Preemergence Research Articles

Growth and Productivity of Black Gram (Vigna mungo L.) as Influenced by Residual Effect of Triafamone Herbicide Applied for Transplanted Rice (Oryza sativa L.)

Background: The major area under black gram are cultivated as rice fallow crop to harness the available soil moisture and other resources without application of any inputs as that of other input intensive crops. Weeds are one of the important biotic factors which affect the growth and yield of black gram. The weeds can be effectively managed in black gram by the herbicide applied in the previous crop viz., transplanted rice. Since, the black gram has quick ground cover, hence initial weed management is very much important. In order to manage the weeds in rice fallow black gram crop evaluation of Triafamone herbicide applied to the transplanted rice crop was carried out in succeeding black gram crop in terms of the growth and yield of black gram. Methods: Field experiments were conducted during Kharif, 2019 (July to August) and Rabi 2019-20 (November to January) at Wetland farm of Tamil Nadu Agricultural University, Coimbatore to study the residual effect of herbicides applied in transplanted rice on succeeding black gram growth and productivity. The experiment was laid out in a randomized complete block design with three replications. The treatments consisted of four doses (30, 40, 50 and 100 g/ha) of new rice herbicide Triafamone 20% SC each as pre emergence and early post emergence, along with check herbicides Pretilachlor 50% EC 750 ml/ha and Pyrazosulfuron ethyl 10% WP 15 ml/ha as early post-emergence along with farmers practice (two hand weedings), weed free and weedy checks. Result: The weed flora of the experimental field consisted of weed complex including grasses, sedges and broad leaved weeds. Among the different dose of herbicides applied, Triafamone 20% SC at 100 g/ha markedly suppressed the weeds growth. There were no phytotoxic effects of herbicides on succeeding black gram. Different doses and time herbicides applied in transplanted rice did not affect the germination of succeeding black gram. Higher weed control efficiency, growth and yield component and yield of black gram were recorded with the Triafamone at 40 g/ha as pre emergence and early post emergence application.

EFFECT OF WEED CONTROL METHODS AND SEEDLING GROWTH STAGESON THE GROWTHOF TRANSPLANTED RICE(Oryza sativa L.) IN DUTSE, JIGAWA STATE

The experiments were carried out in 2020 and 2021 rainy seasons to determine the performance of rice as influenced by seedling age and weed control treatments. The treatments consists of three seedling age (14, 21 and 28 day old seedling) and four weed control methods (hoe weeding, pre emergence application of gramozone (200g/L of paraquat/ha), pre and post emergence of gramozone (200g/L of paraquat/ha) and premix of propanil360g/L + 2,4_D 200g/L) and weedy check). The treatments were laid out in split-plot in a Randomized Complete Block Design (RCBD) and were replicated three times. The results revealed that the plots weeded twice and those treated with pre and post emergence application of gramozone and propanil respectively resulted in taller plant height, large leaf area, and more growth rate than the others weed control methods while weedy check gave the least value. The effect of seedling age on the rice growth revealed that rice transplanted under 14 days old seedling gave tallest plant height, high value of growth rate, relative growth rate and net assimilation value compared to the other methods while 28 days old seedling resulted in the least value of the parameters than others methods. Therefore, it can be concluded that rice farmers in the Sudan savanna zone of Nigeria can adopt pre and post emergence application of gramozone and propanil with transplanting 14 days old seedling since the combination of these treatments gave better weed control and growth of paddy rice.

Financial Return from Weed and Disease Management Practices in Peanut (Arachis hypogaea L.) in Southern Ghana

Peanut (Arachis hypogaea L.) yield and financial return can be negatively affected by weeds and the combination of early leaf spot disease [ Passalora arachidicola (Hori) U. Braun] and late leaf spot disease [ Nothopassalora personata (Berk. & M.A. Curtis) U. Braun, C. Nakash., Videira & Crous] in Ghana. Research was conducted in southern Ghana to evaluate hand-weeding, herbicide applied preemergence (PRE) or herbicide applied postemergence (POST), a combination of PRE and POST herbicides, and PRE or POST herbicides supplemented with hand-weeding and disease management practices (i.e., no fungicide or a two sequential fungicide applications 45 and 60 days after planting). Although some differences in leaf spot severity were observed based on weed management, peanut pod yield and financial return based on yield and cost of pest management practices were affected by weed management and disease management practices individually but not the interaction of these treatment factors. The weed management practices with the highest financial return included a POST herbicide with or without hand weeding and a PRE herbicide followed by hand-weeding or a POST herbicide.

