Unweeded Control Research Articles

Early post-emergence application of penoxsulam for weed control in transplanted rice

Results of field experiments conducted during kharif 2016 and 2017 to study the effect of penoxsulam on weeds in transplanted rice are reported. The study comprised 7 treatments consisting of 3 doses of penoxsulam 2.5 per cent OD (20, 22.5 and 25 g ha−1), bispyribac-Na 10 per cent SC (20 g ha−1), pretilachlor 50 per cent EC (750 g ha−1), hand weeding (20 and 40 d after transplanting, DAT) and un-weeded control. Echinochloa crusgalli, Leptochloa chinensis, Caesulia axillaris and Cyperus iria were the major weeds. Application of herbicides reduced weed density and increased grain yield as compared to un-weeded control during both the growing seasons. Penoxsulam at 25 g ha−1 provided effective control of grasses and broad-leaved weeds and sedges with 88.24 and 87.05 per cent weed control efficiency at 45 and 60 DAT. The treatment recorded significantly more panicle length, though the grain yield was at par with penoxsulam @ 22.5 g ha−1 (7.14 and 7.12 t ha−1 and 7.23 and 7.37 t ha−1, during 2016 and 2017 respectively). Penoxsulam at 25 g ha−1 recorded 21.5 and 23.9 per cent increase in grain yield over unweeded control during 2016 and 2017 respectively.

CHEMICAL AND NONCHEMICAL CONTROL OF WEEDS IN THE CULTIVATION OF LEMON BALM FOR SEEDS

The fight against weeds in the organic cultivation of herbal plants, both raw and for seeds, is a big challenge for growers. The paper compares the chemical (bentazon, 960 g·ha–1 and fluazifop-P-butyl, 150 g·ha–1) and nonchemical (scattering mustard seed meal in two doses 1.5 and 3.0 t·ha–1) control of weeds in the cultivation of lemon balm for seeds. Additionally, the influence of these factors on the yield of fresh herb and seeds of lemon balm and the sowing value of seeds was evaluated. The best method to control weed infestation was to use mustard seed meal in an amount of 3.0 t∙ha–1. Scattering of mustard seed meal in that dose reduced the number and weight of weeds on average from two years of research by 52.1 and 60.2% in relation to unweeded control. Slightly less effective methods were successively: bentazon and application of mustard seed meal in quantity of 1.5 t·ha–1. The largest yield of fresh lemon balm herb was collected from plots where mustard seed meal was used in an amount of 3.0 t∙ha–1. Seeds harvested from plots, on which mustard seed meal was used in a larger quantity was characterized by the lowest sowing value determined by the lowest energy and capacity of germination and the highest share of nongerminated seeds. Lowering the amount of used mustard seed meal to 1,5 t·ha–1 significantly improved their sowing value. Although this method was less effective in counteracting weeds than using larger dose, it provided comparable effects of reducing the number and weight of weeds in relation to chemical protection.

Integration of Chemical and Cultural Methods for Weed Control Management in Soybean (Glycin Max. L)

A field experiment was conducted during kharif season 2012 and 2013 at Rajmata Vijayaraje Scindia Krishi Vishwa Vidhyalaya RVSKVV, College Farm Gwalior (M.P.) to asses the suiTable method for weed control in soybean. On the basis of two years pooled data results weeding twice at 20 and 40 DAS significantly highest growth, yield attributes and seed yield as compared to the un-weeded control and was at par with pendimethalin (750 g a.i./ha) + one hand weeding, trifluralin (1000 g a.i./ha) + one hand weeding at 20 DAS and imezathapyr(100 g a.i./ha) + one hand weeding at 40 DAS. These treatments also recorded lower weed dry biomassand higher weed control efficiency. Pendimethalin (750 g a.i./ha) + one hand weeding at 20 DAS resulted higher net return (` 63500) and B:C (2.58) ratio followed by trifluralin + one hand weeding and hand weeding twice at 20 and 40 DAS. In addition to hand weeding twice, pre emergence herbicide Pendimethalin (750g a,i/ha) + one hand weeding at 20 DAS can be effectively used as an alternative for controlling weeds for obtaining optimum seed yield in soybean.

