Critical Period Of Weed Control Research Articles

Effects of solarization on critical period of weed control in sesame (Sesamum indicum L.)

In order to determine the critical period of weed control in sesame, field studies were conducted during the 2014 and 2015 growing seasons in Estahban, Iran. The experiments were conducted based on factorial arrangement which involved a randomized complete block design with three replications. The first factor was conducted in two weed-infested and weed-free series until different phonological stages of sesame growth. These stages included a third pair true leaf initiation, first bud emergence, 50% opened flowers, and minor plants stop flowering, and the second factor was related to solarization which was achieved using light and dark polyethylene plastics and control. The results showed that the critical period of weed control was influenced by solarization so that solarization using light polyethylene plastic could severely shorten the critical period. Weed dry weight also gradually reduced, with increase in weed control, and the formation of first flower buds decreased significantly. Solarization did not have a great effect on the number of Convolvulus arvensis L. among the weeds, but its effect on one-year-old weeds was evident. Thus, weed infestation until the third pair true leaf initiation did not reduce sesame yield.

Estimation of Critical Period for Weed Control in Soybean on Agro-forestry System with Kayu Putih

Estimation of Critical Period for Weed Control in Soybean on Agro-forestry System with Kayu Putih

WEED INTERFERENCE IN COTTON PLANTS GROWN WITH REDUCED SPACING IN THE SECOND HARVEST SEASON

ABSTRACT Changes in row spacing may result in changes in crop and weed behavior and crop-weed competition. A study was performed to determine the periods of weed presence and weed control in cotton sown with 0.76 m spacing between planting rows. Cotton cultivar FM 993 was sown on 01/08/2010 with the aim of reaching a density of 190,000 seeds ha-1. Treatments with either weed presence or weed control during the first 0, 5, 10, 15, 22, 29, 36, 43, 50, 57, 64, 71, and 190 days of cultivation were established to determine the period prior to weed interference (PPI), total period of interference prevention (TPIP) and critical period of weed control (CPWC). The weed species with high relative importance were Amaranthus retroflexus, Bidens pilosa, Eleusine indica, Digitaria horizontalis, Alternanthera tenella, and Commelina benghalensis. Considering a maximum yield loss of 5%, the PPI was established 11 days after cotton emergence (DAE), the TPWC at 46 DAE, and the CPWC between 11 and 46 DAE, for a total duration of 35 days. Considering a maximum acceptable yield loss equal to the standard deviation for the weed-free treatment, the PPI was established at 6 DAE, the TPWC at 55 DAE, and the CPWC between 6 and 55 DAE for a total duration of 49 days

Weed management in direct seeded rice: A review

Weeds are the major biological constraint in direct seeded rice (DSR) due to the concurrent emergence of competitive weeds, absence of water to suppress weeds at the time of seedling emergence and emergence of difficult to control weeds. Strategies on weed management in direct seeded rice depend on critical period of weed control, weed flora and method to be adopted. In order to achieve the long term and sustainable management of weeds in DSR an integration of different weed management strategies like integrated weed management (IWM) are essential. The literature regarding the critical period of weed control, weed flora and different methods for the sustainable management of weeds in direct seeded rice are reviewed in this paper.

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.

Interference of a weed community in the soybean crop in functions of sowing spacing

The use of double row spacing on soybean crop is recent and consists of a new soybean production technology in Brazil and worldwide, so weed interference may be different in relation to single crop row. Thus, the objective of this work was to evaluate the weed interference in soybean crop in function of sowing spacing. The experimental design was randomized blocks and treatments were arranged in a factorial (2x16): two spacings, a double row spacing [(0.20 x 0.20m) x 0.67 m] and a conventional single row spacing (0.45 x 0.45m) and sixteen periods of weed management, being eight control periods in which soybean was kept free of weeds by increasing periods of 7; 14; 21; 28; 35; 42; 49 and 145 days after emergence and eight coexistence periods, when the crop was maintained in the presence of the weed community for the same periods. The Critical Timing of Weed Removal (CTWR) was lower in the double row spacing, with eight days, compared with single spacing that was of 18 days. The Critical Weed-Free Period (CWFP) was of 36 and 31 days for double and single row spacing, respectively, and the emergence of weeds after this period did not cause damage to the productivity, but the Critical Period of Weed Control (CPWC) was higher in double row spacing (28 days) compared to the single row, which was of 13 days. The spacing in double row had a higher grain yield than the spacing in single row.

