Seed production of Stylosanthes guyanensis. 2. The consequences of defoliation

1976 ◽  
Vol 16 (79) ◽  
pp. 226 ◽  
Author(s):  
DS Loch ◽  
JM Hopkinson ◽  
BH English
Keyword(s):  
Seed Production ◽  
Field Experiments ◽  
Shoot Development ◽  
Flower Initiation ◽  
Crop Canopy

The consequences of defoliation on seed production of stylo (Stylosanthes guyanensis) were examined in field experiments at Walkamin in north Queensland. The practical aim of defoliation is to present a level uncompacted crop canopy to the harvester without a reduction in the quantity of seed carried at harvest ripeness. It was concluded that the latest date at which defoliation is reasonably certain to achieve its objectives is about four weeks before first flower initiation. In north Queensland, this means late February for cvv. Cook and Endeavour and early April for cv. Schofield. The results suggest that development of the population of individual shoots must be synchronized to produce the highest peaks of standing seed; that this is best achieved by ensuring that a closed crop canopy with a ceiling shoot population exists at the time of first flower initiation; and that poorly synchronized shoot development is a consequence of defoliating too late and a cause of reduced seed production.

scholarly journals Rattail fescue (Vulpia myuros) interference and seed production as affected by sowing time and crop density in winter wheat

Weed Science ◽  
2020 ◽  
pp. 1-10
Author(s):  
Muhammad Javaid Akhter ◽  
Per Kudsk ◽  
Solvejg Kopp Mathiassen ◽  
Bo Melander
Keyword(s):  
Winter Wheat ◽  
Grain Yield ◽  
Seed Production ◽  
Yield Components ◽  
Field Experiments ◽  
Growing Season ◽  
Sowing Time ◽  
Growing Seasons ◽  
Crop Density ◽  
Wide Range

Abstract Field experiments were conducted in the growing seasons of 2017 to 2018 and 2018 to 2019 to evaluate the competitive effects of rattail fescue [Vulpia myuros (L.) C.C. Gmel.] in winter wheat (Triticum aestivum L.) and to assess whether delayed crop sowing and increased crop density influence the emergence, competitiveness, and fecundity of V. myuros. Cumulative emergence showed the potential of V. myuros to emerge rapidly and under a wide range of climatic conditions with no effect of crop density and variable effects of sowing time between the two experiments. Grain yield and yield components were negatively affected by increasing V. myuros density. The relationship between grain yield and V. myuros density was not influenced by sowing time or by crop density, but crop–weed competition was strongly influenced by growing conditions. Due to very different weather conditions, grain yield reductions were lower in the growing season of 2017 to 2018 than in 2018 to 2019, with maximum grain yield losses of 22% and 50% in the two growing seasons, respectively. The yield components, number of crop ears per square meter, and 1,000-kernel weight were affected almost equally, reflecting that V. myuros’s competition with winter wheat occurred both early and late in the growing season. Seed production of V. myuros was suppressed by delaying sowing and increasing crop density. The impacts of delayed sowing and increasing crop density on seed production of V. myuros highlight the potential of these cultural weed control tactics in the long-term management programs of this species.

Inter-row Cultivation Timing Effects on Waterhemp (Amaranthus tuberculatus) Control and Sugarbeet Yield and Quality

2021 ◽  
pp. 1-39
Author(s):  
Nathan H. Haugrud ◽  
Thomas J. Peters
Keyword(s):  
Weed Management ◽  
Field Experiments ◽  
Leaf Tissue ◽  
Sucrose Content ◽  
Climate Data ◽  
Crop Canopy ◽  
Control Practice ◽  
Amaranthus Tuberculatus ◽  
Residual Herbicide ◽  
Weed Emergence

