weed emergence in the bands in year II. As the system excludes inverting soil tillage between years I and II, the prevention of weed seed shedding in year I turned out to be a key factor in achieving the desired effect of the system. This was seen with spring barley grown in year I, but not with winter wheat, where the system actually resulted in an increase in intrarow weed numbers in spite of the measures taken in year I. Cultivating the crop-free bands in spring barley in year I with conventional goose-foot shares in order to enhance seed germination and mortality further had no significant effects regardless of time and intensity. Results from two other experiments, in which freshly shed weed seeds were incorporated into the soil, supported the finding that cultivating the bands was of no advantage.

Response of Corn Genotypes to Weed Interference and Nitrogen in Nigeria

The effects of nitrogen (N) rate and weed interference on the grain yield of four corn genotypes were investigated in 2002 and 2003 at Ikenne (7°38′N, 3°42′E), Shika (11°11′N, 7°38′E), and Samaru (10°24′N, 7°42′E) in Nigeria. Nitrogen (N) at 0, 30, 60, and 90 kg N ha−1were the main plot treatments. Weed-free (weeded weekly), low (intrarow weeds only), and high (zero weeding) weed pressure were the subplot treatments. Four corn genotypes (ACR8328 BN C7, Low-N-Pool C2, Oba Super II, TZB-SR) were the sub-subplot treatments. Weed density was higher at Shika and Samaru than at Ikenne, and the order of average weed biomass 8 to 10 weeks after planting was Samaru (271 g m−2) &gt; Ikenne (236 g m−2) &gt; Shika (161 g m−2). Corn genotype and N rate had no effect on weed biomass except at Samaru where fertilized treatments had higher weed biomass than the unfertilized treatments. Corn leaf area (LA) increased with increasing N rate at all locations regardless of weed pressure and genotype, except at Shika where ACR8328 BN C7, Oba Super II, and TZB-SR did not show any clear N response; LA was highest in the weed-free and lowest in the unfertilized treatments for all genotypes and locations, and weed pressure treatments. Low-N-Pool C2had the highest LA, which was 1.3 times larger than in Oba Super II, which had the lowest LA. Nitrogen rate, weed pressure, and genotypes significantly affected corn leaf chlorophyll content. Chlorophyll content was higher in the fertilized treatments than the unfertilized treatments, and higher in the weed-free treatments than the low or high weed pressure treatments. ACR8328 BN C7and Oba Super II had significantly more chlorophyll than the other genotypes. Low-N-Pool C2showed a linear grain yield response with the increase in N rates. ACR8328 BN C7did not respond to N application. Compared with the results in the weed-free treatment, high weed pressure reduced grain yield in all genotypes by more than 65% at Samaru, 50% at Shika, and 35% at Ikenne.

Infrared laser sensor for depth measurement to improve depth control in intra-row mechanical weeding

Mechanical weeding is considered as an essential component in organic farming because there are few alternative methods to control intra-row weeds. However, intra-row mechanical weed control still has problems with efficacy due to the absence of, or poor, working depth control, of intra-row mechanical weeders. To improve depth control, intra-row mechanical weeders need to be combined with a sensor, whose output is used to control the depth of the weeders. The purpose of this work was to develop and evaluate a laser-based optical sensor that can be used to improve the working depth control of intra-row mechanical weeders. The performance of the depth sensor in frame height measurement and soil/crop discrimination was investigated under different soil properties and crop types representing field conditions during mechanical weeding. The results showed that the sensor depth measurement was not affected by the soil texture and soil moisture content of Belgian soils under organic farming conditions. The range of depth measurement is approximately 190 mm comprising a mid-point at 365 mm from the measured surface with a precision of at least 1 mm. Because optic filters were used the depth sensor was not influenced by sunlight. The sensor had a mean measurement speed of 35 ms. Furthermore, the sensor has been proved to be able to discriminate between soil and crop samples with a maximum error of 5% and is able to detect the depth in motion with a repeatable precision of 5 mm. In conclusion, the sensor has the ability to detect the working depth and to provide improved depth measurement to enhance depth regulation of intra-row mechanical weeders.

