Weed-free Plots Research Articles

Response of onion (Allium cepa L.) to plant population and weed control methods in a chicken weed (Portulaca quadrifida L.) infested field In Sudan Savanna, Nigeria

Chicken weed is a significant weed in India and it occurs under onion cultivated field at Birnin Kebbi in the Sudan Savannah, Nigeria. On-farm experiment was conducted at Birnin Kebbi during the 2017/2018 and 2018/2019 dry season to evaluate the effect of plant population and weed control methods on the management of chicken weed (Portulaca quadrifida) alongside other weeds in onion field. The experiment consisted of three plant populations (500,000, 333,333 and 250,000 plants per hectare) and twelve weed control methods (Pendimethalin at 1.0 kg a.i. ha-1, + 1Hw; pendimethalin at 1.5 kg a.i. ha-1 + fluazifop-p-butyl at 2.0 kg a.i. ha-1; pendimethalin at 2.0 kg a.i. ha-1; butachlor at 2.0 kg a.i. ha-1 + 1Hw; butachlor at 2.8 kg a.i. ha-1 + oxyfluorfen at 1.0 kg a.i. ha-1; butachlor at 3.6 kg a.i. ha-1; fluazifop-p-butyl at 2.0 kg a.i. ha-1; oxyfluorfen at 1.0 kg a.i. ha-1 + 1Hw; hoe weeding at 3 (WAT); hoe weeding at 3 and 6 WAT; weed free and weedy check). The experiment was laid out in a randomized complete Block design replicated three times. Results showed that weed, growth and yield parameters were not significantly affected by plant population. Pendimethalin at 1.5 kg a.i. ha-1 + fluazifop-p-butyl at 2.0 kg a.i. ha-1 and weed free plots consistently recorded the lowest weed cover and highest weed control efficiency. Butachlor at 2.0 kg a.i. ha-1 + 1 Hw recorded the lowest crop injury score. Increase in plant height was observed when pendimethalin at 1.0 and 1.5 kg a.i. ha-1 + 1 Hw and fluazifop-p-butyl at 2.0 kg a.i. ha-1 respectively was applied, while application of pendimethalin at 2.0 kg a.i. ha-1 and butachlor at 2.0 kg a.i. ha-1 + 1 Hw recorded highest number of leaves and leaf area. Cured bulb and marketable bulb yield were greater with the use of pendimethalin and butachlor at 1.0 and 1.5 kg a.i. ha-1 + 1 Hw and the pooled data respectively. Application of pendimethalin and butachlor at the rate of 1.0 and 2.0 kg a.i. ha-1 followed by 1 Hw at 6 WAT respectively was therefore recommended for the control of chicken weed alongside other weed species in the ecology

Effect of different doses of fomesafen + fenoxaprop + chlorimuron-ethyl (ready-mix) against weeds in soybean

Field experiment was conducted at Research Farm, Department of Agronomy, Jawaharlal Nehru Krishi Vishwa Vidyalaya, Jabalpur (MP) during (rainy season) Kharif 2018. Ten weed control treatments comprising of five doses of ready-mix formulation (ready-mix) of fomesafen + fenoxaprop + chlorimuron-ethyl (187, 234, 280, 327 and 584 g/ha), imazethapyr (100 g/ha) alone and combined with fluazifop-p-butyl + fomesafen (222 g/ha) as early post-emergence (PoE), hand weeding (HW) twice at 15 and 30 days after seeding (DAS), weed free and weedy check were laid out in randomized complete block design with three replications. The fomesafen + fenoxaprop + chlorimuron-ethyl (ready-mix) 327 g/ha as early post-emergence (early PoE) recorded lower weed density and biomass, with 98.0 and 99.0% weed control efficiency (WCE) of monocot and dicot weeds, respectively. The higher seed yield (1.91 t/ha) was recorded with fomesafen + fenoxaprop + chlorimuron-ethyl 327 g/ha and it was at par with HW twice (2.11 t/ha) and weed free plots (2.15 t/ha). The highest dose of fomesafen + fenoxaprop + chlorimuron-ethyl (584 g/ha) was found effective against monocot and dicot weeds but caused phytotoxicity on crop and reduced seed yield marginally (1.73 t/ha).

