Weed Control Regimes Research Articles

EFFECTS OF GRASS-WEED INTERACTIONS ON MORPHO-ECOLOGICAL TRAITS AND WEEDING BENEFITS OF RANGE GRASSES IN SOUTHERN KENYA RANGELANDS

<p><strong>Background:</strong> Weeds invasion into rangeland ecosystems is a precursor for biodiversity loss, increased soil erosion, declining wildlife habitats, and decline in carrying capacity for livestock. These weeds are fierce competitors with range grasses often possessing attributes of high seedling vigor and short life cycles compared to the grasses. Weeds invasion to a pasture land, can starve the grasses grown in the land. <strong>Objective:</strong> To investigate the competitive interactions of three range grasses with weed infestation. <strong>Methodology:</strong> The grasses evaluated were; <em>Chloris roxburghiana </em>(CHLORIS)<em>,</em> <em>Cenchrus</em> <em>ciliaris </em>(CECI), and <em>Eragrotis superba </em>(ERASU). Four weed control regimes were applied: Continuous weeding (T<sub>1</sub>), weeding on the 8<sup>th</sup> week (T<sub>2</sub>), weeding on 10<sup>th</sup> week (T<sub>3</sub>) and the control (T<sub>4</sub>). The grass species Morpho-ecological data was collected on parameters such as; tiller density, grass height, grass density and biomass yield at the grass bloom stage. <strong>Results:</strong> A significant difference in morpho-ecological traits of all the weeding regimes was found. Continuous weed management and weeding at 8<sup>th</sup> week of establishment, respectively showed the highest performance in all the parameters measured. None-weeding management demonstrated the least performance. <strong>Implication:</strong> These research findings will help in developing a long term pasture weeds management plans to prevent encroachment of problematic weed species and to rehabilitate the already degraded rangelands. <strong>Conclusion:</strong> On all the grass species, continuous, weeding, periodic weeding at 8 weeks and 10 weeks demonstrated an increase in dry matter biomass respectively. None-weeding had the least pasture performance. </p>

Physio-biochemical and nutrient constituents of peanut plants under bentazone herbicide for broad-leaved weed control and water regimes in dry land areas

The abundance of broad-leaved weeds in peanut fields represents the handicap in weed management programs, since limited specific herbicides can be recommended to control them. Moreover, the physio-biochemical constituents and nutritional status in peanut plants as affected by available herbicides, i.e., bentazone under water stress conditions are not well known. Therefore, field trials were conducted during the growing seasons in 2016 and 2017 to investigate the interactional impact of irrigation levels (I50, I75 and I100, representing irrigation by 50%, 75% and 100% of crop evapotranspiration, respectively) and weed control practices (bentazone, bentazone+hoeing once, hoeing twice and weedy check as control) on dominant broad-leaved weeds as well as peanut physiological and agronomic traits. Result indicated that the efficiency of weed control for each weeded treatment under I50 significantly equaled with its counterpart under I75 or I100. Bentazone+hoeing once diminished weed biomass by 89.3% and enhanced chlorophyll content of peanut plants by 51.2%. Bentazone relatively caused a reduction in carotenoides. Hoeing twice and bentazone+hoeing once under I100 in both growing seasons as well as hoeing twice under I75 in 2017 were the superior combinations for boosting pod yield of peanut plants. Treatment of bentazone+hoeing once and I75 recorded the lowest reduction in N utilization percentage and the highest increase in potassium utilization percentage of peanut plants. Eliminating weeds enhanced water use efficiency by 37.8%, 49.6% and 34.7% under I50, I75 and I100, respectively. In conclusion, peanut seems to be tolerant to bentazone at moderate water supply, thus it can be safely used in controlling the associated broad-leaved weeds.

