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Oilseed Meal Effects on the Emergence and Survival of Crop and Weed Species  [PDF]
Katie L. Rothlisberger,Frank M. Hons,Terry J. Gentry,Scott A. Senseman
Applied and Environmental Soil Science , 2012, DOI: 10.1155/2012/769357
Abstract: Oilseed crops are being widely evaluated for potential biodiesel production. Seed meal (SM) remaining after extracting oil may have use as bioherbicides or organic fertilizers. Brassicaceae SM often contains glucosinolates that hydrolyze into biologically active compounds that may inhibit various pests. Jatropha curcas SM contains curcin, a phytoxin. A 14-day greenhouse study determined that Sinapis alba (white mustard), Brassica juncea (Indian mustard), Camelina sativa, and Jatropha curcas applied to soil at varying application rates [0, 0.5, 1.0, and 2.5% (w/w)] and incubation times (1, 7, and 14?d) prior to planting affected seed emergence and seedling survival of cotton [Gossypium hirsutum (L.)], sorghum [Sorghum bicolor (L.) Moench], johnsongrass (Sorghum halepense), and redroot pigweed (Amaranthus retroflexus). With each species, emergence and survival was most decreased by 2.5% SM application applied at 1?and 7?d incubations. White mustard SM incubated for 1?d applied at low and high rates had similar negative effects on johnsongrass seedlings. Redroot pigweed seedling survival was generally most decreased by all 2.5% SM applications. Based on significant effects determined by ANOVA, results suggested that the type, rate, and timing of SM application should be considered before land-applying SMs in cropping systems. 1. Introduction Research involving oilseed crops for biodiesel production has increased due to greater needs for renewable energy sources. Biodiesel is an EPA-approved renewable fuel that can be produced from oilseed crops. The oil extracted from seed is chemically reacted with an alcohol, such as methanol, to form chemical compounds known as fatty acid methyl esters, or “biodiesel.” The oil contained in the seed is most often extracted mechanically using a screw press. The residue remaining after oil extraction is referred to as either a press cake or seed meal (SM). In order for biodiesel production to be economically and environmentally sustainable, a feasible and profitable means of byproduct or SM disposal and/or usage needs to be developed. Utilization of SM in organic agricultural production systems offers a possible solution. Oilseeds have the potential to produce significant energy and renewable fuels and include such oilseeds as soybean [Glycine max (L.) Merr.], canola and rapeseed (Brassica napus), Indian mustard (Brassica juncea), white mustard (Sinapis alba), physic nut or jatropha (Jatropha curcas), camelina (Camelina sativa), and castor bean (Ricinus communis). Brassicaceae oilseeds have been reported to contain 30 to
Weed-Crop Competition in Maize in Relation to Row Spacing and Duration  [PDF]
A. Tanveer,M. Ayub,A.Ali,R. Ahmad
Pakistan Journal of Biological Sciences , 1999,
Abstract: A field experiment comprising two row spacing viz. 60 and 75 cm and five durations of weed-crop competition i.e. competition for 20, 30, 40, 50 days after emergence and till harvest was conducted to observe growth and yield response of maize. There was gradual increase in dry weight of weeds with increased weed-crop competition duration. Decrease in number of grains per cob and 1000-grain was recorded with increased competition duration of weeds. Maize grain yield was increased from 1911.61 kg ha-1 in plots where weeds competed with crop till harvest to 3708.33 kg ha-1 in plots where weeds were allowed to compete for 20 days after emergence.
Role of Weed Emergence Time for the Relative Seed Production in Maize
Stefano Benvenuti
Italian Journal of Agronomy , 2011, DOI: 10.4081/ija.2007.23
Abstract: Trials were carried out in 2000 and 2001 to investigate the effect of weed emergence time on weed seed production in a maize field. Datura stramonium L., Solanum nigrum L. and Abutilon theophrasti Medicus were selected for their importance as summer weeds. Emergence time was found to be crucial since delay would involve an unfavourable light environment determined by crop canopy elongation and resulting shade production. Only the early emergence of D. stramonium and A. theophrasti showed the capacity to exposing their leaves over the crop canopy. Generally the weed seed production under shade conditions decreased for the reduction of the fruit per plant since the number of seed per plant showed only a light reduction. However, while D. stramonium and A. theophrasti compete with the crop by increasing height, Solanum nigrum tends to adjust to shade without excessive reduction in number of seeds produced. Thus in D. stramonium and A. theophrasti late emergence reduced seed production to only 15%, while S. nigrum maintained 25% of the seed production level generally observed with greater light exposure. This environmental adaptation was confirmed by the less marked decrease in S. nigrum harvest index. Agroecological involvements are discussed.