Peanut Cultivar Response to Diclosulam in the Southwest Peanut Growing Region

Field experiments were conducted in the south Texas and Texas High Plains area during the 2018 through 2020 growing seasons and in southwestern Oklahoma in 2020 to evaluate runner peanut cultivars (Georgia-13M, Georgia-09B) and the Spanish cultivar (Ole´) tolerance to diclosulam at 0.026 (the manufacture’s recommended use rate) and 0.052 (twice the manufacture’s recommended use rate) kg ai/ha applied preemergence (PRE) or peanut cracking (CRACK). No diclosulam injury was noted in south Texas; however, in the Texas High Plains and Oklahoma locations significant stunting was noted with diclosulam applied PRE especially under sprinkler irrigation. In 2018 at the High Plains location, under furrow irrigation, no peanut stunting was noted. In 2019 and 2020, under sprinkler irrigation, diclosulam at 0.026 and 0.052 kg/ha applied PRE resulted in early-season stunting of 18 to 59% in both Oklahoma and the Texas High Plains. No late-season stunting was noted in Oklahoma; however, up to 20% stunting was still visible at the Texas High Plains location. No yield differences were noted in south Texas or the High Plains region in 2018 or 2020; however, in 2019 at the High Plains location, peanut yield decreased as diclosulam rate increased but application timing had no effect. At the Oklahoma location, application timing and rate effect were noted. Diclosulam applied PRE and the high rate of diclosulam reduced peanut yield. Issues still exist with diclosulam in the southwest peanut growing areas as seen previously in 2000 despite the different varieties planted. There may be opportunities to utilize diclosulam postemergence (POST) since peanut injury was 5% or less and yields were not reduced when applied CRACK.

Economics of reducing Palmer amaranth seed production in dicamba/glufosinate/glyphosate‐resistant soybean

AbstractIncreased prevalence of glyphosate‐resistant (GR) weeds within agronomic cropping systems has led to the readoption of pre‐emergence (PRE) herbicides and use of multiple herbicide‐resistant soybean [Glycine max (L.) Merr.] cultivars. Herbicide programs were evaluated in the recently commercialized dicamba/glyphosate/glufosinate‐resistant (DGGR) soybean for weed control, reduction of Palmer amaranth (Amaranthus palmeri S. Watson) seed production, crop safety, and economic performance. At 35 days after pre‐emergence herbicides, acetochlor plus dicamba plus metribuzin, acetochlor/fomesafen plus dicamba, dicamba plus flumioxazin, and imazethapyr/pyroxasulfone/saflufenacil provided 80–99% control of velvetleaf (Abutilon theophrasti Medik.), Palmer amaranth, common lambsquarters (Chenopodium album L.), and Poaceae species. Evaluation at 14 days after early postemergence herbicides indicated PRE followed by (fb) POST applications of mixtures of acetochlor, dicamba, glufosinate, and glyphosate provided 80–99% weed control compared with 67–93% control in POST‐only programs. Most herbicide programs provided 83–99% control of grass and broadleaf weeds, with 85–91% weed biomass reductions at 28 days after late‐POST. The PRE fb POST programs reduced Palmer amaranth seed production by 94–99%, whereas POST‐only programs provided 75–83% reduction. In 2020, most programs provided gross profit margins ≥US$1,000 ha−1, with glufosinate fb glufosinate and imazethapyr/pyroxasulfone/saflufenacil fb acetochlor plus glufosinate providing $1,481 and $1,466 ha−1, respectively. Benefit/cost ratios ranged between 0.3 and 3.9 in 2019 due to hail but increased to 2.9–10.9 in 2020. Results of this study support use of PRE herbicides with multiple sites of action in DGGR soybean and indicate that glufosinate can provide POST control of GR Palmer amaranth.

Preemergence and postemergence spiny amaranth (Amaranthus spinosus) and common lambsquarters (Chenopodium album) control in lettuce on organic soils