Effects of cereals as agro-ecological service crops and no-till on organic melon, weeds and N dynamics.

ABSTRACTIn a two-year field experiment undertaken in Central Italy, different agro-ecological service crops (ASCs), terminated by the no-till roller crimper technology before organic melon production (Cucumis melo L.), were evaluated by assessing soil-plant N dynamics, weed management and crop performance, and by comparing with a tilled control without ASC. The ASCs (Poaceae, i.e. rye, barley, wheat, spelt and their mixture), were characterised in terms of aboveground biomass, N uptake, C : N ratio and degradation rate. During the melon growth cycle, soil mineral N (SMN), weed density and biomass were measured and the design of trial included weeded and unweeded plots. The yield and concentrations of soluble solids of the melon was measured. The ASC mulches differed in their N supply capacity and degradation rate. Rye and spelt were the best in terms of weed control, with approximately 80% lower weed density and weed biomass for either rye or spelt compared with the control. Wheat was the least effective against weeds, but it enhanced SMN. Melon yields were similar in plots with spelt and rye, weeded and unweeded treatments, but were reduced in the unweeded control (−58.5%) and barley treatment (−41.2%), compared with the respective weeded treatments. The low melon yield in the plots with rye suggested a negative allelopathic rye-melon interaction. The results highlighted that the ASCs were able to regulate, to different extents, the agro-ecosystem interactions.

Carry-over effect of brown manuring supplemented with nitrogen on productivity and profitability in succeeding wheat (Triticum aestivum)

A field experiment was carried out on wheat (Triticum aestivum L.) (2017-18) in succession to maize (Zea mays L.) crop grown with several brown manuring (BM) practices (2017) at ICAR-Indian Agricultural Research Institute, New Delhi. The field layout was fixed for both maize and wheat. The 12 brown manuring/weed control treatments adopted in maize were taken as main plot treatments, and three levels of N, viz. 0, 60 and 120 kg N/ha were taken as sub-plot treatments. At 40 DAS, with respect to weed control, all BM/weed control treatments were inferior to weed-free control, which was freshly employed in both seasons, but was superior to un-weeded control. Among the BM treatments, the Sesbania + Crotalaria mixture (12.5+12.5 kg/ha) and 2,4-D applied at 35 DAS resulted in lowest total weed density (~31.8/m2), which was 46.5% lower than that in the un-weeded control. Total weed density was positively correlated with N level. Total weed density was highest at the highest dose of nitrogen at 120 kg/ha (~37.1/ m2) and was significantly higher than those in no nitrogen (~32.0/m2). Sesbania + Crotalaria mixture (12.5+12.5 kg/ha) and 2,4-D applied at 35 DAS was superior to others with respect to wheat’s ear bearing tillers (419.6), grains/ spike (49.1), 1000-grain weight (40.3 g), harvest index (38.5%), grain yield (4.41 t/ha) and biological yield (11.42 t/ ha), gross returns (111500 `/ha) and net returns (80600 `/ha). This treatment also resulted in higher grain yield (4.80 t/ha) and net returns (89400 `/ha) than other treatments at 60 kg N/ha, and was at par with weed-free control with 120 kg N/ha (5.19 t/ha and 92200 `/ha, respectively). Therefore, the carry-over effects of 1:1 mixture of Sesbania bispinosa and Crotalaria juncea (12.5+12.5 kg/ha) and 2,4-D 0.5 kg/ha applied at 35 DAS in combination with 60 kg N/ha can lead to higher wheat productivity and profitability.

