Wheat and ryegrass competition for pulses of mineral nitrogen

1984 ◽  
Vol 24 (126) ◽  
pp. 421 ◽  
Author(s):  
F Forcella
Keyword(s):  
Biomass Accumulation ◽  
Crop Growth ◽  
Mineral Nitrogen ◽  
Growth Stages ◽  
Annual Ryegrass ◽  
Replacement Series ◽  
Leaf Stage ◽  
True Leaf ◽  
Early Phases

The ability of wheat to compete with annual ryegrass for pulses of extra nitrogen was examined by replacement series competition experiments. Nitrogen pulses were added to wheat and ryegrass monocultures and mixtures when wheat was at one of the following growth stages: first true leaf, two leaf, three leaf, four leaf and six leaf. Wheat competed effectively with ryegrass in terms of biomass accumulation if nitrogen was supplied before the three leaf stage. However, at the three to four leaf stage, wheat lost its ability to use mineral nitrogen effectively, while ryegrass maintained this ability at these same times. Thus, if mixtures of wheat and ryegrass are not supplied with adequate nitrogen in early phases of crop growth, ryegrass may predominate.

scholarly journals Integrating Economics in the Critical Period for Weed Control Concept in Corn

Weed Science ◽  
2014 ◽  
Vol 62 (4) ◽  
pp. 608-618 ◽  
Author(s):  
Martina Keller ◽  
Geoffroy Gantoli ◽  
Jens Möhring ◽  
Christoph Gutjahr ◽  
Roland Gerhards ◽  
...  
Keyword(s):  
Weed Control ◽  
Critical Period ◽  
Logistic Models ◽  
Crop Growth ◽  
Growth Stages ◽  
Corn Yield ◽  
Leaf Stage ◽  
Weed Interference ◽  
Free Interval ◽  
Crop Growth Stages

The effect of weed interference on corn yield and the critical period for weed control (CPWC) were determined in Germany and Benin. Treatments with weed control starting at different crop growth stages and continuously kept weed-free until harvest represented the “weed-infested interval.” Treatments that were kept weed-free from sowing until different crop growth stages represented the “weed-free interval.” Michaelis–Menten, Gompertz, logistic and log–logistic models were employed to model the weed interference on yield. Cross-validation revealed that the log–logistic model fitted the weed-infested interval data equally well as the logistic and slightly better than the Gompertz model fitted the weed-free interval. For Benin, economic calculations considered yield revenue and cost increase due to mechanical weeding operations. Weeding once at the ten-leaf stage of corn resulted already profitable in three out of four cases. One additional weeding operation may optimize and assure profit. Economic calculations for Germany determined a CPWC starting earlier than the four-leaf stage, challenging the decade-long propagated CPWC for corn. Differences between Germany and Benin are probably due to the higher yields and high costs in Germany. This study provides a straightforward method to implement economic data in the determination of the CPWC for chemical and nonchemical weed control strategies.

Effective barley grass (Hordeum spp.) control in annual medics with 2,2-DPA herbicide

1995 ◽  
Vol 35 (6) ◽  
pp. 725 ◽  
Author(s):  
A Wallace ◽  
PM Evans ◽  
D Bowran
Keyword(s):  
Seed Yield ◽  
Treatment Time ◽  
Growth Stages ◽  
Leaf Stage ◽  
True Leaf ◽  
Pasture Legumes ◽  
Annual Grasses ◽  
Annual Medics ◽  
Seed Yields ◽  
Spray Adjuvants

The ability of 2,2-dichloropropionic acid (2,2-DPA) to control annual grasses was examined in a 4-year-old medic (Medicago polymorpha var. brevispina cv. Circle Valley) pasture. Six rates of 2,2-DPA with and without spray adjuvants (1% spray oil + 0.25% wetting agent) were used: 0.37, 0.56, 0.74, 1.11, 1.48, 2.22 kg a.i./ha. The pasture was sprayed in July at the 4-true-leaf stage of the medic, after identifying and counting grasses and medics. Plants were counted again after spraying and grass seed heads were counted in spring. At the end of the season, medic seed yields were obtained. Nine annual pasture legumes were later evaluated for their tolerance to 2.22 kg 2,2-DPA/ha at 3 growth stages [post plant, pre-emergence (PPPE); 3-5-true-leaf stage; flowering] under weed-free conditions. A rate of 1.11 kg 2,2-DPAJha was found to reduce barley grass density by 85%. Efficacy was improved, however, with higher rates and/or the addition of spray adjuvants. Because of low silvergrass (Vulpia spp.) and ryegrass (Lolium rigidurn) plant numbers, it was not possible to assess whether 2,2-DPA controlled these species effectively. There was no effect of herbicide on medic seed yields, seed weight, seed number per pod, or seed germination. Medic seed yields were well correlated with plant density of medic but not with herbicide rates. There was a wide variation in biomass production of the 9 pasture legumes in the evaluation of tolerance, when assessed by visual rating and seed yield, with significant biomass and yield reductions at all timings of application of 2,2-DPA. Subterranean clover (Trifoliurn subterraneum L.) was the most severely affected. Generally, medic species tolerated 2,2-DPA well. Serena was the most susceptible medic cultivar at any treatment time, with seed yield reductions at the first 2 times of application. The results suggest that 2,2-DPA could be used safely on annual medics for the control of barley grass, and possibly other annual grasses.

