Effects Of Weed Interference Research Articles

Effect of weed interference on rice yield under elevated CO2 and temperature

Effect of weed interference on rice yield under elevated CO2 and temperature

Effect of weed interference in the production components of ‘Lucy Brown’ american lettuce

One of the main challenges faced bylettuce producers is the interference of weeds whichaffectscrop development and productivity.The aim of this study was to evaluate the occurrence of programmed weeding on the growth and production of Lucy Brown American lettuce.The experiment was carried out between March and May 2017 at the Federal University of Roraima Cauamé campus, in Boa Vista, Roraima, Brazil. The experimental design used was randomized blocks with six treatments, four replications and four lettuce plants per experimental unit. The treatments tested were as follows: 100% weed control (100% WC); weed control 5 days after transplanting (WC 5 DAT); weed control 10 days after transplanting (WC 10 DAT); weed control 15 days after transplanting (WC 15 DAT); weed control 20 days after transplanting (WC 20 DAT) and 100% without weed control (100% WWC). The following variables were evaluated: shootheight, stem height, stem diameter, number of leaves, leaf length, leaf width, root length, shoot freshweight, total fresh weight, shoot dry weightand productivity. The ‘Lucy Brown’lettuce crop must be weed-freeafter 5 days of transplanting the seedlings to avoid productivitylosses. The lack of weed control in the cultivation of ‘Lucy Brown’ lettuce causes a 71.88% decrease in its productivity.

Response of soybean and corn to halauxifen-methyl

AbstractPreplant (PP) herbicide applications are an important tool within an integrated weed management system, specifically in no-till production. An understanding of crop tolerance regarding PP applications is important for effectively integrating a new herbicide into no-till cropping systems. Twelve field trials (six in corn and six in soybean) were conducted over a 2-yr period (2018 and 2019) near Exeter and Ridgetown, ON. The purpose of these studies was to evaluate the tolerance of soybean and corn to halauxifen-methyl applied PP, PRE, or POST at the registered rate (5 g a.i. ha−1) and twice the registered rate (10 g a.i. ha−1), hereafter referred to as the 1× and 2× rate, respectively. All trials were kept weed-free throughout the growing season to remove the confounding effect of weed interference. Halauxifen-methyl applied 14 d preplant (DPP), 7 DPP, 1 DPP, and 5 d after seeding (DAS) at the 1× and 2× rates caused ≤10% visible soybean injury. In contrast, halauxifen-methyl applied POST (cotyledon–unifoliate stage, VE-VC) caused 67% to 87% visible soybean injury, a 50% to 53% reduction in height, 65% to 81% decrease in population, 56% to 67% lower biomass, and 53% to 63% decline in yield. Halauxifen-methyl applied 10 DPP, 5 DPP, 1 DPP, 5 DAS, and POST (spike–one leaf stage, VE-V1) at the 1× and 2× rate caused ≤3% visible corn injury and caused no effect on corn height or biomass. Halauxifen-methyl applied at VE-V1 at the 2× rate reduced corn yield 10%. Based on these studies, the current application restriction of 7 DPP in soybean and 5 DPP in corn is conservative and could be expanded. Expanding the application window of halauxifen-methyl would increase the utility of this herbicide for producers.

Response of Barley Genotypes to Weed Interference in Australia

Weed-competitive genotypes could be an important tool in integrated weed management (IWM) practices. However, weed competitiveness is often not considered a priority for breeding high-yielding cultivars. Weed-competitive ability is often evaluated based on weed-suppressive ability (WSA) and weed-tolerance ability (WTA) parameters; however, there is little information on these aspects for barley genotypes in Australia. In this study, the effects of weed interference on eight barley genotypes were assessed. Two years of field experiments were performed in a split-plot design with three replications. Yield loss due to weed interference ranged from 43% to 78%. The weed yield amongst genotypes varied from 0.5 to 1.7 Mg ha−1. Relative yield loss due to weed interference was negatively correlated with WTA and WSA. A negative correlation was also found between WSA and weed seed production (r = −0.72). Similarly, a negative correlation was found between WTA and barley yield in the weedy environment (r = −0.91). The results suggest that a high tillering ability and plant height are desirable attributes for weed competitiveness in the barley genotypes. These results also demonstrated that among the eight barley genotypes, Commander exhibited superior WSA and WTA parameters and therefore, could be used in both low- and high-production systems for weed management. Westminster had a superior WSA parameter. Therefore, it could be used for weed management in organic production systems. These results also implied that genotypic ranking on the basis of WSA and WTA could be used as an important tool in strengthening IWM programs for barley.