Comparison of safe weed control methods with chemical herbicide in potato field

BackgroundMulching and manual or mechanical hoeing are the backbone of weed control strategies in organic agriculture. So, two field experiments were established in the village of Kafer El-Khawazim, Talkha district, Dakahlia Governorate, Egypt, during the winter seasons of 2017 and 2018. The experiments were conducted to evaluate the efficiency of the safe weed control methods of mulching and manual hoeing in comparison with metribuzine herbicide on potato plants and associated weeds.ResultsThe results indicated that the treatment of black plastic mulch was the superior treatment in controlling broadleaved, grassy, and total weeds as compared to other treatments under study. Metribuzin herbicide came in the second rank in controlling broadleaved weeds. Concerning to grassy and total weeds, banana leaf and cheeseweed straw mulches follow the black plastic mulch ideal treatment. The results also revealed that the use of black plastic mulch and banana leaf mulch followed by cheeseweed straw mulch led to the highest significant increase in growth characteristics and tuber yield of potato plants. This in turn correlated with a significant increase in tuber contents of phosphorus, potassium, and carbohydrate percentage than unweeded control treatment.ConclusionBlack plastic mulch followed by banana leaf mulch and cheeseweed straw mulch were the ideal safe treatments in controlling total weeds. This in turn reflected on potato plants by scoring the maximum values of yield characters as compared to unweeded check.

Management of grass weeds with quizalofop in soybean [Glycine max (L.) Merrill

Post-emergence herbicides are useful for managing weeds in soybean fields. Use of post-emergence herbicide(s) is increasing in India because of the ease of use and control of broad spectrum of weeds. As soybean is a rainy season crop in India, weed control remains an important concern for soybean farmers. An experiment was laid out at Research Farm of Punjab Agricultural University, Ludhiana to study effect of different herbicides for control of grass weeds in soybean. Treatments comprised of post-emergence application of quizalofop 25, 37.5 and 50 g/ha, fenoxaprop 100 g/ha, weed free and unweeded control. Phyto-toxic evaluation of herbicides was carried out on succeeding wheat crop. Quizalofop 37.5–50 g/ha significantly reduced weed density and biomass of grass weeds compared to weedy check. Quizalofop 50 g/ha gave complete control (100%) of Dactyloctenium aegyptium, Digitaria sanguinalis, Acrachne racemosa and Eragrostis spp. till 40 days and > 85% till 80 days after treatment. Quizalopfop 50 g/ha recorded soybean seed yield and yield attributes similar to that of weed free check; it gave highest B:C (2.61) and net returns ($660/ha) All weed control treatments provided higher soybean seed yield compared to unweeded control. Quizalofop at all doses was safe to succeeding wheat crop.

Herbicide mixtures for weed management in wet-seeded rice

Three herbicidal mixtures, viz. triafamone 20% + ethoxysulfuron 10% (pre-mix) 67.5 g/ha, 12 days after sowing (DAS), cyhalofop-butyl+ penoxsulam 6% OD (pre-mix) 150 g/ha, 20 DAS, and fenoxaprop-p-ethyl 6.9 EC 60 g/ha+ ethoxysulfuron 15 WDG (tank mix) 15 g/ha, 20 DAS were evaluated for their efficacy against weeds in wet-seeded rice. These treatments were compared with bispyribac-sodium, hand weeding twice and unweeded control. Application of triafamone + ethoxysulfuron, and cyhalofop-butyl + penoxsulam, significantly reduced the weed biomass followed by the treatments bispyribac-sodium, and hand weeding at 60 DAS. Fenoxaprop-pethyl + ethoxysulfuron had significantly lower weed control efficiency, probably due to its inability to control Echinochloa crus-galli effectively. Considering rice grain and straw yields, all herbicide treatments were at par except for fenoxaprop-p-ethyl + ethoxysulfuron, which recorded significantly lower values. Among yield attributes, significantly higher number of panicles/m2 was recorded in the treatments triafamone + ethoxysulfuron, and hand weeding, followed by cyhalofop-butyl+ penoxsulam. Grain and straw yields were lowest in unweeded control.