Evaluating the double knockdown technique: sequence, application interval, and annual ryegrass growth stage

2007 ◽  
Vol 58 (3) ◽  
pp. 265 ◽  
Author(s):  
Catherine P. Borger ◽  
Abul Hashem
Keyword(s):  
Growth Stage ◽  
Field Experiments ◽  
Growth Stages ◽  
Annual Ryegrass ◽  
Application Time ◽  
Lolium Rigidum ◽  
Single Application ◽  
Herbicide Application ◽  
Leaf Stage ◽  
The Difference

Applying glyphosate followed by a mixture of paraquat + diquat in the same season for pre-planting weed control may reduce the risk of developing resistance to either herbicide. Glasshouse and field experiments at Merredin and Beverly, Western Australia, were conducted over 2 seasons to determine the best herbicide application sequence, growth stage of annual ryegrass at which to apply the 2 herbicides, and application time and interval to be allowed between applications for optimum control of annual ryegrass (Lolium rigidum Gaud.). Annual ryegrass plants were treated at 3 growth stages with either glyphosate 540 g a.i./ha alone, paraquat + diquat 250 g a.i./ha alone, glyphosate followed by paraquat + diquat 250 g a.i./ha, or paraquat + diquat 250 g a.i./ha followed by glyphosate 540 g a.i./ha (the double knockdown treatment). The herbicides were applied at different times of the day, with varied intervals between herbicides when applied in sequence. The glasshouse experiment showed that herbicides in sequence more effectively killed annual ryegrass plants at the 3–6-leaf stage than a single application of either herbicide. Field experiments showed that applying glyphosate followed by paraquat + diquat provided 98–100% control of annual ryegrass plants when applied at the 3- or 6-leaf stage in 2002 and at all 3 growth stages in 2003. Generally, the sequence of paraquat + diquat followed by glyphosate was less effective than the reverse sequence, although the difference was not large. Averaged over 2 seasons, herbicides in sequence were most effective when the first herbicide was applied at the 3- or 6-leaf stage of annual ryegrass. An interval of 2–10 days between applications of herbicides was more effective than 1 day or less. The application time did not significantly affect the efficacy of double knockdown herbicides on annual ryegrass plants under field conditions.

Response of canola to simulated diamondback moth (Lepidoptera: Plutellidae) defoliation at different growth stages

2000 ◽  
Vol 80 (3) ◽  
pp. 639-646 ◽  
Author(s):  
Suresh Ramachandran ◽  
G. David Buntin ◽  
John N. All
Keyword(s):  
Diamondback Moth ◽  
Maximum Yield ◽  
Field Trials ◽  
Crop Growth ◽  
Growth Stages ◽  
Economic Injury Level ◽  
Leaf Stage ◽  
Filling Stage ◽  
Crop Development ◽  
Economic Injury

In field trials conducted during 1995–1998, canola cultivar "Falcon" was subjected to different levels of simulated insect defoliation at four stages of crop growth. Plants were 0, 33, 67 and 100% defoliated at rosette and flowering stages during the 1995–1996 season as well as 2–4 leaf stage during the 1996–1997 and 1997–1998 seasons. Plants were 0, 50 and 100% defoliated at pod filling stage during all seasons. Over all seasons, defoliation did not consistently affect the number of plants per unit area, plant height, 1000 seed weight, and oil content of seeds for most of the defoliation treatments. However, defoliation at the 2–4 leaf and rosette stages made plants more susceptible to cold injury. Generally, canola could withstand a higher level of defoliation as crop development progressed. Maximum yield reductions occurred for defoliations at the 2–4 leaf stage followed by the rosette and flowering stages of the crop. No significant yield losses were recorded for defoliations at the pod filling stage. Results suggest that canola is most sensitive to defoliation in its early stages of growth. Greater amounts of defoliation can be tolerated as crop development progresses. The relationships between defoliation and yield loss were used to establish diamondback moth economic injury levels for canola at different crop growth stages. Key words: Canola, Brassica napus, oilseed rape, simulated defoliation, economic injury level