Assessing the Potential for Fluridone to Reduce the Number of Postemergence Herbicide Applications in Glyphosate-Resistant Cotton

With the evolution of glyphosate-resistant weeds, cotton producers now rely on multiple applications of soil-residual herbicides tank-mixed with postemergence (POST) herbicides. However, the current soil-residual herbicides represent a relatively low number of herbicide mechanisms of action (MOAs), with the same few MOAs being utilized year after year. Therefore, it is important to introduce new MOAs to slow the likelihood of further resistance development. A field experiment was conducted in 2012 and 2013 to determine if fluridone, a bleaching herbicide currently not used in any agronomic cropping system, applied preemergence (PRE) would provide effective season-long control of Palmer amaranth as well as reduce the number of POST applications throughout the season. Fluridone PRE at 224, 336, and 448 g ai ha-1 did not eliminate the need for POST herbicides for Palmer amaranth control in cotton in either year. Fluridone, regardless of rate, provided comparable control to fluometuron in 2012; however in 2013, fluometuron provided less control than fluridone. Although moderate season-long control was observed in 2013, greater seed cotton yields were obtained in 2013 than in 2012, which is likely a result of greater control during the critical period for weed control. Based on this experiment, fluridone will not provide effective season-long Palmer amaranth control in the absence of a multiple POST-herbicide program.

Periods of weed interference in maize crops cultivated in the first and second cycles

The interference of weeds in maize production may be reflected in grain yield losses that vary as a function of the density, stage and degree of aggressiveness of the species present. In the agricultural ecosystem, crops and weeds demand light, water, nutrients and space, which are frequently not available in sufficient quantities, leading to competition. The aim of this work was to determine the period of interference of weed plants, in particular of naked crabgrass (Digitaria nuda) on maize crop in the first and second harvest. The treatments were defined as increasing periods of coexistence and increasing control of weed community (7, 14, 21, 28, 35, 42, 49, and 56 days), two more controls, a control including one with weed control until the end of the culture cycle and another with coexistence until the harvest. For each period, were evaluated the stand of maize plants, length of ear, number of grains per row, number of rows per ear, cob, 100-grain weight, and grain productivity. The data obtained were subjected to analysis of variance using the F test, with average treatments compared using Tukey’s test at 5% probability. Crop productivity was evaluated by means of regressions, the critical periods of interference were estimated. The critical timing of weed removal was 25 days for both harvests. The critical weed free period was 54 and 27 days for the first and second harvest respectively. For the conditions of the first and second harvest, the critical period of weed control was of 29 and 2 days respectively.

Determination of Critical Period of W eed Control in Kala Zeera ( Buniumpersicum bios ) in Gurez V alley of Kashmir

Critical P eriod of W eed Control (CPWC) is the period in crop growth cycle during which w eeds must be controlled to prev ent unacceptable yield losses.T w o sets of treatments w ere imposed to represent both increasing duration of w eed interference and the length of the w eed-free period measured after germination. The first set of treatments consists of increasing duration of w eed interference by delaying w eed control from the time of crop emergence up to predetermined w eek (w eedy up to 2,4,6,8,10 and 12 w eeks after germination (W AG) of Kala Zeera ) . The second set of treatments established six lev els of increasing length of the w eed-free period (w eed free upto 2, 4, 6, 10 and 12 W AG). Besides tw o controls (W eed free and w eedy check). These comprised of 14 treatments which w ere laid out in randomized complete block design with three replication. It w as rev ealed that v ariation in Kala zeera seed yield due to w eeds is upto 88% and yield gets reduced as low as 48 % in w eedy check plots. Early w eed competition does not hav e hav e profound influence in Kala zeera crop.According to av erage data of tw o y ears inv estigation, it w as concluded that W eeds emerging betw een 6-12 W AG appear to be most detrimental to Kala zeera growth and yield and hence qualifies critical stage for w eed competition.

Critical Period for Weed Control in Grafted and Nongrafted Fresh Market Tomato

Field experiments were conducted to determine the critical period for weed control (CPWC) in nongrafted ‘Amelia’ and Amelia grafted onto ‘Maxifort’ tomato rootstock grown in plasticulture. The establishment treatments (EST) consisted of two seedlings each of common purslane, large crabgrass, and yellow nutsedge transplanted at 1, 2, 3, 4, 5, 6, and 12 wk after tomato transplanting (WAT) and remained until tomato harvest to simulate weeds emerging at different times. The removal treatments (REM) consisted of the same weeds transplanted on the day of tomato transplanting and removed at 2, 3, 4, 5, 6, 8, and 12 WAT to simulate weeds controlled at different times. The beginning and end of the CPWC, based on a 5% yield loss of marketable tomato, was determined by fitting log-logistic and Gompertz models to the relative yield data representing REM and EST, respectively. In both grafted and nongrafted tomato, plant aboveground dry biomass increased as establishment of weeds was delayed and tomato plant biomass decreased when removal of weeds was delayed. For a given time of weed removal and establishment, grafted tomato plants produced higher biomass than nongrafted. The delay in establishment and removal of weeds resulted in weed biomass decrease and increase of the same magnitude, respectively, regardless of transplant type. The predicted CPWC was from 2.2 to 4.5 WAT in grafted tomato and from 3.3 to 5.8 WAT in nongrafted tomato. The length (2.3 or 2.5 wk) of the CPWC in fresh market tomato was not affected by grafting; however, the CPWC management began and ended 1 wk earlier in grafted tomato than in nongrafted tomato.