Weed management in rice established by different methods

The field experiment was conducted at Agronomy Department Farm, College of Agriculture, Dapoli, during Kharif (rainy) seasons 2016 and 2017 to study the effect of established by different methods of rice establishment on weeds. The field experiment was laid out in a strip plot design comprising of twenty five treatment combinations replicated thrice. The horizontal strips comprised five rice establishment methods, viz. sowing of dry seeds by drum seeder at onset of monsoon, sowing of sprouted seeds (Rahu) by drum seeder in puddled field, broadcasting of sprouted seeds (Rahu) in puddled field, system of rice intensification (SRI) method and conventional transplanting. The vertical strips consisted five weed management practices, viz. need based two hand weedings at 20/30 and 40/60 DAS/DAT, pre-emergence application of oxadiargyl 80 WP 100 g/ha + 1 hand weeding at 20/30 DAS/DAT, pre-emergence application of oxadiargyl 80 WP 100 g/ha + 1 hand weeding at 40/60 DAS/DAT, pre-emergence application of oxadiargyl 80 WP 100 g/ha + post-emergence application of Almix 20 WP 4 g/ha and unweeded control. SRI method with two hand weedings carried out at 20 and 40 DAT recorded highest grain and straw yield of rice and lowest weed density and dry weight of weeds as compared to remaining treatment combinations during both the seasons.

Bio-efficacy of readi-mix herbicides on weeds and productivity in late-sown wheat

A field experiment was conducted during 2015–16 and 2016–17 at Rajasthan College of Agriculture, Udaipur, India to evaluate the bio-efficacy of readi-mix herbicides in late sown wheat. The experiment consisting of fifteen treatments was laid out in randomized block design with four replications. The results revealed that Readi-mix application of sulfosulfuron + metsulfuron (32 g/ha)) and mesosulfuron + iodosulfuron (14.4 g/ha) gave higher weed control index (95.36, 94.72%), lower weed index (2.00, 2.75%) and weed persistence index (0.349, 0.351) whereas, higher index value of crop resistance index (CRI), weed management index (WMI) and herbicide efficiency index (HEI) (28.61, 0.38 and 5.50). Both of these treatments recorded 34.3 and 33.3 per cent grain yield enhancement along with 49.0% and 47.7% higher net returns over the unweeded control with the highest benefit-cost ratio (2.34 and 2.32). Results from contract analysis indicated significant (p < 0.0001) interaction of year x treatments and response of Readi-mix v/s single/sequential herbicide application on grain yield, weed density and dry matter. The joint effect of parameters on grain yield was significant with high magnitude (RGY. Weed density total, Weed dry weight total, Total N, P and K uptake = 0.98; p < 0.0001). Additionally, the regression model for grain yield on total weed density (R2 = 0.84), weed dry weight (R2=0.79), total N uptake (R2=0.98), P uptake (R2=0.93) and K uptake (R2 = 0.97) demonstrated significant dependence. Moreover, no symptoms of phytotoxicity were seen in any of the treatment in the crop at 21 days after herbicide application.

Relative density of weeds and weed indices as influenced by weed control options in cotton

Field experiments were conducted at Professor Jayashankar Telangana State Agricultural University, Rajendranagar during Kharif 2017 for the evaluation of efficacy different doses of diuron in both red and black soils. The treatment consisted of test herbicides such as, diuron 80% WP at 0.5 kg/ha, 0.75 kg/ha and 1.0 kg/ha along with registered formulation of pendimethalin 38.7% CS at 677 g/ha, intercropping with green manure crop, mechanical weeding thrice at 20, 40, 60 DAS and unweeded control. The experiment was laid out in a randomised block design replicated thrice. The weed flora of the experimental field in red soil was dominated by Cynodon dactylon, Rottboellia exaltata, Parthenium hysterophorus, Trianthema portulacastrum and Commelina benghalensis. While in case of black soil, predominant flora was Cynodon dactylon, Cyperus rotundus, Parthenium hysterophorus, Euphorbia geniculata, Tridax procumbens, Cyanotis cristata, Digera arvensis and Celosia argentia. The treatments, mechanical weeding thrice at 20, 40 and 60 DAS, polymulch treatments reduced the weed growth in both red and black soils. Among the herbicides, diuron at 1.0 kg/ha fb pyrithiobac-sodium + quizalofop-ethyl in red soil and both diuron at 1.0 kg/ha and 0.75 kg/ha along with sequential application of herbicides reduced the density of weeds. Diuron could reduce the broad-leaved weeds and grasses except itch grass. Sedges are also could not be reduced by diuron. The lower values of weed persistence index was obtained with herbicidal treatments i.e., diuron at 1.0 and 0.75 kg/ha fb pyrithiobac-sodium + quizalofop-ethyl. The crop resistance index and treatment efficiency index were superior in case of polymulch and mechanical weeding thrice at 20, 40 and 60 DAS.

