Weed Treatment Research Articles

Influence of Different Tillage Systems and Weed Treatments in the Establishment Year on the Final Biomass Production of Short Rotation Coppice Poplar

In this study the influence of three different tillage systems in combination with eight varying weed treatments applied within the establishment year and its effect on the final above ground leafless biomass production (after the third growing season) of short rotation coppice poplar is presented. The three tillage systems included variants with ploughing and harrowing, variants with cultivation and ley cropping and variants without tillage. Weed treatments included the application of different herbicides, but also more environmentally sound variants such as mulching and the use of mulch materials to avoid the use of herbicides. To estimate the influence on final biomass production, regression analysis was undertaken using DBH as the predictor variable. Based on 1056 DBH measurements the biomass production of the different variants was compared. The interactions of tillage system and weed treatment on biomass yield were found to be statistically significant. Between tillage systems the ploughing variant displayed a better overall performance than the cultivation with ley crop variant and the variant without any tillage. Differing weed treatments reveal greater success for the whole area application of herbicides than band application, both being better than the use of mulch materials. These results suggest that the right tillage system in combination with effective chemical weed control is the key to the successful establishment of Short rotation coppice (SRC) poplar plantation following the principles of an integrated weed management approach. Furthermore, ecological variants such as ploughing in combination with the use of mulch materials and mechanical vegetation control between the rows could be a solution to reduce dependence on chemical control. However, this comes at the expense of a considerable loss in yield.

MAXIMIZING WHEAT PRODUCTIVTY BY USING SOME IMPROVED SOWING METHODS AND WEEDING TREATMENTS

MAXIMIZING WHEAT PRODUCTIVTY BY USING SOME IMPROVED SOWING METHODS AND WEEDING TREATMENTS

Damage and Recovery of Cranberry Vines from Exposure to Handheld Flame Cultivators

Damage and recovery responses of four cranberry varieties (‘Mullica Queen’, ‘Crimson Queen’, ‘Stevens’, and ‘Howes’) to handheld propane flame cultivation (FC) torches were evaluated. All combinations of four levels of exposure duration of three FC torches (open flame 0, 3, 6, and 9 seconds), infrared (IR) and IR with a 4.5-cm metal spike (0, 15, 30, and 45 seconds), were tested on rooted cranberry uprights (vertical stems) planted in clay pots. Pots were subjected to a single treatment from one FC torch at one exposure duration; a glyphosate wipe was also included as a treated control (industry standard). Treatments were replicated five times. All cranberry plants were damaged by all levels of exposure duration as evident by visual damage ratings, reduced net cumulative stem lengths, reduced number of uprights, and reduced proportion of reproductive uprights when compared with untreated plants. All cranberry plants treated with glyphosate had total mortality; all cranberry plants from all varieties treated with FC survived, and all had net positive stem growth in the year after treatment except for ‘Stevens’ treated with open flame and IR with spike. The non-fatal response of cranberry to FC indicates that FC will cause less damage than glyphosate to cranberry plants that are incidentally exposed during spot treatment of weeds and thus could be integrated into weed control in certain situations, including organic farming.

Impact of Fallow Programs and Fumigants on Nutsedge (Cyperusspp.) Management in Plasticulture Tomato

With the loss of methyl bromide (MeBr) and high prices of alternatives, tomato growers are applying lower fumigant rates or adopting a reduced system. Without the broad-spectrum control provided by the complete fumigant system, a fallow weed program might be needed to avoid an increase in pest pressure with consecutive years of application of the reduced-fumigant system. Nutsedges are among the pests of interest due to their fast reproduction by underground structures and ability to spread and quickly infest a field. Field trials were conducted between February and December of 2011 in Balm, FL, to evaluate the impacts of fallow treatments, fumigants, and halosulfuron on nutsedge control. The trial design was a split–split plot with main, sub-, and subsubplots being fallow, fumigant, and herbicide treatment, respectively. Fallow treatments were spaced evenly throughout the fallow season and consisted of sequential combinations of cultivation (C) and/or glyphosate (G) applied at 2.24 kg ae ha−1; including: C, CC, G, GG, CG, GC, GCG, and NO (nontreated control). Fumigant treatments included a reduced-fumigant system of 1,3-dichloropropene plus chloropicrin 40:60 (1,3-D + pic) at 281 kg ha−1, a complete fumigant system of dimethyl disulfide plus chloropicrin 79:21 (DMDS + pic) at 545 kg ha−1, and no fumigant (NoFum). Herbicide treatments were either two POST applications of halosulfuron at 39 g ai ha−1(Hal) or no halosulfuron (NoHal). In general, the fallow weed treatment GCG was the most effective in reducing nutsedge shoot emergence through the plastic mulch. When the reduced-fumigant system 1,3-D + pic was combined with GCG fallow treatment and halosulfuron (GCG:1,3-D + pic:Hal), no differences were found between this combination and the complete fumigant system DMDS + pic with halosulfuron and combined with CC, G, GG, CG, GC or GCG. This study shows the importance of adding a fallow weed program and halosulfuron to either a reduced or complete fumigation system to minimize the reproduction and growth of nutsedges.