Potential for Adventitious Regeneration of Selected Weed Species

Weed Science ◽  
1984 ◽  
Vol 32 (3) ◽  
pp. 360-363 ◽  
Author(s):  
Vernon B. Langston ◽  
Thomas R. Harger ◽  
Paulette S. Johnsey
Keyword(s):  
Growth Stage ◽  
Adventitious Shoots ◽  
Cotyledonary Node ◽  
Growth Stages ◽  
Weed Species ◽  
Adventitious Regeneration ◽  
Leaf Stage ◽  
True Leaf ◽  
Vegetative Regeneration

The potential of several common weed species to produce adventitious shoots when the plants were excised approximately 1.0 cm below the cotyledonary node at the cotyledon growth stage and at the four true-leaf stage is reported. Indian jointvetch (Aeschynomene indica L. ♯3 AESIN), northern jointvetch [Aeschynomene virginica (L.) B.S.P. ♯ AESVI], and wild poinsettia (Euphorbia heterophylla L. ♯ EPHHL) produced adventitious shoots at both growth stages after shoot excision. Adventitious and vegetative regeneration of wild poinsettia damaged by herbicides was similar to that from decapitation.

Effect of crop growth stage on tolerance to low doses of thifensulfuron:tribenuron

Weed Science ◽  
1997 ◽  
Vol 45 (4) ◽  
pp. 538-545 ◽  
Author(s):  
David A. Wall
Keyword(s):  
Field Studies ◽  
Crop Growth ◽  
Growth Stages ◽  
Low Doses ◽  
Seed Oil Content ◽  
Leaf Stage ◽  
Time Of Application ◽  
Crop Growth Stages ◽  
Sublethal Doses ◽  
Crop Growth Stage

Field studies were conducted at Morden, Manitoba, in 1994 and 1995 to investigate the effect of crop growth stages on canola and sunflower tolerance to sublethal doses of thifensulfuron:tribenuron (2:1). Thifensulfuron:tribenuron at doses of 0, 0.23, 0.45, 0.9, 1.8, and 3.6 g ai ha−1plus a nonionic surfactant at 0.5% v/v were applied to canola and sunflower at the two- to three-leaf, four- to five-leaf, and six- to seven-leaf stages. Crop leaf stage at the time of application affected tolerance of both crops to thifensulfuron:tribenuron. Crop injury was lowest, and flowering, seed yield, and seed oil content were least affected when low doses of thifensulfuron:tribenuron were applied at the two- to three-leaf stage. At the highest dose, there was little practical difference among growth stages since yield of both crops was severely reduced. Producers with drift-affected canola or sunflower can expect less effect on crop yield when thifensulfuron:tribenuron injury occurs during early crop growth.

scholarly journals Quantitative Response of Maize Vcmax25 to Persistent Drought Stress at Different Growth Stages

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1971
Author(s):  
Xingyang Song ◽  
Guangsheng Zhou ◽  
Qijin He ◽  
Huailin Zhou
Keyword(s):  
Drought Stress ◽  
Early Warning Systems ◽  
Growth And Yield ◽  
Leaf Water Content ◽  
Growth Stages ◽  
Leaf Stage ◽  
Maximum Value ◽  
Maize Varieties ◽  
Persistent Drought ◽  
Different Growth Stages

Drought stress has adverse effects on crop growth and yield, and its identification and monitoring play vital roles in precision crop water management. Accurately evaluating the effect of drought stress on crop photosynthetic capacity can provide a basis for decisions related to crop drought stress identification and monitoring as well as drought stress resistance and avoidance. In this study, the effects of different degrees of persistent drought in different growth stages (3rd leaf stage, 7th leaf stage and jointing stage) on the maximum carboxylation rate at a reference temperature of 25 °C (Vcmax25) of the first fully expanded leaf and its relationship to the leaf water content (LWC) were studied in a field experiment from 2013 to 2015. The results indicated that the LWC decreased continuously as drought stress continued and that the LWC decreased faster in the treatment with more irrigation. Vcmax25 showed a decreasing trend as the drought progressed but had no clear relationship to the growth stage in which the persistent drought occurred. Vcmax25 showed a significantly parabolic relationship (R2 = 0.701, p < 0.001) with the LWC, but the different degrees of persistent drought stress occurring in different growth stages had no distinct effect on the LWC values when Vcmax25 reached its maximum value or zero. The findings of this study also suggested that the LWC was 82.5 ± 0.5% when Vcmax25 reached its maximum value (42.6 ± 3.6 μmol m−2 s−1) and 67.6 ± 1.2% (extreme drought) when Vcmax25 reached zero. These findings will help to improve crop drought management and will be an important reference for crop drought identification, classification and monitoring as well as for the development of drought monitoring and early warning systems for other crops or maize varieties.

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