مجله دانش زراعت
پیاپی 3 (1388)

In order to study the effects of drought stress on agronomical traits and seed yield of new hybrids of sunflower there individual experiments were conducted on nine hybrids of sunflowers under three irrigation regimes (irrigation after 60,120,180 mm evaporation from evaporation pan class A) in 2006. The experiment was a randomized complete block design with 3 replication, performed in the research field of Karaj Seedling and Seed Breeding Agency. Results showed drought stress had significant effects on some sunflower traits such as number of total and active leaves, final plant height, stalk diameter, head diameter, diameter of empty seed, head weight, stalk weight, 1000 seed weight, seed yield and oil seed percent at the level of 1%. Also the phenological processes of plant, were affected by water deficit stress at the level of 1%. Given hybrids showed significant differences in all traits except head weight. The highest yield was obtained from control trait at 2778 kg.ha-1 decreasing by 62 and 81% under moderate and severe stress, respectively. The highest yield was obtained from A75×R196 and A46×R73 at 1687 and 1630 kg.ha-1, respectively due to head diameter and seed number. Comparison of stress and hybrid interaction levels showed that water deficit had negative effect on all recorded traits. The highest yield was obtained from control trait A112×R82 at 3482 kg.ha-1. A148×R65 and A75×R196 resulted in the highest seed yield of 1394 and 643 kg.ha-1 under moderate and sever drought stress, respectively.

An experiment was conducted to study the effect of different methods of magnesium sulfate application and cultivar on yield and yield components of lentil (Lens culinaris Med.) under Khorramabad climatic condition. This experiment was a factorial based on a randomized complete block design with three replications performed at the Agricultural Collage of Lorestan University in 2008. Different methods of magnesium sulfate application as the first factor (control treatment, soil application, foliar application, seed inoculation with fertilizer, foliar+ soil application and foliar+ seed inoculation method) and cultivar as the second factor (Gachsaran variety and Filip-92-12L variety) were applied. Analysis of variance showed that the interactions among different methods of fertilizer application and variety on plant characteristics were significant. Also, analysis of variance showed that plant height and 1000 seed weight (P<0.05) were significantly affected by the variety factor. The varieties did not have any significant effect on other characteristics. Also the effect of different methods of magnesium sulfate application on 1000 seed weight was non-significant. However, grain yield, the number of pods per plant, biological yield and harvest index (P<0.01), plant height (P<0.05) were significantly affected by different methods. Among the different methods of fertilizer application, soil application resulted in the highest grain and biological yield and plant height. Also, the highest 1000 seed weight, the number of pods per plant and plant height all were obtained using foliar+ soil application treatment. The highest harvest index was obtained using seed inoculation method. Grain yield showed a significant positive correlation with the number of pods per plant and biological yield (P<0.01). A significant and negative correlation was observed between grain yield and harvest index (P<0.01). Accordingly, soil application of magnesium sulfate and Filip-92-12L variety may result in the highest amount of lentil yield.

Agroforestry is one of the sustainable agricultural aspects in which the perennial woody plants grow in selective method with annual plants, domestic or both. This experiment was conducted to evaluate the effects of different sowing densities and nitrogen fertilizer rates on quantitative and qualitative characters of corn forage yield as well as weed population in an agroforestry system with orange trees. The treatments consisted of 4 nitrogen fertilizer levels of 0, 100, 200, and 300kg N/ha (allocated to main plots) and 4 sowing densities of 80000, 110000, 140000 and 170000 of corn plants per hectare (allocated to sub plots). The treatments were arranged as split plots based on a randomized complete block design with three replications. The forage dry matter yield followed an increasing trend as nitrogen fertilizer and sowing density increased. The highest forage dry matter of 33000 kg/ha was achieved at 170000 plant/ha density while received 300kg/ha of nitrogen. The highest crude protein (CP) percentage was obtained at 110000 plant/ha while received 100Kg N/ha. The yield CP increased as nitrogen fertilizer application increased. The highest digestible dry matter percentage was obtained at 110000 plant/ha with 200 Kg N/ha application. Weed dry matter weight per square meter significantly decreased as nitrogen fertilizer and sowing density increased to 300 Kg N/ha and 170000 plant/ha, respectively. Soil pH in 100Kg N/ha and 170000 plant/ha treatment significantly increased compared to other treatments. The largest orange fruit diameter was observed in 100Kg N/ha and 80000 plant/ha which was not significantly different from 300kg N/ha and 17000 plant/ha treatment.

German Chamomile (Matricaria recutita L.) is an annual plant from the compositeae family. Effects of three levels of urea (0, 40, 80 Kg.ha-1) and triple super phosphate (0, 30, 60 [Kg.ha-1) on the yield and essential oil production of chamomile was investigated. The experiment was a factorial on the basis of randomized complete block design with three replications conducted at Shaded University. Results showed that there was a significant effect of nitrogen fertilization on plant yield (number of flower and dry weight in bush) at the level of %1. Urea at 80 kg/ha resulted in the highest amount of yield by producing 742.2 number of flower and 20.63 g in each bush in comparison with control treatment with 507.06 number of flower and 10.06g in per bush. Phosphorous treatment at 60 kg/ha resulted in the highest amount of yield at 816.26 number of flower and 30.14g in per bush, respectively. Hence, use of 80 kg/ha urea and 60 kg/ha phosphorous is recommended for the highest amount of yield and essence.