The critical period for weed control in three corn (Zea mays L.) types

Knowledge of the crop-weed competition period is vital for designing effective weed management strategies in crop production systems. Field studies were conducted at the Agricultural Research Institute, Kahramanmaras, Turkey in 2013 and 2014 to determine the critical period for weed control (CPWC) in three corn (Zea mays L.) types (field corn, popcorn, and sweet corn). A four parameter log-logistic model described the relationship between relative crop yield to both increasing duration of weed interference and length of weed-free periods. The relative yield of corn was influenced by duration of weed-infested or weed-free period, regardless of corn types. Increasing periods of weed interference significantly reduced corn yields in both years. In field corn, the CPWC ranged from 175 to 788 growing degree days (GDD) in 2013 which corresponded to V2–V12 growth stages, and 165–655 GDD (V1–V10 growth stages) in 2014 based on the 5% acceptable yield loss (AYL) level. In popcorn, the CPWC ranged from 92 to 615 GDD (VE–V10 growth stages) in 2013 and 110–678 GDD (V1–V10 growth stages) in 2014. In sweet corn, the CPWC ranged from 203 to 611 GDD in 2013 (V2–V10 growth stages) and 182–632 GDD (V2–V10 growth stages) in 2014. The practical implication of this study is that weed management should be initiated around V1 stage and maintained weed-free up to V12 stage in all corn types to prevent yield losses greater than 5%. These findings could help corn producers improve the cost effectiveness and efficacy of their weed management programs.

Optimal planting date, row width, and critical weed-free period for grain amaranth and quinoa grown in Ontario, Canada

The popularity of grain amaranth and quinoa is growing in Ontario, increasing the interest in their cultivation. Two experiments were conducted in southern Ontario in 2013 and 2014 to evaluate optimal planting date (every two weeks from early May to late July), row width (38 or 75 cm), and critical weed-free period (the component of the critical period of weed control that defines the number of days that the crop must remain weed-free to prevent yield loss) in each crop. Grain amaranth and quinoa both reached physiological maturity and produced yields when planting dates ranged from mid-May to late-June. When either crop was seeded in July, yields decreased by more than 50% and the crop did not always reach maturity before the first frost. While row width did not have an impact on yield, it is advisable to grow the crops in wider rows (75 cm) to facilitate weed control early in the growing season (up to 30 d after emergence (DAE)). The critical weed-free period was 24 and 16 DAE for grain amaranth and quinoa, respectively, after which yields were maintained at 95% of the weed-free control. Based on these data, both crops could easily be integrated into the normal cropping rotations found in southern Ontario.

Weed Competition Periods Affect Grain Yield and Nutrient Uptake of Black Seed (Nigella Sativa L.)

The combination of the relatively open plant canopy and slow growth, especially at early growth stages, results in lower competitiveness of black seed (Nigella sativa L.) than weeds. Thus, weed interference is known as an important factor affecting black seed yield. Therefore, to determine the critical period of weed control and its effects on nutrients uptake of black seed field experiments were conducted in 2011 and 2012. Two quantitative series of weed removal treatments including weed-infested and weed-free treatments were implemented from black seed emergence to maturity harvest. To determine critical period of weed control, plots were weed-infested or weed-free for 0, 14, 28, 42, 56, 70 days after emergence, in weed-infested and weed-free treatments, respectively. The results revealed that N, P and K contents in weed tissues significantly increased with increasing weed-infested periods during both years of the experiment. The reduction in grain and oil yield due to longer periods of weed-infested conditions or shorter periods of weed-free conditions were accompanied by simultaneous reduction of N, P and K uptake in black seed grains and tissues. Overall, N, P and K contents in weed tissue were found to be 1.8 to 2 times higher than that of black seed. It was concluded that 58 or 49 days weed-free periods are required to avoid yield loss (above 5% or 10%) in black seed.