Influence of Different Types of Organic Manure and Weeding Frequencies on Weed Parameters and Leafy Yield of Jute Mallow (Corchorus olitorious)

Field trials were carried out during 2018 and during 2019 dry season period at Federal College of Forestry and Mechanization Afaka Kaduna, located between latitude 10° 35”N and longitude 007° 21”E at altitude 644 m above sea level, to determine the influence of different types of organic manure and weeding frequencies on weed parameters and leafy yield of jute mallow (Corchorus olitorious). The experimental treatments consists of ten combinations of poultry manure + weed free, cow dung + weed free, goat dropping + weed free, poultry manure + weeding at 2 WAT, cow dung + weeding at 2 WAT, goat dropping + weeding at 2 WAT, poultry manure + weeding at 4 WAT, cow dung + weeding at 4 WAT, goat dropping + weeding at 4 WAT and no organic manure application + no weeding which were laid out in a randomize complete block design (RCBD) and replicated 3 times. The weed parameters and yield component observed and measured were common weeds that infested the plots, weed dry weight, weed control index, weed competition index and cumulative leaf yield at 2, 4, 6 WAT and at harvest. The result revealed that the plots were highly infested with three major weed species namely Synedralla nodiflora Gaertn, Gomphrena celosiodes and Cyperus esculentus. Highest weed completion index was obtained from poultry manure + weeding at 2 WAT while the least weed competition index was observed with application of cow dung + weeding at 4 WAT and goat dropping + weeding at 4 WAT respectively. The result also revealed that application of poultry manure + weed free plots had the highest mean cumulative yield value of 236 kg per hectare, closely followed by plots with application of poultry manure + weeding at 4 WAS (223 kg) per hectare compared to the control treatment that plots that have no organic manure + no weeding that had the least mean cumulative yield value of 111 kg per hectare. The study concludes that the use of poultry manure plus weed free gave the best yield of jute mallow compared to other types of organic manure and the control. It is therefore recommended that farmers in the study area should adopt the use of poultry manure plus weed free treatment to obtain bumper harvest from cultivation of jute mallow (Corchorus olitorious).

Herbicide-Based Weed Management for Soybean Production in the Far Eastern Region of Russia

This study was conducted to establish a weed management system based on the sequential application of pre-emergence (PRE) and post-emergence (POST) herbicides for soybean production in Primorsky krai. Field experiments were conducted for two years in a field located in Bogatyrka, Primorsky krai, Russia (N43°49′, E131°36′). No herbicide application resulted in significant soybean yield loss, 0.03–0.3 t ha−1, which is more than 91.6% yield loss compared with that of the weed-free plot. The PRE application of acetochlor showed good weed control efficacy (greater than 90% weed control) with acceptable soybean safety (less than 10% soybean damage), while the other PRE herbicides performed poorly in terms of weed control. The POST application of bentazon + acifluorfen, bentazon, and imazamox at 30 days after soybean sowing (DAS) showed good weed control efficacy with good soybean safety. Neither the PRE nor POST application alone showed a sufficient soybean yield protection, resulting in much lower soybean yield than the weed-free plot. The sequential application of acetochlor (PRE), followed by either bentazon + acifluorfen (POST) at 30 DAS in 2012 or bentazon + imazamox (POST) at 60 DAS in 2013 showed the best performance in soybean yields, 1.7 t and 1.9 t ha−1, respectively, provided with 724.5 US$ and 1155.6 US$ ha−1 of economic returns. For alternative PRE herbicides of acetochlor, which is now banned, our tests of the sequential application of S-metolachlor with other POST herbicides and the sole application of other PRE herbicides revealed that S-metolachlor and clomazone could also be considered. Our results thus demonstrate that the sequential applications of PRE and POST herbicides should be incorporated into the weed management system for soybean production in Primorsky krai, Russia.

Teosinte (Zea mays ssp parviglumis) growth and transcriptomic response to weed stress identifies similarities and differences between varieties and with modern maize varieties.