Rice (Oryza sativa L.) is the most important food for half of the world's population. Rice is sensitive to salinity, which is one of the important stresses to limit rice growth and yield in Asia. In order to evaluate the effects of salinity stress on rice vegetative and agronomic characters an experiment was conducted using forty genotypes. The genotypes were tested at 4 salinity levels (0; 6; 8; 12 ds m-1), in factorial arrangement based on a complete randomized block design with 3 replications in greenhouse at the University of Agricultural Science and Natural Resources, Sari, Iran, 2008. The vegetative growth of rice cultivars was reduced under salt stress. Effect of salinity, genotypes and their interaction were significant on all measured traits including, number of tillers, plant height, shoot and root length, shoot and root and leaf dry weight and biomass. By increasing the level of salinity, biomasses of genotypes were reduced. In 12 ds m-1 salinity treatment, biomass in Sahel, Neda, Nemat, IR229, IR28, line 5, line 7 and line 19 was less than IR29 (sensitive check), but biomass in Shastak mohammadi, Fajr, line 109 was more than Pokkali (tolerant check) at the same salinity level. Grouping genotypes was performed by the Ward cluster analysis method and two clusters were identified. Genotypes such as Shastak mohamaddi, Hasani, Gerdeh, Tarom, Deilamani, Anbarbo, Nok siyah, Dom siyah, IR229, Lines 3, 7,19, 39, 75, 76, 83, 109, 126, MTM2, Sang tarom, F114, Musa tarom, Fajr, Dasht, Khazar and Ghasrodashti were located in same cluster as the tolerant group and other genotypes were grouped as the susceptible group.

This study was conducted to evaluate plant response of Brachiaria brizantha cv. MG5 to nitrogen (N) forms and different pH's of nutrient solution. In this study, under controlled conditions in growth chamber with hydroponics culture, seedlings after germination were treated with different N forms as nitrate, ammonium, and ammonium nitrate, as well as with different nutrient solution pHs. A solution of 5 mM morpholinoethanesulfonic acid (MES), or/and calcium hydroxide or/and calcium carbonate were used for pH adjustment. Nutrient solution containing ammonium and ammonium nitrate were fixed at pH 4, 6 or 8, and nutrient solution containing nitrate was fixed at pH 6. In another experiment seedlings of Brachiaria were grown in nutrient solution with different N forms, but without pH adjustment. The results showed that plants grown in ammonium or ammonium nitrate at pH 4 had better growth and plant performance, followed by pH 6, compared to plants grown at pH 8 (buffered with calcium carbonate). The presence of calcium (bicarbonate) in nutrient solution significantly reduced plant growth, particularly root growth and development. It seems that the negative effect of carbonate at high pH was higher than low pH. High concentration of carbonate in presence of ammonium was also toxic for plants. However plants were able to grow normally with different N forms under hydroponics culture, independent of pH effect. In this case, there was no significant difference between root and shoot biomass production at 5% of probability level. So the presence of carbonate but not pH, determined as an inhibiting factor for growth of B. brizantha cv. MG5 seedlings.

To study the effect of irrigation periods on the yield of two Agropyron species in climatic conditions of Damghan, an experiment was conducted as split plot in a randomized complete block design with four replications at the Ahvano rangelands. Main plots consisted of four irrigation periods: no irrigation and irrigation periods of 20, 40 and 60 days and the subplots were devoted to two A. elongatum and A. desertorum species. Analysis of variance along with mean comparison between treatments indicated that there were significant differences among irrigation regimes for plant species. There was also considerable variation observed among species in dry matter yield. Maximum dry matter yields for the 20-day period with 141.5 kg/ha belonged to A. desertorum. For the latter treatment, dry matter yield was reduced by 22.8 % as compared with the non irrigation conditions. Minimum dry matter yield was 96.4 kg/ha obtained from A. elongatum in non irrigation conditions, however, at 20 days periods dry matter yield increased by 34.8 %.

Beetles (Coleoptera) are the largest order of insects, which exist in all agroecosystems and natural ecosystems. Since rice fields include both aquatic and subterranean ecosystems, diverse fauna of beetles are active in rice fields of the world. In regard to the importance of these insects in chain foods of biosphere, fauna of some coleopteran families was surveyed in north rice fields of Iran (including, Mazandaran, Guilan and Golestan provinces) through 2001-2006. In total 69 beetle species of 9 families including, Alleculidae (3 species of one genus), Bruchidae (3 species of 3 genera), Cleridae (3 species of one genus), Curculionidae (15 species of 8 genera), Histeridae (6 species of 5 genera), Nitidulidae (4 species of 4 genera), Silphidae (6 species of 5 genera), Staphylinidae (17 species of 11 genera) and Tenebrionidae (12 species of 11 genera) were collected from rice fields and surrounding grasslands of Northern Iran.