مجله دانش زراعت
پیاپی 8 (1391)

Abstract In order to determine the best water production function (CWPF) for predicting grain yield of a soybean crop four models were evaluated. The four functions evaluated were Jensen (1968)، Minhas et al (1974) and modified Stewart et al (1977) and modified Bras and Corodova (1981) models. Field experiments were carried out for evaluation of the models. The grain yields simulated by the crop water production function were compared with the field measured data. The grain yields simulated by the crop water production function were compared with the field measured data. The base moisture stress sensitivity indices obtained for the vegetative، flowering and grain filling growth stages of the soybean crop were 0. 23، 0. 82، and 1. 1 respectively for Jenson (1968) and 0. 73، 2. 72 and 3. 4 respectively for Minhos et al (1974) model. The moisture stress sensitivity indices for the vegetative، flowering and grain filling growth stages for the modified Bras and Corodova (1981) model were 0. 25، 0. 73، and 1. 05 respectively and 0. 25، 0. 73 and 1. 05 respectively for modified Stewart et al (1977) model. The indices of the grain filling stage were noticed to be higher than the other growth stages، followed by the flowering stage and then the vegetative، for all models. The trend of the indices therefore implies that the grain filling growth stage was more critical to moisture deficit. Results showed that the models give good estimates of soybean grain yield with modified Bras and Corodova (1981) model performing slightly better than the other three models.

In order to study the effect of drought stress on qualitative and quantitative traits of sunflower cultivars and use of drought tolerance stress to determine the most tolerant cultivar to drought stress، this experiment was conducted on six cultivars of sunflower under two irrigation regimes (normal irrigation and drought stress) at agricultural and natural resources center of Yazd in 2010. The experiment was carried out in split plot in randomized complete block design with three replications. Results showed that effect of drought stress was significant on all of the characteristics and cultivars. The highest seed yield was produced by Azargol cultivar (1874 kg/ha) and lowest seed yield was produced by super grows (757 kg/ha) in drought stress condition. Therefore results indicated that Azargol is the most resistant cultivar to drought stress and Supergrow is the most sensitive cultivar to drought stress.

A field study was conducted at Aboureihan research field of Tehran University in 2009 to find out the effect of nitrogen pellet fertilizer on the grain yield and nitrogen use efficiency of corn (Single Cross 704). The factorial design of the study comprised of randomized complete block with three replications. Factors of this experiment including: first factor was two levels of fertilizer application method (pellet and mixed with soil) and second factor was four levels of nitrogen fertilizer pulse manure (46+600، 92+600، 138+600 and 184+600 kg/ha). In this research، a screw extruder setup was designed and manufactured. Increasing N fertilizer from 46 to 184 kg/ha had significant effect on all yield and yield components traits except number of seed rows per ear. Maximum grain yield was obtained with pellet and 184 N kg/ha treatment. Statistical analysis indicated that NUE، as well as agronomic efficiency (AE) were reduced while physiological efficiency (PE) increased with increasing N (pellet) rates.

In order to study effect of plant density on yield and seed yield components of forage vetch in rain-fed and supplemental irrigation conditions، two separate experiments were conducted at the research filed of faculty of agriculture، Lorestsn University، during 2008-2009. Three species of forage vetch (Vicia narbonensis، V. sativa and V. dasycarpa) and in three plant densities (100، 150 and 200 plant/m2) were combined factorially based on a randomized complete block design in each experiment. The highest dry forage yield (4912 kg/ha) was found in V. sativa under rain-fed condition and 150 plant/m2. Also the lowest dry forage yield (1750 kg/ha) was found in V. dasycarpa under supplemental irrigation condition and 100 plant/m2. The highest and the lowest pods yield (4282 and 1426 kg/ha) were recorded under supplemental irrigation condition and 100، 150 plant/m2 for V. narbonensis and V. dasycarpa، respectively. The highest and the lowest seed yield (3352 and 3/870 kg/ha) were recorded under supplemental irrigation condition for 200، 150 plant/m2 for V. narbonensis and V. dasycarpa، respectively. The highest and the lowest 1000 grain weight (133. 10 and 29. 73 gr) were recorded under supplemental irrigation condition for 100، 200 plant/m2 for V. narbonensis and V. dasycarpa، respectively. The highest biological yield (8243 kg/ha) was found in V. sativa under rain-fed condition and 150 plant/m2. Also the lowest biological yield (3268 kg/ha) was found in V. dasycarpa under supplemental irrigation condition and 150 plant/m2. The maximum and the minimum harvest index (52/82% and 21/10%) were recorded under rain-fed condition for 100، 150 plant/m2 for V. narbonensis and V. dasycarpa، respectively. The 1000 grain weight of the two experiments were significantly different using T- test (P 1%) and dry forage yield and harvest index of the two experiments showed significant difference using T-test (P= 5%).

