Weed interference in Marandu palisade grass pastures under renewal or maintenance conditions

ABSTRACT The presence of weeds as a consequence of pasture degradation is one of the main problems facing livestock worldwide. Thus, knowing the interference aspects and the appropriate time for weed management is essential for applying a particular control measure. This research aimed to study the weed interference on the morphostructural and nutritional quality of the Marandu palisade grass in conditions of renewal or maintenance of pasture. The experiments were conducted in a randomized block design, with four replicates and treatments consisted of eight growth periods of coexistence between Marandu palisade grass and weeds (0, 15, 30, 45, 60, 75, 90, and 120 days). Forage grass was characterized at the end of the experimental period, corresponding to 120 days of coexistence, and the main morphostructural and nutritional components were determined. Under the renewal or maintenance process, the weeds interfere in the morphostructural and nutritional quality of pasture areas with Marandu palisade grass. In vitro organic matter digestibility of Marandu palisade grass is negatively influenced by weeds, suggesting that control measures for renewal or maintenance areas should be adopted within 24 and 18 days of coexistence, respectively.

Weed coexistence in carioca bean inoculated

The supply of nitrogen (N) to the carioca bean plant via inoculation with Rhizobium tropici can prevent competition with the weed community by allowing the crop to absorb the nutrient available in the soil. On this basis, this study proposes to examine the period before weed interference (PBI) in the carioca bean plant following inoculation with R. tropici or N topdressing. The experiments were carried out under field conditions during the summer seasons of 2014 and 2015. A randomized-block experimental design with four replicates was adopted, in a 2 × 11 factorial arrangement (common bean plant inoculated or topdressed with N × 11 periods of coexistence with weeds, namely, 0, 7, 14, 21, 28, 35, 42, 49, 56, 63, or 90 days after emergence [DAE]). Nitrogen topdressing increased the crop's tolerance to coexist with weeds from 6 to 14 DAE, compared with inoculation with R. tropici The PBI for the inoculated common bean plant was 24 and 16 DAE in the years 2014 and 2015, respectively. For the N-topdressed plant, the PBI was 30 DAE in both years.

REVIEW ON HERBICIDES RESISTANCE AND THEIR MODE OF ACTION

Herbicides play a vital role in the reduction of crop yield losses by the use of effective weed control and weed interference capability, their ability to improving soil conservation practices. This review covering herbicide's resistance to specific weed and the mode of action of herbicides in the crops of agronomic fields. In most countries, input-intensive agriculture is adopted. For a better understanding, it is necessary to know about the mode of action of herbicides, management, organization, classification, and weed control capacity of herbicides. On other conditions, it also contributes insight into herbicide resistance; therefore it is a big problem of sustainable agricultural management. However, more use of herbicides, pesticides, and insecticides cause resistance among the weeds and it causing injury in plants and also removes beneficial plants in agricultural fields, industries, and management of lands. This review mainly focuses on the thorough determination of different modes of action of different classes of herbicides. The mechanism of action of various herbicides is as variable as their complex composition as they concentrate on managing the susceptible weeds utilizing different biochemical means. Herbicides based on their specific mode of action, they may involve plant enzymes or a biological system. However, these herbicides may break up thus injury or disturb the uniform plant growth and development, the result affects uneven plant death. For proper weed control, it is essential to know the mode of action of specific herbicides and it is important to choose specific herbicides for a specific crop, also understood the symptoms of injury, and using proper crop management practices.

Weed Interference and Management in Cucumber (Cucumis sativus L.)

Weed interference is a major problem in cucumber farming, leading to 45–95% yield reduction. Weed control practices employed to avoid such losses are predominantly hand weeding and herbicides application. All the weed control methods used in cucumber farming have their own limitations. Hand weeding is tedious, time consuming and associated with high labor demands. Only few herbicides are registered for weed control in cucumber, and these herbicides does not provide season-long weed control when used alone, neither can they control the entire weed spectrum with diverse physiology, morphology and time of emergence. Therefore, to optimize yield, financial and environmental costs and benefits, integrated weed management approaches are advocated. A good tillage operation, use of competitive cultivars, appropriate plant population and row spacing, application of pre and post emergence herbicides are important in reducing weed density. The combination of these approaches provides effective weed control, and helps in environmental conservation. The world is now moving toward precision weed management techniques which involve remote sensing, modelling and use of robotics to control weeds. These technologies are the future of weed management in crop production and have a substantial role to play in modern cucumber production. Right selection of one or more of these techniques with reference to environmental, socioeconomic, and geographic conditions will provide effective weed control in cucumber. Future research should therefore be focused on delivering information for the implementation of these approaches.