Abstract The invasion of waterhemp into northern sugarbeet growing regions has prompted producers to re-integrate inter-row cultivation into weed management programs as no currently registered herbicides can control glyphosate-resistant waterhemp POST in crop. Inter-row cultivation was a common weed control practice in sugarbeet until the release of glyphosate-resistant sugarbeet cultivars in 2008 made the use of inter-row cultivation unnecessary. In the late 2010s, producers began again to use inter-row cultivation to remove weeds that glyphosate did not control, but producers need information on the effectiveness and safety of inter-row cultivation when used with soil residual herbicide programs. Efficacy and tolerance field experiments were conducted in Minnesota and North Dakota from 2017 to 2019. Results from the efficacy experiment demonstrated cultivation improved waterhemp control 11% and 12%, 14 and 28 DAT, respectively. Waterhemp response to cultivation was dependent on crop canopy and precipitation after cultivation. Cultivation had minimal effect on waterhemp density in three environments, but at one environment, near Galchutt, ND in 2019, waterhemp density increased 600% and 196%, 14 and 28 DAT, respectively. Climate data indicated Galchutt, ND in 2019 received 105 mm of precipitation in the 14 days following cultivation and had an open crop canopy which likely contributed to further weed emergence. Results from the tolerance experiment demonstrated root yield and recoverable sucrose were not affected by cultivation timing or number of cultivations. In one environment, cultivating reduced sucrose content by 0.8% regardless of date or cultivation number, but no differences were found in three environments. In-season cultivation can damage/destroy leaf tissue which is likely responsible for the reduction in sucrose content. Results indicate cultivation can be a valuable tool to control weeds that herbicide cannot, but excessive rainfall and open crop canopy following cultivation can create an environment conducive to further weed emergence.

Weed Seedling Emergence and Survival as Affected by Crop Canopy

2008 ◽  
Vol 22 (4) ◽  
pp. 736-740 ◽  
Author(s):  
Randy L. Anderson
Keyword(s):  
Winter Wheat ◽  
Seed Production ◽  
Spring Wheat ◽  
Seedling Emergence ◽  
Crop Canopy ◽  
Cool Season ◽  
Common Lambsquarters ◽  
Green Foxtail ◽  
Seedling Emergence And Survival ◽  
Weed Dynamics

This study measured impact of cool-season crops on seedling emergence, survival, and seed production of weeds common in corn and soybean. Weed dynamics were monitored in permanently marked quadrats in winter wheat, spring wheat, and canola. Three species, green foxtail, yellow foxtail, and common lambsquarters, comprised more than 80% of the weeds observed in the study. Seedling emergence was reduced by winter wheat, but not by spring wheat or canola, when compared with adjacent quadrats without a crop canopy. Approximately 10% of seedlings in spring wheat and canola developed into seed-bearing plants, but no seed-bearing plants were present in winter wheat at harvest. Common lambsquarters produced more than 1,100 seeds/plant, whereas a foxtail plant produced 85 seeds, averaged across spring wheat and canola. At harvest, new seedlings were present in all crops; thus, control after harvest will be required to prevent seed production in the fall. Winter wheat may provide an opportunity to disrupt population dynamics of weeds common in corn and soybean without requiring herbicides.

scholarly journals Ecologically safe methods for presowing treatment of cereal seeds

2019 ◽  
Vol 9 (3) ◽  
pp. 198-207
Author(s):  
V. V. Bezpal'ko ◽  
L. V. Zhukova ◽  
S. V. Stankevich ◽  
Yu. H. Ogurtsov ◽  
I. I. Klymenko ◽  
...  
Keyword(s):  
Winter Wheat ◽  
Seed Production ◽  
High Frequency ◽  
Field Experiments ◽  
Spring Barley ◽  
Ecological Features ◽  
Extremely High Frequency ◽  
Presowing Treatment ◽  
Before And After ◽  
Crop Capacity