Sensitivity of Annual Weeds Against Metolachlor + Bensulfuron - Methyl Herbicide in Transplanted Rice

&#x0D; Field trials were conducted at Bangladesh Rice Research Institute (BRRI), Gazipur during aman, 2014 and boro, 2014-15 to evaluate the efficacy of metolachlor + bensulfuron methyl 20% WP on weed suppression of transplanted rice. Metolachlor + bensulfuron methyl 20% WP @ 150, 190 and 230 g ha-1 were applied and pyrazosulfuran ethyl @ 125 g ha-1, weed free and unweeded control were the treatment variables. Visual observations indicated that this herbicide possesses high selectivity and not toxic to rice plants. The results revealed that the major weed flora associated with the transplanted rice was mainly comprised of two grasses, two sedges and three broadleaf in aman and two grasses, two sedges and two broadleaf in boro season. The most dominant weeds were Cyperus difformis, Echinochloa crus-galli, Scirpus maritimus and Monochoria vaginalis in both the growing seasons. Application of metolachlor + bensulfuron methyl 20% WP @ 190 g ha-1 was most effective to suppress weeds in both the seasons resulting in increased grain yield more than 40% as compared to unweeded control. Therefore, metolachlor + bensulfuron methyl 20% WP@ 190 g ha-1applied at one to two leaf stage of weed effectively controls the weed infestation in transplanted rice.&#x0D; Bangladesh Agron. J. 2018, 21(1): 61-70&#x0D; &#x0D;

Influence of integrated weed management on growth, productivity and economics of wheat (Triticum aestivum L.)

A field experiment was conducted at College of Agriculture, Loni Farm during 2015 and 2016 on silty clay loam soil with 7.4 pH. The climatic conditions during experimental period were favourable. The experiment was laid out in randomized block design with three replications. The treatments consisted of combination of cultural treatments, pre-and postemergence herbicides as well as unweed check. The results showed that the growth parameters, yield attributes, seed yield and straw yield were increased significantly by treatment 3 HW at 20, 40 and 60 DAS which was at par with treatments pendimethalin @ 750 g a. i./ha as preemergence fb hoeing at 30 DAS, metsulfuron methyl @ 5 g a. i./ha POE at 20 DAS fb hoeing at 30 DAS, metribuzin @ 200 g a. i./ha POE at 20 DAS fb hoeing at 30 DAS and 2, 4-D @ 500 g a. e./ha POE at 20 DAS fb hoeing at 30 DAS which was followed by treatment metsulfuron methyl @ 5 g a. i./ha POE at 20 DAS and metribuzin @ 200 g a. i./ha POE at 20 DAS. The B: C ratio and net returns were found significantly higher in treatment pendimethalin @ 750 g a. i./ha as pre-emergence fb hoeing at 30 DAS. Minimum growth parameters, yield attributes, yield and economics were noticed in treatment unweeded control.

Impact of flucetosulfuron on weed seed bank in wet seeded rice

An experiment was conducted to assess the impact of flucetosulfuron, a new generation sulfonylurea herbicide, on weed seed bank dynamics of wet land paddy field. Field experiments were carried out during two consecutive seasons (Kharif 2016 and Rabi 2016-’17), to assess the bio-efficacy of flucetosulfuron in wet seeded rice which was accompanied by weed seed bank assay. Weed seed bank assay of the soil was carried out before and after the field experiments in both the seasons by the seedling emergence method. The experiment on weed seed bank was laid out in Completely Randomised Block Design (CRD) with 12 treatments replicated thrice. Flucetosulfuron @ 20, 25, and 30 g ha-1applied at 2-3, 10-12, and 18-20 days after sowing (DAS) along with two control treatments viz., hand weeding at 20 and 40 DAS and unweeded control comprised the treatments. The emerging weeds were uprooted at 14 days interval up to a period of two months; categorized as grasses, broad leaved weeds, and sedges and counted. Results revealed that non-herbicidal plots recorded significantly higher count of total emerged weeds compared to herbicide applied plots. In all the herbicide applied plots, effective reduction in weed seed bank could be obtained irrespective of the dose of the herbicide. Regarding the time of application, flucetosulfuron applied at 10-12 and 18-20 DAS recorded significantly lower weed seed bank during both the seasons, compared to its application at 2-3 DAS.

