جستجوی مقالات مرتبط با کلیدواژه « سرعت رشد گیاه » در نشریات گروه « زراعت »

The camelina plant is a little-known plant Brassicaceae family. Camelina is an example of renewable vegetable oil that is considered a sustainable energy source. Seed yield and oil quality are the most obvious breeding objectives in the Brassicaceae family, while seed yield in agricultural plants, as their most complex trait, is influenced by a large number of physiological processes and the measurable expression is manifested in the physiological and morphological characteristics of the plant. Therefore, the analysis of physiological (growth) indicators is considered essential to understanding and interpreting changes in plant performance in response to environmental conditions. However, there is very limited information on the comparison of growth and functional traits of Camelina genotypes in the country. Therefore, the objective of this study was to compare the effects of physiological characteristics of 40 double haploid Camelina lines in the country.

In this study, 40 Camelina genotypes in terms of physiological traits and yield including leaf area index, crop growth rate, relative growth rate, net assimilation rate, specific leaf area, grain yield and oil yield were compared in a randomized complete block design with three replications in the research farm of Faculty of Agricultural Technology (Aburaihan), the University of Tehran, Pakdasht in 2020. It is worth mentioning that for measurement of the traits studied, the Soheil cultivar, which has long been grown both in the test area and in other parts of the country and is considered one of the well-known and widespread cultivar in the country, is considered as a control and other lines were compared with Soheil cultivar.

The results of the present study showed a significant difference between the Camelina lines in terms of physiological growth characteristics, the differences eventually led to significant differences in seed yield and thus had an impact on seed yield and oil content. This theme also shows and confirms the high and differential roles of genotype on camelina yield. In general, the results of this research showed that there is a positive correlation between the seed yield of camelina with the crop growth rate and the net assimilation rate, and there is a negative correlation with the specific leaf area at the 5% probability level. So, line 134 with the maximum leaf area index (2.34), and line 110 with the maximum growth rate (14.49) and net assimilation rate (8.13 g/m2 per day), in terms of the final grain yield were identified as the superior lines with 3178 and 3120 kg/ha, respectively. Also, the specific leaf area, which is directly related to the amount of light loss, was higher in low-yield genotypes than in lines 134 and 110.

The results of the present study showed the direct effect of seed yield on camelina oil yield. So that the greater compatibility of lines 110 and 134 with the studied culture environment has increased the dry matter accumulation and seed yield in the mentioned lines by increasing the plant growth rate and as a result has brought about a significant increase in seed oil yield in these lines. Since the purpose of cultivating Camelina oilseeds is, in addition to the seed harvest, to obtain oil of adequate quantity and quality, we can consider lines 134 and 110 as a whole as superior and promising double haploid lines, compatible with the climate conditions of the region.

Saffron can be cultivated in many regions of the world with different climates. But the best climate for growing saffron is the Mediterranean climate with its warm and dry summers. The present study was conducted to evaluate some indicators of saffron growth in 2019-2020 in four region with different altitudes above sea level in Sari, Iran. These regions include Sari plain (level with sea level), Sarkat (350 meters above sea level), Reskat (900 meters above sea level) and Margav (1350 meters above sea level). These experiments were performed in a randomized complete block design with three replications. The treatment was includes corm size in three weight groups: small (4±2 g), medium (10±2 g) and large (15±2 g) and Measured traits include leaf area index, cumulative dry matter, growth rate, relative growth rate and saffron yield. The results showed that the trend of saffron leaf area development in all studied regions has a non-linear trend and follows a logistic-peak function. Based on the results, a significant difference was observed between the leaf area development trend among different sizes of mother corm in all regions and the trend of leaf area index changes during the growing season was higher for larger corms than for smaller corms. The trend of changes in dry matter accumulation also had a sigmoidal trend in all experiment region. Total dry matter changes were higher for larger corms. Although the trend of changes in crop growth rate in higher altitude region was lower; But the rate of growth rate fluctuation or in other words the difference between the minimum and maximum growth rate during the season in the two higher regions was less than the lower regions. The growth trend of saffron in four regions showed that it grows during the season in region with higher altitudes above sea level and following more vegetative growth and more dry matter allocation to the storage organ, larger corm is produced and the potential to increase the yield of dried saffron flowers and stigmas will increase next year.