Role of Weed Emergence Time for the Relative Seed Production in Maize  [cached]
Stefano Benvenuti
Italian Journal of Agronomy , 2005, DOI: 10.4081/ija.2007.23
Abstract: Trials were carried out in 2000 and 2001 to investigate the effect of weed emergence time on weed seed production in a maize field. Datura stramonium L., Solanum nigrum L. and Abutilon theophrasti Medicus were selected for their importance as summer weeds. Emergence time was found to be crucial since delay would involve an unfavourable light environment determined by crop canopy elongation and resulting shade production. Only the early emergence of D. stramonium and A. theophrasti showed the capacity to exposing their leaves over the crop canopy. Generally the weed seed production under shade conditions decreased for the reduction of the fruit per plant since the number of seed per plant showed only a light reduction. However, while D. stramonium and A. theophrasti compete with the crop by increasing height, Solanum nigrum tends to adjust to shade without excessive reduction in number of seeds produced. Thus in D. stramonium and A. theophrasti late emergence reduced seed production to only 15%, while S. nigrum maintained 25% of the seed production level generally observed with greater light exposure. This environmental adaptation was confirmed by the less marked decrease in S. nigrum harvest index. Agroecological involvements are discussed.
Evaluation of Pre-emergence Herbicides and their Application Methods for Weed Control in Soybean  [PDF]
Mukhtar Ahmad Khan,Sher Mahmood Shah,M. Yasin Mirza
Pakistan Journal of Biological Sciences , 1999,
Abstract: Four pre-emergence herbicides (pendimethalin @ 1.48 kg ai/ha, oxadiazon @ 0.45 kg ai/ha, trifluralin @ 0.75 kg ai/ha and isoproturon @ 1.0 kg ai/ha) were tested with three different methods of application, i.e., spray, sand mix broadcast and soil incorporation during spring 1992 and 1993 at NARC, Islamabad. A total of 12 weed species were recorded. The lowest weed density and week biomass was recorded in pendimethalin treatment. Highest plan height and number of pods per plant were obtained from weed free treatment. No negative effect on the germination and growth of the crop was observed. Pendimethalin proved to be the best herbicide for weed control in soybean applied by soil incorporation method. Highest grain yield (1523 kg ha -1) was obtained from weed free treatment followed by pendimethalin (1475 kg ha -1) while the lowest yield (1127 kg ha -1) was produced in weedy check.
Weed Management Practices in Cotton Crop  [PDF]
F.C. Oad,M.H. Siddiqui,U.A. Buriro,G.S. Solangi
Asian Journal of Plant Sciences , 2007,
Abstract: The field trial was conducted to assess weed management practices in cotton at Students Farm, Sindh Agriculture University, Tandojam, Pakistan. The herbicides applied were: T1 = Dual Gold 960 EC @ 2.0 L ha-1 pre-emergence, T2 = Dual Gold 960 EC @ 2.5 L ha-1 pre-emergence, T3 = Stomp 330 EC @ 2.5. L ha-1 pre-emergence, T4 = Stomp 330 EC @ 3.75 L ha-1 pre-emergence, T4 = Hand weeding and T5 = Control. Weed flora after 71 days of sowing competing with experimental cotton were: Cyperus rotundus (40.03%), Portulaca oleraceae (17.77%), Cynodon dactylon (13.70%), Echinochlor columum (10.00%), Convolvulus arvensis (9.25%), Digeria arvensis (3.70%), Euphorbia hirta (1.85%), Cressia cretica (1.85%) and Chorchorus depressus (1.85%). Highest weed density (54.25 m2) and weed intensity (25.00 m2) were recorded in weedy (control) fields, while highest weed control percentage (74.07%) was observed in hand weeded plots. Among herbicide treatments, Dual Gold 960 EC @ 2.5 L ha-1 pre-emergence produced maximum weed control (56.66 %), followed by Dual Gold 960 EC @ 2.0 L ha-1 pre-emergence (36.66 %). Stomp 330 EC @ 3.75 L ha-1 pre-emergence resulted 33.33% weed control, while Stomp 330 EC @ 2.5 L ha-1 pre-emergence recorded 29.62% weed control. Mean cotton plant height (103.65 cm), monopodial branches (3.06) and sympodial branches (39.00) plant-1, productive bolls (32.3) plant-1 and seed cotton yield (3942.50 kg ha-1) were maximum in hand weeded plots. Among, herbicidal treatments, Dual Gold 960 EC @ 2.5 L ha-1 pre-emergence produced best results with 93.05 cm cotton plant height, 2.66 monopodial branches, 29.0 sympodial branches and 23.20 productive bolls plant-1 and seed cotton yield of 2992.50 kg ha-1. It was observed that weed control practices in cotton were more effective in controlling weeds and producing higher seed cotton yield, when integrated efforts which include manual weeding as well as use of herbicides are employed simultaneously. However, Dual Gold 960 EC @ 2.5 L ha-1 pre-emergence may be preferred for chemical control of weeds in cotton.