We analyzed various sources of scientific literature and our data at the experimental field of the National Academy of Agrarian Sciences Plant Growing Institute named after V.Ya. Yuryev within 2010-2013. The irradiation of winter wheat and spring barley seeds with the electromagnetic fields of the extremely high frequencies (MWF of EHF) was carried out with the help of the equipment of the Kharkiv Technical University of Radio Electronics. The treatment of seeds with the microwave oscillations of the extremely high frequency electromagnetic field (MWF of EHF) that is widely used for the operation of many radio and home microwave devices was done at the frequency range of 2.5-3.4 GHz, at the power of 0.9-1.8 kW for 5-95 seconds per 1 kg of seeds. The sowing quality of the seeds before and after treatment was determined in accordance with the current State Standard of Ukraine 4138-2002 in the laboratory of the seed production and seed science of the Plant Growing Institute named after V.Ya. Yuryev. The field experiments were performed in the crop rotation laboratory of the seed production and seed science. Pea for grain was sown before spring barley and the black fallow preceded winter wheat. During the experiments the area of the studied plot was 20 m2, the recurrence was four-times, and the placement of the plots were systemic.We suggested the optimum regimes of seeds irradiation with the microwave field of an extremely high frequency (MWF of EHF). They should be at range of 2.4-3.4 GHz with the power consumption of 0.9 kW per 1 kg of seed and at exposure of 45 seconds of 1.8 kW per 1 kg of seeds and exposure of 15-20 seconds. Such regimes cause the increased energy of germination, seeds sprouting, and crop capacity. We proposed to use this solution for improving and increasing the ecological features of winter wheat and spring barley by using the presowing microwave irradiation of seeds instead of chemical treatment. We considered the complex presowing treatment of seeds with MWF of EHF in combination with the plant growth regulators should be adopted and further enhanced.

Cultural Practices Affecting Season-Long Weed Control in Irrigated Corn (Zea mays)

Weed Science ◽  
1984 ◽  
Vol 32 (4) ◽  
pp. 460-467 ◽  
Author(s):  
Russell S. Moomaw ◽  
Alex R. Martin
Keyword(s):  
Zea Mays ◽  
Weed Control ◽  
Seed Production ◽  
Field Experiments ◽  
Cultural Practices ◽  
Fine Sand ◽  
Corn Yield ◽  
Weed Seed ◽  
Weed Growth ◽  
Herbicide Use

Season-long weed control has been a goal of some producers of irrigated corn (Zea maysL.) to reduce competition, lessen weed seed production, facilitate crop harvest, improve water efficiency (particularly with furrow irrigation), and improve aesthetic properties of fields. Field experiments were conducted for 3 yr on sprinkler-irrigated corn on a loamy fine sand. Five herbicides applied at layby generally provided season-long control of grass weeds and reduced weed seed production up to 100%. Pendimethalin [N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine] was particularly effective. Yields of irrigated corn were not increased by layby herbicide application. Use of corn rows spaced 91 cm apart and use of a shorter, early-maturing, horizontal-leaf corn cultivar resulted in greater weed growth and weed seed production than did use of 76-cm rows and a taller, full-season, upright-leaf corn cultivar. After nearly complete weed control with herbicides for 2 yr, withholding herbicide use in the third year allowed weed growth which reduced corn yield. Indications were that weed control efforts need to be continuous in irrigated corn production.

Competition betweenElymus elymoidesandTaeniatherum caput-medusae

Weed Science ◽  
1999 ◽  
Vol 47 (6) ◽  
pp. 720-728 ◽  
Author(s):  
David W. Clausnitzer ◽  
Michael M. Borman ◽  
Douglas E. Johnson
Keyword(s):  
Soil Moisture ◽  
Interspecific Competition ◽  
Seed Production ◽  
Intraspecific Competition ◽  
Field Experiments ◽  
Block Design ◽  
Low Oxygen ◽  
Competitive Effects ◽  
Growing Seasons ◽  
Randomized Block Design