Effect of Variety and Weed Management Practices on Yield and Yield Attributes of Wheat

An experiment was conducted at Agronomy Field Laboratory of Rajshahi University to evaluate the effect of variety and weeding regime on yield and yield components of wheat. Four varieties viz. Prodip -V1, Gourab -V2, Shatabdi -V3, Bijoy -V4 and five weeding regime viz. a) No weeding -W0, b) Weed free -W1, c) One hand weeding at 20 DAS -W2, d) Two hand weeding (1st at 20 DAS and 2nd at 42 DAS) -W3 and e) Lintur 70 WG @ 250 g ha-1 -W4 were included as treatments in the experiment. The experiment was laid out in a Split-plot Design with three replications. The results revealed that Prodip produced the highest grain yield (5.33 t ha-1) followed by Gourab (4.85 t ha-1), while the lowest grain yield (3.98 t ha-1) was obtained from Shatabdi. The highest grain yield (5.09 t ha-1) was obtained in Weed free (W1) followed by W3 (Two hand weeding) (4.89 t ha-1) and the lowest grain yield (4.13 t ha-1) was obtained in no weeding treatment (W0). The highest grain yield (5.64 t ha-1) was obtained from the combination of Prodip and weed free treatment (V1W1) and the lowest (3.57 t ha-1) was obtained from the combination between Shatabdi and no weeding treatment (V4W0).DOI: http://dx.doi.org/10.3329/jesnr.v5i2.14800 J. Environ. Sci. & Natural Resources, 5(2): 91-96 2012

배 과원에서 잡초방제 방법에 따른 제초효과와 배나무생육

일반적으로 과수원에서는 배의 생육기 동안 제초방법에 따라 연간 2~4회정도 제초하게 된다. 현재까지 개발된 잡초방제 방법 중 제초제 사용이 가장 생력적이고, 효과적이며 경제적인 것이 사실이나 장기적인 측면에서 생태적 및 생물적 잡초방제를 할 필요가 있다고 하여 배 과원에 비선택성 제초제 GLU 540 g a.i. <TEX>$ha^{-1}$</TEX>를 매년 2회, 3회 처리, 부직포, 기계 예취 등의 방법으로 처리하여 최적의 잡초방제방법을 구명하고 방제방법이 과수에 미치는 영향을 조사하였다. 배 과원에서는 주름잎, 쑥, 갈퀴덩쿨, 쇠뜨기, 뚝새풀 등이 생육기 중 우점하였다. 처리방법에 따른 방제효과는 생육초기 1번 부직포 피복처리가 시기와 상관없이 방제효과가 100%로 가장 높았으며 GLU 540 g a.i. <TEX>$ha^{-1}$</TEX> 3회 처리, GLU 540 g a.i. <TEX>$ha^{-1}$</TEX> 2회 처리, 기계 예취 순으로 잡초방제가가 높았다. 수관 하부 제초방법에 따른 수체 생육은 GLU 540 g a.i. <TEX>$ha^{-1}$</TEX> 2회, 3회 살포한 처리에서 간주비대량과 신초의 생장량이 높고, 신초의 발생개수가 많았으며 부직포 피복, 기계 예취, 무처리와 유의한 차이가 인정되었다. GLU 540 g a.i. <TEX>$ha^{-1}$</TEX>를 3회 처리하여 시기별 방제효과를 비교하였을 때 6월보다 8월에서 방제효과가 증대되었다. 잡초방제 방법차이 및 제초제 2회 처리와 3회 처리 간의 차이는 없었다. 시험기간 동안 제초제 처리에 따른 배나무에 약해 증상은 나타나지 않았다. This study was conducted to clarify effects of weed control methods on damages from agricultural chemicals of pear trees, growth of weeds and states of pear trees after treating pear orchards with different methods of weed controlling, density of GLU and application times. The growth and occupation rate were investigated after 10, 20 and 40 days of weeding treatment. According to a result of the first treatment conducted when weeds in the lower parts of crown in a pear orchard began to grow and grew about 20 cm, unwoven cloth covering showed the highest control value with 100% in all 14 kinds of grasses. In comparison, Stellaria aquatica and catchweed bedstraw showed 96.7% and 97.3% respectively in the 20 DAT investigate after the first treatment of GLU 540 g a.i. ha-1 and the high control value of 100% in other all kinds of grasses. According to an investigation of stalk enlargement, length of new shoot and the number of new shoot made to know differences in tree growth following treatment of the lower part of crown, to use weed killers two or three times a year or to eliminate grasses with machines have positive effects on cross growth of pear trees.