Modeling the Effects of Elevated Temperature and Weed Interference on Rice Grain Yield

A 3-year phytotron study was conducted in Suwon (37.27°N, 126.99°E), Korea, to evaluate and model the effects of elevated temperature on rice-weed competition. The dry weight and the number of panicles in rice were the most susceptible components to weed interference during the early growth of rice, regardless of weed species, while other yield components, including the number of grains, % ripened grain, and 1000-grain weight, were more susceptible to elevated temperature. A rectangular hyperbolic model well demonstrated that rice grain yield was affected by weed interference under elevated temperature, showing that the competitiveness of late watergrass (Echinochloa oryzicola) and water chestnut (Eleocharis kuroguwai) increased under elevated temperature conditions. Quadratic and linear models well described the effects of elevated temperature on the weed-free rice grain yield and weed competitiveness values of the rectangular hyperbolic model for the two weed species, respectively. Thus, a combined rectangular hyperbolic model incorporated with the quadratic and linear models well demonstrated the effects of elevated temperature and weed interference on rice grain yield across years. Using the combined model and estimated parameters, the rice grain yields were estimated to be 58.9, 48.5, 41.3, and 35.9% of the yields under weed-free conditions for 80 plants m−2 of late watergrass and 86.8, 64.3, 51.1, and 42.3% of the yields under weed-free conditions for 80 plants m−2 of water chestnut at 1,300, 1,500, 1,700, and 1,900°C·days of accumulated growing degree days (GDD; from transplanting to flowering, 89 days), respectively. The combined model developed in this study can provide an empirical description of both the elevated temperature and weed interference effects on rice yield and can be used for predicting rice grain yields due to weed interference under future elevated temperature conditions.

Effect of Variety and Planting Arrangement on Weed Control and Yield Performance of Transplanted Aman Rice

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during June to November 2016 in order to find out the effect of variety and planting arrangement on weed control and yield performance of transplanted Aman rice. The experiment consisted of four varieties viz., Binadhan-7, Binadhan-12, Binadhan-17 and Binadhan-16 and five planting arrangement viz. 25cm × 20cm, 25cm × 15cm, 20cm × 20cm, 20cm × 15cm and 15cm × 15cm. The experiment was laid out in Split Plot Design with three replications. Results indicated that the highest weed density (90.93 m-2), weed biomass (131.87 gm-2), leaf chlorophyll content (SPAD value) (40.02), sterile spikelets panicle-1 (76.86) ,% sterility panicle-1 (28.66), grain yield (4.51 t ha-1) and straw yield (4.63 t ha-1) were obtained from Binadhan-17. The variety Binadhan-7 showed the best performance in respect of number of total tillers hill-1 (11.06), number of effective tillers hill-1 (10.12) compared to the other varieties used in the study. The highest leaf chlorophyll content (SPAD value) (36.48), plant height (99.72 cm), panicle length (22.03 cm), number of total tillers hill-1 (10.21) and number of effective tillers hill-1 (9.45) were found at 25 cm × 20 cm planting arrangement. The highest grain yield (4.31 t ha-1) was recorded from 20cm × 15cm planting arrangement. The interaction between variety and planting arrangement showed numerically higher grain yield (5.38 t ha-1) from Binadhan-7 at 20cm × 15cm planting arrangement, whereas the lowest grain yield (2.61 t ha-1) was achieved from the variety Binadhan-12 at 15cm × 15cm planting arrangement. It can be concluded that Binadhan-7 at 20cm × 15cm planting arrangement may be used for achieving the best yield with less weed interference in Aman season.

Weed interference capacity on soybean yield

Among biological factors, weeds are the most important limiting factor for crop yields, as well as increasing production costs. The aim was to determine the influence of control and coexistence of weed community on soybean crop yield and to define the period before interference, the critical period of interference prevention and the total period of interference prevention, with the comparative use of chemical and mechanical methods for weed eradication. The study was conducted in an experimental field in the 2018/2019 harvest. A randomized block with four replications was implemented as experimental design, using two methods for control. The evaluated periods were 0-10, 0-20, 0-30, 0-40, 0-50, 0-60 and 130 days after crop emergence. It was possible to observe that the use of the chemical method generated a higher yield compared to mechanical method. The period before the interference in both chemical and mechanical management was similar, approaching 20 days after crop emergence. The critical period of interference prevention was between 20-50 and 40.5 days after crop emergence in chemical and mechanical methods, respectively. The total period of interference prevention was extended to 50 and 40.5 days after crop emergence in chemical and mechanical methods, respectively. The reduction in productivity due to weed interference was 1639 kg ha-1 (55%)and 947 kg ha-1 (34.6%) in chemical and mechanical methods, respectively.