Primena modela za izračunavanje gubitaka prinosa gajenih biljaka u zavisnosti od sastava, brojnosti i vremena suzbijanja korova

Program of Integrated Weed Management (IWM) involves a combination of different methods (agrotechnical, mechanical, biological, genetic and chemical) for efficient and eco­nomical weed control. Successful implementation of the concept of integrated weed control is not possible without knowledge about characteristics of weeds and crop, and weed emergence dynamics. The yield loss of cultivated plants depends of many factors, of which the most im­portant is crop density, the number of weeds and soil fertility. The dependence of yield loss can be explored through the understanding effects of one weed species and different weed species ('mixed infestation') to yield loss. Research can be empirical and mechanistic, and the results of these studies can be used to predict yield loss, at an acceptable level of accuracy through the use of mathematical models. It is important to determine which is the optimal time to remove weeds. One of the first steps in the conception of the integrated weed control is to identify the critical period for weed control (CPWC). Knowing of this period is used to make decisions about the need for control, time of control, and all depending on the specific crop. A critical period for weed control is defined as the time period between two stages of crop growth within which it is necessary to perform the weed control, in order to prevent yield loss greater than 5%.

English

Right timing of weed control is one of the most important challenges farmers in North Benin are facing. Weed infestation rates in maize production in the dry savanna zone in Northwestern Benin are often very high causing significant yield losses. The aim of the study was to determine reasons for late weed control in maize, which is the dominating crop in this area. A survey was conducted among 100 representative farmers in Northwestern Benin. Descriptive statistical methods were used to calculate proportion, frequency or mean of socio-economic data assessed. The descriptive analysis aimed to select relevant variables for regression analysis. Regression models were applied to identify reasons for low weed control efficacy in maize. The results revealed that poor weed control in maize often occurred in small family farms with diverse cropping systems. These famers are often in conflict to control weeds in several crops simultaneously. Weeds are mostly removed by hand-hoeing. Due to their economic situation, they have usually no access to hired labor. Maize yields in the surveyed area could be increased if farmers had access to credit services (1), if farmers would get better recommendations of critical periods of weed control (2) and if more efficient weed control methods would be available to suppress weed populations (3). Key words: Manual weeding, critical period of weed control, small producer, crop diversification, credit access facilities.

The Critical Period for Weed Control (CPWC) in Potato (<i>Solanum tuberosum</i> L.)

Accurate assessment of crop-weed control period is an essential part for planning an effective weed management for cropping systems. Field experiments were conducted during the seasonal growing periods of potato in 2012 and 2013 in Kayseri, Turkey to assess critical period for weed control (CPWC) in potato. A four parameter log-logistic model was used to assist in monitoring and analysing two sets of related, relative crop yield. Data was obtained during the periods of increased weed interference and as a comparison, during weed-free periods. In both years, the relative yield of potato decreased with a longer period of weed-interference whereas increased with increasing length of weed free period. In 2012, the CPWC ranged from 112 to 1014 GDD (Growing Degree Days) which corresponded to 8 to 66 days after crop emergence (DAE) and between 135-958 GDD (10 to 63 DAE) in the following year based on a 5% acceptable yield loss. Weed-free conditions needed to be established as early as the first week after crop emergence and maintained as late as ten weeks after crop emergence to avoid more than 5% yield loss in the potato. The results suggest that CPWC could well assist potato producers to significantly reduce the expense of their weed management programs as well as improving its efficacy.

Critical period for weed control in field pea

Field studies were conducted during 2008-09 and 2009-10 at Hisar, India to assess the effect of weed competition on crop growth and yield of field pea. Weed density increased up to 60 days and then decreased at later stages of crop growth. Seed yield of field pea was decreased by 50% when weeds were allowed to compete for the entire season. The critical period for weed control was 21-63 days in year 1 and 20-70 days in year 2 to achieve 95% of weed-free yield. It is therefore concluded that, to minimize yield loss due to weed competition in field pea, weed control measures should be targeted to avoid weed competition between 20-70 days after sowing.