Influence of crop rotation and meteorological conditons on biodiversity of weed communities in spring barley (Hordeum vulgare L.)
Magdalena Jastrz?bska,Maria Wanic,Marta K. Kostrzewska
Acta Agrobotanica , 2010, DOI: 10.5586/aa.2010.025
Abstract: The paper presents the analysis of changes in weed biodiversity in spring barley cultivated in the years 1990-2004 in crop rotation with a 25% proportion of this cereal (potato - spring barley - sowing peas - winter triticale), when it was grown after potato, and in crop rotation with its 75% proportion (potato - spring barley - spring barley - spring barley), when it was grown once or twice after spring barley. In the experiment, no weed control was applied. Every year in the spring (at full emergence of the cereal) and before the harvest, the composition of weed species and numbers of particular weed species were determined, and before the harvest also their biomass. On this basis, the constancy of species in particular years, Shannon-Wiener species diversity indices and diversity profiles according to Rényi were determined. Weed species richness increased linearly at all plots during the 15-year period. Chenopodium album was a constant and dominant species in terms of weed species density and biomass year after year. The quality of the plot had no clear influence on the diversity of weeds in barley. Weed density and biomass showed high year-to-year variability and a positive correlation with the amount of precipitation and a negative correlation with temperature during the period of the study. The significance of the correlation between the productivity of barley and weed diversity was not confirmed.
IMPORTANCE OF CRITICAL PERIOD OF WEED COMPETITION FOR CROP GROWING
Marijana Ivanek-Martin?i?,Zvonimir Ostoji?,Klara Bari?,Matija Gor?i?
Poljoprivreda (Osijek) , 2010,
Abstract: A concept of critical period of weed competition has been introduced for more than 40 years ago. The conceptis based on the assumption that weeds are not equally harmful to a crop during the whole season and thatthere is a period in crop development in which weeds impact on the yield is the biggest. This period is calledcritical period of weed competition (CPWC), critical period of weed interference, or critical period of weedcontrol. There is a difference in CPWC between crops, but CPWC for a certain crop can vary a lot because itdepends on many factors which can affect the crop or weeds competition ability. The critical period of weedcompetition identification is essential for integrated weed control and precise planning of a weed controlstrategy as well as for rationale use of herbicides and other weed control measures.
Post Emergence Weed Control in Wheat
U.A. Buriro,F.C. Oad,S.K. Agha,G.S. Solangi
Journal of Applied Sciences , 2003,
Abstract: The experiment was carried at Student’s Experimental Farm, Sindh Agriculture University Tandojam, Pakistan on post emergence weed control in wheat. It was noted that most of the weeds present in wheat were broad leaved weeds, whereas narrow leaved grasses and sedges were in small number. With the application of herbicides though the number of weeds of all species decreased but in most of the cases their intensity increased. All the growth, yield and yield parameters increased with the application of herbicides as compared to un-weeded plots. The additional yield (49.98%) was exhibited with the application of Topik 240WP at 250 g ha ̄1 herbicide followed by Arelon 50 dispersion at 0.75 l ha ̄1, which increased 43.74% grain yield. It is concluded that weeds reduce the economic yield by competing for nutrients, light and moisture. The cost and maintenance of cultivation are increased and soil fertility is degraded due to weed problem. Thus, it is prime important to control weeds and an increase in the yield up to 50% or more can be achieved.
Weed emergence in autumn under temperate conditions
Calado, J.M.G.;Basch, G.;Carvalho, M.;
Planta Daninha , 2011, DOI: 10.1590/S0100-83582011000200012
Abstract: the emergence of weed plants depends on environmental conditions, especially temperature and soil moisture. the latter is extremely important in mediterranean environments which are characterized by irregular amount and distribution of rain throughout the year, which influences the beginning of the growth cycle of the annual species (seed germination). this paper studies the influence of rainfall, in particular accumulated rainfall in autumn, on the emergence of weed plants. the experiment was carried out on luvisols, and the appearance of flora under field conditions was observed. through analysis of the results, it can be concluded that a high percentage of weed plants (> 85% related to the highest registered value) was obtained with more than 90 mm of accumulated rainfall from the beginning of september. thus, in those years in which this amount of rainfall (90 mm) is registered until the end of october, the appearance of potential weed plants can be ensured, under mediterranean conditions, in a period before sowing the autumn-winter crops.
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