Innovative strategies for on-farm weed management in organic carrot

AbstractWeed management is often the most troublesome technical problem to be solved in organic farming, especially in poorly competitive crops like vegetables. A four-year (2000–2003) series of trials was established to assess the possibility of adopting an innovative non-chemical weed management system in organic carrot grown on the Fucino plateau, i.e., the most important carrot-growing area in Italy. The system utilized for physical weed control was based first on a false seedbed technique followed by pre-sowing weed removal, performed with a special 2 m wide 6-row spring-tine harrow. Prior to crop emergence, a pass with a flame weeder equipped with four 50 cm wide-open flame burners was also performed. Post-emergence weed control consisted of one or more hoeing passes with a purpose-designed 11-tine precision hoe equipped with spring implements (torsion weeders and vibrating tines), in addition to hand weeding. This innovative system was applied to a novel planting pattern (sowing in ten individual rows within 2 m wide beds) and compared to the standard management system of the area (sowing within 2 m wide beds but in five bands, use of spring-tine harrowing and flame weeding pre-emergence and of traditional hoeing post-emergence). The new system was tested in different commercial farms including both early and late-sown carrot. Assessments included machine operative characteristics, labor time, weed density and biomass, crop root yield and yield quality, and economic data (physical weed control costs and crop gross margin). Compared to the standard system, the innovative system usually resulted in reduced labor time (from 28 to 40%) and total costs for physical weed control (on average −416 € ha−1). Use of the precision hoe resulted in intra-row weed reduction ranging from 65 to 90%, which also led to a marked reduction in the labor required for hand weeding. In 2001 the two systems did not differ in terms of yield and yield quality, whereas in 2002 and 2003 the innovative system showed a higher mean density of carrot plants (from 28 to 55%), root yield (from 30 to 42%), and gross margin (from 40 to 100%). Carrot yield was higher in farms which adopted an early sowing whereas root commercial quality was somewhat variable between systems and years. In general, results obtained with the innovative management system look very promising.

A Mathematical Model of the Kinematics of a Rotating Disc for Inter- and Intra-row Hoeing

The paper describes a mathematical model, which analyses the kinematics of a rotating disc which moves along a path parallel to a crop row. The disc has a cut-out section with peripheral bevels which enable it to avoid the plant stems but to act as a hoe between plants to achieve intra-row weed control. Each plant has a no-till circle surrounding it and the model enables the disc to be designed so that no part of it enters the no-till zone during its passage parallel to the row. The model is used to optimise the effects of the distance of the disc centre from the crop row, the disc radius, the plant spacing within the row and the no-till circle radius. It was found that a disc with a cut-out sector angle of 130°, a radius of 87·5 mm and angled bevels of 25° cut back at 70 mm along the sector edge was a suitable design when moving at 50 mm from a crop with a 300 mm spacing and a 40 mm radius for the no-till circle. A design modification to the disc is required if spacings of 250 mm are encountered in practice. In such a case a cut-out sector angle of 150° is required with a sector length of 61·25 mm with an angled bevel of 35° to the sector cut-out edge. The model has wide applicability for the interactive design of discs for a range of crops.

Effect of intra-row spacing and weeding frequency on the yield performance of sesame/cowpea intercrop

Field experiments were conducted simultaneously at the Abubakar Tafawa Balewa University Teaching and Research Farm, Bauchi, and Bauchi State Agricultural Development Programme experimental sites, Bauchi (Lat. 100 17\'N 90 49’ E, and 609m above sea level), in the Northern Guinea savannah ecological zone of Nigeria during the 2002 wet season to study the response of sesame/ cowpea mixture to weeding frequency and intra-row spacings. The treatments were laid out in a randomised complete block design with three replications. The result showed that the number of capsules per plant, 100-seed weight, capsules and grain yield per hectare of sesame were significantly (P<0.05) increased by one weeding frequency only at location I. The parameters were not significantly affected by weeding frequency in location II. The capsules length, number of capsules per plant, capsules and grain yield were significantly (P<0.05) affected by intra-row spacings. The capsules and grain yield of sesame increased significantly (P<0.05) with decreasing intra-row spacing and conversely capsules length and number decreased with decreasing intra-row spacing. The number of pods of cowpea significantly (P<0.05) increased by two weeding frequencies at location I and pod yield per hectare was also increased significantly by twice weeding at location II. All the other parameters such as pod lands, seeds per pod, 100-seed weight and grain yield per hectare were not significantly affected by the treatments. The interaction between the intra-row spacings and weeding frequency were significant in affecting number of seed per capsules and 100-seed weight of sesame at location I, and number of pods and seed per pod of cowpea at location II. Intra-row spacing of 30cm and twice weedings produced the highest number of seed per capsules (68.2) and 20cm intra-row spacings with twice weeding produced the highest 100- seed weight. However, 30cm intra-row spacings with one weeding had highest number of pods (24.3) in cowpea plant and also 30cm intra-row spacing with twice weedings produced the highest seeds per pod in cowpea.