Abstract   Background and Objectives This study aimed at determining growth indices and temperature requirements at different stages of plant growth in order to optimize the ecology of plants to increase yield due to the availability of appropriate access to many agro technological issues, including appropriate planting dates, timely irrigation, appropriate time of harvesting, proper time to control the pests and diseases, the selection the appropriate cultivars, and achieving the highest yield of crops. The study also aimed at determining the growth indices and the growth rate of oat based on the BBCH scale.   Materials and Methods This experiment was conducted in the experimental field of Shahid Chamran University of Ahvaz during 2013-2014 growing season. Five oat genotypes (V1, V2, V3, V4, and V5) were grown under three different planting densities (including 300, 400, and 500 plants.m-2) using factorial experiment based on a randomized complete block design with three replicates. Growing Degree Days (GDD) of the different growing stages, according to the BBCH scale, and the daily temperature were calculated. Several physiological traits such as CGR, relative growth rate (RGR), net assimilation rate (NAR), SPAD value and total dry matter yield were evaluated.   Results The treatments had different effects on growth indices and physiological traits such as plant growth rate (CGR), relative growth rate (RGR), net assimilasion rate (NAR), leaf chlorophyll content, chlorophyll meter number, and dry matter yield. The results of the mean comparison showed that V2 had the highest level of NAR, RGR, CGR and TDW among oat genotypes, with an average of 1.40 g.m-2.day-1, 0.0015 g. g-1.da, 6.34 g.m-2.day and 39.87 g.m-2.day respectively, at a density of 300 plants / m2. In contrast, V1 had the lowest total dry matter yield with an average of 22.95 g.m-2 day. Among the genotypes, V2 had the lowest growth period with a density of 300 plants.m-2 with an average of 162 days of planting and 1899 days of growth (GDD in degrees C) and V4 had the highest growth period among the studied genotypes at a density of 500 plants.m-2 with the average of 175 days of sowing and 2178 days of growth. Discussion Reducing CGR at high densities can result in reduced photosynthetic energy in the growth of organs, or increased respiration or poor nutritional transmission of the growth of leaves from the root (Moradpour et al. 2013). Because of the decreasing RGR trend and the increasing density, dry matter accumulation was mainly attributed to undifferentiated tissues, as well as the shading of leaves on each other. Moreover, the increase in the age of the leaves can be considered effective in this decrease. Reductions in NAR during the increase in density can be attributed to the rapid addition of assimilates to seeds and the aging of the leaves. Considering the results of this research, it is suggested that using a GDD scale can lead to better at the growing season by estimating the time table as well as the time of phenological stages of oat in order to manage agricultural production, and therefore to determine the necessary conditions for plant growth.

To determine the best sowing time and cultivar of forage sorghum in summer cropping as a substitute for maize under water deficit conditions in the temperate region of Koohdasht, Lorestan, Iran, a split plot
experiment in randomized complete block design layout was conducted with four replications and four planting times (June 25 and 2th, 9th and 16th July) (after wheat harvest) and two forage sorghum cultivars (Pegah and Speedfeed) in main and sub plots, respectively, in the summer of 2013 and 2014 at Lorestan Agricultural and Natural Resources Research and Education Center, Khorramabad, Iran. Results showed that delayed planting reduced dry matter accumulation and crop growth rate (CGR) and Pegah cultivar performed better than Speedfeed cultivar. Maximum plant height was achieved in Speedfeed cultivar in second planting time in first and second years (173.3 and 211.6 cm, respectively). Pegah cultivar had better performance than Speedfeed in leaf area index and stem diameter in most planting times. Pegah cultivar in first planting time had highest fresh forage yield (94.0 and 110.2 ton.ha-1 in first and second years, respectively) and delay planting reduced dry and fresh forage yield. It concluded that the maximum dry and fresh forage yield of sorghum
(cv. Pegah) could be produced in June seed sowing and seems to be more suitable for temperate regions like Koohdasht, Lorestan, Iran.

