Journal of Research in Weed Science
Volume:4 Issue: 1, Mar 2021

The experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh during November 2016 to May 2017 to study the effect of weed management strategies on the yield of aromatic fine rice in Boro season. The experiment comprised three aromatic fine rice varieties viz. BRRI dhan50, BRRI dhan63 and Basmati, and five weed management strategies viz. weedy check (no weeding), two hand weeding at 15 and 30 days after transplanting (DAT), pre-emergence herbicide, Panida 33 EC @ 2.5 l ha-1 + one hand weeding at 30 DAT, post emergence herbicide, Granite 240 SC @ 95 ml ha-1 + one hand weeding at 30 DAT, pre-emergence herbicide, Panida 33 EC @ 2.5 l ha-1 + post emergence herbicide, Granite 240 SC @ 95 ml ha-1. The experiment was laid out in a randomized complete block design with three replications. BRRI dhan50 produced the highest number of effective tillers hill-1 (8.87), number of grains panicle-1 (95.51 grain) and 1000-grain weight (21.45 g) and straw (5.59 t ha-1) yields compared to BRRI dhan63 and Basmati. The highest grain yield (4.31 t ha-1) was produced in BRRI dhan50 which was at par with BRRI dhan63 and the lowest one (3.21 t ha-1) was recoded in Basmati. In case of weed management, the highest number of effective tillers hill-1 (9.62), 1000-grain weight (21.70 g), grain (5.22 t ha-1) and straw (5.64 t ha-1) yields were obtained in pre-emergence herbicide + post emergence herbicide compared to other treatments. In interaction, the highest grain yield (5.54 t ha-1) was obtained in BRRI dhan50 with pre-emergence herbicide + post emergence herbicide, which was statistically identical to BRRI dhan63 with pre-emergence herbicide + post emergence herbicide. Therefore, BRRI dhan50 or BRRI dhan63 can be cultivated with pre-emergence herbicide + post emergence herbicide in Boro season for appreciable grain yields.

Sugar beet (Beta vulgaris L.) is considered as the second most important crop in the world after sugar cane in sugar production. Weed competition is considered as one of the major constrains to achieve maximum sugar beet yield. The objective of this study was to evaluate the efficacy and selectivity of the herbicide Pendimethalin for weed control and their effect on sugar beet growth and yield. A field experiment was conducted during 2017/18 winter season at the experimental farm, Faculty of agricultural Sciences Gezira University, Sudan. The herbicide Pendimethalin (Pendico50% EC) at two rates (3.6 and 4.8 kg a.i. ha-1) was applied as per-sowing, two weeks before planting and irrigated immediately after application. Hand weeded and un-wedded treatments were added as controls. The treatments were arranged in a randomized complete block design in 4 replicates. Data were subjected to analysis of variance procedure (P ≤ 0.05). Pendimethalin at the lower rate (3.6 kg a.i. ha-1) exhibited slight phytotoxicity on sugar beet plant. The herbicide at the lower rate gave 82% grass weed control and 56% broadleaved weed control. The herbicide treatments significantly increased the root length, root diameter and root weight of sugar beet as compared to un-weeded check. Pendimethalin at the two rates tested gave significantly high root weight compared to un-weeded check. The herbicide treatments increased the gross sugar yield. Pendimethalin at 3.6 and 4.8 kg a.i. ha-1 gave significantly high gross sugar yield (0.74 – 0.52 tonha-1) compared to 0.15 kgha-1 gross sugar yield of the un-weeded control. It could be concluded that Pendimethalin at 3.6 kg a.i. ha-1 could be used for weed control in sugar beet to be applied and immediately irrigated two weeks before sowing of sugar beet. Further studies are needed to confirm their safety and inclusion in a management program.

The spread of Chromolaena odorata in some parts of Serengeti district has stimulated interest in the prediction of their soil seed bank and mapping its distribution. Thirty clusters from each agro-ecosystem namely fallow land, grazing land, and cultivated land were sampled for soil seed bank assessment. Each cluster was randomly demarcated into five 20 m2 plots. Soils were collected from 0-5 cm, 5-10 cm, and 10-15 cm depths using a 10 cm diameter and 5 cm length cylinder. Coordinates were taken using a hand held GPS (Map76 cx) along transects. Each soil sample was soaked for a minimum of 30 minutes in a solution of sodium hexametaphosphate (50 g/L) and sodium bicarbonate (25 g/L) and poured over a set of three different sieve sizes to remove debris. The results were converted to number of weed seeds per square meter, and statistically analysed using R software version 3.5.1. Quantum GIS (1.8.0) was used to map the distribution of the weed. The soil seed bank in all agro-ecosystems decreased significantly (p <0.05) from 0-5 cm to 10-15 cm soil depths. Mean weed seed densities varied depending on land use but significantly highest in fallow land followed by cultivated land (p <0.05). In cultivated land the top soil had more than twice Siam weed seed densities (1254 seeds/m2) than in the bottom soil layers (597 seeds/m2). The Siam weed was found to have ability to thrive in a wide variety of soils, hence increase its invasion success. Distribution maps of C. odorata in Serengeti district and surrounding areas provide insight on the aggressiveness of the weed according to its spread and infestation levels. Future research work should be carried out to study fallow age in relation to soil seed bank of Chromolaena odorata and physio-chemical properties of the soil and their influence on distribution of the weed.