Transcriptomic responses of plants to weed presence gives insight on the physiological and molecular mechanisms involved in the stress response. This study evaluated transcriptomic and morphological responses of two teosinte (Zea mays ssp parviglumis) (an ancestor of domesticated maize) lines (Ames 21812 and Ames 21789) to weed presence and absence during two growing seasons. Responses were compared after 6 weeks of growth in Aurora, South Dakota, USA. Plant heights between treatments were similar in Ames 21812, whereas branch number decreased when weeds were present. Ames 21789 was 45% shorter in weedy vs weed-free plots, but branch numbers were similar between treatments. Season-long biomass was reduced in response to weed stress in both lines. Common down-regulated subnetworks in weed-stressed plants were related to light, photosynthesis, and carbon cycles. Several unique response networks (e.g. aging, response to chitin) and gene sets were present in each line. Comparing transcriptomic responses of maize (determined in an adjacent study) and teosinte lines indicated three common gene ontologies up-regulated when weed-stressed: jasmonic acid response/signaling, UDP-glucosyl and glucuronyltransferases, and quercetin glucosyltransferase (3-O and 7-O). Overall, morphologic and transcriptomic differences suggest a greater varietal (rather than a conserved) response to weed stress, and implies multiple responses are possible. These findings offer insights into opportunities to define and manipulate gene expression of several different pathways of modern maize varieties to improve performance under weedy conditions.

Effect of different integrated weed management practices on weed dynamics and growth attributes of Mungbean (Vigna radiata L. Wilczek)

A field study was conducted in kharif season of 2014 and 2015 on Mungbean to evaluate the effect of different weed management practices upon the growth and yield attributes of Mungbean at Agriculture Research Station, Badnapur. The soil was clayey in texture, moderate in available nitrogen, low in available phosphorus, high in available potassium and moderately alkaline in reaction. The field experiment was laid out in randomized block design with nine treatments which include one pre emergence herbicides Pendamethalin (30%E.C.) @ 0.75 kg a.i. ha-1, two post emergence herbicides Quizalofop ethyl (5%E.C.) @ 50 g a.i. ha-1, Imazethapyr (10%S.L.) @ 40 g a.i. ha-1 with solely application and applied with combination of each other, one cultural treatment (HW: 10, 30, 25 DAS) with control. Sowing was date on 11th July 2014 by dibbling method at 30 x 10 cm spacing. Among the weed free plot (2HW-10 and 30 DAS) (T9) significantly higher grain yield (994.33 kg ha-1) over all of the treatment. The second best treatment was (T7) T2 + Hand weeding at 25 DAS (951.67 kg ha-1) seed yield ha-1 followed by (T4) T2 + Quizalofop ethyl @ 50g ha-1 POE at 15 DAS recorded (904.33 kg ha-1) seed yield ha-1. Lowest seed yield was recorded by (T8) weedy check treatment (542.33 kg ha-1) seed yield.

Sugar beet varieties tolerant to ALS-inhibiting herbicides: A novel tool in weed management

The main aim of the present study was to evaluate benefits of the new technology of sugar beet varieties tolerant to foramsulfuron (FSN) + thiencarbazone-methyl (TCM) herbicides commercialised as Conviso® Smart (four weed management strategies were tested) compared to conventional herbicides (two weed management strategies). Plot-field trials were carried out in Prague (Czech Republic) in 2016–2019. Efficacy on Chenopodium album L., Amaranthus retroflexus L., Echinochloa crus-galli (L.) P. B., Abutilon theophrasti Med. and weed beet were evaluated.FSN + TCM controlled all tested weeds very well (efficacy more than 97%) in case of split application with an oil adjuvant. When only one application of FSN + TCM was performed in dry weather conditions, efficacy on C. album and A. theophrasti was insufficient (less than 90%). FSN + TCM fully controlled weed beet at all tested weed management strategies in all experimental years and a residual activity of this herbicide did not allow new plants to emerge. The conventional tank-mixes (TM) controlled C. album and A. retroflexus well (efficacy more than 96%). Efficacy of conventional TM on E. crus-galli ranged from 78 to 100%. Efficacy on A. theophrasti was affected by herbicides used and weather conditions, but did not exceed 92% with either of the conventional TM. The tested conventional herbicides were not able to control weed beet.A relatively high reproductive ability of C. album and A. retroflexus (13,000–157,000 and 7000–10,000 seeds m−2, respectively) was seen in plots where these weeds were not fully controlled. The seed production of A. theophrasti was relatively low (not exceeded 25,000 seeds m−2). However, mature seeds were present in most plots. The reproductive ability of E. crus-galli in sugar beet canopy was much lower (200 - 1800 seeds m−2) compared to the other species, due to its late emergence. Weed beet competed with sugar beet only when other weeds were controlled and weed beet survived the treatment. In these plots, fruit production of weed beet was significantly higher (5000–75,000 fruits m−2).The highest sugar beet yields (78–100 t ha−1) were in weed-free plots or plots with a low weed infestation (split application of FSN + TCM). A significantly lower yield (45–52 t ha−1) was recorded when C. album and A. theophrasti were not sufficiently controlled. In plots where the weed beet was the only weed not controlled, sugar beet yield ranged from 23 to 61 t ha−1. The lowest sugar beet yield (less than 10 t ha−1) was observed in untreated plots where mainly C. album and A. theophrasti predominated. There was a negative relationship between sugar beet yield and total weed biomass.