Pinto bean (Phaseolus vulgaris L.) is one of the most important bean types in Iran. Cultivation area of pinto bean is about 50% of the total bean cultivation area and more than half of the grain bean production belongs to this type of bean. Drought is the most important environmental stresses that affected agricultural production in arid and semiarid areas and reduced crop productions. About 90 percent of Iran located in arid and semi-arid areas where water stress in the plants is inevitable. In addition, 60% of bean cultivation area in the world are faced with drought. Quantitative analysis of crops growth under water limitation condition is a good way to identify genotypes differences in response to drought stress.
In order to study the impact of deficit irrigation on pinto bean genotypes, an experiment was conducted as split plot based on randomized complete block design, at Shahrekord University, during 2013. Main plot was irrigation regime (supply of 100, 80 and 60 percent of crop water requirement) and sub plot was pinto bean genotype (Taylor, Sadri, C.O.S.16, KS21193 (Koosha193) and KS21486). Seeds were disinfected with benomyl fungicide before planting. Planting was conducted in 30 plant m-2 density. Crop water requirement was calculated by FAO Penman-Monteith equation. Irrigation regimes were applied at V4 stage (4th three foliate leaf has unfolded) and continued until the end of the growing season.
Results showed that there is genotypic variation in stem, leaf and seed dry weight, leaf area index (LAI), leaf area duration (LAD), crop growth rate (CGR), relative growth rate (RGR), net assimilation rate (NAR) and radiation use efficiency (RUE) in response to deficit irrigation. The dry matter accumulation of bean genotypes was sigmoidal shape and reduction in water use causes degradation of dry matter both in terms of the amount of dry matter and dry matter accumulation rate.
The highest RUE was recorded in KS21486 in supply of 80 percent of crop water requirement (3.21 g MJ-1). RUE changes to the reduction of irrigated water vary from genotype to genotype. So that, RUE of Taylor, Sadri and C.O.S.16 reduced and RUE of KS21193 and KS21486 increased in supply of 80 percent of crop water requirement condition. Moreover, RUE of all genotypes reduced in supply of 60 percent of crop water requirement condition. In fact, the amount of light absorption and biomass production reduced due to deficit irrigation. Under drought conditions, reduction in water availability decreases cell growth and subsequent reductions in leaf area index. Thus ratio of dry matter produced by the absorbed light is low and radiation use efficiency will be less. Drought stress reduced total dry weight. KS21486 had more rapidly seed dry weight enhancement rather than the other genotypes in the early stages, however Taylor and KS21193 had highest seed dry weight in all three levels of irrigation. Deficit irrigation decreased leaf area index in supply of 60 and 80 percent of crop water requirement condition compared to supply of 100% of crop water requirement condition. Maximum leaf area index in supply of 100, 80 and 60 percent of crop water requirement conditions were 3.1, 2 and 1.5, respectively. Average reduction of LAD in supply of 80 and 60 percent of plant water requirement conditions were 27 and 42 percent respectively. C.O.S.16 showed the highest CGR and maximum NAR and RGR, in supply of 100 percent of plant water requirement. In supply of 80% and 60% of plant water requirement conditions, KS21486 had the maximum NAR and RGR.
Biomass duration (BMD), LAD, LAI showed the highest correlation with grain yield, thus they are appropriate indicators to estimate grain yield under different moisture conditions. With the increase in leaf area index, leaf area duration and biomass duration, seed yield increased. To obtain more seed yield, the area of photosynthetic levels (leaves) and stay green must be increased to produce more photosynthetic products and allocated to seeds.

