Allelopathic effects of Knotweed (Polygonum avicular) on emergence and seedling growth of tomato and corn

In recent years, allelopathy has received special attention by scientists in integrated weed management (IWM). To study the effect of different amount of Knotweed residue on emergence and growth of tomato and corn seedlings, two experiments were conducted at Ferdowsi University of Mashhad. The type of design was completely randomized, with 5 and 4 replications for tomato and corn, respectively. The Knotweed residues (zero, 0.33, 0.67, 1 and 1.33 %( W/W) were added to the pot soil. Seedlings showed different response to different amount of Knotweed residues. Increasing residues increased the emergence percentage of tomato but decreased corn emergence. Increasing residues resulted in increasing 33.9% and 39.3% of leaf area in tomato and corn, respectively. Knotweed residues resulted in 36.5% and 46.7% increase in shoot dry matter of tomato and corn, respectively. Increasing dry matter resulted in increasing up to 67.2% and 54.5% root dry matter of tomato and corn, respectively. Different doses of Knotweed had stimulatory effect on emergence of tomato but had inhibiting effect on corn. Knotweed residues had stimulating effect on seedling growth of corn and tomato. Root dry matters of both species were more influenced by Knotweed residue than foliage

Seasonal scouting of weeds in a sugarbeet field in Mashhad

Weed scouting is an important part of integrated weed management system. In order to evaluate weed emergence pattern and management efficiency on weed populations, a 2 ha sugarbeet field in Mashhad was selected and evaluated during 2002 growing season. Weeds were identified and counted at 441 points at the intersection of a 7m by 7m grid within 0.15 m2 quadrates. The evaluations were done 3 times [pre management (1) and post management (2)]. Geostatistical techniques (kriging) were used to analyze the spatial structure of weeds and dynamics of weed patches. 34 weed species were observed across the field. Wide ranges of weeds were observed during growing season including, winter annual (e. g. Sinapis arvensis and Fumaria officinalis), summer annual (e. g. Echinochloa crus-galli), biennial (Dacus caraota) and perennal (e. g. Convolvulus arvensis). Solanum nigrum, Chenopodium album, Amaranthus spp., Convolvulus arvensis, Polygonum aviculare and Echinochloa crus-galli were the common weeds over growing season. In early growing season, Solanum nigrum with 404.71 seedlings per m2 was present in all samples constituted 81.32% of weed community, but in 2nd and 3rd sampling time, Convolvulus arvensis was the dominant species with 33.29% and 29.26% of weed community. Relative density percentage of perennial and grassy weeds (generally C4 species) was increased over the season but the relative density percentage of broadleaf annual weeds was decreased. Main locations of weed emergence were persisted as elliptical patches east ward and west ward of field over the season. The results of this study indicated that scouting and understanding of weed emergence behavior could be used to design effective strategies of weed management

The competitive aspect of soybean ( Glysine max) and velvetleaf ( Abutilon theophrasti) in response to population density and planning date

In order to study different of velvetleaf ( Abutilon theophrasti Medicus) and simultaneous planting date of ( Glisine max (L.) Merril) and velvetleaf on yield and yield components of soybean, an experiment was conducted in 2004, at Ferdowsi University of Mashhad, College of Agriculture Experimental Station. \ud The type of experiment was Completely Randomized Design in factorial arrangement with 3 replication in witch velvetleaf density ( 0, 2, 4, 8, plan/m2) and planting date of soybean and velvetleaf at 3 levels( April 23, May 13 and June 3) were used. Study of grain yield and yield components indicated that increase in velvetleaf density due to significant decrease in pod and grain number of soybean plant caused significant reduction of grain yield. Different planting dates had significant effect on yield and all yield components and delaying planting date, resulted in a significant reduction of yield components and yield. The interaction between density and planting date, was based on number of pod in plant and number of grain in soybean pod but significant effects on grain number per plant, 1000 grain weight and grain yield of soybean

Study on infestation levels and spatial distributions of Amaranthus blitoides, Chenopodium album and Solanum nigrum in corn field