The Effect of Weed Interference, Sowing Date and Method on Phenology, Growth, Protein and Yield of Red Bean (Phaseolus vulgaris L.)

The Effect of Weed Interference, Sowing Date and Method on Phenology, Growth, Protein and Yield of Red Bean (Phaseolus vulgaris L.)

Critical period of weed control in radish (<i>Raphinus sativus</i> L.)

A field study was carried out at Crop Farm of the Eastern University of Sri Lanka to determine the critical period for weed control and the effects of weed interference in radish in the regosols of the Batticaloa District. An increasing series of the duration of weed interference and length of the weed-free periods were imposed weekly from 0 to 40 days after emergence (DAE). The beginning and the end of CPWC were based on 5, 10 and 20% acceptable yield loss levels (AYL), which were determined by fitting logistic and Gompertz equations to relative yield data, representing increasing duration of weed-interference and weed-free periods. The critical period for weed control increased to 31 days, starting at 7 days and ending at 38 days, at 5% yield loss level. At 10% and 20% yield loss levels, the CPCW decreased to 12 and 8 days respectively, starting at 18 DAE and ending at 30 DAE, and beginning at 13 DAE and ending at 21 DAE, respectively.

Weed Interference Effects on Leaves, Internode and Harvest <span style="font-size: 12.0pt; font-family: 'Times New Roman',serif"> Index of Dry Bean (<i>Phaseolus vulgaris</i> L.)

The development of appropriate weed management strategies and efficient use of herbicides relies upon understanding weed-crop interactions. A field study was carried out to assess the effect of weed interference on leaves, internode and harvest index of dry bean (Phaseolus vulgaris L.). The experiment was established under a randomized complete block design with two types of weed interference treatments: plots with weeds and plots without weeds at different time intervals (0, 10, 20, 30, 40 and 50 days after crop emergence). The sigmoid Boltzmann model was used to quantify the crop traits as influenced by weed interference. Prolonged delays in weed removal reduced gradually the number of leaves of the crop. Weed interference decreased dry weight of leaves as well, so that the lowest value of it (33.49 g plant-1) was observed in full season during weed-infested treatment. Infestation of weeds affected the length of the crop internodes. While the weed interference duration increased, the length of the internodes decreased. Harvest index was also sensitive to weed competition. As the crop was kept weed-infested from the emergence for increasing periods of time, harvest index decreased to a value of 28.01%. A significant negative correlation between total biomass of weeds and dry bean traits (number of leaves, leaves dry weight, internode length and harvest index) was observed. Therefore, weeds are able to adversely affect dry bean growth through constraining environmental resources and impairing leaves as the photosynthetic areas.

Integrating Economics in the Critical Period for Weed Control Concept in Corn

The effect of weed interference on corn yield and the critical period for weed control (CPWC) were determined in Germany and Benin. Treatments with weed control starting at different crop growth stages and continuously kept weed-free until harvest represented the “weed-infested interval.” Treatments that were kept weed-free from sowing until different crop growth stages represented the “weed-free interval.” Michaelis–Menten, Gompertz, logistic and log–logistic models were employed to model the weed interference on yield. Cross-validation revealed that the log–logistic model fitted the weed-infested interval data equally well as the logistic and slightly better than the Gompertz model fitted the weed-free interval. For Benin, economic calculations considered yield revenue and cost increase due to mechanical weeding operations. Weeding once at the ten-leaf stage of corn resulted already profitable in three out of four cases. One additional weeding operation may optimize and assure profit. Economic calculations for Germany determined a CPWC starting earlier than the four-leaf stage, challenging the decade-long propagated CPWC for corn. Differences between Germany and Benin are probably due to the higher yields and high costs in Germany. This study provides a straightforward method to implement economic data in the determination of the CPWC for chemical and nonchemical weed control strategies.