IIntegrated weed control in corn (Zea mays L.) through combinations of seed priming and reduced dosages of various commonly used herbicides

Field experiments were conducted during 2017 and 2018 to evaluate the efficacy of herbicides NICOSULFURON and EPTC alone or in combination with seed priming on weed control and corn yield. NICOSULFURON (80 g a.i. ha‒1) was applied at four- to six-leaf stage of corn as post-emergence and EPTC (4920 g a.i. ha‒1) applied as pre-plant incorporation (PPI). Among the herbicide treatments, the lowest total weed biomass was observed in plots treated with prime + EPTC PPI at ½ recommended dose followed by one hand weeding and NICOSULFURON applied at label recommended dose or 33% reduced dose integrated with seed priming, while the least performance was observed in plots treated with EPTC alone. Weed biomass reduction by seed priming alone was 32% (average of two years) compared with control. The highest grain and biological yield were observed in weed free plots and hand hoeing three times, followed by prime + EPTC followed one hand-hoeing and NICOSULFURON at recommended rate and at 33% reduced dose integrated with seed priming. The present study demonstrated that seed priming can improve the weed competitiveness of corn.

Effect of weeding frequency and interval on onion (Allium cepa L.) bulb yield grown under irrigation condition at Arba Minch, Southern Ethiopia

Field experiment was conducted at Arba Minch during 2017 and 2018 cropping seasons under irrigation condition to determine the effect of weeding frequency and interval on weeds and bulb yield of onion. The experiment was laid out in factorial arrangement in randomized complete block design with three replications and comprised of 18 treatments: four weeding frequencies (2, 3, 4 and 5 times) and four weeding intervals (at 10, 13, 17 and 25 days) compared with weedy and weed-free checks. Results showed that all the parameters considered in this study were significant (p<0.05) among the treatments. The lowest weed density (27.33 m-2 in 2017 and 24.26 m-2 in 2018) and dry weed biomass weight (0.83 t ha-1 in 2017 and 0.82 t ha-1 in 2018) were recorded in the weed free check without statistical difference with the values received from weeding interval at 10, 13 and 17 for four and five times weeding frequency in both cropping seasons. The highest weed control efficiency (83.70% in 2017 and 82.82% in 2018) was computed in the weed free plots. In the 2017 cropping season, the highest marketable bulb yield (32.8 t ha-1) was recorded in the weed free check, which was statistically similar with the result obtained in four and five times weeding frequency at 10, 13 and 17 days weeding interval. Similar trends were observed during 2018 cropping season. Thus, three to five times frequency of weeding at 10 days weeding interval could be recommended in the study area for efficient weed management and optimization of the bulb yield and profits in onion production.

Timing of weed management and yield penalty due to delayed weed management in soybean

Background: Weed interference is a major limiting factor for economically viable soybean production. Appropriate timing of weed management would enable farmers to make more efficient use of resources for weed management. Objective: The objective of this study was to determine the critical period for weed competition and appropriate timing of weed management for optimum yield of soybean. Methods: The treatments consisted of periods of weed infestation and weed removal for the first 14, 28, 42 and 56 days after sowing (DAS), and till harvest in a randomized complete block design with three replications in 2016 and 2017. Results: Soybean yields in both years ranged from 914-945 kg ha-1 with no weed control to 1,984-2,127 kg ha-1 in the weed-free plots; a yield loss of 53-56. Weed infestation for the first 14 DAS had no detrimental effect on growth and yield of soybean provided the weeds were subsequently removed. Increasing period of weed interference from 14 to 42 DAS resulted in a steady decline in growth and yield of soybean. Yield losses equivalent of 32-37 kg ha-1 resulted for each day that weed control was delayed between 14 and 42 DAS. Subsequent weed control after 42 DAS did not improve growth and yield significantly, nor obviate yield depression of the crop compared to crop weed-infested till harvest. Conclusions: Results indicated that the critical period of weed competition in soybean was between 14 and 42 DAS. Hence soybean should be maintained weed-free during this period to avoid high yield loss.