Performance of Maize/Rice Intercrop as Affected by Maize (Zea mays L.) Spacing and Weed Control

This trial was conducted to determine maize spacing and weed control effect on the performance of maize/rice intercrop in the Guinea Savanna of Ghana. The study was a 4 x 4 factorial experiment laid out in Randomised Complete Block Design with 3 replications. Four maize spacing’s: 90 x 40 cm, 85 x 40 cm, 80 x 40 cm and 75 x 40 cm and four weed control regimes: weeding at 3 & 6 WAP, weeding at 3, 6 & 9 WAP, weed free and weedy check (no weeding) were used as treatments. Rice was planted at 20 x 20 cm within maize rows, resulting in a 1:2 row arrangement. Data were collected on growth parameters, grain yield, weed biomass and weed species richness. Days to 50% flowering of rice, panicle weight and rice grain yield were significantly enhanced by the interaction effect of maize spacing and weed control. It was evident that, weeding at 3 & 6 WAP and 3, 6 & 9 WAP were best for controlling weeds and resulted in significant influence in almost all of the data taken likewise rice in maize spacing of 85 x 40 cm and 80 x 40 cm. Therefore, to ensure that plant densities are not reduced, farmers are adviced to intercrop maize with rice, using maize spacing of 80 x 40 cm. Similarly, to save time, small-scale farmers are advised to weed only twice at 3 & 6 WAP. However, it was prudent not to suggest any recommendation from the two and three hand weeding’s in interaction with maize spacing, since the results for the interaction appeared not consistent.

Effects of Peanut Stand Uniformity and Herbicide Regime on Weed Management and Yield

ABSTRACT Crop stand directly affects ability of any crop to compete with weeds. To capture this form of cultural weed control, final crop stands need to be uniform. Peanut stands are frequently non-uniform, despite the use of precision vacuum planters. Trials were conducted from 2009 through 2011 in Tifton, GA to determine the effect of non-uniform peanut stands on weed control, grade, and marketable peanut yield. Non-uniform peanut stands were established by modifying vacuum planter discs that created skips 18 cm wide and 36 cm wide at regular intervals and compared with peanut at a uniform stand. The weed control regimes chosen reflected differing degrees of residual weed control provided by flumioxazin or imazapic and addressed the need for residual weed control when peanut stands are non-uniform. Postemergence (POST) herbicides bentazon, paraquat, and 2,4-DB were chosen to test the theory that properly timed applications of non-residual herbicides will control weeds in skips without the need for preemergence (PRE) herbicides. There was no significant interaction between peanut stand uniformity and weed control regime for any parameter. Weed response to peanut stand was variable among species and inconsistent. Weed densities tended to be lower when the residual herbicides flumioxazin and/or imazapic were part of the herbicide regime. Peanut yields and percent total sound mature kernels were not affected by narrow (18 cm) skips, but were reduced two years out of three by wide (36 cm) skips. Peanut yields and grade were similar among weed control regimes that used PRE herbicides and POST herbicides with no residual weed control properties. These results indicate that weed control considerations are not a factor when peanut skips are <18 cm. The herbicide choices evaluated are capable of controlling weeds allowing peanut to compensate for non-uniform stands and not have yield reduction when skips are <18 cm.

Impact of quarantine procedures on weed biodiversity and abundance: Implications for the management of the golden potato cyst nematode, Globodera rostochiensis

In 2006, the golden nematode, Globodera rostochiensis, a regulated pest causing heavy losses in potato fields was discovered in Quebec, Canada. The rapid application of quarantine measures by the Canadian Food Inspection Agency significantly changed the use and management of infested fields. The objectives of this study were to assess the evolution of weed populations following these measures and assess their impact on the management of G. rostochiensis. A comparison of weed inventories conducted in 2008 and 2011 on the edges of the affected fields has shown that the composition of the flora had changed considerably. Alarmingly, the presence of Solanaceae that could potentially serve as host plants for the potato cyst nematode increased significantly. The biodiversity index was also significantly affected by this change and decreased by more than 50% between the two years. Interestingly, the lowest biodiversity was observed in one of the few fields where potatoes were grown in 2011 and where an explosion of Solanum sarrachoides was observed. Meanwhile, eight species of nightshade were evaluated for their ability to support the growth of G. rostochiensis. Solanum villosum allowed the greatest rates of reproduction while only a few cysts were produced on Solanum nigrum and Solanum dulcamara. This study has shown that the modifications in weed control regimes associated with the implementation of quarantine procedures could hamper its success by favouring the multiplication of potential pest refuges.