Determination of the critical period of weed control in potato (Solanum tuberosum L.)

Field studies were conducted in north-eastern Iran in 2010 and 2011 to establish the critical period of weed interference in potato (Solanum tuberosum L.) and to investigate the effects of weed interference on weed biomass. The critical period for weed control in potato based on a 5% acceptable yield loss level was calculated by fitting logistic and Gompertz equations to relative yield data. Total dry biomass and total number of weeds increased as the duration of weed infestation increased. The beginning of the critical period for weed control was 19 days after potato emergence in both years. The end of the critical period for weed control in 2011 was 22 days after potato emergence, whereas in 2010 the beginning and end of the critical period for weed control occurred simultaneously. Tuber yields of potato were reduced by prolonged delays in weed removal in both years. The practical implication of this study is that weeds must be controlled during the first 3 weeks of the crop's growing season. Such an approach would keep yield loss levels below 5%.

The Critical Period for Weed Control in Corn in Turkey

Field studies were conducted in 2001 and 2002 in the Black Sea Region of northern Turkey to determine the critical period for weed control (CPWC) in corn and the effects of weed interference on corn height. Treatments of increasing duration of weed interference and weed-free period were imposed at weekly intervals from 0 to 12 wk after crop emergence (WAE). The CPWC was determined with the use of 2.5, 5, and 10% acceptable yield loss levels by fitting logistic and Gompertz equations to relative yield data. With 5% yield loss level, the CPWC was 5 wk, starting at 0.2 WAE and ending at 5.2 WAE, which corresponded to the one- to five-leaf stage of corn. The CPWC increased to 8.9 wk, starting at 0 WAE and ending at 8.9 WAE, at the 2.5% yield loss level. At 10% yield loss level, the CPWC decreased to 1.7 wk, starting at 2.1 WAE and ending at 3.8 WAE.

The effects of nitrogen and period of weed interference on the fibre yield of kenaf ( Hisbiscus cannabinus L.) in the northern Guinea Savanna of Nigeria

The effect of weed interference on kenaf was evaluated at three nitrogen application rates. The vegetative phase was reduced but the growth and yield were increased by N (86 kg N/ha was the optimum N-rate). Plots kept weed-free had better growth and yield than the weed infested. Unchecked weed growth reduced fibre by 31.5–53.3% compared to the highest yield in the trials. The critical period of weed competition was between 3 and 6 WAS. Within this range, additional initial weed-free period of 1 day increased fibre yield by 19.1 kg/ha, while additional weed infestation period of 1 day reduced the yield by about 13.0 kg/ha.

Effect of weed interference and nitrogen on yields of a maize/rice intercrop

Field experiments were conducted in the Nigerian savanna during the 1994 and 1995 wet season toassess the influence of nitrogen application on weed interference, and determine the critical period of weed competitionin a maize/rice intercrop. Treatments were laid out in a split-plot design with three replications. Three levels of nitrogen (0, 60 and 120 kg/ha) were assigned to the main plot, and ten periods of weed interference to the sub-plots. In both seasons, N-application resulted in significant increases in grain yields of maize and rice in the plots that were kept weed-free for 6 weeks and more. Uncontrolled weed growth resulted in 83.03% and 93.85% reductions in average grain yield of maize and rice respectively. Weed control for 9 weeks after sowing at 120 kgN/ha gave the best crop yields. However, it is recommended that for resource-poor farmers, rather than keeping plots weed-free for long periods, n-application of 60 kg/ha in combination with a weed-free regime of 6 weeks after sowing will be adequate to provide a good crop yield for the intercrop.