Sensitivity of Annual Weeds against Sulfentrazone 48 SC herbicide in Rice Cultivation

Herbicides are used successfully for weed control in rice fields for rapid effect, easier to application and low cost involvement in comparison to the traditional methods of hand weeding. Sulfentrazoneis a new pre-planting herbicide in Bangladesh. Field trials were conducted at Bangladesh Rice Research Institute (BRRI), Gazipur during Aman 2014 and Boro 2014-15 to evaluate the efficacy of sulfentrazone 48 SC on weed suppression and performance of transplanted rice. Treatments were Sulfentrazone 48 SC @ 150, 200 and 250 ml ha-1, pretilachlor 500 EC @ 1000 ml ha-1, weed free and unweeded control. Visual assessment indicated that this herbicide possesses high selectivity and not toxic to rice plants. The results revealed that the major weed flora associated with the transplanted rice was mainly comprised of two grasses, two sedges and four broadleaves in Aman 2014 and two grasses, two sedge and two broadleaves in Boro 2014-15. The most dominant weeds were Cyperus difformis, Echinochloa crus-galli, Scirpus maritimus and Monochoria vaginalis in both the growing seasons. Application of Sulfentrazone 48 SC @ 200 ml ha-1 was most effective to suppress weed density and dry masses in both the seasons resulting increased grain yield more than 50% as compared to unweeded control. Therefore, Sulfentrazone 48 SC @ 200 ml ha-1 should apply two or three days before plantingfor effectively control weeds in riceBangladesh Rice j. 2017, 21(1): 67-76

Effect of nitrogen fertilizer and weed management on the yield of transplant aman rice

The research work was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during aman season from July to December 2015 to study the effect of nitrogen fertilizer and weed management on the growth and yield of transplant aman rice cv. BRRI dhan46. The experiment consisted of four fertilizer treatments viz. 0 kg N ha−1 (N0), 40 kg N ha−1(N1), 80 kg N ha−1(N2) and 120 kg N ha−1(N3) and four weeding treatments viz. one hand weeding at 20 DAT (W1), two hand weedings at 20 and 35 DAT (W2), three hand weedings at 20, 35 and 50 DAT (W3), weeding by Japanese rice weeder twice at 20 and 35 DAT (W4) and unweeded control (W5). The experiment was laid out in the randomized complete block design with three replications. The highest plant height (113.00 cm), number of total tillers hill−1 (8.74), number of effective tillers hill−1 (6.18), panicle length (21.98 cm), number of grains panicle−1 (114.20), grain yield (4.00 t ha−1), straw yield (5.25 t ha−1) and biological yield (9.25 t ha−1) were recorded in N2 (80 kg N ha−1) treatment. The lowest plant height (106.00 cm), number of total tillers hill-1 (7.20), number of effective tillers hill−1 (5.00), panicle length (20.70 cm), number of grains panicle−1 (97.60), grain yield (3.52 t ha−1), straw yield (4.46 t ha−1) and biological yield (7.97 t ha−1) were recorded from N0 (No nitrogen fertilizer control) treatment. On the other hand, the highest grain yield 4.23 t ha−1 was observed in three weedings condition because of the highest number of effective tillers hill−1 (6.81), number of grains panicle−1(111.10). The highest straw yield (5.51 t ha−1) was also found in three weeding condition. The lowest grain yield (3.40 t ha−1) was recorded in W5 (unweeded control) treatment. The lowest straw yield (4.31 t ha−1) was also observed in W5 (unweeded control) treatment because of the smallest plant (106.97 cm) and lower number of total tillers hill−1 (7.20). Therefore, 80 kg N ha−1along with three hand weedings at 20, 35 and 50 DAT may be used for obtaining the highest grain and straw yields of BRRI dhan46J. Bangladesh Agril. Univ. 16(1): 12-16, April 2018

Effect of age of seedlings at staggered transplanting and weed management on the growth and yield of aromatic Boro rice (cv. BRRI dhan50)

An experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during December 2015 to May 2016 to study the effect of age of seedlings at staggered transplanting and weed management on the growth and yield of aromatic Boro rice (cv. BRRI dhan50). The experiment comprised four seedling ages at staggered transplanting viz. 30, 45, 60 and 75-day old seedlings with five different weed management treatments viz. unweeded controls, two hand weeding at 20 and 35 DAT (days after transplanting), pre-emergence herbicide (Pendimethaiin, Panida 33EC) applied at 3 DAT + one hand weeding at 35 DAT, post-emergence herbicide (Penoxsulam, Granite 240 SC) applied at 12 DAT + one hand weeding at 35 DAT, pre-emergence herbicide (Panida 33 EC) applied at 3 DAT + post-emergence herbicide (Granite 240 SC) applied at 12 DAT. It was observed that the experiment was laid out in a randomized complete block design with three replications. The highest plant height and total dry matter hill–1 were recorded in 30-day old seedlings with pre-emergence herbicide (Panida 33EC) applied at 3 DAT + post-emergence herbicide (Granite 240 SC) applied at 12 DAT. Younger seedlings (30-days old) produced the highest number of total tillers hill–1 (11.08), effective tillers hill–1 (8.47), grains panicle–1 (80.76) and grain yield (3.94 t ha–1) compared to aged seedlings at staggered transplanting. In case of weed management, pre-emergence herbicide (Panida 33EC) applied at 3 DAT + post-emergence herbicide (Granite 240 SC) applied at 12 DAT produced the highest number of effective tillers hill-1 (8.89), grains panicle–1 (81.66), 1000-grain weight (18.44 g), grain yield (4.47 t ha–1) and straw yield (5.13 t ha–1). Grain yield was reduced by 59.82% in unweeded control compared to pre-emergence herbicide (Panida 33EC) applied at 3 DAT + post-emergence herbicide (Granite 240 SC) applied at 12 DAT. In interaction, 30-day old seedlings combined with pre-emergence herbicide (Panida 33 EC) applied at 3 DAT + post-emergence herbicide (Granite 240 SC) applied at 12 DAT produced the highest effective tillers hill–1 (9.58), grains panicle-1 (89.47), 1000-grain weight (18.93g), grain yield (5.31 t ha–1) and straw yield (5.75 t ha–1). Therefore, 60-day old seedlings at staggered transplanting with pre-emergence herbicide (Panida 33EC) applied at 3DAT + post-emergence herbicide (Granite 240 SC) applied at 12 DAT appears as the promising technique for aromatic Boro rice cultivation.J. Bangladesh Agril. Univ. 16(1): 5-11, April 2018

Weed flora of aerobic rice and their effect on growth, yield and nutrient uptake by rice Oryza sativa in the coastal region of Karaikal of Puducherry, India

A field experiment was conducted at farm lands of Pandit Jawaharlal Nehru College of Agriculture and Research Institute, Karaikal to know the weed floristic composition and their effect on growth, yield and nutrient uptake by aerobic rice (Oryza sativa). The results revealed that totally 29 species of weeds from 22 genera belonging to 17 families were noticed. Among them, four were grasses, six were sedges, and nineteen were broad leaved weeds. Of this 29 species, four were perennials, and the rest were annuals. During initial stages (30 DAS), sedges dominated (38.3%) whereas at later stages (60 DAS) broad leaved weeds dominated the aerobic rice fields (42.5%). Grasses were found to be comparatively less dominant at both the stages. Echinochloa colona Link. (28.1%) followed by E. cruss-galli (L.) Beauv. (6.1%) among the grasses; Cyperus difformis L. (19.8%) followed by C. iria L (9.9%) among the sedges and Ludwigia abyssinica (28.0%) among the broad leaved weeds, were the predominant weed species in aerobic rice cultivation. Weeds, when left unchecked, competed with rice for all resources like nutrients, space, light and soil moisture. The unweeded control recorded the maximum nutrient depletion by weeds (76.6, 6.4 and 106.8 Kg of N, P andK ha-1 ). Due to severe competition, weeds suppressed the growth of rice which resulted in lower growth and yield attributes leading to lower grain (333 kg ha-1 ) and straw yields (1903 kg ha-1 ).