Impact of weed control on arbuscular mycorrhizal fungi in a tropical agroecosystem: a long-term experiment

Cover crop species represent an affordable and effective weed control method in agroecosystems; nonetheless, the effect of its use on arbuscular mycorrhizal fungi (AMF) has been scantily studied. The goal of this study was to determine root colonization levels and AMF species richness in the rhizosphere of maize plants and weed species growing under different cover crop and weed control regimes in a long-term experiment. The treatment levels used were (1) cover of Mucuna deeringian (Muc), (2) "mulch" of Leucaena leucocephala (Leu), (3) "mulch" of Lysiloma latisiliquum (Lys), (4) herbicide (Her), (5) manual weeding (CD), (6) no weeding (SD), and (7) no maize and no weeding (B). A total of 18 species of AMF belonging to eight genera (Acaulospora, Ambispora, Claroideoglomus, Funneliformis, Glomus, Rhizophagus, Sclerocystis, and Scutellospora) were identified from trap cultures. Muc and Lys treatments had a positive impact on AMF species richness (11 and seven species, respectively), while Leu and B treatments on the other hand gave the lowest richness values (six species each). AMF colonization levels in roots of maize and weeds differed significantly between treatment levels. Overall, the use of cover crop species had a positive impact on AMF species richness as well as on the percentage of root colonized by AMF. These findings have important implications for the management of traditional agroecosystems and show that the use of cover crop species for weed control can result in a more diverse AMF community which should potentially increase crop production in the long run.

The effects of whole-tree harvesting on three sites in upland Britain on the growth of Sitka spruce over ten years

Summary Three experiments were established in the 1990s to examine the impact of complete residue (brash) and above-ground biomass removal (i.e. ‘whole-tree harvesting’, WTH) at clearfelling on the subsequent growth and yield of replanted Sitka spruce (Picea sitchensis). The sites were of varying fertility; two would now be considered to be of ‘medium’ risk for brash removal, while one would be a ‘high’-risk site. The interactions between brash removal and regular remedial fertilizer applications and weed control regimes were also investigated at each site. After 10 years, trees had been successfully established at all sites, and in most cases, the treatments were close to canopy closure. The main effects observed at all sites were due to brash retention and fertilizer application. The benefits from the former were not evident until the last stages of the establishment period, whereas benefits from fertilizer application were evident once the trees had reached 5–6 years of age. The impacts of weed control were inconsistent, providing temporary benefits on the more fertile sites, and having a negative effect on the poorest site, primarily because the herbicide regime favoured the development of ericaceous vegetation which competed with the planted trees for nutrients. After 10 years at the two medium-risk sites, the difference in growth between plots with brash retained and those where brash was removed was 5–9 per cent for height growth and 5–7 per cent for diameter. However, at the poorest site, the equivalent differences were ~9 per cent and 19 per cent. The results show that the impact of brash removal due to WTH are significantly affected by site type and soil fertility and also that it may take nearly a decade before the impacts of such practices are evident.

The influence of environmental factors and dredging on chironomid larval diversity in urban drainage systems in polders strongly influenced by seepage from large rivers

Interest in the biodiversity value of urban waters is growing. Understanding key ecological processes is essential for effective management of these aquatic ecosystems. Our paper focuses on identifying the key factors that structure chironomid assemblages, such as water quality and dredging, in urban waters strongly influenced by seepage of large rivers. Chironomid assemblages were studied in urban surface-water systems (man-made drainage ditches) in polder areas along lowland reaches of the rivers Rhine–Meuse in The Netherlands. Multivariate analysis was used to identify the key environmental factors. Taxon richness, Shannon index (H′), rareness of species, and life-history strategies at urban locations were compared with available data from similar man-made water bodies in rural areas, and the effectiveness of dredging for restoring chironomid diversity in urban waters was tested. Three different chironomid associations were distinguished by Two-Way Indicator Species Analysis. Variation within and among chironomid associations were significantly related to substrate (sludge layer and substrate type: sand vs clay), % cover of lemnids, submerged vegetation, filamentous algae, and water transparency. Chironomid taxon richness and H′ were similar in urban and rural waters, probably because of their similar hydrologic, morphologic, and water-quality conditions and their similar dredging and weed-control regimes. Rareness was slightly higher in urban than in rural waters. In urban water systems, chironomid taxon richness was negatively related to sludge layer and % cover of lemnids. Dredging changed chironomid species composition, and increased taxon richness and life-history strategies indicative of good O2 conditions. Therefore, dredging can be regarded as an effective measure to restore diversity of chironomid communities in urban waters affected by nutrient-rich seepage or inlet of river water.