This study was conducted to investigate the effects of water deficit stress, nitrogen fertilizer and zeolite on growth parameters, biomass and seed yield of fenugreek. A split factorial experiment based on a randomized complete block design with three replications was conducted at the Research Field of Tarbiat Modares University in 2014 and 2015. Five irrigation regimes (unstressed, mild stresses during the vegetative and reproductive stages, respectively; severe stresses during the vegetative and reproductive stages, respectively) were randomized to the main plots. Subplots consisted of six treatments of a factorial combination of three levels of nitrogen fertilizations (untreated plots, vermicompost fertilizer at a rate of 2.7 t.ha-1 and nitrogen chemical fertilizer at a rate of 11 kg.ha-1) and two rates of zeolite (0 and 9 t.ha-1). In both years, increasing severity of water deficiet stresses reduced leaf area index, crop growth rate, plant height, biological and seed yield of fenugreek; Thus, severe water deficit stress at the reproductive stage without fertilizer and zeolite (with the least amount of biological and grain yield) compared with that of control, caused 60.96 and 48.09 percent reduction in biological yield and 80.18 and 75.62 percent reduction in grain yield, in both years, respectively. Application of nitrogen fertilizer, especially vermicompost, resulted in a significant increase in the leaf area index, crop growth rate of fenugreek in various stages of development, thereby increased biological and grain yield in different irrigation regimes. In various irrigation regimes, higher leaf area index, crop growth rate and finally more yield produced with application of vermicompost or zeolite.

To compare the yield and physiological growth indices of three Iranian sesame cultivars under the application of chemical and biological potassium fertilizers a pot experiment was conducted in the summer of 2015 in greenhouse. This study was performed as factorial arrangement based on a randomized complete block design with three replications. The potassium fertilizer application, based on soil test, was in four levels (K1:K2SO4 50%, K2: Bacillus circulans L., K3: Bacillus megatherium L. and K4: KSB1⤠ and three sesame cultivars used were Ultan, Yekta and Dashtestan 2. The plant samples were taken from 30 to 105 days after sowing with 15 days intervals. LAI, TDM, CGR, NAR and RGR were measured during the different growth stages. The results showed that the Yekta cultivar produced the highest seed yield (18.62 g.plant-1). Ultan produced highest growth rate as compared to the other cultivars. Furthermore, it responded differently to the application of biologic KSB1 fertilizer as compared to the other treatments and cultivars. KSB1 improved and accelerated plant growth rate at 90 days after sowing. While, the use of chemical potassium sulfate, KSB2 and combined application of Bacillus circulans L. with KSB1 and 2 improved growth 105 days after sowing.

The maize as the oldest cultivated plant, is ranked second and first in terms of cultivated area and amount of production, in the world respectively. Although, researchers have improved the yield of corn by introducing new lines and hybrids, new genotypes alone cannot increase agricultural production, and it is necessary that appropriate and advanced agricultural techniques also be used to maximize corn yield. Maize is one of the most important crops in Golestan province, which is planted in more than 5000 hectares of agricultural land. In Golestan Province, different tillage systems are used for planting maize. Conservation tillage is a new and widespread method in this province, which many farmers use this method every year for cultivating their crops. The main objective of this study was to investigate the effects of different tillage systems on growth indices and yield of maize.
To study the effects of different tillage systems on qrowth indices and forage yield of corn, an experiment was conducted using a Nested design at Azadshahr city. Treatments included no-tillage, minimum-tillage and conventional tillage. Each treatment was carried out in a separate 30 × 50 m plot. Cultivar 770 was planted in all plots with row spacing of 75 cmand the distance between plants on the ridges was 14 cm. Sampling was done by a 1*1 m2 quadrate in six phenological stages of maize including two leaf-stage (9 days after planting), six-leaf stage (26 days after planting), flowering (55 days after planting), (71 days after planting), (85 days after planting) and 86 days after planting. At each stage, 15 quadrates were randomly sampled in each plot. Leaf area and dry weight, height of each plant and total fresh and dry weight of maize was measured at laboratory.
Net assimilation rate decreased following a quadratic equation in all treatments. Although the amount of NAR was estimated 13.5, 13.16 and 13.11 g.m-2.day-1 for conventional, minimum and no tillage, respectively but there was not significance different between the tillage systems in this regard. The maximum amount of NAR occurred at 17.3, 17.4 and 17.5 days after planting for conventional, minimum and no tillage, respectively. The value of this index at the end of the growing season (86 days after planting) was estimated as 0.41, 0.45 and 0.47 g.m-2.day-1 for conventional, minimum and no tillage, respectively.
Relative growth rate decreased following a quadratic trend for all tillage systems. In conventional tillage, RGR declined from 0.24 g.g-1.day-1 at the beginning of the growing season to 0.01 g.g-1.day-1 at the end of the growing season. There was no difference between estimated RGR of the tillage systems both at beginning and at the end of growing season.
Maximum crop growth rate occurred at 54 days after planting in all three tillage systems. The maximum value of CGR was estimated 41, 41 and 40 g.m-2.day-1 for maize in conventional, minimum and no tillage systems, respectively. CGR was estimated as 3 g.m-2.day-1 at the beginning of the growing season for all treatments; this index was estimated 15, 15 and 14 g.m-2.day-1 at the end of the growing season, for conventional, minimum and no tillage systems, respectively.
Result showed that although tillage systems did not effect on dry weight of maize, forage yield of maize in conventional system (71 ton.ha-1) was significantly more than minimum (67 ton.ha-1) and no tillage (64 ton.ha-1) systems.