The study of the effect of nitrogen rate and duration weed interference periods on yield and yield components of corn (Zea mays L.)

Performance elements, an experience is implemented in summer 2010, at the station of Ahvaz agricultures research center as broken plot in a design framework of accidental blocks with 3 repetition. The main factor of different amount of nitrogen include 3 level N60, N120, N180 kg/lit pure nitrogen of urea resource & secondary factor of weeds intervention include 3 levels (i) continuous weed until the end of corn growth period (w1), (ii) one time weed in 6 leave level (w2), (iii) complete intervention of weed with corn until the end of corn growth period. The acquired results indicated that weed intervention on yield & yield component has a meaningful effect & by increasing the period of weed intervention, the grain yield is reduced. Increasing weed competition make a meaningful effect on grain weight, performance, biological performance & harvesting index. But increasing amount of nitrogen from N120 kg/lit to N180 kg/lit had not a meaningful effect on grain performance & in some cases due to high pressure, the competition from weed make reduction of grain performance, (once weed treatment & all season intervention). In low & high level of nitrogen, biological performance & corn performance is respectively affected by weed. According to the results of this experience, it can be resulted that by reducing competition time of weed, increasing N can make grain performance enhancement. In contrast to weed competition time, increasing nutritive ingredient is an affected weed growth more than agriculture plant &makes weedcompetitionpowerenhancement.

Growth and Yield of Seed Cotton Response to Plant Spacing and Weeding Frequency under Flood Irrigation

A field experiment was conducted for two years to study the effect of three plant space and four weeding frequency on growth, yield and yields components of seed cotton. Cotton plant spacings were 25, 50and 75 cm whereas the weeding treatments consisted of four levels of hand hoeing (no weeding, weeding once, weeding twice and weeding three times). The experiment was laid out in randomized complete block design (RCBD) with four replications. The results showed that the increased weeding frequencies increased plant height, leaf area index, number of bolls per plant, cotton seed yield. Minimum seed cotton yield (7.1g plant-1) was obtained at non weeded treatments. The plant spacing of 75cm caused significant increase in sympodial branches, total number of bolls per plant, seed cotton weight per plant. The intra row-spacing of 25 cm produced the highest lint and cotton seed yield per unit area. Lint yield showed increasing trend with increase in weeding frequency.

