PIGWEED (Amaranthus retroflexus L.) is one of the common weeds that grow in northwest of Iran. PIGWEED poisoning was reported in cattle, sheep and pigs from United States, Canada, Brazil and Israel. This study was conducted to assess the clinical signs, clinical pathology and pathological findings in experimental PIGWEED poisoning in calves. Ten native calves aged 5 to 7 months were divided into two groups (experiment and control groups). The plant was collected from farms and fed to calves. One calf of experimental group died, without showing any clinical signs on day 38. Statistical analysis revealed an increase of serum creatinine, BUN, sodium and GGT. The significant elevation of creatinine, BUN and sodium indicated possible lesions of kidneys and of GGT might be indicative of hepatic lesions. Remarkable histopathological lesions were seen in liver, kidneys, lymph nods, heart and nervous system.

To study the competitive effects of redroot PIGWEED (Amaranthus retroflexus) and lambsquarter (Chenopodium album) on potato, an additive experiment was conducted in the spring of 2004 in split-split plot based on randomized complete block design with 4 replications at the Seed Potato Production Station of RAN in Firouzkooh. Treatments were included 2 weed species in main plots (Amaranthus retrot1exus and Chenopodium album), weed density in sub plots (2,66, 5.32 and 10.64 plants per m") and relative time of weed emergence in sub-sub plots (8 and 4 days prior to potato and the same time with potato emergence). Potato, cultivar Agria, was planted in constant density 53000 plants per hectare by row space of 75 cm. To interpret the competitive effects, the Cousens's regression model was used. The results showed that both species of weeds significantly reduced tuber yield. 2, 4 and 8 lambsquarter per meter of row reduced tuber yield 12.8, 22.3 and 27.2 percent, respectively. These values for redroot PIGWEED increased to 18, 29.4 and 39.6 percent. Parameters i and a estimated by the model were higher for redroot PIGWEED. Parameter "i" for three levels of lambsquarter and redroot PIGWEED emergence time were 10.05, 7.95, 4.48 and 19.44, 13.22, 8.86 respectively. Parameter "a" for lambsquarter was estimated 56.99, 48.7 and 31.16. This parameter for redroot PIGWEED was 61.92, 52.88 and 48.72. Regarding to these estimation, sooner weed emergence will result more tuber yield. Weeds did not affect mean tuber number per plant significantly. But, mean tuber weight was affect significantly. According to the results of this investigation mean tuber weight is the main factor for potato yield loss.

Field experiment was conducted in the College of Agriculture and Natural Resources of Tehran University, Karaj to evaluate the effect of intercropping two soybean cultivars on redroot PIGWEED biomass. The experimental design was a completely randomized block with factorial arrangement of treatments with three replications. Two soybean cultivars including Kelark (tall) and Interprice (dwarf) were planted in sole and under intercropping in competition with redroot PIGWEED at (0, 2, 4 and 8 plants/m2). The results revealed that yield of both cultivars were decreased with increasing redroot PIGWEED density, but the yield of Interprice was reduced 45% more than Kelark. In comparison to Interprice, yield of Kelark in intercropping was higher than sole cropping. LER calculated in intercropping under weed free condition was 1.11. Under intercropping, redroot PIGWEED had lower LAI (0.58), cumulative dry matter (283 g/m2) and CGR (4.7 g/m2day) compared to when grown with sole crops.