AbstractSuccessful weed management, particularly use of chemical control, is very important for commercial lettuce production on organic soils in the Everglades Agricultural Area in south Florida. Field experiments were conducted in 2016 and 2017 to determine the efficacy of herbicides (pronamide, bensulide, imazethapyr, or oxyfluorfen) applied preemergence (PRE) either alone or followed by a postemergence (POST) application of imazethapyr for weed control and lettuce (romaine and iceberg) yield. Preemergence-applied oxyfluorfen (0.56 kg ha−1) resulted in significant lettuce injury, including stand loss, while PRE applications of pronamide (4.44 kg ha−1), bensulide (5.6 and 10.1 kg ha−1), or imazethapyr (0.035 g ha−1) resulted in transient lettuce injury and no significant stand loss. Similarly, PRE-applied pronamide, bensulide, and imazethapyr followed by POST-applied imazethapyr did not result in significant lettuce stand loss or injury. When contrasted as a group, PRE-applied herbicides followed by a POST application of imazethapyr provided better spiny amaranth and common lambsquarters control compared with PRE-applied herbicides or POST-applied imazethapyr-only treatments. Lettuce yield was highest with PRE herbicides followed by POST imazethapyr compared with PRE herbicides or POST-applied imazethapyr-only treatments, indicating a yield benefit of having a PRE followed by POST herbicide weed control program in lettuce grown on organic soils. However, oxyfluorfen is not an option for lettuce on organic soils because of unacceptable stand reduction and crop injury. Whether to apply pronamide, bensulide, or imazethapyr PRE followed by a POST application of imazethapyr for broadleaf weed control in lettuce on organic soils depends on the species present, cost, and ease of application.

Effect of Weed Management Practices of Small Onion (Allium cepa var. Aggregatum) Nursery on the Weed Flora, Weed Control Efficiency and Seedling Production

Control of weeds in nursery is necessary for production of healthy and sturdy seedlings. In this regard, field experiments were conducted to study the effect of different weed management practices on weed control efficiency and performance of onion seedling in nursery at two phases. The results from the first experiment revealed that, among the herbicide treatments, lowest weed density and weed dry weight was observed in Pre-emergence (PE) application of oxyfluorfen at 0.250 kg a.i ha-1 followed by PE application of oxyfluorfen at 0.125 kg a.i ha-1. Whereas, the highest weed control efficiency was observed in hand weeded plots followed by pre-emergence application of oxyfluorfen at 0.250 kg a.i ha 1. In the second experiment, lower weed density, weed dry weight and higher weed control efficiency was observed in lay by application oxyfluorfen @ 0.125 kg ha-1 as PE + 2nd application @ 0.0625 kg ha-1 at 20 DAS. Seedling characters viz., higher root length, seedling height, 100 seedling weight and seedling yield was recorded in PE application of oxyfluorfen at 0.125 kg a.i ha-1 and PE application of oxyfluorfen at 0.125 kg a.i ha-1 + oxyfluorfen at 0.0625 kg a.i ha-1 (lay by) at 20 DAS in the first and second experiments respectively.

Evaluation of sulfentrazone and S-metolachlor in brassica vegetables

AbstractSmall-acreage brassica vegetables need additional herbicide options. Among the vegetables grown in California are a number of niche crops, such as bok choi and brussels sprouts, that have a limited number of registered herbicides, such as DCPA. Sulfentrazone and S-metolachlor have food use tolerances for use on brassica head and stem Group 5-16, which includes crops like bok choi and brussels sprouts, as well as brassica leafy greens Subgroup 4-16B, which includes crops like kale. However, there is a lack of data for S-metolachlor and sulfentrazone on a wide variety of seeded and transplanted brassica vegetables. S-metolachlor applied preemergence (PRE) was evaluated on six direct-seeded brassica vegetables during 2019 and 2020, including bok choi, broccoli rabe, collard, mizuna, radish, and mustard greens. S-metolachlor and sulfentrazone were both evaluated PRE in transplanted brussels sprouts and kale. The results indicate that most of the seeded brassica vegetables were tolerant of S-metolachlor and that transplanted brassica vegetables were tolerant of both S-metolachlor and sulfentrazone. Broccoli rabe was moderately injured in 2020, but yields did not vary among treatments either year.

Cucumber tolerance to glufosinate applied preplant or preemergence

AbstractGeorgia vegetable growers produce more than 27% of the nation’s fresh-market cucumbers. To maximize yields and profit, fields must be weed-free when planting. Limitations with current burndown herbicide options motivated academic, industry, and U.S. Department of Agriculture partners to search for new tools to assist growers. One possibility, glufosinate, controls many common and troublesome weeds, but its influence on cucumber development through residual activity when applied before or at planting is not understood. Thus, four different studies were each conducted two to four times from 2017 to 2020 to determine 1) transplant cucumber response to preplant glufosinate applications as influenced by rate, overhead irrigation, and interval between application and planting; and 2) seeded cucumber response to preemergence (PRE) glufosinate applications as influenced by rate, overhead irrigation, and planting depth. Glufosinate applied at 330, 660, 980, and 1,640 g ai ha−1 the day before transplanting caused 11% to 53% injury on sandy, low organic matter soils. Cucumber vine lengths and plant biomass were reduced up to 28% and 46%, respectively, with the three highest rates. Early-season yield (harvests 1 to 4) noted a 31% to 60% yield loss with glufosinate at 660 to 1,640 g ha−1 with similar trends observed with total yield (11 to 13 harvests). Irrigation (0.75 cm) after application and before transplanting reduced injury to less than 21%, eliminated vine length and biomass suppression except at the highest rate, and eliminated yield loss. Extending the interval between glufosinate application and transplanting from 1 to 4 d was not beneficial, and further extending the interval to 7 d significantly reduced injury half the time. When applied PRE to seeded cucumber and combining the data across locations, glufosinate caused less than 7% injury even at 1,640 g ha−1. Seeded plant vine lengths, biomass, and marketable yield were not influenced by the PRE application, and neither irrigation nor planting depth influenced seeded crop response to glufosinate.