Weed Management in Mature Coconut Plantations in Sri Lanka

Weeds are a perennial problem in coconut plantations and cause significant losses in terms of nut yield. The occurrence of a wide range of weeds also causes difficulties in their eradication. The influence of buffalo grazing on weed biomass and nut yield was evaluated to determine the economical and effectiveness of this method to control weeds in coconut plantations in the low country wet zone of Sri Lanka. Treatments imposed were: tractor slashing as control (T1), cover cropping with Pueraria phaseoloides (T2) and buffalo grazing (T3). Slashing treatment was applied three times per year and buffalo grazing was practiced once a month to control grasses and weeds. The treatments were arranged in a Randomized Complete Block Design with three replicates. Based on the reduction of the weed biomass, treatments T2 and T3 were found to be significantly effective (P&lt;0.05) over slashing treatment. Coconut yield was increased significantly (P&lt;0.05) in buffalo grazing plots and decreased in cover cropping plots. Control of weeds with buffalo grazing and cover cropping with Pueraria resulted in 7% increase and 6% decrease in nut yield over the slashing plots respectively. Buffalo grazing was found to be the most effective method of controlling weeds in coconut plantations. Cover cropping with Pueraria phaseoloides was effective in controlling weeds in the long term, but was not economically beneficial compared with the buffalo grazing. Establishment of cover crop was helpful to conserve soil moisture but it appeared to compete with palms for soil nutrients. A high soil penetrometer resistance in the grazing plots pointed to a significant change in the soil structure as a result of buffalo traffic in the area. Harrowing the buffalo grazing plots appeared to be the best method to overcome soil compaction and finally increase soil aeration and create more favorable environment for palm growth.DOI: http://dx.doi.org/10.4038/cocos.v19i2.4755

Response of weed flora to conservation agriculture systems and weeding intensity in semi-arid Zimbabwe

A field study was conducted in the fifth (cowpea crop) and sixth (sorghum crop) seasons of a long-term conservation agriculture trial at Matopos Research Station to determine the effect of tillage, maize mulch rates and intensity of hoe weeding on weed density and community diversity. The experiment was a split-plot randomized complete block design with three replications. Tillage was the main plot factor; conventional tillage versus the minimum tillage (MT) systems of ripper tine and planting basins. Maize mulch rate (0, 4 and 8 t ha-1) was the sub-plot factor to which was super-imposed the intensity of hoe weeding treatment (low and high) as from the fifth season. Tillage system had no significant (P<0.05) effect on weed density and diversity. Whereas the maize mulch rate of 4 t ha-1 increased weed density in both crops, the mulch rate of 8 t ha-1decreased the density of Portulaca oleracea and Corchorus tridens in sorghum. Weed density was lower and community diversity higher in the high than the low weeding intensity treatment in sorghum. Although, frequent hoe weeding can be used to control weeds in MT systems, labour shortages may ultimately limit the area under MT in smallholder agriculture. Key words: Tillage, maize mulch, weed density, community diversity, cowpea (Vigna unguiculata (L.) Walp.), sorghum (Sorghum bicolor (L.) Moench).

Eficiência no uso da água e interferência de plantas daninhas no meloeiro cultivado nos sistemas de plantio direto e convencional

Com o objetivo de avaliar o efeito dos sistemas de plantio direto e convencional e estratégias de manejo de plantas daninhas na economia de água de irrigação na cultura do melão (Cucumis melo), conduziu-se um experimento na horta didática do Departamento de Ciências Vegetais da Universidade Federal Rural do Semiárido, em Mossoró-RN, utilizando o delineamento experimental de blocos casualizados, no esquema de parcelas subdivididas. Nas parcelas foram avaliados dois sistemas de plantio (plantio direto e convencional) e, nas subparcelas, três sistemas de manejo de plantas daninhas (cobertura com filme de polietileno, mantido no limpo por meio de capinas e testemunha sem capinas). Avaliaram-se a densidade e a massa seca das plantas daninhas aos 30 dias após o transplante, a produtividade comercial e total e o consumo diário de água. O manejo da água foi realizado mediante a curva característica de água no solo para cada sistema de plantio a 15 e 30 cm de profundidade, e o controle da lâmina de água foi feito com base na leitura diária de um conjunto de tensiômetros instalados nas mesmas profundidades, de modo que se mantivesse a umidade do solo sempre acima de 75% da água disponível total. A partir da produtividade e do consumo de água, determinou-se a eficiência no uso da água (EUA), dada em kg m-3. Verificou-se que o sistema de plantio direto na palha reduziu a densidade populacional e a massa seca acumulada pelas plantas daninhas em 86,7 e 61%, respectivamente, em relação ao plantio convencional, e a interferência destas reduziu a produtividade comercial em 100% no plantio convencional e 36,5% no direto. A cobertura do solo com filme de polietileno no plantio convencional e no plantio direto e a palhada no plantio direto reduziram o consumo de água em 23% (388,8 m³ ha-1), 21% (363,0 m³ ha-1) e 13% (215,0 m³ ha-1), respectivamente, em relação ao tratamento com capinas no plantio convencional. A cobertura do solo com filme de polietileno nos dois sistemas de plantio ou com cobertura morta no plantio direto aumentou a eficiência no uso da água em relação ao solo sem cobertura. No tratamento sem capinas no sistema de plantio convencional, além da perda total na produtividade comercial, a interferência das plantas daninhas aumentou o consumo de água em 9,6%.