Dragonhead or Moldavian dragonhead (Dracocephalum moldavica L.), which belong to Lamiaceae family is an annual medicinal herbaceous and aromatic plant that its essential oil is used widely in medicine, food, cosmetic and health industries. Due to the importance and role of medicinal plants in various industries, there is an increasing demand for herbal medicines. The indiscriminate use of chemical fertilizers has increased crop production, but has also harmed ecosystems. Some studies show that the use of some microbial species that are collectively designated as plant growth promoting rhizobacteria (PGPR) can improve yield and quality of medicinal plants. Given the importance of environmental health and food safety, this study aimed to investigate the effect of PGPR on morphological traits and essential oil content of Moldavian dragonhead.
This experiment was conducted in randomized complete block design with eight treatments and three replications at research station of faculty of agriculture, Shahrekord university. No bacterial inoculation was used as control and seeds inoculated with Rhodococcus sp., Corynebacterium sp., Mycobacterium sp., Bacillus sp., Azotobacter sp., Pseudomonas putida, Pseudomonas fluorescens were considered as bacterial treatments.
The results showed that all bacterial treatments had a significant effect on plant height, number of branches, number of flowering shoot, leaf dry weight, shoot dry weight, biological yield, crop growth rate (CGR), leaf area (LA), chlorophyll a, chlorophyll b, essential oil content and yield. Mycobacterium sp. treatment had the most effect on plant height, number of branches, leaf and shoot dry weight, number of flowering shoot, biomass and chlorophyll b. Bacillus sp. treatment had the most effect on leaf dry weight, number of flowering shoot, leaf area and essential oil content and yield. The highest crop growth rate and chlorophyll a were observed in Rhodococcus sp.treatment.
In general, the Bacillus sp., Mycobacteriumsp., Rhodococcus sp., andPseudomonas putida treatments had the most influence on Moldavian dragonhead. Since the purpose of medicinal production is obtaining the highest content of essential oil and biomass yield, based on these results, the use of Bacillus sp., and Mycobacterium sp., bacterial inoculation treatments, as biopriming, can be recommended for increasing biomass and essential oil content in Moldavian dragonhead.

To find out the effects of Urea and animal manure as pellet and some microelements on total dry matter and physiological indices of medicinal pumpkin a split plot experimental design based on a randomized complete block with three replicates was conducted at University of Tehran, college of Abouraihan. The animal manure and Urea as pellet with four levels (150 Kg Urea, 50 Kg Urea.5 tone animal manure, 100 Kg Urea.5 tone animal manure and 150 Kg Urea.5 tone animal manure) as main factor and microelements with three levels (1000, 2000 and 3000 ppm) including Iron, Zinc, Manganese in chelate form and Boron in Boric Acid form as minor factor were considered. The results showed that use of pelleted manure and urea after 30 days had significant effect on total dry matter (p