Screening of Herbicides for Rice Seedling Safety and Echinochloa colona Management under Australian Conditions

Different herbicides are currently required for sustainable weed management in aerobic rice. Three pot experiments were conducted using different herbicides to evaluate rice safety and for the control of Echinochloa colona, a major weed of aerobic rice. Among the pre-emergence (PRE) herbicides, it was found that pendimethalin (594 g ai ha−1) and flumioxazin (60 g ai ha−1) were relatively safe herbicides for rice and provided 100% control of E. colona. All other PRE herbicides, such as atrazine, cinmethylin, clomazone, dimethenamid-P, isoxaflutole, metribuzin, prosulfocarb + S-metolachlor, pyroxasulfone, trifluralin, and S-metolachlor reduced the biomass of rice compared with the non-treated control. Dose-response studies revealed that flumioxazin and pendimethalin even at low doses (30 g ai ha−1 for flumioxazin and 294 g ai ha−1 for pendimethalin) provided excellent control (>95%) of E. colona. Post-emergence (POST) application of paraquat (360 g ai ha−1) at the time of rice emergence caused toxicity in the crop, but also provided excellent control of E. colona. When applied just after crop emergence (11 days after sowing), Pendimethalin was found to be safe for rice (2% mortality) and reduced the biomass of E. colona by 88% compared with the non-treated control. It is quite possible that the rice variety Reiziq used in this study may have a tolerance to flumioxazin, which needs further investigation involving more rice varieties. This study suggests that flumioxazin can be used as an alternative to pendimethalin for the sustainable management of E. colona in aerobic rice.

Weed Control With Preemergence Herbicides in Azuki Bean

Three field experiments were completed over a three-year period (2019 to 2021) in Ontario, Canada to develop weed management programs in azuki bean with herbicides (pendimethalin, S-metolachlor, halosulfuron, and imazethapyr) applied alone and in combination, and metribuzin, applied preemergence (PRE). At 2 and 4 weeks after emergence (WAE), there was ≤ 8% azuki bean injury from the herbicide treatments evaluated, with the exception of the treatments that included S-metolachlor which caused up to 19% azuki bean injury. Pendimethalin (1080 g ai ha-1) and S-metolachlor (1600 g ai ha-1) controlled green foxtail 83-94% but provided poor control of common lambsquarters, wild mustard, redroot pigweed, common ragweed, and flower-of-an-hour. Imazethapyr (75 g ai ha-1) controlled common lambsquarters, wild mustard, redroot pigweed, and flower-of-an-hour 90-100% but provided 76-82% control of common ragweed and green foxtail. Halosulfuron (35 g ai ha-1) controlled wild mustard 100%, common ragweed 81-84%, common lambsquarters 77-83%, flower-of-an-hour 72-75%, redroot pigweed 59-72%, and green foxtail 19-23%. The tankmix of pendimethalin + S-metolachlor controlled green foxtail and common lambsquarters 87-97% but the control was only 23- 83% on wild mustard, redroot pigweed, common ragweed, and flower-of-an-hour. The tankmixes of pendimethalin + imazethapyr and pendimethalin + S-metolachlor + imazethapyr provided 90-100% control of common lambsquarters, wild mustard, redroot pigweed, flower-of-an-hour, and green foxtail, and 78-87% control of common ragweed. The tankmixes of pendimethalin + halosulfuron and pendimethalin + S-metolachlor + halosulfuron controlled common lambsquarters and wild mustard 91-100%, green foxtail 76-95%, flower-of-an-hour 70-94%, redroot pigweed 68-91%, and common ragweed 78-79%. Metribuzin (280 g ai ha-1) controlled common lambsquarters, wild mustard, redroot pigweed, common ragweed, flower-of-an-hour, and green foxtail up to 94, 98, 81, 58, 98, and 61% respectively; control improved to 99, 100, 97, 84, 99, and 83%, respectively when the rate was increased to 560 g ai ha-1. Generally, weed density and dry biomass reflected the level of weed control. Weed interference reduced azuki bean yield by 91% in this study. Generally, azuki bean yield reflected the level of weed control.