Ecophysiological responses of a young blue gum (Eucalyptus globulus) plantation to weed control

Early weed control may improve the growth of forest plantations by influencing soil water and nutrient availability. To understand eucalypt growth responses to weed control, we examined the temporal responses of leaf gas-exchange, leaf nitrogen concentration (N) and water status of 7-month-old Eucalyptus globulus L. trees in a paired-plot field trial. In addition, we monitored the growth, leaf N and water status of the competing vegetation in the weed treatment. By the end of the 11-month experiment, complete weed control (WF treatment) of largely woody competitors increased the basal diameter of E. globulus by 14%. As indicated by pre-dawn water potentials of > - 0.05 MPa, interspecies competition for water resources was minimal at this site. In contrast, competition for N appeared to be the major factor limiting growth. Estimations of total plot leaf N (g m(-2) ground) showed that competing vegetation accounted for up to 70% of the total leaf N at the start of the trial. This value fell to 15% by the end of the trial. Despite increased leaf N(area) in WF trees 5 months after imposition of weed control, the photosynthetic capacity (A(1500)) of E. globulus was unaffected by treatment suggesting that the growth gains from weed control were largely unrelated to changes in leaf-level photosynthesis. Increased nutrient availability brought about by weed control enabled trees to increase investment into leaf-area production. Estimates of whole-tree carbon budget based on direct measurements of dark respiration and A(1500) allowed us to clearly demonstrate the importance of leaf area driving greater productivity following early weed control in a nutrient-limited site.

Impact of selective flame weeding on onion yield, pungency, flavonoid concentration, and weeds

Field experiments were conducted to evaluate the effects of multiple selective flame weeding treatments on onion (Allium cepa L.). Onions were flamed between one and six times over the course of the season with a high (72 kg propane ha−1) or low (45 kg propane ha−1) propane dose. In each treatment, one subplot was hand-weeded in addition to flame treatment to remove differential weed effects, while the other received only the prescribed flame weeding regimen as weed control. Overall, control of broadleaf weeds was better than that of grass species. Broadleaf weed density and shoot mass were reduced as propane dose and the number of flame treatments increased. Grass density was reduced by 50% in all flamed treatments compared to the non-treated control, but no differences between flamed treatments were observed. Effects of flame treatments on grass shoot mass were minimal. Among weed-free treatments, onion was able to tolerate up to six flame treatments at either dose without a loss of yield. Treatments that received only flame weeding as weed control had total onion yields 37 and 80% of the weed-free flamed treatments in 2006 and 2007, respectively. Flame weeding treatments had little effect on the time to reach maturity, onion pungency, or quercetin concentration.

Establishment of Fabaceae Tree Species in a Tropical Pasture: Influence of Seed Size and Weeding Methods

The successful establishment of trees in pastures may be related to species, seed size, and weed control treatments. This study experimentally evaluated the emergence, establishment after 2 years, and growth of individuals of 7 tree species with different seed sizes sowed under three weeding methods (no weeding, grasses clipped, and grasses removed). The experiment was carried out in a tropical abandoned pasture in Midwestern Brazil, dominated by the exotic invasive grass Urochloa brizantha. The effect of seed size on seedling emergence was significant and was more intense in the no weeding and weeding treatment plots than in grasses clipped. Furthermore, an increase in seed size resulted in an increase in the probability of establishment of tree species, although this pattern also differed among weeding treatments. The increase in seed size reflected negatively on tree growth in the absence of grasses, whereas in the presence of grasses there was an inverse relationship. The experimental results suggested that the use of seeds of different sizes for direct seeding in pastures is a possible strategy of Fabaceae tree species reintroduction in pastures within the Cerrado. Fabaceae species with seeds larger than 100 mg can establish in areas with no weeding, whereas species with seeds smaller than 50 mg can establish preferentially in areas with weeding, growing faster than larger ones. Thus, weeding strategies can determine the success of direct seeding of different species in restoration projects of tropical pastures.