In order to study the effect of Ca، K، and Mn foliar spray on vegetative traits of safflower (Padideh cultivar) under salt stress، a factorial experiment was conducted based on randomized complete blocks design with three replications in Vali-asr university greenhouse. Factors included salinity with four levels representing 0، 500، 1000، and 1500 mg NaCl kg -1، and foliar spray with four level representing 10 mM spray of distilled water، CaNo3، K2HPO4 and MnSo4، 1 mM spray، respectively، sprayed two weeks after emergence، one application per 2 weeks. Results showed that increasing salinity level، reduced plant dry weight، leaf area، height، while salinity and foliar spray treatments has no effect on number of leaves. Highest leaf area was obtained after K2HPO4 and CaNo3 foliar spray، and lowest leaf area was obtained from MnSo4، K2HPO4 and CaNo3 foliar spray prevented somewhat early plant growth rate reduction treated with 500 and 1000 mg NaCl. Applying 1500 mg NaCl reduced SPAD value، and leaf chlorophyll fluorescence. MnSo4، K2HPO4 and CaNo3 foliar spray nutrients، also reduced SPAD value.

Peanut are one of the paired plants of oilseed and protein seed oil is a rich source. In order to evaluate effects sulphur and zinc on growth characteristics and yield of peanuts، a experiment was conducted in Bandar Kiashahr، Guilan province، Iran in 2008. The experiment laid out in a factorial arrangement with two factors sulphur (0، 40، 80، 120 kg ha) and zinc chelate on (0، 0. 5، 1 and 1. 5 g per lit) in a completely randomized complete block design with three replications. Results showed that amounts of sulphur and zinc significant effects were on Peanut plant traits، as pod yield، seed yield and oil content. The mean comparison of the properties studied showed that rate of 120 kg. h-1 sulphur was better than other treatments. Also had better efficacy between treatments of zinc chelate on treatment to 1. 5gr per lit. Also، the interaction of the sulphur and zinc had the most increase on these parameters.

Effects of nitrogen (100 and 200 kg/ha) and irrigation levels (water stress at 8-10 leaf stage، water stress at milk till dough ripening and full irrigaiton) on grain filling and yield of two corn (Zea mays L.) cultivars (SC 500 and SC 647) evaluated through conducting field experiment in research farm of Bu-Ali-Sina University. The experiment was established as a completely randomized block design in a factorial split arrangment with three replications in 2008 growing season. Fertilizer and irrigation levels allocated to main plots and corn cultivars conducted to the subplots. Plant growth rate at flowering per kernel (PGRflw-kernel)، grain filling rate (GFR)، effective grain filling duration (EGFP)، plant growth rate at milk till physiological maturity (PGRM-M)، kernel number، kernel weight، SPAD at grain dough ripening، correlation between these characteristics and indexes were measured. application of 100 kg/ha nitrogen and water deficit stress at grain milk till dough ripening stages lead to decrease in PGRM-M، reduction in grain filling rate and grain weight. Water deficit stress at 8-10 leaf stage، reduced duration of effective grain filling. Highest yield obtained from applying 200 kg/ha nitrogen and full irrigation. Least effect of water stress on yield obtained from application of 200 kg/ha nitrogen and water deficit stress at grain milk till dough ripening stage.