The present investigation was focused on enumeration of medicinal potential of weeds and biodiversity of Arbuscular mycorrhizal fungi (AMF) associated with them. For AMF analysis, fourteen medicinal weeds were selected, roots and their respective rhizosphereic soil samples collected from different localities of Hamirpur district, Himachal Pradesh. The results revealed that number of AM spores in the rhizosphere of plant was not correlated to percent of AM root colonization. The highest percentage of root colonization was reported in Solanum nigrum (73.54±07.15 %) and minimum in Ageratum conyzoides (22.22±00.55 %). AM spore count was recorded maximum in rhizosperic soil sample of Parthenium hysterophorus (135.32±06.05 spores per unit 50g soil) and minimum (32.26±04.10 spores per unit 50g soil) in Fumaria officinalis. Twenty five AM species belonging to four genera i.e. Acaulospora, Entrophospora, Gigaspora and Glomus were isolated during course of study. Calotropis procera preserve maximum AM spore richness in their rhizospheric soil followed by Solanum nigrum and least in Amaranthus viridis. Among variety of spores, G. geosporum is most frequently occurred species in studied soil samples. The study confirmed the weeds potential to provide hostile environment for conservation, sporulation and propagation of competent AM spores to ensure their ubiquitous distribution.

The parasitic weed Striga hermonthica (Del.) Benth, is a major biotic constraint to the production of cereal crops, particularly sorghum in Africa. The research was aimed to evaluate the allelopathic properties of local plants to inhibit Striga hermonthica weed from Burkina Faso. In this respect, the bio-herbicidal effect of essential oils from 10 local aromatic plants on the germination of S. hermonthica seeds, was evaluated. The research was conducted in 2017 at the phytopathology and weed science laboratory of INERA (Institut de l’Environnement et de Recherches Agricoles) located at Kamboinsé, Burkina Faso.The research using essential oils with 10% dilutions from 10 local aromatic plants were evaluated to inhibition of S. hermonthica germination. Dilutions of 0.2% and 0.4% were applied on conditioned Striga seeds to test their ability to induce Striga germination. Parameters were analyzed using the ANOVA, and the means were compared using DMRT at level of 5%. Germination data of Striga seeds were analyzed using the GenStat Release 12.1 software. The results showed that oils from Cymbopogon citratus (10%)inhibited completely the germination. The ones from Cymbopogon nardus L. and Lippia multiflora Moldenke also inhibited significantly the germination rate compared to the untreated control. Dilutions of 0.2% from four plants essential oils significantly stimulated germination by 5.26% to 60.64% (C. citratus). As we can observe from the above, the oil some essential oils contain metabolites that can be used as bio-herbicides to control S. hermonthica and improve cereal yield. Their use in field conditions can limit environmental pollution and contribute to fight against climate change.

The selection of appropriate variety and proper weed management remains the most significant agronomic problem associated with wheat production in Bangladesh. We, therefore, conducted the current experiment to study the effect of weed management on the weed density and yield performance of some wheat varieties. The experiment was conducted at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh, from November 2016 to March 2017. The experiment consists of three wheat varieties viz. BARI Gom-25, BARI Gom-26 and BARI Gom-29, and four weed managements viz. no use of herbicides (farmers manual hand weeding), herbicide pendimethalin at the dose of 2.5 L ha-1 (pre-emergence), herbicide 2, 4-D at the dose of  2 L ha-1(post-emergence), and combine herbicide of pendimethalin + 2, 4-D.  The experiment was laid out in a randomized complete block design (RCBD) with three replications. Weed parameter and most of the yield contributing characters and yield were significantly influenced by wheat varieties, weed management practices and their interactions. Among the varieties, the highest grain yield (4.59 t ha-1) was recorded in BARI Gom-29, whereas for weed management practices, the highest grain yield (4.76 t ha-1) was obtained in pendimethalin + 2, 4-D treatment.  In interactions,BARI Gom-29 with pendimethalin + 2, 4-D treatment produced the highest grain yield (5.10 t ha-1). Therefore, BARI Gom-29 along with combine herbicide of pendimethalin @ 2.5 L ha-1 (pre-emergence) + 2, 4-D @ 2 L ha-1 (post-emergence) might be taken in consideration for obtaining higher yield in wheat.

Weeds in agriculture are responsible for yield reduction and poor crop quality if not controlled. In maize production, new user-friendly herbicides are being adopted by smallholder farmers. Stellar star whose active ingredients are Topramezone and Dicamba is a selective, systemic post-emergence herbicide used in maize. This poses a threat to crop rotation, especially legumes, due to residual effects. Therefore, the study was carried out to evaluate the phytotoxicity effect of Topramezone and Dicamba herbicide on selected legumes. The trials were conducted in the field and greenhouse. Topramezone and Dicamba herbicide was applied at 4 rates (0, 1.0, 2.0 and 4.0 L ha-1) while legumes were planted at 0, 30, 60, 90 and 120 days residual period. The experimental designs used were CRD for the greenhouse trial and split-split plot design for the field experiment, replicated three and two times respectively. Phytotoxicity effects on legumes were highest at 0, 30 and 60 days residual periods. The coefficient of determination (R2) indicated 96-100% variation in the relationship between days and plant stand count. 4 L ha-1 had the worst average phytotoxicity score of 98%, with control having the lowest at 0%. Results showed whitish, greyish, pale germinated plants which mostly dried after 3 to 5 days. There were highly significant differences (p ≤ 0.01) amongst the treatment means for all parameters.  This means that within 120 days residual period, legumes under study should not be rotated with maize as the herbicide has phytotoxicity effects both at varying application rates and residual period.