English

The present investigation entitled with “yield and yield attributes of pigeonpea influenced by different weed management practices (Cajanus cajan L. Mill sp.)” was carried out during kharif season of 2015-16 at Instructional cum Research Farm, Indira Gandhi Krishi Vishwavidyalaya, Raipur (C.G.). The soil of experimental field was clayey in texture, low in nitrogen, medium in phosphorus and high in potassium contents with neutral pH. the maximum weed control efficiency was observed under treatment(T3) two hand weeding twice at 30 and 60 DAS followed by (T10) PE pendimethalin @ 1.25 kg ha-1 + oxyfluorfen @ 125 g ha-1tank mix fb imazethapyr @ 60 g ha-1 at 20 DAS . The lowest weed control efficiency was observed under treatmen(T1) unweeded control at all the observational stages. Weed growth rate showed increasing trend upto 60-80 DAS and decreasing trend thereafter till harvest.

Impacts of tillage and herbicide mixture on weed interference, agronomic productivity and profitability of a maize – Wheat system in the North-western Indo-Gangetic Plains

Weeds comprising of annual monocotyledons, dicotyledons and perennial Cyperus rotundus L. (hereafter referred to as nutsedge) are important constraints in maize-wheat production system in India. They can cause yield losses of 25–30% in maize and 10–25% in wheat. Recently, continuous use of selective herbicides has led to an increase of nutsedge and other annual weeds in maize. There is need for a broad-spectrum weed control strategy that includes control of nutsedge in maize. Herbicide mixtures, containing a nutsedge killer partner herbicide may prove to be more effective for this. Imazethapyr among herbicides available in India possesses nutsedge-killing action, but the tolerance of maize to this herbicide, which is usually recommended for application as post-emergence in soybean and groundnut, is variable. We observed dose-dependent selectivity/tolerance of maize to imazethapyr when applied as post-emergence in a previous trial. Imazethapyr’s pre-emergence application may prove more useful in offering selectivity to maize, but is hardly studied. In addition, its residual/carry-over effect may lead to weed control in following wheat crops grown in sequence with maize, economizing production costs of the maize-wheat system. Therefore, this experiment was designed to evaluate the efficacy of imazethapyr against weeds including nutsedge, and its selectivity in maize crops when applied as pre-emergence in tank-mixture with pendimethalin; to compare these tank-mixtures effects with that of the sequential applications of pendimethalin (pre-emergence) and imazethapyr (post-emergence) in maize; and to evaluate their residual actions combined with tillage and crop residue in wheat under a maize- wheat system. The application of pre-emergence tank-mixture of pendimethalin 0.75 kg a.i. ha−1 + imazethapyr 0.050 kg a.i. ha−1 caused significant reductions in densities of broad-leaved (30%), nutsedge (45.2%), grassy (79.7%) and total weeds (49.1%) compared with un-weeded control (UWC) in maize. It reduced total weed dry weight by 58.3% and gave 56.1% higher maize yields than UWC. Among the tillage treatments adopted in the wheat crop, zero tillage (ZT) + residue (R) resulted in 14.0% greater reductions in weed dry weight and 6.9% higher wheat yields than conventional tillage (CT). It increased maize-wheat system productivity by 5.4% and 7%, respectively over CT and ZT without residue. The application of a tank-mixture of pendimethalin + imazethapyr gave 2.9% lower system productivity, but 8.2% higher net returns than the weed-free control, reducing the weed seed bank by 65% at 0–15 cm soil layer in two years. The application of this tank-mixture (in maize), followed by ZT + residue (in wheat) was more remunerative and could lead to better weed control with 25% and 50% lower doses of pendimethalin and imazethapyr, respectively, and 50% reduction in application cost. This practice can be adopted in maize-wheat system under irrigated conditions in the North-western Indo-Gangetic Plains of India, and in similar agro-ecologies of the tropics and sub-tropics. This result can also be applicable to cropping systems like maize – mustard, maize – barley/oat, subject to further evaluation and refinement under field conditions.