In order to evaluate the effect of deleting of ray flower on the unfilled grain and seed formation، two cultivars of sunflower (Helianthus annuus L.) were used during 2008-2009 growing season in the research field of Kerman University. The experiment was conducted as factorial under RCBD. The main and sub factors were cultivars (two levels، Master and Euroflower)، respectively and deleting ray flower (three levels، 0%، 50%، 100%) percentage of unfilled grain in the center of the head، number of unfilled grain around the head، weight of one thousand seeds، diameter of the head and yield. The combined results of two years study showed that there is significant difference between ray flower deleting treatment and cultivars related to percentage of unfilled grain at the center of head and yield. The Linear regression analysis was revealed a positive effect of deleting of ray flower on the recorded characteristic at the center of head and yield. Deleting 100% of ray flower deleting led to 307 and 201kg/ha yield of Euroflower cultivar in the first and second growing season. Also the yield of Master cultivar was calculated as 429 and 476 kg/ha in the first and second growing season، respectively.

Priming is an effective method to improve seed viability that might be resulted to increase of seed germination percent and germination rate under stress conditions، such as drought stress. So، in this research the effect of seed priming on seed germination characteristics of safflower were evaluated under drought stress. A factorial experiment based on completely randomized design (CRD) with three replications was carried out at faculty of Agriculture، Bu-Ali Sina University. Treatments were priming at two levels (non priming and hydro-priming) and drought stress at seven levels (0، -2، -4، -6، -8، -10 and -12 bar). Results showed that with increasing drought stress from 0 to -12 bar، germination properties such as germination percent، germination rate and weight of seedling decreased. But، this decrease in non seed priming treatment was more than priming treatment. Therefore، at all levels of drought stress، germination rate and seedling fresh weight of safflower in control treatment was less than hydro-priming treatment. This reduction for germination percent at control treatment in compare to hydro-priming treatment was 70%. In general، hydro-priming improved germination characteristics of safflower under drought stress conditions and increased the resistance of safflower to drought stress in germination phase.

In order to evaluate the salinity tolerance of oat genotypes (Avena sativa L.)، at seedling and reproductive stages، an experiment with three replications was carried out in greenhouse condition (based on Randomized Completely Design). Experiments were carried out in research field of Esfahan University of Technology. which is located in Lourk’s Najafabad without stress، EC=4 ds/m، as well as in research field of Sharifabad of Ardakan، saline condition، EC=10 ds/m. The Na+، K+ concentration and Na+/K+ ratio in seedling stage، and plant height، number of tiller، panicle length، number of grain، 1000-grain weight، yield and harvest index in field condition were recorded. The analysis variance results at seedling stage showed significant difference among genotypes for standard evaluation system (SES)، but no significant difference was observed for Na+، K+ concentration and Na+/K+ ratio، that indicated that the existence of the other controlling mechanisms in salinity tolerance in these genotypes. The results of the combined analysis، showed significant difference among genotypes for in the studied traits. The interaction between genotype and environment was significant for all traits. Field and greenhouse evaluations on different oat genotypes established no clear correlation between seedling and reproductive stage، that indicates the existence of genetic variation in tolerance in the adult plants and in seedling stage، and the existence of different tolerant mechanism in two growth stages. Based on obtained results، lines No. 28، 32، 80 and 84 were introduced as high yielding genotypes، that due to the significant interaction between genotype and environment، lines No. 80 and 84 are introduced for Esfahan and line No. 17 for Yazd.