Effect of phosphorus (P) rates and weeding frequency on the growth and grain yield of extra early cowpea (Vigna unguiculata L. Walp) in the forest-savanna agro-ecological zone of southwest Nigeria

Field experiments were conducted at the Teaching and Research Farm of the Federal University of Agriculture, Abeokuta (7o 20?N, 30 23?E) during the 2014 early and late cropping seasons to evaluate the effect of weeding frequency and phosphorus fertilizer application on the growth and grain yield of the early maturing cowpea variety (Vigna unguiculata L. Walp). The experiment was laid out in a split-plot arrangement fitted into a Randomized Complete Block Design with three replications. The main plot consisted of three phosphorus fertilizer rates (0, 15 and 30 P2O5kg ha-1) while the subplot comprised five weeding frequencies (no weeding, weed-free, hoe weeding at 3 weeks after sowing (WAS), hoe weeding at 3 and 6 WAS and weeding at 3, 6 and 9 WAS). The results showed that plots treated with phosphorus fertilizer at 15 kg ha-1 produced the highest number of leaves and the tallest plant in the late season while the highest grain yield was recorded in the early trials. Weeding at 3, 6 and 9 WAS during the early season trial gave the highest grain yield compared with other weeding treatments. Unchecked weed infestation reduced yield by 53.10 % and 49.9 % in the early and late seasons respectively compared to the maximum obtained from weed-free plots. This study concluded that application of 15 kg P2O5 ha-1 and weed removal at 3, 6 and 9 WAS were effective for effective weed control and optimum grain yield in cowpea production.

Effect of weed control technologies on chickpeas (Cicer arietinum L.) and weeds

Purpose. In our experiment, effect of weed technologies on chickpeas (Cicer arietium L.) was set up in 2018 and 2019 at the Szeged-Othalom experimental area.Methods. In the first year we applied mechanical weed control in addition to pre-emergence herbicide (May 19, 2018) and 6–8 leaf chickpeas (June 20, 2018) in addition to post-emergence herbicide treatments. The year 2019 was different in that after the pre-emergence treatment (April 10, 2019), the post-emergence treatment of chickpeas with 6–8 leaf condition (May 15, 2019) was repeated in the budding state (June 18, 2019). The yield components one way analysis of variance was prepared using SPSS 22 software and graphic representation of the development of the plants was carried out Svab's cumulative yield analysis.Results. The effect of the treatments of 2018 and 2019 on the yield elements of chickpeas can be illustrated graphically in Figure 1 and Figure 2. For both years, the data are from plots of the ʻRealeʼ variety, where the 100% level is made up of the yield elements of the weed-free plots, and the yield elements of the other treatments are compared to this. Figure 1 shows that the number of shoots per unit area (1 m2) of weed-free plots that did not control weeds was 15%, the number of pods 45%, the number of seeds 58% and the weight of seeds 49% less than the weed-free control plots the same crop elements. Weeds were also significantly present in the plots treated only with pre-emergence treatment in the second half of the growing season, so the number of shoots per unit area was 3 %, the number of pods 23 %, the number of seeds 34% and the seed weight 35 % lower, as on weed-free plots. In the case of herbicide treatments, the decrease in yield elements was much smaller: the number of plants per unit area by 1%, the number of shoots by 3–10%, the number of pods by 5–12%, the number of seeds by 13–18%, the seed weight was by 1–5% less than on mechanically weed-controlled plots. Conclusions. Our two-year weed survey results show that the later sowing time of chickpeas favored warm-loving weeds. This is in complete agreement with the opinion of Nagy (2017), who found that sowing time determines the predominant weed species in a given area. At the same time, the statement of Kurnik (1970) was not confirmed, since in our experiment we proved in the case of ʻRealeʼ cultivar that the later sowing stock in 2018 gave higher yields than the plots with earlier sowing time in 2019. The changing weather caused by climate change makes the site characteristics of the given period much more unpredictable, so the yield is determined much more by the field factors developed during the growing season than by the calendar period.