Introduction: Grass pea is an annual plant which produces adequate yield in unfavorable conditions. South Khorasan is one of the areas where grass pea cultivation has been spread, but due to rainfall rate and high evaporation and transpiration in this region, plants are facing drought stress; On the other hand, Amaranthaceae family weed (PIGWEED and tumble PIGWEED) also among the most important weed in farm fields in this region of Iran. Since the studies of multi-species competition provide more detailed information about relationships circumstance between plants, the aim of this study is to evaluate the competitiveness of PIGWEED, tumble PIGWEED and grass pea under drought stress using experiments with replacement series. Materials and methods: The experiment was carried out in a factorial based on RCBD with three replications. Experimental treatments consisted of two levels of water stress (80 and 50% of soil water field capacity), different weed interference ratios with grass pea (tumble PIGWEED + PIGWEED-grass pea) including (0-100, 75-25, 50-50, 25-75 and 100-0%), as well as different two weed interference ratios with each other (tumble PIGWEED-PIGWEED) containing (0-100, 50-50 and 100-0). Optimum density of eight plants per pot was fixed. Plants were cultivated after soil preparation and addition of chemical fertilizers and at four leave stage, the desired density was reached. At the end of the experiment, all plants were harvested from each species separately and weighed after drying. Finally, for results analyzing of the experiment, relative yield indices, total relative yield (LER) were used and relative competition Intensity index and aggressiveness index were used. Results and discussion: The results showed that grass pea, PIGWEED and tumble PIGWEED dry matter, decreased with reducing soil water content of 80 to 50 % of field capacity by 33, 30 and 12 % respectively. Also, the results showed that predicted yield of tumble PIGWEED was close to the actual yield. The results of relative yields showed that in sowing ratio of 50-50% grass pea and PIGWEED, 50-50% of grass pea and tumble PIGWEED, also 50-50% of grass pea and both two weed together in 80% treatment of soil water field capacity, the relative yield of grass pea were 0. 33, 0. 36 0. 39 respectively, that with drought stress increasing to 50% of soil water field capacity, increased by 36, 50 and 31% reached to 0. 45, 0. 54 and 0. 51 respectively. Changes in relative yield curve of grass pea under 80% treatment of soil water field capacity irrigation, in competition with tumble PIGWEED, PIGWEED and both weeds together was convex; which indicates that with enough water in the soil, grass pea competitiveness is less than Amaranthaceae family weed. The results of relative competition Intensity index showed that numerical value of this index for grass pea, tumble PIGWEED and PIGWEED, in all sowing ratios is a positive value, which shows higher inter-specific competition than intra-specific competition in different sowing ratios. Also the results showed that in the sowing ratio of 50% grass pea with 25% tumble PIGWEED and 25% PIGWEED in 50% treatment of soil water field capacity, Grass pea aggressiveness index against both weed separately and together was positive value, which indicates a relative superiority of grass pea under drought stress in competition with these two weed. Conclusion: In generally, the results of this study showed that water stress reduced all three plants growth but, decline in tumble PIGWEED was lower. The results also showed that the competition formed between these three species was Inter-specific and have negative effects on all three plants. Although the aggressiveness index indicates that the grass pea was beaten in most sowing ratios, but with the increase of drought stress and water deficit, due to inter-specific competition between weed, competition between weed and grass pea has been reached to lowest level.

In order to study the influence of redroot PIGWEED interference with sunflower, Allstar RM hybrid, an experiment was carried out at research station of Islamic Azad University of Tabriz in 2004, with three different densities of 5, 15 and 25 plants per meter of row and three interference times of emerging with sunflower, 15 and 30 days after sunflower emergence in a distance of 15 cm from both side of the sunflower rows. The experiment was established as a factorial based on randomized complete block design. Analysis of variance indicated that stem height at the ripening stage, antodium diameter, seed number in each antodium, hollow seed percentage, 1000 kernels weight, grain yield, seed oil percentage and oil yield were affected by density and interference time of redroot PIGWEED. Interaction of density interference time on stem height at the ripening stage, 1000 seeds weight, grain yield, seed oil percentage and oil yield were significant. The lowest and highest hollow seed percentage obtained from density of 5 plants per meter of row at 30 days after sunflower emergence and full season interference of 25 plants per meter of row, respectively. The highest seed number in each anthodium was obtained in the second level of density. The highest 1000 seeds weight and grain yield observed from density of 5 plants m-1 of row and interference time of 30 days after sunflower emergence. Seed oil percentage in all treatments except density of 5 plants per meter of row and interference time of 30 days after sunflower emergence had significant difference in comparison with the control. It seems that, weed plant number has higher effect than weed interference time on seed oil percentage. This research showed that in studied cultivar, with the short height, lower leaf area and lower competition ability with redroot PIGWEED, yield loss is affected more by density than interference time.