Tine Cultivation Effects on Weed Control, Productivity, and Economics of Peanut under Organic Management

ABSTRACT Identifying effective weed control regimes for organic peanut is paramount for improving the feasibility of organic production. Tine cultivation is a proven effective method for reducing in-row weed populations in several crops. Field trials were therefore conducted in 2008 and 2009 to assess the effects of tine cultivation combined with sweep cultivation and supplemental hand-weeding on weed control and overall productivity of two peanut cultivars under organic management. Tine cultivation regimes consisted of two frequencies (once per week or twice per week) for three durations (3 wk, 4 wk, or 5 wk). All cultivation treatments were also cultivated with flat sweeps at least once and hand-weeded periodically during the growing season. A non-cultivated, non-weeded control was included for comparison. All cultivation treatments significantly reduced annual grass populations in 2008 and Florida pusley populations both years. Cultivated treatments also resulted in denser plant stands for peanut (9.2 plants/m to 13.2 plants/m) than the non-cultivated control (5.9 plants/m to 7.9 plants/m). Pod yields in cultivated treatments ranged from 3502 kg/ha to 3823 kg/ha and were all significantly greater than yields in the non-cultivated control (1630 kg/ha). Also, net revenues generated by cultivated treatments ranged from ($3333/ha to $3637/ha) and were greater than that of the control ($1795/ha). Cultivation frequency had little effect on weed control and peanut productivity. However, the 4- and 5-wk durations displayed potential for improving peanut yield, grade, and net revenue over the 3-wk duration, especially when annual grass weeds were predominant. Cultivating once weekly for 4 or 5 wk with a tine cultivator, along with at least one sweep cultivation and supplemental hand-weeding, is a viable, economical option for providing adequate weed control and maximizing productivity of organically-managed peanut at current market premiums.

Assessing the effects of cultivating genetically modified glyphosate-tolerant varieties of soybeans (Glycine max(L.) Merr.) on populations of field arthropods

We assessed the effects of cultivating two genetically modified (GM) glyphosate-tolerant soybean varieties (Glycine max (L.) Merr.) derived from Event 40-3-2 and a Japanese conventional variety on arthropods under field conditions, with weed control using glyphosate and conventional weed control for two years. Plant height and dry weight of the conventional variety were significantly larger than those of the GM varieties, but the GM varieties bore more pods than the conventional variety. We found arthropods of nine taxonomic orders (Araneae, Acari, Thysanoptera, Homoptera, Heteroptera, Coleoptera, Diptera, Lepidoptera, and Hymenoptera) on the plants. The arthropod incidence (number per plant unit weight pooled for each taxonomic order) on the soybean stems and leaves generally did not differ significantly between the GM and conventional varieties. However, the incidence of Thysanoptera and total incidence (all orders combined) were greater on the GM variety in the second year. The weed control regimes had no significant influence on the arthropod incidence on the soybean stems and leaves. The number of flower-inhabiting Thysanoptera (the dominant arthropod in the flowers) was not significantly different between the GM and conventional varieties. Asphondylia yushimai (Diptera, Cecidomyiidae) was more numerous on the pods of the GM variety in both years. Neither the soybean variety nor the weed control regime significantly affected the density of soil macro-organisms. However, the glyphosate weed control affected arthropods between the rows of plants by decreasing the abundances of Homoptera, Heteroptera, Coleoptera and Lepidoptera, and diversity of arthropods.