To investigate the effects of on-farm seed priming and weed control on some traits in corn (single cross 301), an experiment was arranged in a factorial experiment based on randomized complete block design with three replications at experimental field of the Bu-Ali Sina University, Hamedan, Iran, in 2010. Experimental factors included, on-farm seed priming in four levels (non-primed, priming with urea solution, priming with zinc sulfate solution and priming with tap water) and weed control in three levels (non-weeding, weeding in 20 days after planting and weeding in 20 and 40 days after planting). For on-farm priming the seeds were placed for 16 hours in solutions of urea (6 g.l-1), zinc sulfate (0.34 g.l-1) and tap water, and after surface drying were planted. The results showed that priming with urea and zinc sulfate solutions had highest emergence rate and lowest time to 50 percent emergence (E50) using urea solution caused the most emergence percentage and emergence energy. The maximum emergence index was observed in urea solution. All treatments compared to non-primed non weeding treatment had higher leaf area index. In other words priming could compensate decreasing effect of weeds on leaf area index. Priming treatments with zinc and urea solutions had highest crop growth rate and total dry weight (Crop Growth Rate: 21.76 and 18.99 gr.m-2.d-1, respectively), (Total Dry Weight: 1086.76 and 1080 gr.m-2, respectively). Corn leaf area index duration was not affected by priming, but increased under once and double weed control respectively 22% and 23.9%. Crop growth rate increase with weed control and priming treatments showed most increase. Urea-once weed control and Zinc Sulfate-once weed control treatments had most biological yield. Zinc sulfate and urea treatments showed respectively, 14 and 12% higher yield than the control. Generally results showed that emergence rate and vigor increased by priming with urea and zinc sulphate solutions, also weed control in companion with seed priming increased the studied growth indices and biological yield.

In order to evaluate the effects of nitrogen levels and its split application on growth indices and their relationship with grain yield of rice (cv. Khazar), a field experiment was conducted at Rice Research Institute of Iran with 11 treatments arranged in a randomized complete block design with 3 replications in 2008. Nitrogen fertilizer levels (10, 20 and 30 kg.ha-1) were applied according to three chlorophyll meter (SPAD-502 reading thresholds) (36, 38 and 40) of fully developed leaf of rice plant. Results showed that in S38N30 (SPAD38+30 kgN) and S40N30 (SPAD40+30 kgN) treatments which were received maximum rate of nitrogen fertilizer (103 kgN.ha-1), maximum LAI (3.13 and 3.28) and CGR (29.86 and 29.34 g.m-2) were observed and in S40N30 treatment maximum LAD (1392.86 cm2.day-1) was observed. Analysis of regression showed that there was a significant linear relationship between grain yield and CGR (r2= 0.87**), LAI (r2= 0.88**) and LAD (r2= 0.76**). Maximum grain yield and nitrogen agronomic efficiency (5955 kg.ha-1 and 23.5 kg.kg-1, respectively) were also observed in S40N30 treatment. It seems that the main reason of increasing grain yield in this treatment was improvement of growth indices (CGR, LAI and LAD, respectively) and effective consumption of nitrogen fertilizer. Considering higher grain yield and nitrogen use efficiency in this treatment, it seems that split application of nitrogen in proper rate according to plant demand, may economize nitrogen fertilizer and prevent of its losses in rice production.

Weeds are reported as one of the most serious problems in red kidney bean production. To evaluate the competitive ability of red bean cultivars with red root pigweed an experiment was conducted at the Research Farm of the University College of Agriculture and Natural Recourses, University of Tehran in 2006. Different densities of pigweed including 0, 4, 8, 16 and 32 plants/m2 along with three cultivars of red bean (AKHTAR, SAYYAD and Line D81083) were employed in a factorial experiment with complete randomized block design. The effects of pigweed density on leaf area index, crop growth rate, biological and grain yield of dry bean were investigated during the study. Results indicated that at a density of 32 plants/m2 of pigweed, cultivar SAYYAD and Line D81083 had the most vs the least leaf area index and crop growth rate, respectively. Differences between grain and biological yield of cultivars were significant with Line D81083 exhibiting the least grain and biological yield. The density of 32 plants/m2 of pigweed, reduced grain yield of cultivars SAYYAD, AKHTAR and Line D81083 about, 42, 57 and 72%, respectively. Grain yields of red bean cultivars were more seriously affected by pigweed interference, in comparison with their biological yields. Based on the coefficients of yield loss models (a & m), red bean cultivar of SAYYAD had the most competitive ability among the red bean cultivars. The Line D81083 suffered from the most grain and biological yield loss. Also cultivar SAYYAD and Line D81083 had the most vs the least effect on biomass and leaf area index of pigweed respectively, indicating that cultivar SAYYAD has the most competitive ability against pigweed.