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

Evaluation of the CERES-wheat model in Ahvaz condition

In order to calibrate and validate the CERES-wheat model, two experiments were carried out at Agricultural and Natural Resources Research Center of Khouzestan during 1382-83 and 1383-84 growing seasons. In addition, we used results of experiments, which were performed in previous years at this Research Center. The values of root mean square error (RMSE) for anthesis and maturity dates, grain yield and biomass production were 2.5d, 5d, 640 kg/ha and 460 kg/ha, respectively. These RMSE values were less than 10 percent of observed data means. The results indicated that the CERES-wheat model can satisfactorily predict phonological stages, grain yield and biomass of wheat. Then calibrated and validated CERES-wheat model can apply to research purposes in Ahvaz conditions

Spatial relationships between seed bank and seedling populations of Hordeum spontaneum and Cardaria draba in saffron (Crocus sativus L.) fields

Geostatistical techniques were used to characterize the spatial relationship between Hordeum spontaneum and Cardaria draba seedling and seed bank over the course of one growing season (2004-2005) in three saffron fields, located in Southern Khorasan, Iran. The density and spatial distribution of weeds varied widely with fields. The emergence percentage was higher for Cardaria draba than for H. spontaneum in all fields. Semivariograms showed spatial autocorrelation in seed bank and seedling populations of H. spontaneum and C. draba in all fields. Cross-semivariograms showed moderate to strong (63.3 to 94.7%) and strong spatial continuity (78.4 to 95.4 %.) between seed bank and seedling population densities of H. spontaneum and C. draba, respectively. Grey-scale field maps of C. draba seed banks corresponded visually to maps of seedling populations and could have been used to target control efforts, but visual correspondence between H. spontaneum seed bank and seedling maps was poor. Seed bank and seedling mapping may be useful for site-specific management, but additional information is needed to understand variation in the relationships between these two populations over time and space

Effects of amount and timing of nitrogen application and weed density on wild mustard (Sinapis arvensis) seed production in winter wheat

In order to study the effects of amount and timing of nitrogen application and weed density on wild mustard (Sinapis arvensis) seed production in winter wheat, an experiment was conducted in 2001 at Research station of college of agriculture, Ferdowsi University of Mashhad. A Split plot design with three replications were used with factorial combination of weed density (0, 8, 16, and 32 plant/m2) and nitrogen (low=100, optimum= 150, and high= 225 Kg/ha) as main plots.The sub plot factor included nitrogen splitting pattern (P1=1/3 at planting time+2/3 at tillering, P2= 1/3 at planting time + 1/3 at tillering + 1/3 at shooting). According to the results, wild mustard seed production increased with increasing wild mustard density and nitrogen rates, due to high wild mustard biomass production. Seed production of wild mustard was 161, 311, and 488 million/ha in low, optimum and high nitrogen rates, respectively. In the other hand, density and nitrogen rates had a significant effect on wild mustard fecundity. However, nitrogen splitting pattern showed no significant effect on wild mustard seed production