Effect of Planting Methods and Weed Management Practices on Growth and Yield of Paddy (Oryza sativa L.)

The trial was conducted at Crop Research Farm, Department of Agronomy of Naini Agricultural Institute, SHUATS, Prayagraj (U.P), during Kharif 2021.The experiment was bifactorial (two factors) which consists of three different planting methods i.e., Direct seeded rice, Transplanted rice and SRI method, and three different weed management practices i.e., Hand weeding (twice), Oxadiazon 25 EC (as Pre emergence) at 250g/L (2L/ha) and Pyrazosulfuron ethyl 10% WP at 20g/ha (as Post Emergence) and a control plot laid out in randomized block design with ten different treatment combinations which is replicated thrice. The results revealed that at harvest significantly, higher growth attributes like plant height (117.28 cm), Number of tillers (38), plant dry weight (56.36 g/hill) at harvest is recorded in treatment number 7 with a combination of SRI method of planting and Hand weeding twice at critical crop weed competition. Significantly, higher yield attributes like number of effective tillers/ hill (35), number of panicles/ plant (44), number of grains per panicle (216.6), test weight (25 g), grain yield (5.1 t/ha) and straw yield (8.1 t/ha) was highest in the same treatment. From the experiment it can be concluded that treatment 7 where SRI method of planting and hand weeding twice during critical crop weed competition was considered as best treatment combination with maximum effective tillers/hill, number of panicles/plant, number of grains per panicle, test weight, grain yield and straw yield i.e., all the yield attributes.
 

Multiple resistance to imazethapyr, atrazine, and glyphosate in a recently introduced Palmer amaranth (Amaranthus palmeri) accession in Wisconsin

AbstractThe continued dispersal of Palmer amaranth can impose detrimental impacts on cropping systems in Wisconsin. Our objective was to characterize the response of a recently introduced Palmer amaranth accession in southern Wisconsin to postemergence (POST) and preemergence (PRE) herbicides commonly used in corn and soybean. Greenhouse experiments were conducted with the Wisconsin putative herbicide-resistant accession (BRO) and two additional control accessions from Nebraska, a glyphosate-resistant (KEI2) and a glyphosate-susceptible (KEI3) accession. POST treatments were 2,4-D, atrazine, dicamba, glufosinate, glyphosate, imazethapyr, lactofen, and mesotrione at 1X and 3X label rates. PRE treatments were atrazine, mesotrione, metribuzin, S-metolachlor, and sulfentrazone at 0.5X, 1X, and 3X label rates. Plant survival of each accession was ≥63% after exposure to imazethapyr POST 3X rate. Survival of BRO and KEI2 was 44% (±13) and 50% (±13), respectively, after exposure to atrazine POST 3X rate. Survival of BRO was 69% (±12) after exposure to glyphosate POST 1X rate, whereas survival of KEI2 was 44% (±13) after exposure to glyphosate POST 3X rate. After exposure to 2,4-D POST 1X rate, KEI2 and KEI3 survival was 38% (±13) and 50% (±13), respectively. Survival of all accessions was ≤31% after exposure to 2,4-D POST 3X rate or dicamba, glufosinate, lactofen, and mesotrione POST at either rate. Plant density reduction of KEI2 was 77% (±13) after exposure to atrazine PRE 1X rate, whereas density reduction of BRO was 56% (±13) after exposure to atrazine PRE 3X rate. Plant density reduction of all accessions was ≥94% after exposure to mesotrione PRE 1X and 3X rates or metribuzin, S-metolachlor, and sulfentrazone PRE at either rate. Our results suggest that each accession is resistant (≥50% survival) to imazethapyr POST, that BRO and KEI2 are resistant to atrazine and glyphosate POST, and that KEI2 and KEI3 are resistant to 2,4-D POST. The recently introduced BRO accession exhibited multiple resistance to imazethapyr, atrazine, and glyphosate POST. In addition, atrazine PRE was ineffective for BRO control, suggesting that diversified resistance management strategies will be critical for its effective management.