Two field experiments were conducted from 1993–1994 through 1995–1996 growing seasons in Harney County, OR, to determine the relative competitive abilities ofElymus elymoides(squirreltail) a native perennial range grass, andTaeniatherum caput-medusae(medusahead), an exotic annual grass weed. The 1993–1994 growing season was very dry, 1994–1995 was dry, and 1995–1996 was wetter than average. One experiment tested seedlings vs. seedlings in each of three seasons. The second experiment tested seedlings plus second- and third-year establishedE. elymoidesplants vs. 77caput-medusaeover 2 yr. Biomass, seed production, and soil moisture utilization 15, 30, 45, and 60 cm deep by the two species were measured. A randomized block design with factorial arrangement was used, with 25 2.25-m2plots per block. Initial seeding densities of each species were 0, 10, 74, 550, and 4,074 seeds m−2in all combinations of density. In the seedling vs. seedling experiment, intraspecific competition by 77caput-medusaeon itself was always significant (P ≤ 0.10) for both biomass and seed production. Interspecific competition byE. elymoidesseedlings onT. caput-medusaebiomass and seed production was not significant (P ≥ 0.10) in 2 of 3 yr and was always less than intraspecific competition by 77caput-medusae. Only 0.4% ofE. elymoidesseed germinated, and no seed was produced in the very dry first year, but 84% of remaining seed was viable for the next year, which had better moisture conditions for germination and establishment. Interspecific competition affected (P ≤ 0.10)E. elymoidesseedling biomass and seed production throughout the study. Intraspecific competition affected (P ≤ 0.10) seedlingE. elymoidesseed production in the dry year but not in the wetter than average year. In the matureE. elymoidesexperiment, intraspecific competition byT. caput-medusaeon weight and seed production per plant was greater than interspecific competition fromE. elymoides. Seedling/matureE. elymoidesreducedT. caput-medusaeweight per plant in the dry year but the effect was not biologically significant. Larger, matureEelymoidesplants produced 600 to 3,000 seeds per plant during the wet year; neither intra- nor interspecific competition was a factor.Taeniatherum caput-medusaewas better able to access deeper soil moisture and was more aggressive at extracting soil moisture than wereE. elymoidesseedlings in the wet year. Cold soils and low oxygen due to wet soils may have restrictedE. elymoidesseedling root activity. MatureE. elymoidesplants did not appear restricted by cold soils or low oxygen. Established second- and third-yearE. elymoidesplants were able to compete for soil moisture down to 45 cm. The generally greater interspecific competitive effects ofT. caput-medusaeonE. elymoidesthan vice versa suggested that it will be difficult to establish anE. elymoidesstand in an existingT. caput-medusaecommunity without first suppressingT. caput-medusae. IndividualE. elymoidesplants did establish and were productive with and withoutT. caput-medusaecompetition.

Management of Avena ludoviciana and Phalaris paradoxa with barley and less herbicide in subtropical Australia

2001 ◽  
Vol 41 (8) ◽  
pp. 1179 ◽  
Author(s):  
S. R. Walker ◽  
G. R. Robinson ◽  
R. W. Medd
Keyword(s):  
Seed Production ◽  
Weed Management ◽  
Field Experiments ◽  
Management Strategies ◽  
Maximum Yield ◽  
Yield Reduction ◽  
Weed Seed ◽  
Tiller Density ◽  
Weed Emergence ◽  
Subtropical Australia

The competitive advantage of barley compared with wheat was quantified for suppressing seed production of Avena ludoviciana Durieu. (wild oats) andPhalaris paradoxa L. (paradoxa grass), and for improving herbicide effectiveness on these major winter grass weeds of the subtropical grain region of Australia. Eight field experiments were broadcast with weed seed before sowing wheat or barley, in which the emerged weeds were then treated with 4 herbicide doses (0, 25, 50, 100% of recommended rates). Yield reduction from untreated weeds was on average 4 times greater in wheat than in barley, with greater losses from A. ludoviciana than P. paradoxa. Barley did not affect weed emergence, but suppressed weed tiller density and, to a lesser extent, the number of weed seeds per tiller. Seed production was, on average, 4340 and 5105 seeds/m2 for A. ludoviciana and P. paradoxa, respectively, in untreated wheat compared with 555 and 50 seeds/m2 in untreated barley. Weed seed production following treatment with 25% herbicide rate in barley was similar or less than that after treatment with 100% herbicide rate in wheat. Overall, 25% herbicide rate was optimal for both conserving yield and minimising weed seed production in barley. For wheat, maximum yield was achieved with 50% herbicide but weed seed production was lowest with 100% herbicide rate. This indicates that weeds can be effectively controlled in barley with considerably less herbicide than required in wheat, highlighting the importance of including barley as a part of weed management strategies that aim to reduce herbicide inputs.