The Effects of American Black Nightshade (Solanum americanum) Interference in Bell Pepper (Capsicum annuum)

Information about the effects of weed interference on crop yields can help growers make appropriate management decisions. Such information is particularly useful in horticultural crops such as pepper, where the number of registered herbicides is limited. Bell pepper is the second most-valuable vegetable crop grown in Florida, and American black nightshade (Solanum americanum) is one of the primary weeds in Florida pepper production. Additive experiments were conducted in 1997 in Florida to determine the effects of American black nightshade interference on bell pepper yield. One additive experiment was conducted in Gainesville, Fla., in the spring and two additive studies were conducted in the fall in Gainesville and Live Oak, Fla. A randomized complete-block design with four replications was used. Double rows of `Capistrano' peppers were transplanted into white polyethylene mulched beds with 1.22-m centers. Peppers were planted at an in-row spacing of 0.3 m. Weeds were propagated in the greenhouse in polystyrene flats and transplanted at the two-leaf stage simultaneously with the peppers. Overhead irrigation was used and monitored with tensiometers. Fertilizers and pesticides were applied based on Extension recommendations. Weed densities in the spring trial were 0, 2, 4, 8, 12, 16, and 20 plants/m2. Weed densities of 0, 0.5, 1, 1.5, 2, 3, 4, and 8 plants/m2 were planted in the fall. Crop and weed heights were recorded weekly, and fruit number, grade, and weights were recorded at each harvest. Crop and weed dry weights were obtained at final harvest. Data were subjected to analysis of variance and regression. There was an interaction by season, but there was not an interaction by location for the fall season; therefore, the fall data were combined. In all trials, S. americanum had a significant effect of bell pepper fruit yield. In the spring, the biological threshold of weed interference occurred at a density of four S. americanum/m2, but only caused a 50% yield loss. In the spring, the critical density causing 20% yield loss was calculated from the regression model to occur at 0.36 S. americanum/m2. A calculated density of 0.58 S. americanum/m2 caused 20% yield loss in the fall. Plant height and dry weight data indicated that the pepper initially grew more quickly in the fall than in the spring.

Effect of Weed Interference and Soil Nitrogen on Four Maize Hybrids

AbstractIn a mixture of crop and weeds, competition exists between plants for incident solar radiation, soil nutrients, and soil moisture. Integrated weed management manipulates cropping‐system factors such that the competitive relationship favors growth of the crop at the expense of the weeds; however, relatively few studies have been reported on the influence of cropping‐system factors on crop‐weed competition. The objectives of this study were to evaluate the impact of weed interference on the performance of four maize (Zea mays L.) hybrids and to examine the influence of soil N level on the competitiveness of the hybrids. Experiments were conducted during 1990, 1991, and 1992 at the Elora Research Station, Elora, ON, on a London loam (Aquic Hapludalf) soil that had been tile drained. Maize hybrids included an old hybrid (Pride 5, released in 1959) and three more recently released hybrids (Pioneer 3902, DEA, and Pioneer 3953). The maize hybrids were grown at 7 plants m−2 under three weed pressures and at two soil N levels. Weed pressures were established by varying the weed‐free period after planting: all season (weed free), planting to 5‐ to 7‐leaf stage of maize (medium weed pressure), and planting to 3‐ to 4‐leaf stage of maize (high weed pressure). Maize dry matter accumulation and grain yield were measured. Mean grain yield of four hybrids across 3 yr was 65% higher in the high‐N, weed‐free treatment than in the low‐N, high‐weed‐pressure treatment. The effect of weed interference on maize grain yield was higher at low than at high N. Maize hybrids responded differently to N level and weed interference; yield of the old hybrid was reduced more by low N and weed interference than yields of the new hybrids. Consequently, selection of maize hybrid and soil N level should be an integral part in the design of a weed management system.

Effects of weed interference and herbicides on nitrate and carotene accumulation in lettuce

Effects of weed interference and herbicides on nitrate and carotene accumulation in lettuce

The effect of weed interference in fodder beet yields

The effect of weed interference in fodder beet yields