Efficacy of Candidate Herbicides for Post- Emergence Weed Control in Kenaf (Hibiscus cannabinus L.)

Post emergence application of herbicides reduced weed growth, enhanced kenaf agronomic traits and fibre yield. A study was conducted to determine the efficacy of some herbicide formulations for post emergence weed control in kenaf at Ibadan (0.7.38N; 003.84E- Derived savanna agro-ecology) station of the Institute of Agricultural Research and Training (IAR&T), Obafemi Awolowo University, Ibadan in 2016 and 2017 rainy seasons. Herbicides applied were Quazilofop-P-ethyl (100, 150, 200 ml/ha), Oxyfluorfen (0.96, 1.20 and 1.44 kg ai/ha) and Fluazifop-p-butyl 150, 225 and 300 g ai/ha) at three rates each, while weed-free and weedy were the control treatments. Weed flora composition before land preparation was dominated by annual weeds; broadleaves (70%), grass (20%) and spiderwort (10%). At 10 weeks after sowing (WAS), weed flora composition comprised of 64% broadleaf, 14% grass, 8% spiderwort and 14% sedge. Weed flora dynamics after treatments application might have been influenced by herbicide formulations applied. Oldenlandia corymbusa, Cyperus escunlentus, Desmodium scorpurus and Cyperus rotundus were identified as prevalent weeds across the treatments applied while Mimosa pudica, was a minor weed. Herbicides improved kenaf agronomic traits (plant height, stem-butt girth and number of leaves/plant) due to minimal weed competition; reduced weed flora composition and weed weight relative to weed infested kenaf plants in weedy control. Oxyfluorfen (0.96, 1.20 and 1.44 kg ai/ha); fluazilof-p-butyl (225 and 300 g ai/ha); Quazilofop-P-ethyl (100 and 200 ml/ha) reduced weed dry weight by 60-70%. Weed-free plots had the highest weed control efficiency (WCE %). Evidently, acceptable WCE of ≥ 80% and comparable gross fibre yield with the maximum in weed-free recorded in Oxyfluorfen (1.20 and 1.44 kg ai/ha) and Fluazilofop-p-butyl (300 g ai/ha) showed their efficacies. However, low WCE 50 -65% in Quazilofop-p-ethyl (100, 150, 200 ml/ha) might reflected a review of the doses applied for better efficacy. Kenaf gross fibre yield was reduced by 65% in the weedy check plot, due to superior weed infestation and utmost weed dry weight accumulation. Notwithstanding, the benefit-cost ratio and environmental impact assessment of the study must be carried out for economically viable kenaf production and environmental friendliness.

Competition dynamics of Parthenium hysterophorus in direct-seeded aerobic rice fields

AbstractParthenium hysterophorus is a prolific invasive weed species, which infests many crops in over 40 countries around the world. A 2-year field study was carried out to quantify the potential impacts of this weed on direct-seeded rice. Parthenium weed was allowed to compete for 2, 4, 6 or 8 weeks after crop emergence, while full season weedy and weed-free plots were maintained as controls. Parthenium weed plants grew taller and attained more biomass as the competition duration prolonged. The yield and yield-related attributes of rice were negatively affected with increasing competition duration. The season-long competition caused the highest reductions in panicle number (28–34%), panicle length (26–27%), grains per panicle (22–23%) and grain yield (33 and 38%) of rice in both years. Weed competition for 2–8 weeks caused 5–34% and 6–33% losses in rice grain yield during both years, respectively. Importantly, Parthenium weed control after 8 weeks of competition did not improve rice yield significantly. The results suggested that Parthenium weed should be controlled in rice fields between 4 and 8 weeks after crop emergence under direct-seeded conditions to avoid over 10% yield losses.