Interference of Redroot Pigweed (Amaranthus retroflexus) in Corn (Zea mays)

Weed Science ◽  
1994 ◽  
Vol 42 (4) ◽  
pp. 568-573 ◽  
Author(s):  
Stevan Z. Knezevic ◽  
Stephan F. Weise ◽  
Clarence J. Swanton
Keyword(s):  
Zea Mays ◽  
Grain Yield ◽  
Seed Production ◽  
Field Experiments ◽  
Amaranthus Retroflexus ◽  
Corn Yield ◽  
Leaf Stage ◽  
Redroot Pigweed ◽  
Emergence Date

Redroot pigweed is a major weed in corn throughout Ontario. Field experiments were conducted at two locations in 1991 and 1992 to determine the influence of selected densities and emergence times of redroot pigweed on corn growth and grain yield. Redroot pigweed densities of 0.5, 1, 2, 4 and 8 plants per m of row were established within 12.5 cm on either side of the corn row. In both years, redroot pigweed seeds were planted concurrently and with corn at the 3- to 5-leaf stage of corn growth. A density of 0.5 redroot pigweed per m of row from the first (earlier) emergence date of pigweed (in most cases, up to the 4-leaf stage of corn) or four redroot pigweed per m of row from the second (later) emergence date of pigweed (in most cases, between the 4- and 7-leaf stage of corn) reduced corn yield by 5%. Redroot pigweed emerging after the 7-leaf stage of corn growth did not reduce yield. Redroot pigweed seed production was dependent upon its density and time of emergence. The time of redroot pigweed emergence, relative to corn, may be more important than its density in assessing the need for postemergence control.

The effects of frequency and extent of defoliation, summer irrigation, and fertilizer on the production and survival of the grass Danthonia caespitosa Gaud

1976 ◽  
Vol 27 (6) ◽  
pp. 755 ◽  
Author(s):  
KC Hodgkinson
Keyword(s):  
Seed Production ◽  
Death Rate ◽  
Field Experiments ◽  
Seed Set ◽  
Floral Induction ◽  
Early Winter ◽  
Phosphorus Fertilizer ◽  
Nitrogen And Phosphorus ◽  
Plant Survival ◽  
Growth And Survival

The effects of extent and frequency of defoliation on the growth and survival of Danthonia caespitosa were measured in a series of field experiments. Additional treatments, of summer irrigation and application of nitrogen and phosphorus fertilizer, were included in some of the experiments to assess how they modified the effects of defoliation. During the summer, complete defoliation increased the shoot yield of plants which had not been irrigated, but yield was decreased in the irrigated treatments. Frequent, partial defoliation increased yields of irrigated plants but decreased yields of plants not irrigated. Depression of yields was caused by both tiller death and reduced regrowth of individual tillers. In an experiment lasting 2 years, plants were completely defoliated monthly, bimonthly or tri-monthly or left intact, and shoot yields, tillering characteristics and plant survival under the treatments were compared. Monthly defoliation depressed yields and rate of tillering and accelerated the death rate of plants, particularly during the summer and autumn periods. Plants also died when cut bimonthly but the rate was slower. Plants irrigated during the first summer generally died at a faster rate than plants not irrigated. Tillering was more rapid during the autumn and early winter months. Midwinter application of fertilizer to plants cut bimonthly greatly stimulated shoot yields and seed production in the spring but not in the following year. Examination of tiller apices showed that floral induction took place prior to the beginning of July. Many apices were elevated above the 'grazing level' by early September, and flowering and seed set occurred in October.

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