Control of acetolactate synthase-inhibiting herbicide-resistant Palmer amaranth (Amaranthus palmeri) with sequential applications of dimethenamid-Pin dry edible bean

AbstractBiotypes of Palmer amaranth that are resistant to acetolactate synthase (ALS) inhibitor are becoming widespread in western Nebraska. There are limited effective postemergence (POST) herbicides labeled for ALS-inhibitor-resistant Palmer amaranth control in dry edible bean. The objective of this study was to evaluate the efficacy of dimethenamid-Pin a sequential preemergence (PRE) fb followed by (fb) POST program at two POST application timings, the first and third trifoliate stages (V1 and V3, respectively), for controlling ALS-inhibitor-resistant Palmer amaranth in dry edible bean. A field study was conducted in 2019, 2020, and 2021 in Scottsbluff, NE. PRE-alone applications of pendimethalin + dimethenamid-Pprovided inconsistent Palmer amaranth control. Dimethenamid-Papplied POST following a PRE application of pendimethalin + dimethenamid-Pprovided effective (>90%) Palmer amaranth control at 4 wk after V3 only at the V1 application timing in 2019. In 2020 and 2021 dimethenamid-Papplied POST at V1 and V3 following a PRE application of pendimethalin + dimethenamid-Pprovided 99% and 98% Palmer amaranth control at 4 wk after V3, and 98% and 94% Palmer amaranth control at harvest, respectively. Palmer amaranth biomass was reduced by 95% to 99% and by 96% to 98% compared with the -nontreated control when dimethenamid-Pwas applied POST at V1 and V3, respectively, following a PRE application of pendimethalin + dimethenamid-Pin 2020 and 2021. Application of a mixture of dimethenamid-Pwith imazamox + bentazon POST provided similar results to those of the fomesafen-containing treatments and dimethenamid-Palone POST. Dimethenamid-Papplied POST following a PRE application of pendimethalin + dimethenamid-Presulted in similar yield as the fomesafen-containing treatments. If fomesafen is not an option due to the crop rotation interval restriction, using dimethenamid-Pin a sequential PRE fb POST program is the only effective alternative to control ALS-inhibitor–resistant Palmer amaranth in Nebraska. The use of dimethenamid-Pin a sequential PRE fb POST program, alone or mixed with foliar-active herbicides should be considered by dry edible bean growers who are dealing with ALS-inhibitor-resistant Palmer amaranth.

Conservation Agriculture- Based Planting Techniques and Weed Management Practices Influence on Nutrient Content and Their Uptake in Dry Direct-Seeded Rice (Oryza sativa L.)

Conventionally established rice leads to major challenges in crop production like soil health degradation, water table declination and labour scarcity which ultimately increases the cost of production. To address these issues of transplanted rice, different conservation agriculture (CA) based crop establishment practices in combination with suitable weed management options were incorporated to sustain rice productivity. The field trial was conducted for two years during kharif season of 2018 and 2019 at Research Farm, Banaras Hindu University, Varanasi, Uttar Pradesh (India). The experiment was laid out in split plot design having four planting techniques in main plots viz., farmer’s practice (Conventional Transplanting), zero-till direct seeded rice (ZT-DSR), reduced-till direct seeded rice (RT-DSR) (Rotavator single pass) and conventional-till direct seeded rice (CT-DSR) and five weed management practices viz., pendimethalin 1 kg ha-1 pre-emergence (PE) followed by (fb) chlorimuron + metsulfuron (4g + 4g ha-1) at 20 days after sowing (DAS), pendimethalin 1 kg ha-1 PE fb pyrazosulfuron (30 g ha-1) at 20 DAS, bispyribac-sodium + chlorimuron + metsulfuron (25g + 4g + 4g ha-1) at 20 DAS, hand weeding at 20 and 40 DAS and Weedy check in sub-plots and replicated thrice. The results showed that Nitrogen (N), Phosphorus (P) and Potassium (K) content in grain and straw were not significantly influenced by planting techniques and weed management practices. However, among various crop establishment methods CT-DSR recorded significantly higher N, P and K uptake by both grain and straw over rest of the treatments except ZT-DSR during both the years. Similarly, two hands weeding (at 20 DAS and 40 DAS) recorded the highest N, P and K uptake by the crop. With respect to herbicidal treatments, higher N, P and K uptake by crop was found with the application of pendimethalin 1 kg ha-1 (pre-em) fb chlorimuron + metsulfuron (4g + 4g ha-1) at 20 DAS compared to others during both the years of experimentation. Based on the results, it is concluded that application of pendimethalin 1 kg ha-1 PE fb chlorimuron + metsulfuron (4g + 4g ha-1) at 20 DAS to CT-DSR was registered maximum N, P and K uptake by both grain and straw of rice.

Weed Management and Crop Establishment Methods in Rice (Oryza sativa L.) Influence the Soil Microbial and Enzymatic Activity in Sub-Tropical Environment.