Weed biomass and economic yield of wheat (Triticum aestivum) as influenced by chemical weed control under rainfed conditions

A study to investigate the efficacy of different herbicides on rainfed wheat was carried out at the experimental farm, of the University of Arid Agriculture, Rawalpindi during 2004 to 2007. Wheat variety GA-2002 was planted as a test crop. The experiment was carried out in randomized complete block design (RCBD) with three replications. Among different treatments, the lowest weed biomass was achieved in hand weeding treatment. Plots treated with herbicide Buctril super (Bromoxonil + MCPA) also produced excellent results in reducing weed biomass. The highest grain yield was recorded in plots where Buctril Super was sprayed. Weedy check treatment was at the bottom with the lowest grain yield. Economic analysis indicated that Buctril super was the best treatment with the highest benefit cost ratio. Key words : Wheat, weed control, herbicides, rainfed conditions.

The effect of spraying of wheat straw extracts on controlling some weed species.

This experiment was designed to compare the effect of spraying wheat straw aqueous extracts to control broad and narrow leaf weed plants in wheat fields with some common used herbicides in the region. The study consisted of five treatments; wheat straw aqueous extract; grass weeds herbicide clodinafop-propargyl (Topik); broad leaf herbicide tribenuron-methyl (Granstar); zero control (no weed control) and zero or no- weed treatments , chlorophyll a, b and total chlorophyll were indicated for all treatments after 48 hours from herbicide application. Results illustrated significant differences between all treatments, minimum wheat yield was recorded in zero control plots then plots that was treated with wheat straw aqueous extracts, Broad leaf weed herbicide (Granstar), narrow leaf weeds herbicide (Topic) and maximum yield was recorded with zero weed treatments, results of this study elucidate the potentiality of using wheat aqueous extracts for controlling some weed plants due to its obvious effect on reducing the weed plants height and the levels of chlorophyll a, b and total chlorophyll in treated wheat plants. Keywords - Allelopathy, Dicot, Monocot, weed plants.

Microwave Technologies as Part of an Integrated Weed Management Strategy: A Review

Interest in controlling weed plants using radio frequency or microwave energy has been growing in recent years because of the growing concerns about herbicide resistance and chemical residues in the environment. This paper reviews the prospects of using microwave energy to manage weeds. Microwave energy effectively kills weed plants and their seeds; however, most studies have focused on applying the microwave energy over a sizable area, which requires about ten times the energy that is embodied in conventional chemical treatments to achieve effective weed control. A closer analysis of the microwave heating phenomenon suggests that thermal runaway can reduce microwave weed treatment time by at least one order of magnitude. If thermal runaway can be induced in weed plants, the energy costs associated with microwave weed management would be comparable with chemical weed control.

Comparison of Weed Management Programs for Furrow-Irrigated and Flooded Hybrid Rice Production in Arkansas

Whether season-long weed control can be achieved in a furrow-irrigated rice system with similar herbicide inputs to that of a flooded system is not known. Field experiments were conducted in 2007 and 2008 at Pine Tree, AR to evaluate different herbicide programs on the weed control efficacy and rice grain yield in furrow-irrigated and flooded rice production systems. Six herbicide programs were evaluated with and without additional late-season “as-needed” herbicide treatments. Minor injury to rice was noted for quinclorac plus propanil. However, the injury was transient and the plants fully recovered. Overall weed control was greater in the flooded system compared with the furrow-irrigated system (up to 20% greater), because flooding effectively prevented the emergence of most terrestrial weeds. In addition, rice grain yields were 13 to 14% greater in flooded compared with furrow-irrigated plots. Irrespective of the irrigation system, herbicide programs that contained a PRE-applied herbicide provided greater weed control and resulted in greater yield compared with those that did not contain PRE-applied herbicide, indicative of the importance of early-season weed control in achieving higher grain yields. On the basis of weed control, yield, and weed treatment cost, the herbicide program with clomazone PRE followed by propanil at four- to five-leaf rice was more efficient than other programs evaluated in both irrigation systems. However, furrow-irrigated plots required as-needed herbicide applications, which were applied after the four- to five-leaf rice stage when two or more plots within a program exhibited ≤ 80% control for any of the weed species. This suggests that furrow-irrigated rice production demands additional weed management efforts and thereby increases production costs. There is also a possibility for substantial yield reduction in the furrow-irrigated system compared with the flooded system. Nevertheless, furrow-irrigated rice production can still be a viable option under water-limiting situations and under certain topographic conditions.