Integrating physical and cultural methods of weed control— examples from European research

Increasing concerns about pesticide use and a steadily increasing conversion to organic farming have been major factors driving research in physical and cultural weed control methods in Europe. This article reviews some of the major results achieved with nonchemical methods and strategies, especially adapted for row crops (e.g., corn, sugar beet, onion, leek, and carrot) and small-grain cereals (e.g., barley and wheat). In row crops, intrarow weeds constitute a major challenge, and research has mainly aimed at replacing laborious hand-weeding with mechanization. A number of investigations have focused on optimizing the use of thermal and mechanical weeding methods against intrarow weeds, such as flaming, harrowing, brush weeding, hoeing, torsion weeding, and finger weeding. And new methods are now under investigation such as robotic weeding for row crops with abundant spacing between individual plants and band-steaming for row crops developing dense crop stands. The strategic use of mechanical weed control methods in small-grain cereals has been another area of considerable interest. Weed harrowing and interrow hoeing provide promising results when they are part of a strategy that also involves cultural methods such as fertilizer placement, seed vigor, seed rate, and competitive varieties. Although research in preventive, cultural, and physical methods have improved weed control in row crops and small-grain cereals, effective long-term weed management in low external input and organic systems can only be achieved by tackling the problem in a wider context, i.e., at the cropping system level. Basic principles of this approach, examples of cover crop and intercropping use for weed suppression, and an application in a 2-yr rotation are presented and discussed.

Soil steaming to reduce intrarow weed seedling emergence

SummarySteaming the soil prior to crop establishment can be a very effective method of preventing weed seedling emergence on raised beds of vegetable crops. However, current mobile steaming technology for outdoor vegetables is characterized by an extremely high energy consumption and a low work rate. This has led to the concept of band‐steaming, where only a limited soil volume is steamed corresponding to the intrarow area of a row‐grown vegetable crop. Weeds growing in the intrarow area are difficult to remove by traditional non‐chemical means, usually involving substantial input of manual labour in organic cropping. This paper presents the initial results from laboratory studies with steaming a limited soil volume simulating a band. The investigations describe the relationship between maximum soil temperature achieved from soil steaming for different periods and effects seen on subsequent weed seedling emergence. The relationships obtained were generally sigmoid and could appropriately be described by a common dose–response function. Seedling emergence from natural weed species was reduced by 90% when the maximum soil temperature reached 61°C, and a further 10°C rise in temperature gave 99% reduction. Added and non‐imbibed seeds of Lolium perenne and Brassica napus generally required higher temperatures to achieve the same control level as the natural weeds in the soil samples.

Effects of cultural methods and physical weed control on intrarow weed numbers, manual weeding and marketable yield in direct‐sown leek and bulb onion

Manual weeding of intrarow weeds in direct‐sown leek and bulb onion crops grown organically can be very labour‐intensive. Four field experiments, two in direct‐sown leek and two in direct‐sown bulb onion were made in this investigation to study the effects of physical and cultural methods on intrarow weed numbers, time consumption for hand‐weeding and marketable yield parameters. The physical methods considered were: pre‐emergence flaming and harrowing, and post‐emergence hoeing close to the row (only leek) and vertical brush weeding. The cultural methods were: seed priming, slurry placement and cultivar choice (only leek). Generally, flaming plus brush weeding gave the highest intrarow weed control at 92% and 87%, respectively, in the two leek experiments and 39% (only brush weeding was effective) and 74%, respectively, in the two onion experiments. Time consumption for hand‐weeding after the different treatments was linearly related to the remaining numbers of intrarow weeds, with no significant influences of the experimental factors on the general relationship. Generally, the cultural methods had no significant influence on the effects of physical weeding in terms of their effect against intrarow weeds. They did not affect the tolerance or robustness of the crop plants against negative impact from the physical control methods. However, generally, seed priming and cultivar choice did improve yield in the leek experiments and seed priming also did so in the one experiment with onion.

Intra-row weeding with brushes on vertical axes – factors influencing in-row soil height

Interest in mechanical intra-row weed control methods has increased rapidly during recent years due to the public debate about environmental degradation and the growing request of organically grown food. However, since knowledge concerning the working principles, soil influence and weed efficacy is still limited for several of these non-chemical methods, optimum weed control has been difficult to achieve. Intra-row brush weeding experiments were conducted in loamy sand fields (dystric regosol) between 1995 and 1997 to study the influence of early plant development stage of carrots ( Daucus carota L.) and the presence of weeds on in-row soil ridge height. In the laboratory, experiments were carried out to study the influence of brush-rotation direction, forward speed, rotational speed, working depth and soil moisture on in-row soil ridge height in a sandy soil (eutric fluvisol) without carrot plants and weeds. Ridging was achieved with a brush rotation direction which results in soil being brought into the row from the inter-row space, while de-ridging is obtained with a rotation direction causing intra-row soil to be moved into the inter-row space. It was found that brush rotation direction has a crucial influence on the in-row soil ridge. In ridging mode, the soil height obtained was about 20 mm under field conditions and about 55 mm in the laboratory. Furthermore, an increase in working depth and soil moisture increases the ridge height when the brushes are operating in a ridging mode. An increased working depth and soil moisture result in a deeper furrow when the brushes are operating in de-ridging mode. In the field experiments ridge height was increased when brushing was performed in a later crop development stage in weedy fields. The application of these results in methods development work should lead to more effective ways of controlling annual weeds in various row-grown crops.