Weed management has become the most important and inevitable aspect of crop management for achieving a higher rice yield. Nowadays, chemical herbicide application has become a popular practice for managing weeds in different rice cultures. However, herbicide application can have qualitative and quantitative impacts on soil microorganisms and soil enzymes, particularly in the case of new herbicide molecules and their indiscriminate use for a longer period. Further, different rice establishment methods also play a significant role in soil microbial population dynamics as well as soil biological properties. Keeping these in view, a field experiment was conducted at the Agronomy Main Research Farm, Orissa University of Agriculture and Technology (OUAT), India, during the kharif season of 2016 and 2017, on the impact of crop establishment methods and weed management practices on soil microbial and enzymatic status. The field experiment was laid out in a split-plot design with three replications with four crop establishment methods in the main plot, viz., M1, Direct Seeded Rice (DSR); M2, Wet Seeded Rice (WSR); M3,Unpuddled Transplanted Rice (NPTR); M4, Puddled Transplanted Rice (PTR), and six weed management practices in the sub-plot, viz., W1, Weedy check; W2, Bensulfuron methyl 0.6% + Pretilachlor 6% (pre-emergence (PE)) 0.660 kg ha−1 + Hand weeding (HW) at 30 days after sowing/transplanting (days after sowing/transplanting (DAS/T)); W3, Bensulfuron methyl 0.6% + Pretilachlor 6% (PE) 0.495 kg ha−1 + HW at 30 DAS/T; W4, Bensulfuron methyl 0.6% + Pretilachlor 6% (PE) 0.495 kg ha−1 + Bispyribac-Sodium (post-emergence(POE)) 0.025 kg ha−1 at 15 DAS/T; W5, Cono weeding (CW) at 15 DAS/T + hand weeding 30 DAS/T, and W6, Brown manuring/Green manuring. The initial decline in the microbial population was observed due to herbicide application in NPTR and PTR up to 7 DAS/T and then it increased up to 28 DAS/T. There was a reduction in soil microbial and enzymatic status after the application of herbicides Bensulfuron methyl 0.6% + Pretilachlor 6% (PE) and Bispyribac-Sodium (POE) that again followed an upward graph with crop age. Significant variation in enzymatic activity and the microbial count was also observed among treatments involving crop establishment methods. The study revealed that improved microbial population and enzyme activity were noted in unpuddled transplanted rice under organic weed management due to favorable conditions, and chemical weed control initially affected microbial population and activities.

Impact assessment of residual soil-applied pre-emergence herbicides on the incidence of soybean seedling diseases under field conditions

A multi-environmental field study was conducted in 2017 and 2018 in Nebraska to investigate potential interactions between soybean seedling diseases and soil-applied residual pre-emergence (PRE) herbicides. Experiments were established from mid-May to early June in fine-textured, poorly drained soils with a history of seedling establishment problems. PRE herbicides consisted of chlorimuron-ethyl, flumioxazin, metribuzin, saflufenacil, and sulfentrazone applied at labeled rates, in addition to non-treated control. Assessments included soybean injury, seedling root lesion severity (DSI), plant height, population, biomass, and yield. Additionally, symptomatic seedling roots were sampled for fungal and oomycete organisms to expand comprehension of potential biotic associations. Greater soybean injury and reduced root biomass were observed in two distinctive environments following PPO-inhibiting PRE herbicide applications. Exceptionally in one environment, where DSI seemed (P = 0.07) lower for metribuzin in comparison to saflufenacil, PRE herbicides did not affect seedling root rot severity and no yield differences occurred among treatments. Community composition depicting Fusarium, Phytophthora, Pythium, and Rhizoctonia genera varied considerably across environments (P < 0.001) and DSI classes (P = 0.002), representing distinctive ecological environments under investigation. Phytophthora structured a large portion (>40%) of the total primary pathogenic isolates recovered in the highest DSI environment, whereas Pythium frequency ranged from 4.6% to 22% across all surveyed environments, and Rhizoctonia recovery was low (<10.3%) and sporadic. Across environments with varying DSI and soilborne pathogen composition, results indicated a lack of consistent interaction between soil-applied residual PRE herbicides and the incidence of soybean seedling diseases in optimal to delayed planting situations.