In order to evaluate the competitiveness of different varieties of beans and different levels of nitrogen on weed control, a factorial experiment based on randomized complete block design (RCBD) with three replications was done at Shiraz Azad university The first factor included four varieties of beans (Naz, Goli, Shazand and D 801G) and the second factor consisted of four levels of nitrogen (0, 40, 80 and 120 kg /ha urea 46. forme the urea nitrogen resource). Analysis of variance showed the effect of bean cultivars for number of pods, seed 1000 weight, number of seeds per pod, number of seeds per plant and seed yield was significant at one percent probability level but for the pod length was not significant. The effect of fertilizer levels in all treatments was significant at %01 probability level. The interaction between fertilizer levels and different bean cultivars were significant for all traits measured except for leave total Chlorophyll. The results showed that bean varieties responded differently to different levels of nitrogen. Naz cultivar responded to 40 kg/ha of fertilizer and the highest grain yield obtained in 40 kg/ha of nitrogen fertilizer whereas in Goli and Shazand the highest grain yield obtained was 80 kg/ha of nitrogen fertilizer. D801G cultivar compared to the 120 kg/ha of fertilizer had the highest grain yield. Minimum dry weed was related to both Shazand and D801G cultivars and maximum dry weed was related to both Naz and Goli cultivars. Overall the results showed that the reaction of bean cultivars to different fertilizer levels were different and at the presence of weeds should be considered fertilizer management should take into account the capacity of bean cultivars to nitrogen fertilizer.

To evaluate the redroot PIGWEED (Amaranthus retroflexus) reaction with a view to biological yield and seed production at interference with sunflower, a factorial experiment was conducted with sunflower cultivars (Azarghol, Hysun and Allstar), redroot PIGWEED densities (8.3, 25 and 41.7 plants m-2) and relative times of weed emergence (emerged with sunflower; 15 and 30 days after sunflower emergence) during 2006-7 in Tabriz. Results showed that, redroot PIGWEED biomass reduced with decreasing of density and delaying in emergence time. Averaged sunflower cultivars, seed production in redroot PIGWEED in treatment of 25 weeds m-2 at 15 days after emergence with sunflower was 1.7 times greater than full season interference of 8.3 weeds m-2. Averaged weed densities, with each week delay in redroot PIGWEED emergence at between first-second and second-third levels of weed interference, weed seed number per unit area ranged from 23 to 15×103, 55 to 23×103 and 45 to 62×103 in sunflower cultivars, respectively. Each day delay in weed emergence between second-third levels of interference time could decrease seed number per weed plant in Allstar greater than Azarghol and Hysun cultivars. Decrease of weed density and delaying in interference time caused a significant reduction on weed seed production index at interference with all cultivars.

Nitrate toxicosis associated with consumption of PIGWEED red-root (Amaranthus retroflexus) was diagnosed in a small herd of cattle in the suburb of Mashhad, northeastern Iran. The clinical signs were ruminal tympany, incoordination, tachycardia, dyspnea, head pressing, aggressive movements and jugular distension. Seven animals including 3 young calves and 4 cows died of intoxication; other affected cattle were treated by intravenous administration of epinephrine and ascorbic acid. No further mortality was observed after the treatment. One of the treated cows aborted a 6-month-old fetus more than three days after intoxication. Two samples of suspected plants were analysed for nitrate. The nitrate content of those plants was 6.6% and 10.4% in dry matter.

In order to study the effect of different redroot PIGWEED (Amaranthus retroflexus) density on yield, yield components of soybean cultivar and determining competitive cultivar, a field experiment was carried out at Mazandaran agricultural research station 2006. Experiment was set up at a Randomized Complete Block Design with five rates of PIGWEED (0, 4, 8, 12 and 16 plant per square meter) and three cultivars of soybean (Telare, Sari and Sahare) in factorial arrangement with four replications. For calculating pod loss, number of seed per pod, 100 seed weight and yield; three parameter Cousense equation were employed. The results showed that, there were an inverse relationship between PIGWEED density and number of pod, seed per pod and 100 seed weight.The number of pod and 100 seed weight of grain decreased with increasing of the weed density, but the rate of pod number and 100 seed weight decrease in low PIGWEED density were more, than high density of PIGWEED. For this reason the relation between PIGWEED density with pod number and 100 seed weight was not linear, because in higher densities of PIGWEED by initiating intra-specific competition, the rate of competition reduced between weed and soybean, but between seed per pod and PIGWEED density there was a decreasing linear relation. The rate of number of pod per plant and weight of 100 seed decrease reduced with increasing the weed density. The soybean yield loss in 16 PIGWEED plant density in Sari, Telare and Sahare were 46.33%, 57.4% and 58.31% relative to the weed control, respectively. In conclusion the competition ability of Sari was more than other cultivars, and the amount of yield loss was lesser than Telar and Sahar cultivar.