For increasing the effectiveness of weed management and more understanding of weed population dynamics, spatial distribution needs to more attentions. Infestation levels and spatial distributions of Amaranthus blitoides, Chenopodium album and Solanum nigrum were studied in four 10x30 m corn fields. N-fertilizer was applied in two method of whole application at the time of corn planting (T1 and T2) and equal split application at the time of corn planting and at six-leaf stage (T3 and T4). One of either fields with the same method of N-fertilizer application, received herbicide too (T1 and T3). Weeds Samples were taken four times at the intersection of 2.5m square grids with 23days interval. The first sample was taken June 24, before top-dressing and herbicide application in related plots. For studying weed spatial distribution, the parameters of appropriate semivariogram model were calculated and weed contour maps were constructed by using kriging. The weed semivariograms fitted spherical and exponential models, over four sampling times and fields and spatial autocorrelation during growing season, was moderate to strong. In early growing season, Amaranthus blitoides was the dominant weed species in all fields, but lower density was recorded for Chenopodium album and Solanum nigrum. At the first sampling time, mean density of A. blitoides and S. nigrum in fields with split application of N-fertilizer was respectively more- and less than fields with whole application of N-fertilizer. In the case of C. album an evident difference wasn’t observed. Herbicide application in related plots considerably reduced the density of three mentioned species; however density never became zero. In the majority of cases the lack of herbicide application causes to increase in population density at the second sampling time. Spatial structure was observed in all three species and study on contour maps confirmed the existence of patches that the density was high in their center, but decreasing gradually toward edges. In general, despite of some displacement, structure and location of patches were kept and possibly these places were the locations for weed emergence in next year. So site-specific herbicide application and exploitation of its advantages may be possible; however, more researches are necessary. Keywords: Population dynamics, weed mapping, site-specific application, 2,4-D+MCPA, nitrogen

Effects of salinity on growth, yield, elemental concentration and essential oil percent of cumin (cuminum cyminum)

Effects of salinity on growth, yield, elemental concentration and essential oil percent of cumin (cuminum cyminum

Effect of plant density on growth indices of four grain sorghum cultivars

To study the effect of plant density on growth indices of four grain sorghum cultivars an experiment was conducted as factorial based on Compelete Randomized Block Design with 3 replications at Experimental Field of Birjand Azad University in 2003 growing season. In this study 4 grain sorghum cultivars including Sepideh , Saravan local , Payam and Kimia and 3 plant densities 100000 , 180000 and 260000 plant/ha were investigated. The results showed superiority of Saravan local compare to other cultivars because of having maximum total dry matter, leaf area index, crop growth rate, relative growth rate, and net assimilation rate. The highest amount of leaf area ratio and specific leaf area were in Kimia and Payam cultivars, respectively. All of the above mentioned growth parameters were increased by increasing population denseity with exception of relative growth rate and net assimilation rate. From the obtained results Saravan local cultivar in density of 260000 plant /ha had the highest grain yield. The maximum relative growth rate and net assimilation rate were obtained in lowest density

Effects of planting depth and flooding period on germination and emergence of swallow wort (Cynanchum acutum)

Effect of 13 planting depths and 6 flooding periods on germination and emergence of swallow wort were investigated under greenhouse conditions. Results showed that swallow wort seeds emerged from up to 6 cm depth. The highest emergence occurred in the first, second, third and fourth week after emergence from 0.5 cm; 0.5, 1 and 1.5 cm; 1.5 cm; and 1.5 cm planting depth, respectively. At the end of the fourth week, 6.5 cm depth treatment had zero emergence. Increasing burial depth resulted in induced secondary dormancy. Increasing flooding period, did not affect germination percentage. However, fresh weight, radicle and hypocotyle lengths under flooding conditions were decreased significantly compared to control. Seeds flooded for 3 and 21 days had the highest and lowest fresh weight, respectively. Hypocotyle length was highest under zero and one day flooding treatments, but lowest under 14 days flooding treatment. Radicle length was highest under 0, 1, 3 and 7 days flooding treatments and lowest under 14 and 21 days flooding treatments