Tillage, crop establishment, residue management and herbicide applications for effective weed control in direct seeded rice of eastern Indo–Gangetic Plains of South Asia

Weeds are the major production constraint in direct seeded rice (DSR) due to the concurrent emergence of competitive weeds and absence of water at initial growth stages to smother weed growth, leading to decreased crop yield. DSR has emerged as an alternative to the conventional water, labour and energy–intensive puddled transplanted rice (PTPR) in the eastern Indo–Gangetic Plains (IGP) of India. Hence, three field experiments were conducted (2008–2010) to evaluate integrated weed management options that included transplanted rice under puddled and unpuddled conditions, zero till DSR with or without residue retention and cover crops, zero till transplanted rice (ZTTPR) (experiment I); different combination of herbicides with or without cover crops (experiment II and III). Results revealed that during 1st year of study, zero–till direct seeded rice (ZTDSR) with (ZTDSR + R) or without (ZTDSR–R) residue retention and ZTDSR after the cover crops of sesbania [Sesbania aculeata (Willd.) Pers.] (ZTDSR + SB) or cowpea [Vigna unguiculata (L.) Walp.] (ZTDSR + CP) had greater weed density and dry matter accumulation than puddled transplanted rice (PTPR). However, in the 2nd and 3rd years, similar or lower weed density and dry matter accumulation was recorded in zero–tilled (ZT) plots. In 3rd year, plots under ZTDSR–R, ZTDSR + R, ZTDSR + SB, and ZTDSR + CP accumulated 14.3, 33.3, 23.1, and 60%, respectively, less weed dry matter over PTPR. Plots under ZTDSR produced almost similar or more grain yield to PTPR in all the three years of experimentation. On the basis of 3 years’ average data, the highest grain yield was recorded in plots under ZTDSR + R or –R followed by ZTTPR and ZTDSR + CP. While in experiment II, mungbean [Vigna radiata (L.) R. Wilczek] as cover crop fb bispyribac–Na at 25 g ha−1 resulted in the highest grain yield in 2008; but in 2009, weed free plots were superior–most. With regard to herbicides, pre–emergence application of pendimethalin EC at 1000 g ha−1; effectively controlled aerobic grassy weeds such as Eragrostis tenella var. japonica (Thunb.) Roem. & Schult. but was ineffective against Echinochloa colona (L.) Link. Similarly, bispyribac–Na at 25 g ha−1 was most effective for control of E. colona and Commelina benghalensis L., but incompetent against E. tenella. Overall, from the weed management viewpoint, this study recommends combination of pendimethalin at 1000 g ha−1fb bispyribac–Na at 25 g ha−1 for effective control of diverse weed flora encountered in DSR.

Growth and Yield of Okra (Abelmoschus Esculentus L. Moench) as Affected by Planting Date and Weeding Regime in Northern Ghana

This paper examines the effects of planting date (early planting, mid-season planting and late-season planting) and weeding regimes (two weeding before harvesting, three weeding before harvesting and weed free plots) on yield of Okra (Abelmoschus esculentus L. Moench) in the Tolon district of Northern Ghana. The results show that different weed species, categorized as broad leaves, grasses and sedges, were dominant depending on the planting date and weeding regime. While there was no significant interaction (p>0.05) between planting date and weeding regime on fruit yield, nor significant impact of planting date as a sole treatment on fruit yield, the results showed the existence of significant effect of weeding regime as a sole treatment on yield and yield parameters of okra (p<0.05). Triple weeding resulted in okra yields comparable to the weed-free treatments (mean of 6000 kg/ha to 6300 kg/ha, p>0.05) but significantly higher (p<0.05) and about triple the yield observed in the treatments with double weeding regimes (mean of 1800 kg/ha to 2300 kg/ha). As cost of production, besides the cost of weeding, remains same for all treatments, Triple weeding is recommended for the small-holder farmer. It is associated with less labor cost compared to continuous weeding in the weed free treatments, and the triple gains in yield could offset the additional labor cost incurred in the triple weeding compared to the double weeding regimes.

Influence of row spacing and cultivar selection on annual ryegrass (Lolium rigidum) control and grain yield in chickpea (Cicer arietinum)