The effects of cover cropping on yield and weed control of potato in a transitional system

Cover cropping can have various beneficial effects to the cropping system such us the increase of soil nutrient content and weed suppression. In this respect, the species used for covering is of great importance. This paper reports results on the yield and weed control effects in potato crops preceded by different cover crops over a 2-year period (2003 and 2004) in Central Italy (Viterbo). Results were obtained in the frame of a more complex study set up in 2002 where in a 3-year chick-pea/potato/tomato rotation, each crop was preceded by 7 different soil managements: 5 cover crops (rapeseed, Italian ryegrass, hairy vetch, snail medick and subclover) + 1 unfertilised weedy fallow (cover crop absent) + 1 control (weedy fallow fertilised with mineral N at a rate of 170 kg ha −1 for potato). Two different weed control regimes in potato were also applied [weed-free crop (1 inter-row hoeing + 1 hilling up + manual weeding on the row); mechanical control (1 inter-row hoeing + 1 hilling up)]. Cover crops were sown in September and cut and ploughed just before potato planting in March. The potato crops following the cover crops were only fertilised with green manure. Averaged over years, all the cover crops produced more above-ground dry biomass than the weedy fallow (4.79 t ha −1 on average vs 2.36 t ha −1). Hairy vetch and subclover accumulated the highest N in the incorporated biomass (169 and 147 kg ha −1), followed by snail medick (108), rapeseed (99), ryegrass (88) and weedy fallow (47). Rapeseed and ryegrass were the most efficient weed suppressors and had the least proportion of weed biomass (<1%) of the total produced by the cover, while they also reduced weed emergence in the following potato crops (8.8 plants m −2 vs 25.5 plants m −2 with all other cover crops). Following subclover and hairy vetch the potato crop yield was similar to that obtained by mineral N-P-K fertilisation (48.5 t ha −1 of fresh marketable tubers). Mechanical weed control compared to weed free crop always reduced potato yield and the reduction, averaged over years, was greater in N-P-K mineral fertilised control (−23.6%) and smaller in ryegrass (−7.9%).

Variations in relative stomatal and biochemical limitations to photosynthesis in a young blackbutt (Eucalyptus pilularis) plantation subjected to different weed control regimes

Foliar gas exchange and carbon (delta(13)C) and oxygen (delta(18)O) isotope ratios were measured in a young blackbutt (Eucalyptus pilularis Sm.) plantation subjected to four weed control treatments defined by the width of the weed-free strip maintained for the first 12 months after planting. Treatments were: 2-m-wide weed-free strip (50% of plot area, 2.0MWC), 1.5-m-wide weed-free strip (37.5% of plot area, 1.5MWC), 1-m-wide weed-free strip (25% of plot area, 1.0MWC) and no weed control (NWC). Our objectives were to determine (1) if decreasing the width of the weed control strip (decreasing herbicide use) affected growth and leaf photosynthesis of the plantation, and (2) the effects of the weed control regimes on variations in relative stomatal and biochemical limitations to photosynthesis. Trees in the 1.0MWC treatment had lower foliar light-saturated photosynthetic rate (A(sat)) than trees in the 2.0MWC treatment. An increase in metabolic limitation was responsible for the decrease in A(sat) in the 1.0MWC trees, which was also partly confirmed by the isotopic data. Compared with trees in the 1.0MWC, 1.5MWC and 2.0MWC treatments, A(sat) of NWC trees was significantly lower, a difference that was attributable mainly to stomatal limitation and to a lesser extent to biochemical limitation. The results support the conclusion that different weed control regimes cause differences in relative stomatal and biochemical limitations to plantation photosynthesis. This report contributes to a growing body of literature on competition for soil resources between trees and weeds. Our results highlight the usefulness of the stable isotopic method in supporting analysis of the response of net photosynthesis to varying intercellular CO(2) concentration for determining the relative stomatal and non-stomatal limitations to photosynthesis under experimental conditions in the field.

Effects of Weed Control and Irrigation on Pecan (Carya illinoinensis) Growth and Yield

Pecan trees subjected to different weed control and irrigation regimes from planting in 1986 through 1993 produced similar yields when irrigated (400 kg/ha, 3-yr avg) and not irrigated (320 kg/ha, 3-yr avg). Trees receiving total chemical weed control produced over five times more pecans (735 kg/ha, 3-yr avg) than weedy trees (131 kg/ha, 3-yr avg). Trees receiving disking produced more pecans when irrigated (677 kg/ha, 3-yr avg) than when not irrigated (339 kg/ha, 3-yr avg). Growth rate, expressed as increase in tree stem diameter, decreased for trees in all treatments once trees began bearing.