Modeling nitrogen uptake for hybrid poplar with and without weed competition

Quantitative understanding of nutrient uptake by competing plants with different root systems can be a beneficial tool in designing the nutrient management strategies for competing plant environments. A field study was conducted at two sites (Alfalfa and Pasture site) near Meadow Lake, Saskatchewan, Canada to investigate the effect of weed competition on the growth and nitrogen (N) uptake by hybrid poplar ( Populus deltoides × Populus × petrowskyana var. Walker) using the Soil Supply and Nutrient Demand (SSAND) model. Hybrid poplar was grown with and without weeds (mainly dandelion ( Taraxacum officinale F.H. Wigg.) and quackgrass ( Elymus repens (L.) Gould) for 50, 79 and 100 days. Above-ground and below-ground growth of hybrid poplar was adversely affected by the presence of weeds at both sites. At the end of the experimental period, hybrid poplar in the control treatment took up 15.8 and 15.7 mmol N plant −1 while seedlings in the weed treatments accumulated only 1.7 and 2.1 mmol N plant −1 at the Pasture and Alfalfa sites, respectively. The SSAND model predictions for hybrid poplar N uptake at the Pasture site were in close agreement with measured N uptake in the control treatment (slope = 0.95–0.98). Model predictions for the Alfalfa site underestimated N uptake in the control treatment compared to measured values (slope = 0.75–0.77). The SSAND model greatly underestimated N uptake by both hybrid poplar and weeds grown in the weed treatment. Including N mineralization as a model input also did not improve the N uptake predictions; however, including changing soil water content greatly improved the prediction of N uptake by both hybrid poplar and weeds. Results from this study suggest that weed control is an essential practice to successful establishment of hybrid poplar plantations. Furthermore, the SSAND model can be a potentially useful tool for enhancing our understanding of plant nutrient uptake under field conditions where the dynamic nature of soil moisture and mineralization processes influence plant growth.

Intercropping of oat and field pea in Alaska: An alternative approach to quality forage production and weed control

Intercropping of legumes with non-legumes is an ancient crop production method used to improve quality and dry matter (DM) yields of forage and grain, and to control weeds. However, there is little information regarding intercropping at high latitudes. The objectives of this field study were to evaluate performance of (1) sole cropped oat (Avena sativa L.) (cultivars Toral and Calibre) and pea (Pisum sativum L.) (cultivars Carneval and Orb) and their intercrop combinations, and (2) inter- and sole-crop responses to weeds. The different cropping systems were studied with different weed treatments (weed-free all season long, weed-free until flowering, and left weedy all season long). In general intercrops of oat and pea produced DM (forage) and grain yields similar to sole oat crops and higher than sole pea crops although the difference was not statistically significant. Furthermore, forage quality [crude protein (CP), acid detergent fiber (ADF) and neutral detergent fiber (NDF)] was improved by intercropping. Most of the variables measured were unaffected by weed treatments, however weed DM was generally lower in sole oat and oat-pea intercropping than sole pea cropping systems. More than 80% of the weed DM was from common lamb's quarters (Chenopodium album L.). The CP of this weed was higher than oat and pea, and ADF and NDF were equivalent to the sole cropped oat. Thus, including weeds as part of the forage is possible. However, if crops are grown for grain, weeds are likely to produce large numbers of seeds that would enter the seed bank. Thus, pea–oat intercrops show potential as an alternative and sustainable approach for optimum yield and high quality forage and weed control under Alaskan subarctic conditions.