Annual ryegrass (ARG) (Lolium rigidum Gaudin) is a problematic weed for chickpea (Cicer arietinum L.) production in Australia. Understanding the critical period of control of ARG in chickpea is important for developing effective integrated management strategies to prevent unacceptable yield loss. Experiments were conducted over 2 years at the research farm of the University of Queensland, Gatton, to evaluate the effect of chickpea row spacing (25 and 75cm) and cultivar (PBA Seamer and PBA HatTrick) and ARG infestation period (from 0, 3 and 6 weeks after planting (WAP), and weed-free) on ARG suppression and grain yield of chickpea. Year×treatment interactions were not significant for any parameter, and none of the treatment combinations showed any interaction for grain yield. Average grain yield was greater (20%) with 25-cm than 75-cm rows. On average, PBA Seamer had 9% higher yield than PBA HatTrick. Average grain yield was lowest in season-long weedy plots (562kg ha–1) and highest in weed-free plots (1849kg ha–1). Grain yield losses were lower when ARG emerged at 3 WAP (1679kg ha–1). Late-emerged ARG (3 and 6 WAP) had lower biomass (4.7–22.2g m–2) and number of spikes (5–24m–2) than ARG that emerged early; at 0 WAP, weed biomass was 282–337g m–2 and number of spikes 89–120m–2. Compared with wide row spacing, narrow row spacing suppressed ARG biomass by 16% and 52% and reduced number of spikes of ARG by 26% and 48% at 0 WAP and 3 WAP, respectively. PBA Seamer suppressed ARG growth more effectively than PBA HatTrick, but only in the season-long weedy plots. Our results imply that in ARG-infested fields, grain yield of chickpea can be increased by exploring narrow row spacing and weed-competitive cultivars. These cultural tools could be useful for developing integrated weed management tactics in chickpea in combination with pre-emergent herbicides.

Impact of water deficit on critical period of pigweed (amaranthus retroflexus l.) in sunflower

ABSTRACT-The critical period of weed control is a part of crop life cycle during which weeds must be kept weed-free to avoid yield losses due to competition. In order to evaluate the effect of deficit irrigation on critical period of redroot pigweed (Amaranthus retroflexus L.) in sunflower (Helianthus annuus L.), an experiment was carried out as split plot based on randomized complete block design with three replications at the experimental farm of College of Agriculture, Shiraz University, during 2010 and 2011 growing seasons. Factors were water deficit at three levels (100%, 75% and 50% of field capacity) as main plots and weed interference periods in weedy and weed-free plots at five sunflower growth stages (8-leaf, 12-leaf, head emergence, flowering and maturity) as subplots. Results showed that water deficit decreased grain yield and grain yield components in both years. Critical period of redroot pigweed in normal irrigation with accepting 5% yield loss in sunflower was 35-86 DAP (days after planting) in the first year and 49-94 DAP in the second year. By decreasing irrigation water to 75%FC and 50%FC, the length of critical period increased to 34-100 and 32-105 DAP in the first year and 50-101 DAP and 44-98 DAP in the second year of the study, respectively. Generally, our results showed water deficit extended the length of critical period of redroot pigweed in sunflower. Nomenclature: Redroot pigweed, Amaranthus retroflexus L.; Sunflower, Helianthus annuus L.

Influence of Competitive Duration of Blessed Milkthistle (Silybum marianum) with Wheat

AbstractBlessed milkthistle is considered to be a noxious weed in irrigated and rainfed areas of Pakistan due to its strong allelopathic effects on food crops. For sustainable wheat production, it is necessary to know the critical time for weed removal (CTWR) for blessed milkthistle to allow wheat growers to get maximum benefit from control of this weed. A field study was conducted in 2014 and 2015 at the College of Agriculture, University of Sargodha, Pakistan, to investigate the CTWR of blessed milkthistle in wheat. The field experiments were designed with seven treatments; weed free (control); 2, 3, 4, 5, and 6 wk after emergence (WAE); and weedy check. At 6 WAE, a significant reduction was noted in plant height (8% and 17%), number of productive tillers per square meter (16% and 16%), spike length (23% and 54%), grains per spike (13% and 34%), 1,000-grain weight (14% and 37%), grain yield (20% and 21%), and biological yield (24% and 50%) compared with control (weed-free plots) during 2014 and 2015, respectively. The logistic model supports the field study results and suggests that blessed milkthistle’s CTWR for wheat is 1 to 5 WAE based on acceptable yield losses of 5% to 15% during both years. The experimental results and logistic model indicate that blessed milkthistle should be controlled within 1 to 5 WAE to get better wheat crop harvests without compromising farmers’ profits. To our knowledge, this is the first study ever in Pakistan regarding the CTWR in terms of WAE of blessed milkthistle and could help other scientists create weed control strategies for other areas of the country.

Effects of weed management on yield attributes and yield of different varieties of barley.

A research experiment was conducted during rabi season 2010 and 2011 in AICW and BIP, College of Agriculture, Rewa (M.P.). Results revealed that weed free plot and variety Jyoti gave significantly higher yield 4.084 t/ha as compared to other treatments.