Response of no-till and conventionally planted grain sorghum to weed control method and row spacing

Grain sorghum can substitute for corn as a full season crop and replace soybeans in double cropping systems with wheat in the southeastern United States. Relatively few studies have been conducted to measure the response of grain sorghum to tillage, weed control method, and row spacing. These experiments were designed to determine the effects of weed control method and row spacing on no-till planted grain sorghum (Sorghum bicolor L. Moench ‘G1516-BR’) after wheat (Triticum aestivum L. ‘Coker 68–15’) and crimson clover (Trifolium incarnatum L. ‘Bigbee’) grown for winter forage in comparison to sorghum planted on a conventionally prepared seedbed. The experiment included 45, 60, and 90 cm row spacings and three weed control regimes: none, mechanical, and chemical. Grain sorghum planted no-till in crimson clover or wheat sod yielded considerably more grain than conventionally planted sorghum. Grain sorghum produced significantly higher yields in 45-cm rows than in 60-and 90-cm row spacings with all three planting methods. Effects of chemical weed control on weed population with all tillage methods and on grain yield with conventional tillage were significant. There were no significant differences in grain protein content due to row spacing or weed control method.

A Multivariate Assessment of Plant Management Impacts on Macrophyte Communities in a Scottish Canal

SUMMARY (1) A series of aquatic weed control trials was conducted in the Union Canal, Scotland (boat traffic < 500 boat movement ha- ' year-') during 1977-84. The data were used to test the suitability of a multivariate approach for assessing the impacts of plant management on canal macrophyte communities. (2) The procedures detrended correspondence analysis (DCA), and two-way indicator species analysis (TWINSPAN), revealed some fairly subtle trends of plant community change. These were related to the environmental impacts of weed control by herbicides and cutting, and (in a few cases) to shading of submerged macrophytes by accumulations of surface-floating plants. (3) Dissolved oxygen status was significantly negatively correlated with one major axis of the DCA ordination. This axis appeared to reflect a trend of plant community change associated with efficient weed control operations. A second major axis was probably associated with a hydroseral gradient within the (open-water) early stages of vegetational change in the canal plant community. (4) The timing and type of control operations appeared to play an important role in determining the hydroseral age of the plant community present. Sites recently subject to effective weed control generally showed increased dominance by rapid-growing filamentous algae or other opportunists. Untreated sites, sites sampled at long time intervals after control operations, and those where weed control measures had been inefficient, had a lower incidence of opportunist species in the long term. (5) Floating-leaved rooted vegetation (e.g. Potamogeton natans), appeared to be naturally resistant to the weed control regimes used. Such species also compete well with Lemnaceae mats. Because of this relative immunity to the main ecological pressures influencing the submerged community this component of the vegetation is increasing in dominance, and is a cause of major weed problems in the canal. (6) There were significant differences in the efficacy of herbicide and cutting treatments in trials where near-optimal herbicide availance was achieved. Repeated cutting, and early season diquat-alginate application gave acceptable weed control without altering macrophyte community structure to an extent unacceptable in conservation terms. Suboptimal diquat-alginate or terbutryne treatments, and late-season weed-cutting increased the abundance of opportunist algae and Lemna spp., and reduced the diversity of the canal macrophyte community.

Effect of Three Weed Control Regimes on No-Till and Tilled Soybeans (Glycine max)

Postemergence applications or a combination of preemergence and postemergence treatments in double cropped soybeans [Glycine max (L.) Merr. ‘Ransom’] resulted in higher soybean yields than preemergence applications. Preemergence-treated plots were 98% weed free early in the growing season; however, weeds emerged later and reduced yields. Weeds had to be controlled in soybeans for 90% of the growing season to avoid yield loss. Soybean yields were higher under no-till than conventionally tilled management in two of three years and tended to be higher during the third year. Distribution and timing of rainfall were more important in determining soybean yield than the total amount received during the growing season.

Soil Fungi Isolated from Fields Under Different Tillage and Weed-Control Regimes

A qualitative and quantitative survey of soil microfungi isolated from fields under two tillage regimes and three levels of atrazine application was undertaken. Using the soil-plate method, 1,658 c...

Soil Fungi Isolated from Fields under Different Tillage and Weed-Control Regimes

Soil Fungi Isolated from Fields under Different Tillage and Weed-Control Regimes