Weed control, yield and quality of small-grain scented rice as influenced by spacing and weed management in lower gangetic plains

The effect of planting density and weed management on weed control, yield and quality of a non-Basmati type short-grained scented rice (cv. Radhunipagal) was studied at 'C' Block Farm of Bidhan Chandra Krishi Viswavidyalaya, Kalyani, Nadia, West Bengal. The field experiment was conducted in a split-plot design comprising 2 spacings (15 cm × 15 cm and 20 cm × 15 cm) in main plots and 6 weed control practices [weedy check, 2 hand weeding (HW), Butachlor as pre-emergence (PE) + HW, Butachlor (PE) + 2,4-D Na-salt as post-emergence (PoE), HW + 2,4-D Na-salt (PoE), mechanical weeding + HW) in sub-plots during rainy (kharif) season of 2013 and 2014. Mean number of total weeds in 1 m2 field was 94.3 and 118.8 at 28 and 56 days after transplanting (DAT); and weed control efficiency varied among 5 weed management practices over weedy check as: 49.0-67.3% at 28 DAT and 56.5-72.8% at 56 DAT. Close planting (15 cm × 15 cm) resulted in 9.1% greater grain yield (2.27 vs. 2.08 t/ha), higher net income (Rs. 23,700 vs. 20,900/ha) and B:C ratio (1.79 vs. 1.73) over wider spacing (20 cm × 15 cm). Manual weeding twice at 21 and 42 DAT recorded better weed control efficiency (67.3 and 72.8% at 28 and 56 DAT), grain yield (2.51 t/ha), milling recovery (65.9%) and net return (Rs. 25,900/ha). But chemical weed control [Butachlor (PE) + 2,4-D Na-salt (PoE)] was adjudged as less expensive option (Rs. 27,300/ha) for Radhunipagal rice with moderate grain yield (2.16 t/ha ), higher protein content (7.45%) and B: C ratio (1.90).

Dry Matter Accumulation and Growth Indices of Fennel (Foeniculum vulgare Mill.) as Affected by Different Weed Management Practices and Plant Geometry

An experiment was conducted during rabi seasons of 2016-17 and 2017-18 at Agronomy Farm, S.K.N. Agriculture University, Jobner, Jaipur, Rajasthan, to get a suitable combination of sowing at different plant geometries and weed management. The experiment was managed in a split-plot design with three replications. The main plot treatments comprised four plant geometries, viz. 50 x 20 cm, 50 x 25 cm, 60 x 15 cm and 60 x 20 cm and subplots consisted of six treatments of weed management, viz. weedy check, two hand weeding (HW) at 25 and 50 days after sowing (DAS), pendimethalin @ 0.75 kg/ha pre emergence (PE), oxadiargyl @ 75 g/ha (PE), pendimethalin @ 0.75 kg/ha (PE) + one HW at 30 DAS and oxadiargyl @ 75 g/ha (PE) + one HW at 30 DAS. Sowing of fennel with plant geometry 60 x 20 cm showed superior performance in respect of dry-matter accumulation, growth indices and yield as compared to plant geometries 50 x 20 cm, 50 x 25 cm and 60 x 15 cm. Among weed management treatments, hand weeding twice 25 and 50 DAS registered significantly highest dry matter accumulation, growth indices viz. crop growth rate (CGR), relative growth rate (RGR) and yield of fennel, thus, hold a great promise in fennel production under semi-arid conditions of Rajasthan.

Integrated weed management in pearl millet [Pennisetum glaucum (L.) R. Br.

The scarcity of labour in agriculture and change in behaviour, weed management in rain fed pearl millet is very difficult. Further, to improve/ fine tune the existing recommendation of weed management in pearl millet, this experiment was planned. A field experiment was carried out during the rainy (Kharif) seasons of 2012 to 2014 in sandy loam soils at ICAR-All India Coordinated Research Project on Pearl Millet, Research Farm, Agricultural Research Station, Mandor, Jodhpur (Agriculture University, Jodhpur), to evaluate the effect of integrated weed management in rainfed pearl millet (Pennisetum glaucum L.) with pre-emergence application of atrazine 0.5 kg/ha + 1 HW at 35 DAS, four levels of post-emergence application of atrazine (0.1, 0.2, 0.3 and 0.4 kg/ ha) along with one hand weeding at 35 DAS, two hand weeding and hoeing (at 20 and 40 DAS). Eight treatment combinations were laid out in randomized block design in four replications. All weed management practices caused significant improvement in grain and dry fodder yield of pearl millet compared to the weedy check (1943 kg/ha and 30.86 q/ha). The best treatment was found weed free and it was followed by post emergence application of Atrazine @ 0.4 kg/ha. In comparison to the weed dry matter recorded at harvest with weedy check (547.1 kg/ha), all weed management practices recorded quite lower dry matter of weeds and were found to be at par in managing weeds compared to the weed free plot. Efficiency of post emergence application of Atrazine @ 0.2,0.3 and 0.4 kg/ha was found more better in controlling weeds than the recommended practice of managing weeds by pre emergence application of Atrazine. Weed control efficiency were also found higher in weed free and it was followed by two hand weeding and post emergence application of Atrazine @ 0.4 kg treatments, respectively.