نشریه بوم شناسی علف های هرز
سال دوم شماره 2 (پاییز و زمستان 1393)

The mortality rate of ground cherry seed (Physalis divaricata L.) was examined at three different depths (0-10-30 cm) of soil and the biology of their berries was studied after shattering in a field for one year in Alashtar in Lorestan province. The type of experiments was completely randomized design. The viability of seeds within berries was conducted from early formation to completely ripe berry fruits; the emergence method of seedling was studied. The results showed that the berries are formed in late June but seeds within the fruits showed viability 4 weeks later, with 80 percent seed germination. Seeds at depths the 10-30 cm had the least mortality rate, with 98 percent germination, seeds on surface soil showed the most mortality rate, with 86 percent germination after one year. After shedding the berries, a great portion of water was absorbed by them, they were cracked in January, the berries decomposed in March and dispersed completely during April and seeds were shattered. The biology of the germination showed that from each berry under wheat canopy emerged more than 35 seedlings as cluster but after harvesting the wheat, the emergence rate exceeded than 70 germinated seeds per berry.

To evaluate the performance of new Sulfonylurea herbicides in sweet corn weed control, a factorial experimental research was carried out based on a completely randomized block design with three replications in Agriculture and Natural Resources Research Center of Khorasan Razavi in 2012. The first and the second factor, were sweet corn varieties and chemical control treatments respectively. The sweet corn varieties included KSC403su, Merit and Chase. The chemical control treatments included Nicosulfuron (Cruz), Nicosulfuron (Cruz) + Bromoxinyl + MCPA (Brimicide MA), Foramsulfuron (Equip), Rimsulfuron + Nicosulfuron (Ultima), Mesotrion + S-Metolacholor + Terbuthlazine (Lumax 537.5 SE), with weed free, and weed infested in each block. Sampling was done 4 weeks spraying each plot. The result showed that red root pigweed, common purslane, field bindweed, common lambsquarters, purple nutsedge, black night shade dry weight were reduced significantly by all herbicides compared with weedy check. Among the sweet corn varieties, the highest and the lowest weeds density and dry weight resulted by Chase and KSC403su, respectively. Mesotrion+ S-Metolacholor+ Terbuthlazine herbicide had sound effect on dry weight reduction of red root pigweed, common purslane, field bindweed, common lambsquarters, purple nutsedge, black nightshade, with highest control of common lambsquarters. Also, red root pigweed, common purslane and field bindweed should satisfactory control by nicosulfuron and nicosulfuron+ brimicide MA applied, whereas nicosulfuron + rimsulfuron had suitable effect on common purple nutsedge.

Recognizing the composition of weed community in chickpea field is the most fundamental issues in weed crop management. Based on chickpea acreage and overall field areas in Kermanshah province during 2009-2010, fifty-two farms were selected as indicators of chickpea fields in the province. The weeds in sampling points were counted based on overall plants and each species and their population indices were calculated. In each field, at sampling points, the longitudes, latitudes and altitudes were determined via GPS device. By using this information, the distribution maps of different weed species of chickpea fields in Kermanshah produced via GIS software. The results showed that there were sixty-one weed species in chickpea fields of Kermanshah province. The ranking of predominant broadleaf weeds of chickpea fields in Kermanshah were included of succory (Cichorium intybus), field bind weed (Convolvulus arvensis), bed straw (Galium tricornatum), wild safflower (Carthamus oxycantha) and cowcockie (Vaccaria pyramidata), of Kermanshah province, respectively. Dominant grasses of chickpea fields in Kermanshah province were included: wild barley (Hordeum spontaeum), spring wild oat (Avena fatua) and Bermuda grass (Cynodon dactylon), respectively. Based on Shannon-Wiener species diversity index, different cities were classified into three clusters. Being in low value for Simpson abundance index of some cities were similar to being low Shannon-Wiener index and were indicated the presence of non-uniform community with the presence of dominant species in chickpea fields of these cities. There were significant differences among of chickpea field's weeds of different cities in regard to species diversity, only the difference between Kermanshah city and Dalaho and Ravansar cities was significant. The predictive maps of different species based on their soil and climatic requirements showed that shifting of these species toward area with similar ecological conditions are able to infest the area and should prevent weed infestation of new area.

This research was carried out to investigate the population structure of the plant flora of weeds in two different microclimates. To perform this experiment, two pieces of lands located in Mashhad, with dimensions of 95 × 20 m were selected; one of them was an abandoned agricultural land and the other was an abandoned garden. Both areas were without maintenance for about 8 years but the garden was irrigated just for grazing sheeps and goats. Sample taking from intersections of regular grids of 5 × 5 m by 1 × 1 m quadrates was conducted. After fitting the theoretical models of empirical variogram with interpolation of points, the maps of the species were drawn. To study the vegetative cover in both regions the α and β diversity indicators, the relative frequency, species richness, uniformity, Shanon-Veiwer and Simpson indices, and also similarity indicators, Ashtyn house, Jaccard and Sorenson similarity coefficient was determined. Totally 35 species which were belonged to 12 plant families were found, 15 species of which were found in the abandoned agricultural land but Alhagi pseudalhaji and two species of Lactuca genus were common in both lands. In the survey conducted, 31 species were dicots and 4 species were monocots. Climate conditions causes that in each region ecotype of plant species vary in terms of the number and families, thus effects on the diversity and distribution in the region.

This study was carried out to investigate the competition of weeds with different cultivars and planting densities of red beans over two years. The experiment was completely randomized block with factorial arrangement and three replications per treatment. The treatments included beans cultivars (Sayyad, Derakhshan and Zanjan local seed lot), row spacing (20 and 30 cm)anddensities (20, 30, 40 and 50plants persquare meter). The number and the dry weight ofweedspecieswere determined at four-leafstage, 50% flowering and maturity. The resultsshowed thatweedspecies of bean were green foxteil(Setaria viridis),tumble weed(Amaranthus albus),lambsquarter(Chenopodium album),barnyardgrass(Echinochloa crus-galli)andredroot pigweed(Amaranthus retroflexys) within two years. Zanjan local seed lot with densities of 30 and 40 plants per square meter and row spacing of 30 cm and densities of 40 plants per square meter with 20 cm row spacing were the most tolerance to the presence of weeds along with higher yield.

To investigating the density of weeds in direct seeding wheat in the corn straws (no tillage wheat), a split factorial experiment was carried out in randomized complete block design with four replications and three factors including cultivar at 2 levels, (Chamran and Behrang), seed density at 5 levels (50, 100, 150, 200 and 250 Kg/ha) and nitrogen fertilizer from urea source at 6 levels (0, 50, 100, 150, 200 and 250) in fall of 2011 – 2012 in an agricultural farm located 30 km south of Dezful. The result of analysis of variance revealed that the effects of cultivar, seeding and nitrogen fertilizer on weed density and dry weight of weeds and yield and grain yield components were significantly different at 1% level. The least weed density was observed at 250 Kg/ha, with one weed per square meter. Results showed that greater consumption of nitrogen fertilizer will increase the dry weight of weeds per area unit, so that the fertilizer level of 250 kg nitrogen per hectare with an average of 9.9 grams in the square meter had the highest dry weight of weeds per area unit. The no tillage seeding caused increasing the grassy weeds. Using seeds over 100 Kg/ha which decreases yield grain and increases nitrogen consumption to the level 150 (Kg/ha) resulted in significant increase in grain yield. Chamran cultivar, with grain yield average of 413.70 (kg/ha) was preferd to Behrang cultivar.