Row spacing impacts the critical period for weed control in cotton (Gossypium hirsutum)

The knowledge on the critical crop-weed competition period is important for designing an efficient weed management program. Field studies were conducted in 2012 and 2013 at the Agricultural Research Institute, Kahramanmaras, Turkey to determine the effects of three row spacing (50, 70 and 90 cm) on the critical period for weed control (CPWC) in cotton. A four parameter logistic equation was fit to data relating relative crop yield to both increasing duration of weed interference and length of weed-free period. The relative yield of cotton was influenced by the duration of weed-infested or weed-free period, regardless of row spacing. In cotton grown at 50 cm row spacing, the CPWC ranged from 117–526 growing degree days (GDD) (V2–V11 growth stages) in 2012 and 124–508 GDD (V2–V10) in 2013 based on the 5% acceptable yield loss level. At 70 cm row spacing, the CPWC ranged from 98–661 GDD in 2012 (V2–V13) and 144–616 GDD (V2–V12) in 2013. At 90 cm row spacing, the CPWC ranged from 80–771 GDD in 2012 (V1–V14) and 83–755 GDD (V1–V14) in 2013. In order to obtain a 95% weed-free yield, the weed management should start at 16 days after crop emergence (DAE) and continued until 52 DAE (V2–V11) for crops grown in 50 cm row spacing, 15 and 60 DAE (V2–V13) for 70 cm row spacing and 11 and 67 DAE (V1–V14) for crops grown in 90 cm row spacing. This suggests that cotton grown in narrow row spacing (50 cm) had greater competiveness against weeds compared with wider row spacing (70 and 90 cm). Cotton growers can benefit from these results by improving cost of weed control through better timing of weed management.

DETERMINATION OF CRITICAL PERIOD OF WEED COMPETITION AND EFFECT OF PLANT DISTRIBUTION PATTERNS ON WEEDS AND SESAME CROP (SESAMUM INDICUM L.) PRODUCTIVITY

four field experiments were conducted at Agricultural Research Station of Ismailia governorate, Agricultural Research Center, Egypt, in two studies during the two consecutive summer seasons of 2013 and 2014. First study (two experiments) was carried out to determine the critical period for weed control (CPWC) and its effect on weed infestation, sesame yield and its components. Each experiment included twelve treatments of weed removing after 3, 5, 7, 9 and 11 weeks and for the whole season; and weed interference with sesame plants for 3, 5, 7, 9 11 weeks and for the whole season. Second study (another two experiments) was done to evaluate the effect of planting distances (pd), planting distribution pattern and hand hoeing on weed infestation and on sesame yield and its component. The main findings of the first study was that the predicted CPWC in presence of mixed weed populations was found to expand from the 3rd to 11th weeks after planting (WAP). Existence of weed species infestation at fresh weight of 16.7 and 19.4 ton per faddan for whole seasons caused a highly significant reduction of sesame yields which estimated by 75.6% and 77.5% per faddan for first and second seasons respectively, compared to those obtained from weed free treatment for the whole seasons. The weed-free for the whole season treatment, gave significant increase in plant height, length of fruiting zone, number of capsules per plant and total seed yield per Fadden in both seasons. In the second study, planting distribution patterns at 10, 20 and 30 cm with a seeding rate of 1, 2 and 3 seeds per hill respectively, with respecting the recommended planting rate of 70000 plants per faddan revealed that planting of sesame at 10 cm and one seed per hill caused a significant reduction in the number and fresh weight of weeds and has resulted in highest sesame plant height, the number of capsules per plant and seeds yield per faddan in both seasons, compared to either of 20 or 30 cm distribution patterns, or to the weedy check in both seasons. These results demonstrated that planting distance at 10 cm with single plant per hill integrated with hand hoeing twice at 15 and 30 days after planting (DAP) are crucial for the highest sesame yield production per faddan

Nitrogen application influenced the critical period for weed control in cotton

The critical knowledge of crop-weed competition period is important for designing weed management strategies in cropping systems. Field experiments were conducted in 2012 and 2013 growing seasons at the Agricultural Research Institute, Kahramanmaras, Turkey to determine the effect of three nitrogen (N) rates (0, 150 and 300 kg N ha−1) on the critical period for weed control (CPWC) in cotton. A four parameter log-logistic model was fit to the two sets of relating relative crop yield to data obtained from increasing durations of weed interference and lengths of weed-free period. In both the years and regardless of the N application rate, the relative yield of cotton decreased with increasing duration of weed-interference and increased with increasing duration of weed-free period. The application of N fertilizer delayed the beginning of the CPWC in cotton. At the 0 kg N ha−1, the CPWC ranged from 44 to 537 GDD (growing degree days) (7–51 days after crop emergence [DAE]) in 2012 and 87–605 GDD (14–57 DAE) in 2013 based on the 5% acceptable yield loss. At the 150 kg N ha−1, the CPWC ranged from 124 to 597 GDD (18–56 DAE) in 2012 and 183–551 GDD (22–49 DAE) in 2013. Depending on the N application rate, weed-free conditions need to be established as early as one week after crop emergence and maintained as late as eight weeks after crop emergence to avoid more than 5% loss in cotton yield. These findings could help cotton producers improve the cost effectiveness and efficacy of their weed management programme under different N application rates.